lA l internet Archive iri G 20 ,r fB with funding from University of Illinois Urbana-Champaign Alternates https://archive.org/details/landresourceregi2961unse NOTICE: Return or renew all Library Materialsl The Minimum Fee for each Lost Book is $50.00. The person charging this material is responsible for its return to the library from which it was withdrawn on or before the Latest Date stamped below. Theft, mutilation, and underlining of books are reasons for discipli¬ nary action and may result in dismissal from the University. To renew call Telephone Center, 333-8400 : I ■i/t- 32°) Land Resource Regions and Major Land s Resource Areas of The United States UNIVERSITY OF ILLINOIS AGRICULTURE LIBRARY Land Resource Regions and Major Land Resource Areas of The United States United States Department of Agriculture Soil Conservation Service Washington, D.C. Agriculture Handbook 296 Revised December 1981 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 CONTENTS Page Introduction. 1 Northwestern Forest, Forage, and Specialty Crop Region . 3 Northwestern Wheat and Range Region. @ California Subtropical Fruit, Truck, and Specialty Crop Region. n Western Range and Irrigated Region . 16 Rocky Mountain Range and Forest Region . 30 Northern Great Plains Spring Wheat Region . 35 Western Great Plains Range and Irrigated Region. 40 Central Great Plains Winter Wheat and Range Region . 49 Southwest Plateaus and Plains Range and Cotton Region . 56 Southwestern Prairies Cotton and Forage Region . 60 Northern Lake States Forest and Forage Region . 64 Lake States Fruit, Truck, and Dairy Region . 69 Central Feed Grains and Livestock Region . 75 East and Central Farming and Forest Region . 84 Mississippi Delta Cotton and Feed Grains Region . 94 South Atlantic and Gulf Slope Cash Crops, Forest, and Livestock Region. 95 Northeastern Forage and Forest Region. 100 Northern Atlantic Slope Diversified Farming Region . 106 Atlantic and Gulf Coast Lowland Forest and Crop Region . 109 Florida Subtropical Fruit, Truck Crop, and Range Region . 114 Hawaii Region . 117 Southern Alaska Region . 121 Interior Alaska Region . 124 Arctic and Western Alaska Region . ^27 References . 130 Appendix I. Area of LRR’s and MLRA’s. 131 Appendix II. Soil Classification . 137 Appendix III. Caribbean Region . 153 ill INTRODUCTION This handbook is an assemblage of currently available information about the land as a resource for farming, ranching, forestry, engineering, recreation, and other uses. It is a revision of USD A Agriculture Handbook No. 296, Land Resource Regions and Major Land Resource Areas of the United States, published in 1965. Revisions consist of: (1) Refined delineations of land resource regions (LRR’s) and major land resource areas (MLRA’s), (2) identification of the soils of each region and area according to the system of Soil Tax¬ onomy, (1975), (3) a brief discussion concerning the potential natural vegetation of the resource regions and areas, and (4) inclusion of major land resource areas and land resource regions for the states of Alaska and Hawaii and the territory of Puerto Rico (Appendix III). Information is current as of April 1978. The information in this handbook affords a basis for making decisions about national and regional agricultural concerns, identifies needs for research and resource inventories, provides a broad base for extrapolating the results of research within national boundaries, and serves as a framework for organizing and operating re¬ source conservation programs. The land resource categories used at state and na¬ tional levels are land resource units, land resource areas, and land resource regions. Land resource units are geographic areas, usually several thousand acres in extent, that are characterized by a particular pattern of soils, climate, water re¬ sources, and land uses. A unit can be one continuous area or several separate nearby areas. Land resource units are the basic units from which major land resource areas are determined. They are also the basic units for state land resource maps. They are coextensive with state general soil map units, but some general soil map units are subdivided into land resource units because of significant geographic differ¬ ences in climate, water resources, and land use. Land resource units are not described in this handbook, and they are not shown on the national map. Major land resource areas (MLRA’s) are geographically associated land resource units. Identification of these large areas is important in statewide agricultural plan¬ ning and has value in interstate, regional, and national planning. In this handbook major land resource areas are designated by Arabic numbers and identified by a des¬ criptive geographic name. For example, MLRA 1 (North¬ ern Pacific Coast Range, Foothills, and Valleys) is on the west coast; MLRA 157 is on the east coast; and MLRA 175 (Kuskokwdm Highland) is in Alaska. Some major land resource areas are designated by an Arabic number and a letter because previously estab¬ lished major land resource areas have been divided into smaller, more homogeneous areas. The use of numbers and letters to identify the newly created major land resource areas requires fewer changes in existing in¬ formation in records and in data bases. A few major land resource areas consist of two or more parts separated for short distances by other land resource areas. In places one of these parts is widely separated from the main body of the major land resource area and is in an adjoining land resource region. The description of the respective major land resource area also applies to these outlying parts. Land resource regions are designated by capital letters identified by a descriptive name. For example, the descriptive name for Land Resource Region A is the Northwestern Forest, Forage, and Specialty Crop Re¬ gion. The dominant physical characteristics of the land resource regions and of the 204 major land resource areas are described briefly under the headings land use, elevation and topography, climate, water, soils, and potential natural vegetation. The state or states in which an MLRA occurs and the extent of the MLRA are indicated on the first page of each description. The area and proportionate extent of the regions and the MLRA’s are given in appendix I. Land use. —The relative extent of the federally or privately owned land is indicated if significant. The extent of the land used for cropland, pasture, range, forests, industrial and urban developments, and other special purposes is indicated. These fractions or per¬ centages are for the entire resource area unless specifical¬ ly stated otherwise. Also included is a list of the principal crops grown and the type of farming practiced. Elevation and topography. —A range in height above sea level and significant exceptions, if applicable, are provided for the area as a whole. The topography of the area, including natural and cultural features, is described. Climate. —Climatic data discussed are: (1) A range of the annual precipitation for the driest parts of the area to the wettest and the seasonal distribution of precipitation and (2) a range of the average annual temperature and the average freeze-free period charac¬ teristic of different parts of the resource area. Water. —Information is provided concerning surface streamflow and ground water and the source of water for municipal use and for irrigation. Also, land resource areas dependent on other areas for water supply and those that furnish water to other areas are specified. Soils. —The dominant soils of the major land re¬ source area are identified according to the principal suborders, great groups, and representative soil series. 1 General descriptions of the soil orders, suborders, and great groups are provided in appendix II. Potential natural vegetation.—The plant species that the major land resource area can support are identified by their common names. The descriptions are based on information from many sources, mainly from the Soil Conservation Service, U.S. Department of Agriculture. Most information about land use is based on recent reports of state soil and water conservation needs. For additional sources, refer to the list of references. 2 A—NORTHWESTERN FOREST, FORAGE, AND SPECIALTY CROP REGION 204,080 km 2 ( 78,790 mi 2 ) Steep mountains and narrow to broad, gently sloping valleys and plains characterize this region. The average annual precipitation ranges from 1,025 to 1,775 mm in much of the region, but it is 375 mm or less in some valleys and as much as 5,075 mm in some of the higher mountains. All this region is dry during the summer. The average annual temperature is 10 to 13°C in most of the region, but it is 2°C or less in some of the mountains. The freeze-free period is more than 200 days in most valleys, as long as 300 days along the coast in the southern part, and less than 115 days in the mountains. Umbrepts, Ochrepts, Humults, Xerults, Andepts, and Orthents are the principal soils in the mountains and on uplands. Fluvents, Xerolls, Xeralfs, Aquolls, and Aquents are extensive in the valleys. The mountains are heavily forested, and lumbering is a major industry. Dairy farming is an important enterprise in the valleys that have abundant rainfall. Grain crops, grass and legume seeds, fruits, and horticultural specialties are grown extensively in the drier valleys. 1—Northern Pacific Coast Range, Foothills, and Valleys Oregon and Washington 41,020 km 2 ( 15,840 mi 2 ) Land use: About 90 percent of this area is pri¬ vately owned. The area is densely forested, and lum¬ bering is the chief industry. About 9 percent is cleared and used for general agriculture. The cleared areas are mainly in the narrow valleys and on coastal terraces. Hay, pasture, and some grain for cattle are the prin¬ cipal crops. About 1 percent of this area, mainly land bordering water, is used for urban development. Recre¬ ation and wildlife habitat are other important land uses. Elevation and topography: Elevation ranges from sea level to about 900 m, but the average is about 200 m. Most of this area consists of low coastal terraces, hills, and low mountains with gentle to steep slopes. Valleys are mostly narrow and of small extent. Most of the nearly level bottom land on the coast is sus¬ ceptible to tidal influence. Climate: Average annual precipitation —1,400 to 3,175 mm. Precipitation is evenly distributed throughout fall, winter, and spring. Summers are dry. In most of this area, snow falls only a few days each year. Aver¬ age annual temperature —7 to 13°C. Average freeze-free period —60 to 270 days, decreasing with elevation. Water: Precipitation, perennial streams, and lakes pro¬ vide abundant water for all present requirements. Glacial and alluvial deposits in the valleys yield large quantities of ground water. Soils: Most of the soils are Umbrepts or Ochrepts. They are well drained and gently sloping to very steep and have a mesic temperature regime and a mixed mineralogy. Haplumbrepts (Astoria, Hembre, Lytell, Boistfort, and Solleks series) formed in volcanic ash and in material weathered from siltstone, sandstone, and basic igneous rock. Dystrochrepts (Calawah, Hoquiam, Kalalock, and Klone series) and Duro- chrepts (Dabob and Hoko series) formed in glacial drift. The nearly level Udifluvents (Belfast, Greha- lem, and Hoh series) formed on flood plains. Potential natural vegetation: This area supports for¬ est vegetation. The coniferous forest stands are dense, tall, and highly productive. Western hemlock, west¬ ern redcedar, Douglas-fir, and Sitka spruce are com¬ mon, and grand fir grows in places. Red alder is ag¬ gressive on disturbed sites. Lodgepole pine is com¬ mon along the coastal dunes. Mature forests have lush understories with dense growths of shrubs, herbs, ferns, and cryptograms. Tree species in the southern part of the region include Port-Orford-cedar, Califor¬ nia bay, madrone, tanoak, and golden chinkapin. Sal- monberry, ladyfern, swordfern, rhododendron, Pacif¬ ic waxmyrtle, willow, vine maple, evergreen huck¬ leberry, salal, oxalis, and violet are major shrubs and forbs. 2—Willamette and Puget Sound Valleys Oregon and Washington 48,160 km 2 ( 18,590 mi 2 ) Land use: Much of this area is privately owned; about one-sixth is federally owned. Nearly three-fourths of the land in Puget Sound Valley is forested, and lumbering is the major industry. In Willamette Val¬ ley only three-fifths or less is forested, and lumbering is not so important. Urbanization is increasing in much of the area. Less than one-fifth of the total MLRA is in crops or improved pasture, but agriculture is highly diversified. Deciduous fruits, berries, vege¬ tables, seed crops, and grains grown under intensive management are the major crops. A large acreage is also used for growing hay and grain for dairy and poultry feed. High-value crops are grown under irrigation in some places, but rainfall is the source of water for most crops. Elevation and topography: Elevation ranges from sea level to 500 m. Willamette Valley consists of 3 nearly level to gently sloping flood plains bordered by dissected higher terraces. Glacial till, glacial outwash, and lacustrine deposits cover Puget Sound Valley. Climate: Average annual precipitation —Ranges from 375 to 2,550 mm, but it is 750 to 1,150 mm in much of the area. Precipitation is evenly distributed through¬ out fall, winter, and spring, but summers are dry. Average annual temperature —9 to 13°C. Average freeze-free period —120 to 240 days. Water: Moderate precipitation and abundant streamflow provide enough water for present needs. Additional supplies are available from adjoining mountain ranges. Ground water is plentiful in glacial and alluvial depos¬ its. Soils: Most of the soils are Xerolls. These soils are moderately deep to deep and moderately fine textured to fine textured and have a mesic temperature re¬ gime and a mixed mineralogy. The nearly level, well drained Haploxerolls (Chehalis and Puyallup series) and the nearly level, moderately well drained Argixerolls (Woodburn series) are on flood plains and terraces. Poorly drained Albaqualfs (Dayton series) formed in clayey alluvium on ten-aces. Poorly drained Haplaquepts (Bellingham series) formed in glacial till on uplands of the Puget Sound Valley. The sloping to steep, well drained Haplohumults (Jory, Olympic, and Bellpine series) and Haploxeralfs (Melbourne series) are on uplands. The moderately steep to steep, well drained Durochrepts (Alderwood series) are on glacial till uplands. Potential natural vegetation: This area supports forest vegetation in many places, prairie vegetation in some places, and savanna vegetation in others. Douglas-fir is the dominant tree species. Bigleaf maple, western redcedar, grand fir, and western hemlock are also common. Red alder is aggressive on disturbed sites in Washington. Stands of cottonwoods and willows grow on overflow channels, streambanks, and islands. Oregon white oak is common in savan¬ nas, especially in Oregon. Red and western fescues, bromes, and sedges are common in the prairies and savannas. Forest and savanna understory species include tall Oregon-grape, Indian plum, snowberrv, hazel, oceanspray, serviceberry, rose, poison-oak, swordfern, dwarf Oregon-grape, salal, vine maple, red huckleberry, thimbleberry, and oxalis. 3—Olympic and Cascade Mountains Oregon and Washington 65,310 km 2 (25,210 mi 2 ) Land use: About 95 percent of this area is federally or state owned. Most of the area is densely forested, and lumbering is the major industry. At high eleva¬ tions, alpine meadows provide summer range. Min¬ ing is important in some places. Recreation and wildlife habitat are also important land uses. Elevation and topography: Elevation generally ranges from 200 to 1,700 m, but on mountain peaks it is as high as 4,400 m. Steep mountains, narrow valleys, some U-shaped glaciated valleys, and narrow divides are dominant. There are some plateaus. Narrow bands of bottom land and terraces border some of the streams. Climate: Average annual precipitation —1,525 to 2,550 mm in most parts but more than 2,550 mm on the more elevated parts and as much as 6,100 mm on Mt. Olympus. Maximum precipitation is in fall, in winter, and in spring; all the area receives snow in winter. Average annual temperature —2 to 10°C, decreas¬ ing with elevation. Average freeze-free period —0 to 200 days, decreasing with elevation. Some high moun¬ tain peaks receive frost every month of the year. Water: Precipitation and perennial streams fed by glaciers and springs provide abundant water for all present needs. This area supplies water to adjoining MLRA’s at lower elevations that receive less pre¬ cipitation. Soils: Most of the soils are Ochrepts, Andepts, Boralfs, and Orthods. They are well drained and gently sloping to very steep and have a mesic, frigid, or cryic temperature regime. Xerochrepts (Barneston and Skykomish series) formed in glacial outwash materials. Vitrandepts (Cispus series), Dystrandepts (Cinebar, Zynbar, and Larchmount series), and Cryandepts formed in materials that have a high content of volcanic ash. Glossoboralfs (Wilkeson series) formed in materials weathered from andesite and basalt. Haplorthods (Klaus series) formed in glacial drift. Cryorthods and Cryochrepts (Oso se¬ ries) formed in glacial drift and volcanic debris. Potential natural vegetation: This area supports dense forest stands. Douglas-fir, Pacific silver fir, and western hemlock are typical species. Western redcedar, noble fir, and western white pine are common. At higher elevations, mountain hemlock is an important part of the plant community, and subalpine fir and whitebark pine grow near timberlines. Huckleberry, salal, blackberry, twinflower, vine maple, Pacific yew, thimbleberry, violet, triilium, swordfern, insideout flower, oxalis, beargrass, and false-azalea are com¬ mon in the understory. 4—California Coastal Redwood Belt California 13,880 km 2 (5,360 mi 2 ) Land use: Most of this area consists of privately owned farms, ranches, or forests; about 10 percent is federally owned. About 68 percent of the area is densely forested, and lumbering is the major indus¬ try. About 10 percent is grassland used for grazing. Cultivated land in the valleys and along the coast, making up about 3 percent of the area, is used mainly for growing forage and grain for dairy cattle. Vege¬ tables and fruits (apples) are grown in places where 4 the soils and the climate are favorable. Soils in basins and on flood plains are susceptible to flooding, depo¬ sition of sediments, and local streambank cutting. The hazard of erosion is moderate on soils on terraces and coastal benches. If the grass cover on soils on uplands is removed by logging, fire, overgrazing, or cultivation, the hazard of erosion is severe. Elevation and topography: Elevation is from sea level to 800 m, but on some peaks it is 1,200 m. Low but steeply sloping mountains are dominant. Gently sloping marine terraces border the coast, and a few broad valleys extend inland through the mountains. Climate: Average annual precipitation —825 to 2,025 mm. Precipitation is evenly distributed throughout fall, winter, and spring, but it is low in summer. Heavy fogs are common along the coast in summer. Average annual temperature —10 to 13°C. Average freeze-free period —250 to 300 days. Water: Abundant precipitation and many perennial streams provide enough water for most requirements. The drier valleys depend on streamflow from the mountains. Ground water is abundant in the deeper valley-fill deposits. Soils: The dominant soils are Xerults, Xerolls, Ochrepts, and Humults. They have a mesic temperature re¬ gime, but some in the coastal zone have an isomesic temperature regime. Soils on uplands are Haploxerults (Goldridge and Josephine series), Xerochrepts (Hugo and Maymen series), Haplohumults (Sites series), Haploxerolls (Laughlin, Kneeland, and Ben Lomond series), Argixerolls (Yorkville series), and Hapludalfs (Atwell series). Soils on terraces and coastal benches are Argialbolls (Watsonville series), Tropohumults (Empire and Rohnerville series), and Tropudults (Caspar series). Soils in basins and on flood plains are Fluvaquents (Bayside series), Tropofluvents (Femdale series), and Haploxerolls (Soquel series). Potential natural vegetation: This area supports forest and grass vegetation. Redwood, Douglas-fir, grand fir, bishop pine, western redcedar, Port-Orford- cedar, alder, California bay, chinkapin, madrone, tanoak, and California black oak are dominant tree species. California oatgrass, tufted hairgrass, west¬ ern and Idaho fescues, Pacific reedgrass, and native and introduced bentgrasses are common perennial grasses. Soft chess, wild oats, bromes, filaree, and burclover are important naturalized annuals. Gorse- broom and Scotch-broom are dominant in some parts of the coastal zone. 5—Siskiyou-Trinity Area California and Oregon 35,710 km 2 (13,790 mi 2 ) Land use: Nearly half of this area is federally owned. Most of the land is in conifer forests that are impor¬ tant for lumbering, wildlife habitat, and recreation. About 10 percent of the area is grazed, and a smaller acreage is cropped. Livestock is the principal farm enterprise. Truck crops are important in valleys where the water is adequate. On the more sloping parts of the valleys, small grains, hay, and pasture are grown as feed for dairy cattle and other livestock. The erosion hazard is high because of steep slopes, erodible soils, and high rainfall. The erosion hazard is severe if the plant cover is removed. Mass movement in the form of landslides is a serious problem and a major source of sediment in the rivers. Elevation and topography: Elevation ranges from 100 to 1,400 m, but on some mountain peaks it is 2,700 m. Rounded but steeply sloping mountains that are underlain mainly by sandstone and shale but in some places by granodiorite, gabbro, and other in¬ trusive rocks are dominant. The narrow valleys have gently sloping flood plains and alluvial fans and are bordered by strongly sloping foothills. Climate: Average annual precipitation —450 mm in some valleys to 2,150 mm in the mountains. Precipi¬ tation is low in summer but is evenly distributed throughout the rest of the year. Average annual temperature —7 to 13°C. Average freeze-free period —60 to 250 days, decreasing with elevation. Water: The moderate to high precipitation provides enough water in the mountains and higher valleys and, through streamflow, supplies irrigation water in the drier valleys. Ground water is abundant in allu¬ vial deposits in most valleys. Soils: The dominant soils are Ochrepts, Xerults, Orthents, Xeralfs, and Umbrepts. They have a mesic tempera¬ ture regime and a xeric moisture regime. Principal soils of the mountains are Xerochrepts (Sheetiron and Hugo series), Haploxerults (Josephine series), shallow Xerorthents and Xerochrepts (Etsel and Maymen series), Haploxeralfs (Holland and Dubakella series), and Xerumbrepts (Masterson series). Xero- thents and Xerofluvents are on flood plains and alluvial fans. Detailed soil survey information is lacking for much of the area. Potential natural vegetation: This area supports forest, open forest, and prairie vegetation. Douglas- fir, ponderosa pine, sugar pine, incense-cedar, white fir, red fir, tanoak, Oregon white oak, California black oak, canyon live oak, and madrone are the dominant tree species. Poison-oak, snowberry, cean- othus, manzanita, rose, and whipplea characterize the forest understory. Blue wildrye, fescues, bluegrass, mountain brome, and some browse species are in the understory in open stands of timber. Soft chess, wild oats, burclover, fescues, and bromes are major prai¬ rie species. 5 B—NORTHWESTERN WHEAT AND RANGE REGION 239,650 km 2 (92,530 mi 2 ) This region of smooth to deeply dissected plains and plateaus also has a few mountain ranges. The average annual precipitation ranges from 250 to 575 mm in most of the region, but it is as low as 150 mm in some valleys and as much as 1,525 mm or more in some mountains. Summers are dry. The average temperature is 7 to 10°C in most of the region but ranges from 3 to 13°C. The freeze-free period ranges from 120 to 200 days, but it is shorter in the mountains. Xerolls, Borolls, and Ochrepts, derived mainly from loess, are dominant in most of the region. Andepts formed in materials consisting mostly of volcanic ash. Orthents occur on steep slopes underlain by basalt and lava. Fluvents on flood plains are important for agriculture. Wheat grown by dryfarming methods is the major crop in most of the region, but oats and peas are also important. Fruits, mainly apples, are a major crop in the west. Potatoes, sugar beets, beans, and forage corps are grown under irrigation along the Snake River in the eastern part of the region. Grazing is the major land use in the drier parts, especially in the west. 6—Cascade Mountains, Eastern Slope Oregon and Washington 37,750 km 2 (14,570 mi 2 ) Land use: About 60 percent of this area is federally owned; most of the remainder is in farms, ranches, or privately owned woodland. About 75 percent is forested. Lumbering is an important industry. Much of the woodland is grazed by cattle. This area is also important for recreation and for wildlife habitat. Less than 5 percent, mostly in the valleys, is crop¬ land, most of which is irrigated. Crops include tree fruits, small grains, and forage crops. Elevation and topography: Elevation ranges from 300 to 2,400 m, but some mountain crests are 3,000 m. Strongly sloping mountains and U-shaped glaci¬ ated valleys are dominant. Some gently sloping crests and benches are dissected by many streams. Climate: Average annual precipitation —500 to 1,775 mm, generally increasing with elevation, but on some mountain crests it is 2,550. Precipitation falls mainly during the winter, spring, and fall; sum¬ mers are relatively dry. All areas receive snow in winter. Average annual temperature —4 to 10°C, but it is lower on mountain crests. Average freeze-free period —60 to 120 days, decreasing with elevation. Water: Precipitation and perennial streams provide ample water. This area supplies water from the perennial streams and reservoirs to drier and lower lying MLRA’s. Ground-water supplies are mostly untapped. Soils: The dominant soils are Orthods, Andepts, Ochrepts, Xerolls, and Xeralfs. They have a mesic, frigid, or cryic temperature regime. Cryorthods and Haplorthods formed in residuum from weathered bedrock, alpine glacial till, and volcanic debris. Cryandepts (Surgh series) and Vitrandepts (Choral- mont, Molson, and Palmich series) formed in recent and weathered volcanic ash. Shallow to deep Xero- chrepts (Ardenvoir, Kartar, and Nevine series) formed in bedrock residue, glacial drift, and a mixed mantle of volcanic debris. Deep Haploxerolls (Conconully series) formed in glacial till. Haploxeralfs (Cle Elum and Varelum series) formed in material weathered from sandstone. Detailed soil survey information is lacking for most of the area. Potential natural vegetation: This area supports conifer forest and grass vegetation. The kind of vegetation gradually changes with increases in eleva¬ tion and in precipitation. Important species in grass¬ lands at the lowest elevations are bluebunch wheat- grass, Sandberg bluegrass, big sagebrush, bitterbrush, Idaho fescue, and Cusick bluegrass. Ponderosa pine forest has an understory of bluebunch wheatgrass and Idaho fescue. Douglas-fir forest has an under¬ story of pinegrass, bearberry, and currant. Grand fir western larch, and lodgepole pine have an understory of vacciniums and menziesia. Pacific silver fir, moun¬ tain hemlock, subalpine fir, and whitebark pine are at the highest elevations. 7—Columbia Basin Oregon and Washington 18,520 km 2 (7,150 mi 2 ) Land use: About 85 percent of this area is privately owned, and about 15 percent is federally owned or is set aside as Indian reservations. About 60 percent is range of native grasses and shrubs grazed by cattle. About 22 percent is dry-farmed. A wheat-fallow crop sequence generally is practiced. About 15 percent of the area is irrigated, and fruits, vegetables, sugar beets, hops, grain, hay, and pasture are grown under intensive management. There is a rapid increase in the use of sprinkler irrigation. About 3 percent of the area is urban. Elevation and topography: Elevation ranges from 100 to 800 m, but most of the area is 200 to 500 m above sea level. In general, the area is a smooth, 6 gently sloping plain broken by some steep basalt ridges. The smooth plains are also dissected into large areas by drainage ways. Climate: Average annual precipitation —150 to 300 mm, increasing with elevation. Maximum precipita¬ tion is in winter; summers are dry. Average annual temperature —8 to 13°C. Average freeze-free period —120 to 200 days. Water: The Columbia, Yakima, and Snake Rivers supply large quantities of water for irrigation. Most of the irrigation water is diverted from the natural river channel or is pumped to a higher elevation and delivered to individual farms by gravity flow. Water is scarce in all nonirrigated areas. Although ground- water supplies have increased since irrigation has been practiced in the area, they are largely untapped. Soils: Most of the soils are Orthids, Orthents, Psamments, and Aquolls.They have a mesic temperature regime. Camborthids (Shano, Warden, and Ephrata series) formed in loess or in a mixed loess mantle over lacustrine or outwash deposits. Durorthids (Burke, Koehler, and Taunton series) formed in a silty loess or sandy eolian mantle over a lime-silica-cemented duripan. Somewhat poorly drained, very strongly alkaline Torriorthents (Umapine series) formed in alluvium. Torripsamments (Quincy and Winchester series) formed mostly in eolian sand. Somewhat poorly drained, nearly level Haplaquolls (Pasco, Toppenish, and Track series) formed on alluvial bot¬ tom lands. Potential natural vegetation: This area supports shrub-grass associations. Big sagebrush and bluebench wheatgrass are dominant on the medium textured soils. Bitterbrush and needleandthread are abundant on the sandy soils. Very shallow soils support stiff sagebrush and Sandberg bluegrass. Inland saltgrass, basin wildrye, and greasewood grow on saline-alkali soils. 8—Columbia Plateau Oregon and Washington 42,730 km 2 (16,500 mi 2 ) Land use: More than 90 percent of this area is in farms or ranches; about 7 percent is federally owned, and the remainder is urban. Nearly one-half is cropland, most of which is dry-farmed. The main crops are wheat and peas, but a small acreage is in hay and improved pasture. In places where the annual precip¬ itation is less than about 350 mm, a cropping system of alternate grain and summer fallow is practiced. Cropping systems of alternate grain and field peas, continous grain crops, or variations, including rota¬ tions with grasses and legumes, are practiced in places where precipitation is greater that 350 mm. Small acreages along the major streams are irrigated and used for growing vegetables, fruits (mainly apples), and hay. Nearly all the remaining land, about two- fifths of the total area, is in range, but small sections are wooded. Elevation and topography: Elevation ranges from 400 to 1,100 m. These loess- and ash-mantled pla¬ teaus are nearly level to steeply sloping. Steep slopes are common along the walls of major valleys and in scablands. Climate: Average annual precipitation —225 to 450 mm. Maximum precipitation is in winter. Average annual temperature —7 to 13°C. Average freeze-free period —140 to 175 days. Water: The low to moderate precipitation limits the choice of agricultural enterprise. The major rivers provide water for irrigation along their courses, but the small streams provide little water. Ground-water supplies in the underlying basalt are small and mostly untapped. Soils: Most of the soils are Xerolls. They are well drained or somew'hat excessively drained and have a mesic temperature regime. Nearly level to moder¬ ately steep, deep and moderately deep, silty Haplo- xerolls (Ritzville, Walla Walla, Condon, and Valby series) formed in loess on uplands. Nearly level, deep, medium textured Haploxerolls (Onyx, Hermis- ton, and Esquatzel series) are on flood plains. Shallow, stony Haploxerolls (Lickskillet, Bakeoven, and Kuhl series) are on ridgetops and steep south slopes. Moderately deep Haploxerolls (Wrentham series) are on steep north slopes. Potential natural vegetation: This area supports shrub-grass associations. Big sagebrush and bluebunch wheatgrass are dominant on the moderately deep to very deep, gently sloping to moderately sloping soils and on soils that have steep and very steep south exposures. Big sagebrush and Idaho fescue are dom¬ inant on most moist sites and on moderately steep to very steep north exposures. Stiff sagebrush, low 7 sagebrush, and Sandberg bluegrass are dominant on shallow and very shallow, stony soils. Small stands of ponderosa pine, with oak on warmer sites along the Columbia River, are on north slopes, in canyons and draws, and along stream channels. Dwarf hardwoods of hackberry and maple also grow in canyons and draws. Snowberry is the most common shrub in the pine stands. Poison-oak is the most common shrub in the oak stand. 9—Palouse and Nez Perce Prairies Idaho, Oregon, and Washington 23,140 km 2 (8,940 mi 2 ) Land use: Less than 30 percent of this area is federally owned. Nearly all the remainder is in farms and ranches. About 40 percent, including most of the publicly owned land, is rangeland. About 50 percent is cropland, most of w r hich is dry-farmed to wheat, 7 peas, and lentils. About 1 percent is irrigated and used for growing vegetables and other specialty crops. Small wooded areas and urban areas make up about 10 percent. Elevation and topography: Elevation along the major streams is about 200 m, but in most of the plain it ranges from 600 to 1,200 m. The loess-covered basalt plain is moderately to strongly dissected; slopes are mostly hilly and steep. The major streams have cut deep canyons. Climate: Average annual precipitation —375 to 625 mm. Precipitation is evenly distributed throughout fall, winter, and spring; summers are relatively dry. Snow falls in winter. Average annual temperature —7 to 12°C. Average freeze-free period —100 to 170 days, decreasing with elevation. Water: Precipitation is adequate for dry farming. Most irrigated areas are adjacent to large streams. Ground-water supplies are small and mostly untapped. Soils: Most of the soils are Xerolls, but Albolls, Aquolls, and Xeralfs also occur in this area. These soils have a mesic temperature regime and a mixed mineralogy. Haploxerolls (Asotin, Athena, Bakeoven, Caldwell, Calouse, Garrison Linville, Palouse, and Snow series) formed mostly in deep loess or alluvium or in glacial outwash or deposits shallow to bedrock. Argixerolls (Gwin, Larkin, and Waha series), some of which are deep and others shallow, formed in loess or mixed loess and colluvium. Argialbolls (Latah, Tilma, and Thatuna series) are deep soils that formed in loess. Deep, somewhat poorly drained Argiaquolls (Konert and Konner series) formed in alluvium. Deep Haploxeralfs (Freeman and Garfield series) formed in loess. Potential natural vegetation: This area supports grass, shrubs, and trees. Grassland of bluebunch wheatgrass and smaller amounts of Idaho fescue, Sandberg bluegrass, and needleandthread generally are at lower elevations and receive less rainfall. Shrub-grassland of snowberry and Idaho fescue or of big sagebrush with Idaho fescue and bluebunch wheatgrass are mainly at higher elevations. Rose, common cowparsnip, black hawthorn, and arrowleaf balsamroot are also important. Woodlands of ponderosa pine with bluebunch wheatgrass, Idaho fescue, snowberry, and ninebark on south and west slopes merge into Douglas-fir with pinegrass on north and east slopes. 10—Upper Snake River Lava Plains and Hills Idaho and Oregon 44,870 km 2 (17,330 mi 2 ) Land use: Nearly three-fifths of this MLRA is federally owned; most of the remainder is in farms or ranches. More than 90 percent is rangeland. About 5 percent of the total area, land bordering the large streams, is irrigated and used for growing potatoes and small grains and for pasture. Small tracts of deep soils are dry-farmed. Elevation and topography: Elevation ranges from 400 to 2,000 m, increasing from west to east. The lava plains and hills are nearly level to steeply sloping. Deep alluvial deposits are in valleys and on fans adjacent to the mountains. The major streams are deeply entrenched, especially in the western part. Isolated mountain ranges occur throughout the area. Climate: Average annual precipitation —250 to 500 mm. Precipitation is evenly distributed throughout fall, winter, and spring but is low in summer. Aver¬ age annual temperature —4 to 13°C. Average freeze- free period —60 to 165 days, decreasing from west to east and with elevation. Water: The low to moderate precipitation is adequate for dry farming on the smoother areas of deep soils. Streams provide enough irrigation water to meet present needs along the major valleys. Ground-water supplies are small and mostly untapped. Soils: The dominant soils are Xerolls and Argids. They are well drained and moderately fine textured to fine textured and have a mesic temperature regime. Deep, rolling to hilly Argixerolls (Gem, Simas, and Tub series) are on uplands. Shallow, gently sloping to steep, stony Argixerolls (Ruckles series) are on up¬ lands underlain by basalt. Moderately deep, sloping to very steep Haploxerolls (Loveline series) are on uplands. Nearly level to sloping Durargids (Madras and Lookout series) are on plateaus. These soils have a duripan. Potential natural vegetation: This area supports a shrub-grass association. Big sagebrush and bluebench wheatgrass are dominant on the moderately deep to very deep soils and on steep and very steep south exposures. Big sagebrush and Idaho fescue are dom¬ inant on moist sites. Stiff sagebrush, low sagebrush, and Sandberg bluegrass are dominant on drier sites. Antelope bitterbrush and Idaho fescue grow on moist sites at high elevations. Western juniper is common on the drier, stonier sites. Curlleaf mountainmahogany grows at high elevations. 11—Snake River Plains Idaho and Oregon 35,250 km 2 (13,610 mi 2 ) Land use: Nearly half of this area is federally owned; the remainder is in farms and ranches. Most of the federally owned land is rangeland. Forage produc¬ tion is low, and annual grasses have invaded much of the rangeland. The National Reactor Testing Station is in the northeast, and Craters of the Moon National Monument is on bare lava flows in the east. About one-fourth of the area, the plains bordering the Snake River and its tributaries, is irrigated. Pota¬ toes, grain, sugar beets, beans, and alfalfa hay are 8 the principal crops. There is some irrigated pasture. Small tracts in places where the soils and moisture are favorable are dry-farmed. Elevation and topography: Elevation ranges from 600 to 1,700 m. These nearly level to steeply sloping lava plains have a thin to moderately thick cover of loess. In places, the rivers are in deep, steep-walled canyons. Alluvial fans, terraces, and bottom land are gently sloping to moderately sloping. Climate: Average annual precipitation —175 to 325 mm. There is little or no precipitation in summer. Average annual temperature —5 to 11°C. Average freeze-free period —90 to 170 days, lowest in the northeast. Water: Large quantities of water are available for irrigation along the Snake River and its tributaries. Ground water is plentiful in some of the deep alluvial deposits throughout the area and in the lavas north of the Snake River in eastern and south-central Idaho. It is used extensively for irrigation. Water is scarce on sites far from the major rivers, and these sites depend on local precipitation for water. Soils: Dominant soils are Orthids, Argids, and Orthents. They have a mesic or frigid temperature regime. Deep and moderately deep, silty Calciorthids (Portneuf and Pancheri series), Haplargids (Power series) and Camborthids (Trevino and Tenno series) are on loess- covered plains of the west and central parts of the area. Durorthids (Minidoka and Nyssa series) and Durargids (Purdam and Chilcott series) that have a hardpan are on older land surfaces. Moderately coarse textured Torriorthents (Turbyfill and Umapine se¬ ries), Camborthids (Vining series), Calciorthids (Declo series), and Calcixerolls (Bannock series) are exten¬ sive in the central and eastern parts of the area. Potential natural vegetation: This area supports shrub-grass vegetation. Big sagebrush, winterfat, shadscale, Indian ricegrass, needleandthread, Thurber needlegrass, and Sandberg bluegrass grow on the lower Snake River Plains. Big and threetip sage¬ brush, bluebunch wheatgrass, Thurber needlegrass, and arrowleaf balsamroot grow on the middle Snake River Plains. The upper Snake River Plains support bluebunch wheatgrass and big sagebrush. Black sage¬ brush and gardner saltbush are dominant on some soils. Phlox, tapertip hawksbeard, biscuitroot, and penstemon are also important. 12—Lost River Valleys and Mountains Idaho 16,380 km 2 (6,320 mi 2 ) Land use: Nearly all this area is federally owned. The high mountain slopes are forested, and some lumber is produced. The low grass and shrubs on the slopes and in the valleys are grazed. Irrigated land in the valleys, making up about 1 percent of the area, is used mostly for hay and pasture, but potatoes and small grains are also grown. Elevation and topography: Elevation ranges from 1,400 m in the valleys to more than 3,100 m at the highest mountain crests. Steep to very steep moun¬ tains underlain by mixed sedimentary rocks and volcanic rocks make up about 50 percent of the area. The large valleys, deeply mantled by recent alluvium and some lacustrine deposits, are level to moderately steep. Climate: Average annual precipitation —175 to 275 mm in the valleys and 625 mm or more on mountain crests. Average annual temperature —3 to 7°C in the valleys but much lower in the mountains. Average freeze-free period —80 to 110 days in the valleys. Frost occurs every month of the year in the high mountains. Water: The moderate precipitation provides enough moisture for grass and shrubs to grow on mountain slopes. The valleys depend on the streamflow of the Salmon, Lemhi, Pahsimeroi, Big Lost, and Little Lost Rivers for water for livestock and irrigation. Springs and deep wells in the valleys supply a small amount of ground water for domestic uses and for irrigation. Soils: Major soils of the valleys are Orthids, Orthents, Aquolls, and Xerolls, which have a frigid tempera¬ ture regime. The dominant soils of the mountains are Rendolls, Borolls, Orthents, and Ochrepts, which have a cryic temperature regime. Moderately deep, gently sloping, gravelly, medium textured Calciorthids (McCaleb series) and shallow, very gravelly Torrior¬ thents (Ramshorn series) are on low alluvial fans and terraces. Moderately deep, nearly level, poorly drained, medium textured Haplaquolls (Tew series) are on stream bottoms and terraces. Moderately deep, grav¬ elly, medium textured Argixerolls (Soelberg series) are on high alluvial fans near the mountains. Shallow, very gravelly, medium textured Rendolls (Sheege series) are on south-facing slopes. Moderately deep, medium textured Cryoborolls (Pavohroo series) are on north-facing slopes. Shallow, stony Cryorthents and Cryochrepts are on the highest mountains. Potential natural vegetation: This area supports desert shrub, shrub-grass, and forest vegetation. Indian ricegrass, needleandthread, shadscale, gardner saltbush, and scarlet globemallow are major species in the valleys. Big and low sagebrush, winterfat, bluebunch wheatgrass, Sandberg bluegrass, and a variety of forbs grow on mountain foot slopes. Bluebunch wheatgrass, prairie junegrass, oniongrass, Indian paintbrush, lupine, sedge, big and low sage¬ brush, and rabbitbrush grow on low mountain slopes. Curlleaf mountainmahogany, Douglas-fir, aspen, and Rocky Mountain juniper grow on high mountain slopes. 9 13—Eastern Idaho Plateaus Idaho 21,010 km 2 (8,110 mi 2 ) Land use: Nearly three-fourths of this area is in farms and ranches; the remainder is federally owned. Most of the Fort Hall Indian Reservation is in this MLRA. About one-fourth of the area is dry-farmed, and wheat is the major crop. An additional 10 percent, land along some of the large streams, is irrigated and used largely for alfalfa hay, meadows, and pasture, but some small grains and potatoes are grown. About one-half of the area is rangeland. About 10 percent, consisting of high mountain slopes, is in forests that produce some timber. Elevation and topography: Elevation ranges from 1,400 to 2,000 m in plains and plateaus and from 2,300 to 2,600 m on mountain crests, but on some peaks it is more than 3,100 m. The dissected plateaus and plains are underlain mainly by sedimentary rocks and some volcanic rocks that are mantled by loess on gentle and moderate slopes. Lacustrine deposits and deep allu¬ vium fill some level valleys and basins. The plains and plateaus are separated by many rugged but discon¬ tinuous mountain ranges of folded sedimentary rocks. Climate: Average annual precipitation —300 to 625 mm. Minimum precipitation is from midsummer through autumn. Average annual temperature —4 to 7°C., but it is lower in the mountains. Average freeze-free period —50 to 120 days. Frost occurs every month of the year in the high mountains. Water: Precipitation provides water for dry farming and grazing, but careful management is needed to make the best use of the limited amount. Several large streams that flow through the area supply water for irrigation, mainly outside the MLRA. Small but important tracts are irrigated along the Bear, Portneuf, Blackfoot, Snake, and Teton Rivers. Ground water is scarce except near the large streams. Soils: The dominant soils are Xerolls and Borolls. They have a frigid or cryic temperature regime, depending largely on elevation. Deep, silty Argixerolls (Bancroft series) and Haploxerolls (Rexburg series) are major soils on the loess-covered plains. Deep, silty Cryoborolls (Tetonia and Lanark series) are on foothills. Moder¬ ately deep, gravelly, medium textured Cryoborolls (Driggs series) are on alluvial fans and terraces near the mountains. Shallow, skeletal, medium textured Rendolls (Sheege series) are on south-facing slopes of the mountains. Moderately deep, medium textured Cryoborolls (Pavohroo series) are on north-facing slopes. Potential natural vegetation: This area supports grass-shrub vegetation. Bluebunch wheatgrass and big sagebrush are dominant. Arrowleaf balsamroot is common. Prairie junegrass, Sandberg bluegrass, Ne¬ vada bluegrass, oniongrass, slender wheatgrass, milkvetch, lambstongue fawnlily, phlox, penstemon, antelope bitterbrush, rabbitbrush, snowberry, and low Oregon-grape are other important plants. Scattered stands of Douglas-fir and aspen grow on north slopes and on the more moist soils. 10 C—CALIFORNIA SUBTROPICAL FRUIT, TRUCK, AND SPECIALTY CROP REGION 167,570 km 2 (64,700 mi 2 ) This region of low mountains and broad valleys has a long warm growing season and low precipitation. The average annual precipitation ranges from 1,025 mm to less than 250 mm. Very little precipitation falls from late in April through October. The average annual temperature is 16 to 18°C in most of the region but is as low as 0°C at some of the higher elevations. The average freeze-free period is 230 to 270 days in much of the region, but it is 125 days or less in some of the higher mountains and more than 350 days in the valleys of the south. Xeralfs, Xererts, and Xerolls are extensive on uplands and older terraces throughout the region, but Fluvents, Orthents, and Ochrepts on flood plains and alluvial fans are the most important soils for agriculture. Many of the soils on flood plains and low terraces are affected by salts and must be skillfully managed for good crop production. This region has a wide variety of crops and agricultural enterprises. Citrus fruits, other subtropical and tropical fruits, and nuts are major crops in the southern half. Many kinds of vegetables, grown mainly under irrigation, are produced throughout the region. Rice, sugar beets, cotton, grain crops, and hay are also important crops. Dairying is a major enterprise near the large cities. Beef cattle production on feedlots and range is also important. 14—Central California Coastal Valleys California 10,380 km 2 (4,000 mi 2 ) Land use: Most of this MLRA is in farms and ranches; about 20 percent is used for urban development, and the acreage used for this purpose is increasing rapid¬ ly. The gently sloping soils in the valleys are intensively farmed to many kinds of crops. Truck crops, wine grapes, strawberries and other fruits, cut flowers, small grains, hay, and pasture are the principal crops grown on irrigated land. Small grains are the princi¬ pal crops on dry-farmed areas. Dairy farming is an important enterprise near the large cities. The more sloping fans and foothills, making up one-fourth or more of the area, are in native range used for livestock grazing. Sites along streams are susceptible to flooding and bank cutting. If the plant cover on soils on terraces is removed, the hazard of erosion is severe in winter. Soils on hills are coarse textured, and the hazards of soil blowing and water erosion are severe if the plant cover is removed. Elevation and topography: Elevation ranges from sea level to 600 m, but it is less than 300 m in most of the area. This area is a network of gently sloping valley floors bordered by higher and more sloping terraces and fans and by steep uplands. Climate: Average annual precipitation —300 to 750 mm. This area is very dry from midspring to midautumn. Average annual temperature —13 to 17°C. Average freeze-free period —210 to 300 days; the longest period occurs along the coast. Water: The low to moderate rainfall and local streamflow are inadequate to meet present water needs. Water from adjoining MLRA’s is brought in for agriculture and for the domestic and industrial requirements of the many large cities. The yield of ground water in the deeper alluvial deposits, especially in Santa Clara Valley, is declining, and the intrusion of seawater is reducing the quality of the water. Soils: The dominant soils are Xeralfs, Xerolls, Xererts, Xerults, Aquents, Orthents, and Psamments. They have a thermic or isomesic temperature regime. Fluvaquents (Alviso series), Pelloxererts (Clear Lake series), Haploxerolls (Pacheco series), and Hydraquents (Reyes series) are on flood plains and in tidal basins. Pelloxererts (Cropley series), Haploxerolls (Salinas, Sorrento, and Arroyo Seco series), Xerorthents (Yolo series), and Haploxeralfs (Zamora series) are on low terraces. Natrixeralfs (Antioch series), Haploxeralfs (Arbuckle and Pleasanton series), Argixerolls (Chualar series), Haploxerults (Haire series), Palexeralfs (Positas series), and Natrixerolls (Watsonville series) are on old terraces and alluvial fans. The gently sloping Xeropsamments (Oceano and Marina series) are on hills. Potential natural vegetation: This area supports grasses, brush, and trees. Naturalized annual grasses and forbs are dominant in many places. Soft chess, wild oats, bromes, fescues, filaree, burclover, and some remnant perennials are major species. Scattered valley oak grows on the well drained soils. Saltgrass, iodinebush, and other salt-tolerant plants grow in tidal areas. In places, there are a few remnant stands of redwood trees. 15—Central California Coast Range California 21,900 km 2 (8,460 mi 2 ) Land use: More than four-fifths of this area is in farms and ranches; most of the remainder is federally owned. About 10 percent is dry-farmed to grain, and slightly more that 50 percent is in range of native 11 grasses and brush. Open woodland, also used for grazing, makes up nearly 35 percent of the area. Small acreages are forests and urban areas. The erosion hazard is severe in dry-farmed orchards and grainfields. If the plant cover is removed from the soils by fire, overgrazing, cultivation, or logging, the hazard of erosion is severe because of steep slopes and high-intensity rainfall. Elevation and topography: Elevation ranges from sea level to 800 m in most of the area, but it is 1,500 m in some mountains. Gently sloping to steep low mountains underlain mostly by shale and sandstone and partly by igneous and volcanic rocks cover most of the area. Coastal plains are narrow and discon¬ tinuous, and stream valleys are narrow and widely separated. Climate: Average annual precipitation —300 to 1,025 mm, but it is 375 to 750 mm in most of the area. Precipitation is evenly distributed throughout fall, winter, and spring but is very low in summer. Coastal areas receive some moisture from fog in summer. Average annual temperature —13 to 18°C. Average freeze-free period —120 to 270 days. Water: The low to moderate rainfall and moderate streamflow limit agriculture to dryfarming in most of the area. Ground-water supplies are limited. Soils: The dominant soils are Xererts, Xerolls, Och- repts, Xeralfs, Orthents, and Psamments. They have a thermic temperature regime (mesic at the highest elevations). Soils on hills are the rolling to steep Chromoxererts (Altamont series), Argixerolls (Cha- mise and Los Osos series), Xerochrepts (Millsholm series), HaploxeralfslDibble series), andHaploxerolls (San Benito, Linne, and Santa Lucia series). Also on hills are the gently sloping to steep Palexeralfs (Spreckles series), Xerorthents (Shedd series), and Haploxerolls (Nacimiento series). Soils on uplands are the strongly sloping to steep Xeropsamments (Arnold series), Xerorthents (Gaviota series), Ar¬ gixerolls (Los Gatos, Gilroy, and Henneke series), Haploxerolls (Montara, Sheridan, and Sur series), Xerochrepts (Maymen and Toomes series), and Haploxeralfs (Vallecitos series). Rock outcrop is common. Potential natural vegetation: This area supports grasses, grass-oak, and shrub vegetation. Natural¬ ized annuals, including soft chess, bromes, fescues, wild oats, filaree, and burclover characterize the open and oak grasslands. Blue oak, valley oak, and canyon live oak are the dominant trees. California sage¬ brush, coyotebrush, chamise, manzanita, ceanothus, and scrub oak are the major brush species. Along the west side of the Coast Range are forests of Douglas- fir, madrone, grand fir, tanoak, bigleaf maple, and a few remnant stands of redwood trees. Stands of ponderosa pine with madrone, black oak, live oaks, California buckeye, manzanita, and ceanothus are on drier sites. 16—California Delta California 2,310 km 2 (890 mi 2 ) Land use: Nearly all this area is farmed. Important crops are asparagus, sugar beets, potatoes, corn, grain, and hay grown under intensive management. Fruit trees, mainly pear, are grown on slopes of the protecting levee system. Erosion of the levees by wave action is a continuous land use problem. Subsidence of the peat and muck soils is also a problem. Elevation and topography: Elevation ranges from below sea level to slightly above sea level. Many streams divide this nearly level delta into islands. Strong protective levees and adequate drainage are needed to protect this area from flooding. Climate: Average annual precipitation —325 to 375 mm. Summers are dry. Average annual temperature — About 16°C. Average freeze-free period —About 270 days. Water: Water for agriculture comes mostly from the many sloughs and waterways that cross the area. Controlling salinity and salt water intrusion is a major concern of management. Soils: The dominant soils are Saprists, Aquolls, Fluvents, Hemists, Aquents, and Aquepts. They have a ther¬ mic temperature regime. Organic Medisaprists (Rindge and Kingile series) and Haplaquolls (Egbert and Ryde series) formed in freshwater marshes. Moder¬ ately well drained to poorly drained soils on natural river levees are Xerofluvents (Columbia series) and Haplaquolls (Sacramento series). Medisaprists (Joice series), Medihemists (Suisun series), Hydraquents (Reyes series), and Haplaquepts (Valdez series) formed in brackish water marshes. Potential natural vegetation: This area supports marsh vegetation. Fat-hen saltweed, brass buttons, alkali bulrush, cattails, tules, saltgrass, and pickleweed characterize this area. 17—Sacramento and San Joaquin Valleys California 49,580 km 2 (19,140 mi 2 ) Land use: More than 90 percent of this MLRA is in farms and ranches. Much of the remainder is federally owned. About 2 or 3 percent is urban, and the acreage used for this purpose is increasing rapidly. Slightly more than half the area is cropland, three- fourths or more of which is irrigated. The cropland in this MLRA represents 60 percent of the cropland in California, and the irrigated cropland is 80 percent of the irrigated land in the state. Cotton, fruits, nuts, grapes, hay, grain, pasture, rice, alfalfa, citrus, and 12 tomatoes are among the principal crops grown on ir¬ rigated land. The more sloping, nonirrigated crop¬ land is dry-farmed to grain. About a third of the area is in native grasses, brush, and open woodland and is used mostly for grazing. If the plant cover on sloping soils on terraces is removed, erosion is a hazard. The hazard of wind erosion is severe on the sandy, wind-modified soils in the San Joaquin Valley if a plant cover is not maintained. Elevation and topography: Elevation ranges from sea level to 200 m. This area includes the valley basins adjacent to the Sacramento and San Joaquin Rivers, fans and flood plains of tributary streams, and terraces around the edge of the valley. Climate: Average annual precipitation —125 to 625 mm. Summers are long, hot, and dry, and winters are cool and rainy. Average annual temperature —16 to 19°C in most of the area but as low as 13°C in the north. Average freeze-free period —230 to 350 days, increasing from north to south. Water: Because of the low rainfall and relatively small streamflow, water is scarce in many parts of the area. Water for irrigated crops comes from stream diversions, wells, and canals of organized irrigation districts that obtain most of their water from state and federal water systems. Soils: The dominant soils are Xeralfs, Xerolls, Xererts, Aquents, Aquolls, Ochrepts, Orthents, Fluvents, Psamments, and Argids. They have a thermic tempera¬ ture regime. Soils in basins are Xerofluvents (Co¬ lumbia series), Pelloxererts (Willows and Clear Lake series), Chromoxererts (Capay series), Haploxerolls (Merced series), Natrixeralfs (Solano and Pescadero series), Haploxeralfs (Traver series), Haplaquents (Tulare series), and Haplaquolls (Sacramento series). Soils on fans and flood plains are Xerorthents (Yolo and Hanford series), Haploxerolls (Chino and Grange- ville series), Torriorthents (Panoche series), Xero¬ fluvents (San Emigdio series), Haploxerolls (Sorrento series), Natrargids (Lethent series), Haploxeralfs (Wyman and Zamora series), and Haplargids (Panhill series). Soils on low terraces are Durixeralfs (Fresno and Madera series) and Durochrepts (El Peco series). Soils on terraces are Durixeralfs (San Joaquin, Exeter, and Redding series) and Palexeralfs (Red Bluff and Corning series). Sandy soils in the San Joaquin Valley are Xeropsamments (Delhi, Calhi, and Tujunga series). Potential natural vegetation: This area supports naturalized annuals and scattered trees. Wild barley, wild oats, soft chess, ripgut brome, red brome, foxtail fescue, burclover, and filaree are dominant species. Scattered oaks on terraces and oak, willow, and cottonwood grow along the rivers and streams and in the overflow areas. Saltgrass, along with such shrubs as iodinebush and Australian saltbush, grow on saline-sodic soils on terraces and in basins. 18—Sierra Nevada Foothills California 7.300 km 2 (2,820 mi 2 ) Land use: About four-fifths of this MLRA is in farms and ranches; most of the remainder is federally owned. Production of livestock on range is the principal enterprise. Approximately 75 percent of the area is range, 5 percent cropland, and the remainder brushland and open forest. Most of the cropland is dry-farmed to grain, but small tracts are used for growing fruit, nuts, and grapes under irrigation. The hazard of erosion is moderate to severe on the soils if the plant cover is removed by overgrazing, cultivation, or fire. Elevation and topography: Elevation ranges from 200 to 500 m, but on some isolated mountain peaks it is 1,200 m. In this area of rolling to steep dissected hills and low mountains, the stream valleys are narrow and fairly steep. Climate: Average annual precipitation —350 to 900 mm. Summers are hot and dry, and winters are cool and moist. Average annual temperature —13 to 18°C. Average-freeze-free period —200 to 320 days. Water: The moderate rainfall and intermittent streamflow are the major water sources. Ground-water supplies are small and mostly untapped. Numerous stock ponds are scattered throughout the area, but little has been done to construct small reservoirs for irrigation. Soils: The dominant soils are Ochrepts, Xeralfs, Xerolls, and Orthents. They have a thermic temperature regime. Shallow soils include Xerochrepts (Hornitos, Toomes, and Auburn series), Xerorthents (Dauston, Whiterock, and Exchequer series), and Argixerolls (Henneke series). Moderately deep and deep soils are Haploxeralfs (Rescue, Argonaut, Ahwahnee, Auberry, and Sierra series) and Xerochrepts (Vista series). Potential natural vegetation: This area supports naturalized annual grasses, shrubs, and trees. Soft chess, wild oats, filaree, burclover, ripgut brome, and foxtail fescue are dominant species on rangeland. An overstory of scattered individuals to very dense stands of blue oak and Digger pine, with scrub live oak as an important component, grow in some places. Chamise, manzanita, wedgeleaf ceanothus, yerba- santa, and poison-oak are dominant on brushland. Scattered stands of ponderosa pine, mixed with man¬ zanita and black oak, are at the upper elevations of the more moist sites. At the upper elevations, small stands of Douglas-fir grow on north slopes along major streams. 19 —Southern California Coastal Plain California 51,500 km 2 (19,890 mi 2 ) Land use: More than one-fourth of this area is federally owned. About one-fifth is urban or is in built-up 13 areas, and other land is rapidly being converted to this use. One-third or more of the area is brushland used for watershed protection. Preventing fires on this land is a major concern of management. Irri¬ gated cropland, making up 10 to 20 percent of the area, is used for growing subtropical fruits, decidu¬ ous fruits, grain, truck crops, grapes, hay, and pasture. Dairy farming and flower seed production are other important enterprises. Some livestock are produced on rangeland. The erosion hazard is slight on the soils in valleys and on terraces and benches of the valleys. The hazard of sheet and gully erosion is severe on the sloping soils on coastal terraces and benches and on the upland soils if they are unprotected in winter. Elevation and topography: Elevation ranges from sea level to 600 m. These gently sloping to strongly sloping and dissected coastal plains are bordered by steep hills. Climate: Average annual precipitation —250 to 625 mm. Summers are dry, but fog provides some mois¬ ture along the coast. Average annual temperature —16 to 18°C. Average frost-free-period —365 days along the coast, decreasing to 250 days in the hills. Water: The low rainfall and intermittent streamflow provide small quantities of water for local use. Ground-water resources have been heavily exploited, and declining water tables and salt intrusion are reducing both the quantity and quality of the water. Much of the water for irrigation and nearly all the water for large urban areas comes from the Colorado River and from northern California. Soils: The dominant soils are Xeralfs, Ochrepts, Orthents, Xererts, Xerolls, Psamments, and Fluvents. They have a thermic temperature regime. Soils on coastal terraces and benches are Xerofluvents (Camaril¬ lo series), Palexeralfs (Olivenhain, Milpitas, and Las Flores series), Xeropsamments (Marina series), Durixeralfs (Redding series), and Durochrepts (Carls¬ bad series). Soils in valleys are Haploxeralfs (Greenfield and Traver series), Xerorthents (Hanford series), Xerofluvents (San Emigdio series), and Haploxerolls (Sorrento series). Soils on terraces and benches along the sides of the main valleys are Durixeralfs (Monserate series), Natrixeralfs (Placentia series), and Haploxeralfs (Rincon series). Soils on uplands are Haploxeralfs (Cajalco and Fallbrook series), Xerorthents (Cieneba and Gaviota series), Chromoxererts (Alo series), Pelloxererts (Diablo series), Haploxerolls (Hambright, Friant, Lodo, and San Benito series), and Xerochrepts (Vista series). Rock outcrop is common. Potential natural vegetation: This area supports annual and perennial grasses, shrubs, and trees. Wild oats, soft chess, red brome, filaree, burclover, needlegrass, tarweed, mustard, and annual lupine interspersed with scattered individual to dense stands of oak grow on rangeland. Stands of brush include buckwheat, ceanothus, California sagebrush, chamise, and scrub oak. A unique stand of rare Torrey pine grows in this area between Del Mar and Solana Beach. 20—Southern California Mountains California 24,600 km 2 (9,500 mi 2 ) Land use: More than two-fifths of this area is federally owned. About 5 percent is used for urban develop¬ ment, and the remainder is in farms, ranches, or other private holdings. About one-fifth of the total area is open woodland and brushland used for graz¬ ing. About half of the area has a brush cover that is not grazed. Most of the larger valleys are dry-farmed to grain and hay, but in places fruits are grown under irrigation. The erosion hazard is severe on the soils of this area if the plant cover is depleted or destroyed by overgrazing or fire. Preventing or controlling brush fires is a major concern of management. Elevation and topography: Elevation ranges from 600 to 2,400 m in most of the area, but on some peaks elevation is as much as 3,700 m, and a narrow strip along the northern edge is almost at sea level. These strongly sloping to precipitous mountains have un¬ stable slopes and sharp crests. Valleys are narrow, and many have streams actively eroding by bank cutting. Climate: Average annual precipitation —400 to 1,025 mm. Summers are dry. A little snow falls in winter but does not last. Average annual temperature —0 to 16°C, decreasing with elevation. Average freeze-free period —100 to 200 days in most of the area, decreas¬ ing with elevation, but as long as 250 days along the western edge. Water: The moderate rainfall provides water for brushland and range and also meets part of the water needs of adjacent lower areas. Deep sand and gravel deposits in the valleys yield water for livestock and domestic use and for some irrigation. Soils: The dominant soils are Xerolls and Xeralfs. They have a mesic temperature regime. Haploxerolls (Sheep- head, La Posta, Tollhouse, and Crouch series), Haploxeralfs (Holland series), and areas of rock outcrop are on mountain slopes. Well drained Haploxerolls (Calpine, Mottsville, and Oak Glen se¬ ries) and poorly drained Haplaquolls (Bishop series) are on alluvial fans and in basins. Detailed soil survey information is lacking. Potential natural vegetation. This area supports forest, brush, and shrub-grass mixtures. Open stands of Jeffrey pine, Coulter pine, sugar pine, Douglas-fir, incense-cedar, and oak are at the higher elevations. The greater part of the area is covered with sparse to dense stands of brush. Scrub oak, juniper, chamise, ceanothus, manzanita, and red shank are typical 14 species. The soils used as rangeland support natural¬ ized annual and native perennial grasses and brush. California juniper, big sagebrush, flattop buckwheat, needlegrass, wild oats, soft chess, cheatgrass, and filaree characterize the plant cover on the coarse textured soils. Oaks and Jeffrey pine and an under¬ story of soft chess, wild oats, needlegrass, blue wildrye, ceanothus, flattop buckwheat, and other brush species grow on the medium textured soils. Creeping wildrye, pine bluegrass, sedges, native clovers, wiregrass, and blue wildrye are major spe¬ cies in the wet meadows. 15 D—WESTERN RANGE AND IRRIGATED REGION 1,461,300 km 2 (564,210 mi 2 ) This is a semidesert to desert region of plateaus, plains, basins, and many isolated mountain ranges. The average annual precipitation is 250 mm or less in most of the plains and basins but more than 1,275 mm in some of the higher mountains. In the southeast, most of the precipitation falls as rain during the warm season, but elsewhere most of the precipitation falls during the cool season. In most of this region, the average annual temperature is 7 to 13°C, but it ranges from 2°C at the higher elevations in the north to more than 21°C in some of the lowlands in the south. The freeze-free period ranges from less than 90 days in the north and in some of the higher mountains to more than 240 days in the south. Orthids, Fluvents, Orthents, and Xererts are extensive on the plains and plateaus and in valleys throughout the region. Xerolls, Ochrepts, and Boralfs are on mountain slopes. Argids on plains and in basins and Orthents on mountain slopes are also important. Much of the land in this region is used for range, but irrigation is practiced in places where water is available and the soils are suited. Feed crops for livestock are grown on much of the irrigated land. Peas, beans, and sugar beets are grown in many places. Cotton and citrus fruits are important crops in southwestern Arizona. 21—Klamath and Shasta Valleys and Basins California and Oregon 35,350 km 2 (13,650 mi 2 ) Land use: About one-half of this area is federally owned; the remainder is in farms and ranches. Be¬ tween 5 and 10 percent of the land is irrigated and used for growing potatoes, grain, seed crops, hay, and pasture. An additional 1 or 2 percent is dry- farmed to grain. Most of the remaining land, both privately and publicly owned, is grazed. Some forest trees are harvested for lumber. Maintaining good drainage is the principal concern of management in the valley basins. Some sites need protection from overflow, and others are affected by alkali. The erosion hazard is slight except for gullying and flood scour. Elevation and topography: Elevation ranges from 800 to 1,400 m, but on some mountain peaks it is 1,800 m or more. Lava plateaus and many valleys and basins make up most of the area. Steep mountain spurs and rimrock escarpments surround the pla¬ teaus. Climate: Average annual precipitation —250 to 500 mm in most of the area but as much as 750 mm at higher elevations. Summers are dry. Average an¬ nual temperature —7 to 11°C. Average freeze-free period —70 to 140 days, decreasing with elevation. Water: The low precipitation and the consequent er¬ ratic flow of local streams limit the supply of water for agriculture. Ground water is scarce in the dense lava rocks underlying much of the area. On sites underlain by more porous rocks, ground-water sup¬ plies are large but mostly untapped. Soils: The dominant soils are Xerolls, Aquolls, Aquepts, Aquents, Xererts, Albolls, and Argids. They have a mesic or frigid temperature regime. Soils in basins and on flood plains and terraces are Andaquepts (Tulana series), Argialbolls (Goose Lake series), Pelloxererts (Pitts series), Durargids (Trosi series), Halaquepts (Lolak series), Natrargids (Rumbo se¬ ries), Durixerolls (Bieber series), Haploxerolls (Motts- ville series), Argixerolls (Trojan, Galeppi, and Drews series), and Haplaquolls (Ramelli and Deven series). Soils on upland plateaus and mountains are Argixerolls (McQuarrie series), Haplargids (Casuse and Saralegui series), Chromoxererts (Karcal series), and Durargids (Packwood series). Large areas of rock outcrop are on the plateaus and in the mountains. Potential natural vegetation: This area supports a cover of shrubs interspersed with annual and peren¬ nial grasses. Nevada bluegrass, Sandberg bluegrass, Idaho fescue, bluebunch wheatgrass, and cheatgrass are major species. Soils in basins and meadows have a cover of sedges, wiregrass, slender wheatgrass, creeping wildrye, and bluegrass. Sagebrush, rabbit¬ brush, bitterbrush, and mountainmahogany are the dominant shrubs. Western juniper is common, and scattered ponderosa pine grows in places where precipitation is less than 375 mm. In zones where precipitation is higher than 375 mm, there are forests of ponderosa pine, Douglas-fir, white fir, and Cali¬ fornia red fir, and bitterbrush and ceanothus are in the understory. 22—Sierra Nevada Range California and Nevada 65,190 km 2 (25,170 mi 2 ) Land use: More than one-half of this area is federally owned. The Yosemite and Sequoia National Parks are in this area. The remainder is privately owned woodland, farms, and ranches. About 90 percent of the land consists of forests used for timber, recrea¬ tion, wildlife habitat, and watershed. Approximately 8 percent is pasture and range, and less than 1 16 percent is cropland. The erosion hazard is severe if the soils are disturbed by logging, fires, overgrazing, and cultivation. Soils in mountain valleys and mead¬ ows are susceptible to gullying and streambank ero¬ sion. Elevation and topography: Elevation ranges from 500 to 2,400 m, but on some mountain peaks (Mt. Shasta and Mt. Whitney) it is more than 4,300 m. Most of the area consists of strongly sloping to precipitous mountains cut by many steep valleys. Some plateau remnants and mesas are in this area. Climate: Average annual precipitation —1,025 to 1,525 mm in much of the area but as low as 625 mm in the lower valleys and foothills and as much as 1,775 mm on the mountain peaks. Precipitation increases with elevation and from south to north. Summers are dry, but there are occasional thundershowers. Much of the winter precipitation is snow. Average annual temperature —2 to 14°C, decreasing with elevation. Average freeze-free period —30 to 180 days, decreas¬ ing with elevation. Water: The abundant precipitation and snowfields on the higher mountain slopes supply water to many large perennial streams. Much of this water is stored in large reservoirs and is used in the Sacramento and San Joaquin Valleys and in southern California. Soils: The dominant soils are Xerults, Humults, Xeralfs, Xerolls, Ochrepts, Umbrepts, Andepts, Orthents, Psamments, and Boralfs. They have a mesic, frigid, or cryic temperature regime, depending largely on elevation. Soils at an elevation below 1,200 to 1,500 m are Haplohumults (Sites and Aiken series), Haploxeralfs (Secca, Holland, and Cohasset series), Xerochrepts (Chaix and Maymen series), Haploxerults (Josephine and Mariposa series), Vitrandepts (Iron Mountain and Jiggs series), and Haploxerolls (Shaver series). Soils at higher elevations are Xerorthents (Dinkey series), Xeropsamments (Corbett and Toiyabe se¬ ries), Cryopsamments (Cagwin series), Cryoboralfs (Fugawee series), Cryumbrepts (Meeks series), Cryochrepts (Umpa series), Cryandepts (Meiss and Waca series), and Dystrandepts (Windy series). Large areas of rock land are scattered throughout the area and on broad expanses on ridge crests and peaks above timberline (2,400 to 2,700 m). Soils in moun¬ tain valleys are Haploxerolls (Oak Glen series), Xeropsamments (Elmira series), Haploxeralfs (Inville series), Humaquepts (Chummy series), and Crya- quents. Soil survey information is lacking for exten¬ sive areas. Potential natural vegetation: This area supports forest vegetation. Ponderosa pine, Douglas-fir, incense-cedar, sugar pine, white fir, California red fir, lodgepole pine, mountain hemlock, black oak, Oregon white oak, canyon live oak, and tanoak are major tree species. Bristlecone pine grows in protected draws at elevations above 2,400 to 2,700 m. Blue- grass, hairgrass, sedges, wire grass, clovers, and wild iris grow in meadows. Sagebrush, blue wildrye, fescues, bluegrasses, and mountain brome grow under open stands of timber. 23—Malheur High Plateau California, Nevada, and Oregon 73,050 km 2 (28,210 mi 2 ) Land use: About three-fourths of this area is federally owned. Native range vegetation covers much of the area. Livestock production on range is the principal agricultural activity. About 1 or 2 percent of the area is irrigated, and grain and hay for winter feed and pasture are growm. Small areas on upper mountain slopes are forested. Elevation and topography: Elevation ranges from 1,200 to 2,100 m, but on some mountains it is more than 2,700 m. Nearly level basins and valleys are bordered by long, gently sloping alluvial fans. North-south-trending mountain ranges and a few volcanic plateaus rise sharply above the valleys. Climate: Average annual precipitation —200 to 350 mm in most of the area but as much as 500 mm on some of the higher mountain slopes. Precipitation is fairly evenly distributed throughout fall, winter, and spring but is low in summer. Average annual temperature —5 to 10°C. Average freeze-free period —30 to 140 days, decreasing with elevation. Water: Water is scarce except at higher elevations where precipitation is greater. Streamflow is erratic and depends mostly on runoff from melting snow. The large ground-water supplies in the gravel- and sand-filled valleys are mostly untapped. Soils: Most of the soils are Argids or Orthids. They are shallow' to moderately deep, and have a medium textured to fine textured subsoil and a frigid or mesic soil temperature regime. Nearly level to sloping, well drained Durargids and Durorthids have a duripan and are on lake terraces and fans. Somewhat poorly drained Durorthids in low areas are commonly saline and sodic. Sloping to steep, well drained to exces¬ sively drained, shallow, stony Xerolls are on uplands. Potential natural vegetation: This area supports a shrub-grass association. Big sagebrush, rabbitbrush, needlegrasses, and squirreltail are common on the extensive sandy and loamy soils. Big sagebrush and basin wildrye are on bottom lands. Spiny hopsage and bud sagebrush are on the drier sites. Greasewood, saltbush, and saltgrass grow on salty and sodic soils. Silver sagebrush grows on moist sites that have water intermittently, such as playas. Western juni¬ per are on rocky sites. Growing at high elevations are aspen groves on moist sites and isolated stands of grand fir and whitebark pine. 17 24—Humboldt Area Nevada and Oregon 37,310 km 2 (14,400 mi 2 ) Land use: About four-fifths of this area is federally owned. The remainder is used for farms, ranches, industrial enterprises (mining), and some urban and transportation purposes. Livestock grazing on native range is the principal agricultural enterprise. Less than 3 percent of the area, generally consisting of narrow strips along the major streams and margins of valleys, is irrigated and used for growing hay, grain, tame pasture, alfalfa seed, and potatoes. The hay produced in the area is used principally for winter feeding of resident livestock. Concerns of management are mainly use of proper grazing prac¬ tices and efficient use of available surface and ground water supplies. Elevation and topography: Elevation ranges from 1,200 to 1,800 m, but on some mountain peaks it is more than 2,700 m. A series of widely spaced north-south-trending mountain ranges are separated by wide valleys filled with alluvium and lacustrine materials. Climate: Average annual precipitation —150 to 300 mm in most of the area but as much as 500 mm on some mountain slopes. Precipitation occurs mainly as snow in winter and as rain in spring and in autumn. Summers are dry. Average annual temperature —4 to 10°C. Average freeze-free period —60 to 120 days, decreasing with elevation. Water: The low precipitation provides a small amount of water. Surface water is available from perennial and intermittent streams that carry snowmelt from the mountains. Late-season surface water supplies are deficient. Ryepatch Reservoir on the lower Humboldt River is the only large irrigation storage reservoir in the area. Ground water available in limited quantities in valley fill is being rapidly developed in irrigation of crops. Soils: The dominant soils are Argids, Orthids, Orthents, Aquolls, and Psamments, which have a mesic tem¬ perature regime, in valleys and Xerolls, Borolls, and Orthids, which have a frigid or cryic temperature regime, on mountains. They have a mixed or montomorillonitic mineralogy. Soils in this area formed principally in mixed parent materials. Durargids (Cherry Spring and Boulflat series), Naduargids (Golconda series), Natrargids (Beowawe and Tomera series), Camborthids (Orovada and Rad series), Durorthids (Blackhawk and Bliss series), Torripsam- ments (Goldrun series), and Torriorthents (Valmy and Benin series) are on alluvial fans, stream and lake terraces, and flood plains. Haplaquolls (Humboldt and Ryepatch series) are on wet stream flood plains. Cryoborolls (Spinlin and Winevada series), Argixerolls (Gosumi and Sonocan series), and Camborthids (Mullyon series) and areas of rock outcrop are on mountain slopes and upland basins. Potential natural vegetation: This area supports shrub-grass vegetation. In places where the average annual precipitation is about 200 mm or more, big sagebrush is the characteristic plant, but low sage¬ brush has replaced it on some soils. Thurber needle- grass, bluebunch wheatgrass (scarce on drier sites), basin wildrye, squirreltail, Sandberg bluegrass, forbs, spiny hopsage, and Douglas rabbitbrush are common associated plants. Locally important are Idaho fescue and snowberry on sites where moisture is favorable, Utah juniper in a few high, rocky locations, and Indian ricegrass and needleandthread on sandy soils. Shadscale and bud sagebrush associated with Indian ricegrass and squirreltail are dominant on the drier sites. Black greasewood, basin wildrye, and Nuttall saltbush are locally important on some low terraces and flood plains. Winterfat is prevalent in some places. 25—Owyhee High Plateau Idaho, Nevada, and Oregon 73,050 km 2 (28,210 mi 2 ) Land use: About three-fourths of this area is federally owned. Most of the remainder is in farms and ranches. Livestock production on rangelands is the main agri¬ cultural activity. Tracts in valleys, making up 2 or 3 percent of the total area, are irrigated and used for producing grain and forage for livestock. Small acre¬ ages in Idaho are dry-farmed to wheat. Open forests on high mountain slopes are grazed by livestock and wildlife. Elevation and topography: Elevation ranges from 1,400 to 2,300 m on rolling plateaus and in gently sloping basins, but on some steep mountains it is more than 3,000 m. Steep north-south-trending moun¬ tains ranges are separated by broad basins filled with alluvium. Climate: Average annual precipitation —200 to 400 mm in most of the area, but as much as 750 mm on mountain slopes. Precipitation is evenly distributed throughout the year, but it is low from midsummer to early in autumn. Average annual temperature —6 to 8°C. Average freeze-free period —90 to 120 days, decreasing with elevation; less than 60 days on high mountains. Water: The supply of water from precipitation and streamflow is small and unreliable, except along the Owyhee, Bruneau, and Humboldt Rivers. Streamflow depends largely on accumulated snow on the higher mountains. Except in alluvial deposits along large streams, ground-water supplies are small and little used. Precipitation is adequate for dry farming on a few acreages of deep soils in Idaho. 18 Soils: Most of the soils are Xerolls. They are deep to shallow, medium textured to fine textured soils. They have a mesic, frigid, or cryic temperature regime, depending mostly on elevation. Argixerolls (Gem and Gabica series) and Haploxerolls (Bakeoven and Lickskillet series) are on the plateaus. Durixerolls (Donna and Stampede series) are in valleys at an elevation above 1,700 m. Haplargids (Nannyton se¬ ries), Camborthids (Orovada series), and Durargids (Cherry Springs series) are on alluvial fans and terraces in valleys at an elevation below’ 1,700 m. Poorly drained Haplaquolls (Humboldt series) are on flood plains of the few major streams. Argixerolls (Kanlee, Chen, and Ramires series) and Cryoborolls (Harmehl and Mosquet series) are on mountains. Potential natural vegetation: This area supports shrub-grass vegetation characterized by big sage¬ brush or low sagebrush and by bluebunch wheat- grass, western wheatgrass, or Idaho fescue. Other important plants are Sandberg bluegrass, foxtail wheatgrass, penstemon, phlox, milkvetch, lupine, aster, and rabbitbrush. On the high plateaus are juniper and curlleaf mountainmahogany and an un¬ derstory predominantly of snowberry and ceanothus. Conifers, aspen, and very large mountainmahogany are in the Ruby Range and Jarbridge Mountains. The conifers include whitebark pine, limber pine, Engel- mann spruce, subalpine fir, and bristlecone pine. 26—Carson Basin and Mountains California and Nevada 23,960 km 2 (9,250 mi 2 ) Land use: Nearly three-fourths of this area is federally owned. Most of the remainder is used for farms, ranches, urban development, industrial enterprises, and transportation. Grazing of livestock on native grasses and shrubs is the principal agricultural activ¬ ity. About 2 percent of the total area, principally in valleys along major streams, is irrigated, and hay, grain, and tame pasture and some onions, potatoes, and garlic are the crops grow’n. About 10 percent of the area on mountain slopes is woodland. Land formerly used for farming is being converted to urban uses. Controlling erosion on uplands and effi¬ cient use of available water resources are concerns of management. Elevation and topography: Elevation ranges from 1,200 to 2,000 m in valleys, but mountain crests are as high as 4,000 m. Steeply sloping, north-south- trending mountain ranges are separated by broad valleys and basins. Climate: Average annual precipitation —125 to 375 mm in most of the area but as much as 500 mm on mountain slopes. Precipitation is mostly snow in winter, but some rain falls in spring and in autumn. Summers are dry. Average annual temperature —4 to 10°C. Average freeze-free period —60 to 130 days, decreasing with elevation. Water: The low precipitation in the valleys provides little water, but a few large rivers that have their source in high mountains outside the area supply water for irrigation and other uses along the course of the rivers. Reservoirs used principally for storing irrigation water include Washoe Lake, Topaz Lake, and Weber Reservoir. Ground water available in limited quantities in valley fill is being rapidly developed for urban, industrial, and agricultural uses. Soils: The dominant soils are Argids, Orthids, Aquolls, Psamments, and Xerolls. Soils in the valleys have a mesic temperature regime and those in the higher mountains a frigid or cryic temperature regime. They have a mixed or montmorillonitic mineralogy. Soils in this area formed principally in mixed parent materi¬ als. Durargids (Reno and Indian Creek series), Haplargids (Washoe and Greenbrae series), Natrargids (Godecke series), Camborthids (Haybourne series), and Torripsamments (Toll series) are on alluvial fans, stream terraces, and flood plains. Haplaquolls (Bishop and Ophir series), Haploxerolls (Henningsen and East Fork series), and Nadurargids (Dangberg series) are on wet flood plains and terraces. Haploxerolls (Tarloc and Sutro series) and Argixerolls (Nosrac and Deven series) and areas of rock outcrop are on mountain slopes. Potential natural vegetation: This area supports shrub-grass vegetation characterized by big sage¬ brush, but on some soils low sagebrush has replaced big sagebrush. Antelope bitterbrush, squirreltail, desert needlegrass, Thurber needlegrass, and Indian ricegrass are important associated plants. Green ephedra, Sandberg bluegrass, Anderson peachbrush, and several forb species also are common. Juniper- piny on woodland is typical on mountain slopes. Jeffery pine, lodgepole pine, California red fir, white fir, and manzanita grow on the highest mountain slopes. Shadscale is the typical plant in the drier parts of the area. Sedges, rushes, and moisture-loving grasses grow on the wettest parts of the wet flood plains and terraces. Basin wildrye, alkali sacaton, saltgrass, buffaloberry, black gi'easewood, and rubber rabbitbrush grow on drier sites that have a high salt concentra¬ tion. 27—Fallon-Lovelock Area Nevada 32,990 km 2 (12,740 mi 2 ) Land use: About four-fifths of this area is federally owned. Most of the remainder is used for farms and ranches and for some urban and transportation pur¬ poses. Much of the area is used for livestock grazing on range of native grasses and shrubs. About 1 to 2 percent of the area, mostly near Lovelock and Fallon, 19 is irrigated and intensively farmed. Hay, grain, tame pasture, corn silage, alfalfa seed, and small areas of melons are important crops. Improved drainage of cropland and pastureland, control of salinity, and efficient use of range vegetation and available water supplies are major concerns of management. Elevation and topography: Elevation generally ranges from 1,000 to 1,800 m in valleys, but on some mountain peaks it is more than 2,400 m. North-south- trending mountain ranges are separated by broad valleys and basins. The few large rivers terminate in lakes and playas. Climate: Average annual precipitation —100 to 250 mm in most of the area but as much as 450 mm on high mountain slopes. Precipitation is very low from summer to midautumn. Average annual tempera¬ ture —7 to 13°C. Average freeze-free period —60 to 150 days, decreasing with elevation. Water: Water for irrigation is obtained principally from the few large rivers in the area. Water is stored in the Lahontan and Ryepatch Reservoirs for irriga¬ tion of crops in the principal agricultural areas near Fallon and Lovelock. Precipitation is very low, and ground water is scarce and of poor quality in the major valleys. Limited supplies of good- to fair- quality ground water in some of the outlying valleys is being rapidly harnessed for irrigation. Pyramid and Walker Lakes are terminal lakes used principally for recreation. Soils: The dominant soils are Argids, Orthids, Aquolls, Xerolls, Fluvents, Orthents, and Psamments. They have a mesic temperature regime (frigid on higher mountains) and a mixed or montmorillonitic mineral¬ ogy. They formed principally in mixed parent mate¬ rials. Natrargids (Bango and Churchill series), Durorthids (Gardella and Hooten series), Camborthids (Union ville and Toulon series), Toni orthents (Ragtown and Swingler series), and Torripsamments (Stumble and Tepperary series) are on alluvial fans and lake terraces. Haplaquolls (Carson and Humboldt series), Haploxerolls (Dia and East Fork series), Xei’ofluvents (Fallon and Lahontan series), and Salorthids (Parran series) are on wet flood plains, in basins, and on stream and lake terraces. Shallow Torriorthents, shallow Haplargids, Argixerolls, and Haploxerolls are on mountain slopes. Potential natural vegetation: This area supports desert shrub vegetation. Shadscale is widespread. It is mixed with Bailey greasewood on uplands and with black greasewood and seepweed on lower sites. Grasses are generally sparse, although Indian ricegrass is prominent on sandy soils. Fourwing saltbush, winterfat, spiny hopsage, wolfberry, ephedra, dalea, and bud sagebrush are common shrubs. Basin wildrye, creep¬ ing wildrye, alkali sacaton, saltgrass, black greasewood, rubber rabbitbrush, and big saltbush are important plants. A few tule marshes support cattail, bulrushes, sedges, and rashes. Big sagebrush, along with scattered Utah juniper and singleleaf pinyon, on some shallow soils is associated with Thurber needlegrass, basin wildrye, Sandberg bluegrass, and squirreltail on some higher alluvial fans and mountain slopes. 28A—Great Salt Lake Area Idaho, Nevada, and Utah 94,260 km 2 (36,390 mi 2 ) Land use: More than 75 percent of this area is federally owned, large tracts of w 7 hich are used for training and testing purposes by the Armed Forces and the Nuclear Regulatory Commission. A large area west and southwest of Great Salt Lake is a salty playa. The remainder is in farms and ranches. Livestock produc¬ tion on range is the principal agricultural activity in the w 7 est. The production of desert shrubs and grasses is very low. In most of the area, the extent of the livestock industry is determined largely by the amount of hay, pasture, and grain that can be produced under irrigation from the small local water supplies. About 5 percent of the area is irrigated cropland used for growing alfalfa, grain, sugar beets, vegetables, and fruits. About 5 percent is used for dryland w 7 heat. Concerns of management include efficient use of range vegetation and limited water supplies, control of erosion in critical areas, and efficient use of irriga¬ tion water. Elevation and topography: Elevation ranges from 1,200 to 2,000 m in the basins and from 2,000 to 3,400 m in the mountains. Nearly level basins bordered by long, gently sloping alluvial fans are between widely separated north-south-trending, steep moun¬ tain ranges. Climate: Average annual precipitation —125 to 500 mm. The driest period is from midsummer to early autumn. Average annual temperature —7 to 13°C. Average freeze-free period —60 to 160 days, decreas¬ ing w'ith elevation. Water: Water is scarce. Both surface w T ater and ground water are used for irrigation. For the most part, streams are small and intermittent and depend on sources in the higher mountains. Use of deep w r ells is limited by the high cost. Shallow w 7 ells are unreliable in flow 7 , and the w r ater commonly contains large amounts of salt. Soils: The dominant soils in valleys are Orthents, Fluvents, Aquents, Aquolls, Orthids, and Argids, w'hich have a mesic temperature regime. The domi¬ nant soils on mountain slopes are Xerolls, Ustalfs, and Xeralfs, which have a frigid or cryic temperature regime. Mineralogy is mixed, montmorillonitic, or carbonatic. The soils formed in mixed parent materi¬ als, mostly lacustrine sediments. The w r ell drained, deep Torriorthents (Heist, Pomat, and Yuba series), Torrifluvents (Quaker, Redfield, and Sigurd series), and Torripsamments (Yenrab series) are on alluvial 20 fans, flood plains, and other recent surfaces. Haplaquolls (Provo series), Fluvaquents (Poganeab series), Salorthids (Cache and Saltair series), Natraquolls (Airport series), Natrustalfs (Leland, Harrisville, and Jordan series) and Calciaquolls (Chipman, Logan, and Warm Springs series) are on wet flood plains and basin surfaces. Deep Haplargids (Decca, Hansel, and Hoye series), Natrargids (Mellor, Antelope Springs, and Uvada series), Calciorthids (Hiko Peak, Escalante, and Sanpete series), and Paleorthids (Neola and Denmark series) are on older valley surfaces. Haploxerolls (Kearns, Kidman, and Lakewin series), Palexerolls (Pavant, May Day, and Paice series), Calcixerolls (Pleasant Grove, Welby, and Pharo se¬ ries), and Argixerolls (Bingham, Parleys, and Tim- panogos series) are on lake terraces and alluvial fans. Potential natural vegetation: This area supports desert shrub, shrub-grass, and woodland vegetation. In places where precipitation is less than about 200 mm, the soils support shadscale, winterfat, black sagebrush, and associated grasses such as Indian ricegrass and squirreltail. Greasewood and Nuttall saltbush grow on soils having a high salt or sodium content. In places where precipitation is 200 to 300 mm, the soils support big sagebrush, shadscale, winterfat, and associated grasses such as bluebunch wheatgrass, Indian ricegrass, and bluegrasses. In places where precipitation is more than 300 mm, the soils support Utah juniper, singleleaf pinyon, big sagebrush, bluebunch wheatgrass, bluegrasses, and needleandthread. A large nearly barren area west of Great Salt Lake has a very sparse cover of pickleweed, sapphire eriastrum, seepweed, and greasewood. 28B—Central Nevada Basin and Range Nevada and Utah 78,150 km 2 (30,170 mi 2 ) Land use: More than 90 percent of this area is federally owned. Most of the remainder is in farms and ranches. Livestock grazing on range of native grasses and shrubs is the principal agricultural activity. In most of the area, the extent of the livestock industry is determined largely by the amount of hay, pasture, and grain that can be produced under irrigation from the small local water supplies. The irrigated land makes up 1 percent or less of the total area. About 10 percent of the area on mountain slopes is pinyon- juniper woodland. Concerns of management include efficient use of range vegetation and limited water supplies and control of erosion in critical places. Elevation and topography: Elevation ranges from 1,500 to 2,000 m in the valleys and basins and from 2,000 to 4,000 m in the mountains. Nearly level valleys and basins bordered by long, gently sloping to strongly sloping alluvial fans are between north-south¬ trending steep mountain ranges. Climate: Average annual precipitation—125 to 625 mm, increasing with elevation. The driest period is from midsummer to midautumn. Average annual tem¬ perature—A to 10°C. Average freeze-free period —60 to 120 days, decreasing with elevation. Water: Water is scarce. Both surface water and ground water are used for irrigation. For the most part, streams are small and intermittent and depend on sources in the higher mountains. Ground water avail¬ able in the valley fill is being rapidly harnessed for irrigation of crops. A few small reservoirs have been constructed throughout the area for storage of water for irrigation and recreation purposes. Soils: The dominant soils in the valleys are Orthents, Fluvents, Aquolls, Orthids, and Argids, which have a mesic temperature regime. The dominant soils on mountain slopes are Xerolls and Borolls, which have a frigid and cryic temperature regime. Mineralogy is mixed, montmorillonitic, or carbonatic. Most of the soils formed in mixed parent materials but in the eastern part extensive areas of soils formed in parent materials derived from limestone and dolomite. Deep Torriorthents (Penoyer and Hayeston series), Torri- fluvents (Bruffy and Fivemile series), and Torripsam- ments (Tipperary series) are on well drained alluvial fans, flood plains and other recent surfaces. Haplaquolls (Hussa and Settlemeyer series), Xerofluvents (Orizaba and Dianev series), and Salorthids (Vinsad and Parran series) are on wet flood plains and basin surfaces. Shallow to deep Haplargids (Penelas and Buster series), Durargids (Ratto and Deerlodge series), Camborthids (Kobeh and Orovada series), Durorthids (Rubyhill and Umil series), Calciorthids (Tonkin and Holsine series) and Paleorthids (Bit and Denmark series) are on older valley surfaces. Shallow to deep Haploxerolls (Holtle and Alpha series), Palexerolls (Pamsdel series), Durixerolls (Nevu and Drewing series), Calcixerolls (Ansping series), Argixerolls (Belmill and Homestake series), Cryoborolls (Wilpar and Fairydell series), and Rendolls (Sheege and Urtah series) are on mountain slopes. Potential natural vegetation: This area supports saltbush-greasewood, big sagebrush, and pinyon- juniper woodland vegetation in the progression from lowest to highest elevation and precipitation. Shadscale, in association with bud sagebrush, spiny hopsage, ephedra, winterfat, fourwing saltbush, Indian ricegrass, squirreltail, and galleta, characterizes the saltbush- greasewood type. With an increase in moisture, plants assoicated with shadscale are replaced by needlegrasses, bluegrasses, bluebunch or beardless wheatgrass, basin wildrye, and forbs. Bailey grease¬ wood (in the west), black greasewood, and Nuttall saltbush are locally important on some sites. Big sagebrush and black sagebrush, which grow on soils shallow to an indurated pan or bedrock, are domi¬ nant. In the pinyon-juniper woodland, bitterbrush, 21 serviceberry, and snowberry grow in association with Utah juniper and singleleaf pinyon. At the highest elevations there are thickets of curlleaf mountainmahogany and small amounts of mixed coni¬ fer forest with limber, bristlecone, or ponderosa pine, Douglas-fir, or white fir. On bottom lands basin wild rye, creeping wildrye, alkali sacaton, wheatgrasses, bluegrasses, sedges, and rushes are typical. Black greasewood, rubber rabbitbrush, and big sagebrush grow on the drier sites. Inland saltgrass, alkali sacaton, black greasewood, rubber rabbitbrush, and big saltbush typify vegetation on strongly saline- alkali soils. 29—Southern Nevada Basin and Range California, Nevada, and Utah 66,380 km 2 (25,630 mi 2 ) Land use: More than 90 percent of this area is federally owned, much of which is used for training and testing purposes by military forces and the Nuclear Regulatory Commission. Less than 1 percent of the area, mostly in the valleys, is irrigated. Much of the irrigated acreage is used for growing hay and grain for live¬ stock. High mountain areas consist of pinyon-juniper woodland. Rangeland of native grasses and shrubs are grazed by livestock. Concerns of management include proper use of rangeland, control of erosion, and efficient use of scarce water supplies. Elevation and topography: Elevation ranges from 600 to 1,700 m in valleys, but on some high mountain peaks it is more than 2,400 m. The north-south- trending, steep mountains are separated by broad valleys bordered by sloping fans and terraces. Climate: Average annual precipitation —Mainly 75 to 300 mm but as much as 375 mm on mountain slopes. Summers are dry, but sporadic storms are common in July and in August. Average annual temperature —11 to 16°C, decreasing with elevation. Average freeze-free period —60 to 200 days, decreasing with elevation. Water: Precipitation is sparse. Streamflow supplies only a small amount of water for irrigation. Ground water is scarce but is being rapidly developed. In California, most of the water is controlled by Los Angeles and is not available for local use. Soils: The dominant soils are Orthents, Psamments, Orthids, Argids, and Xerolls. They have a thermic, mesic, or frigid temperature regime, depending mostly on elevation, and a mixed or montmorillonitic miner¬ alogy. Some Aquolls are in the valleys. Torriorthents (Fand and Penoyer series) and Tom psamments (Stum¬ ble and Sundown series) are on recent alluvial fans and terraces. Shallow to deep Camborthids (Mina series), Durorthids (Pharoc and Timper series), Naduargids (Timpahute and Monte Cristo series), Natrargids (Nyala series), Calciorthids (Aysees se¬ ries), and Paleorthids (Crystal Springs and Sierocliff series) are on older alluvial fans and terraces and in valley-fill deposits. Torripsamments (Theriot and Pintwater series), Durixerolls (Decan and Vil series), Haploxerolls (Cedaran series), and Argixerolls (Pioche and Itca series) are in the mountains. Potential natural vegetation: This area supports desert shrub vegetation. The major vegetation is saltbush-greasewood. Shadscale is widespread. It is associated with bud sagebrush, Bailey greasewood (in the west), gray molly kochia, spiny hopsage, wolfberry, ephedra, dalea, fourwing saltbush, winterfat, horsebrushes, galleta, and Indian ricegrass. Locally (in warmer parts), shadscale is associated with creosotebush, white bursage, spiny menodora, Joshua- tree, and blackbrush. Black greasewood is dominant on low-lying saline-alkali soils. Big sagebrush and black sagebrush grow on soils that have an indu¬ rated pan or bedrock near the surface and are associated with Indian ricegrass and galleta in cooler parts of the area. Pinyon-juniper woodland is prevalent in the mountains. Associated plants include black sagebrush, big sagebrush, blackbrush, bitterbrush, cliffrose, and other shrubs and a variety of grasses and forbs. 30—Sonoran Basin and Range Arizona, California, and Nevada 194,030 km 2 (74,910 mi 2 ) Land use: About four-fifths of this area is federally owned. Much of the remainder is owned by local governments. Most of the land has a cover of desert vegetation. The area is used only locally for grazing because of the low forage production and the lack of water for livestock. On sites intensively used for recreation, especially where motorcycles and off-road vehicles are driven, the hazards of wind and water erosion are severe. Elevation and topography: Elevation ranges from 100 m below sea level to 1,200 m above sea level in valleys and basins, but on some mountain ranges it is 3,400 m. Broad basins, valleys, and old lake beds make up most of the area, but widely spaced, north-south-trending mountains are throughout. Climate: Average annual precipitation —50 to 250 mm in valleys but as much as 625 mm on mountain slopes. Precipitation is fairly evenly distributed throughout the year. Average annual temperature —16 to 24°C but as low as 10°C in the mountains. Average freeze- free period —Generally 240 days, but it is much shorter on the higher mountains and as long as 320 days in the south. Water: Water is scarce. Irrigation water for agricul¬ ture is obtained almost entirely from the Colorado and Mojave Rivers. Some irrigation water is obtained from large springs in Nevada and from wells in Nevada and in California. Soils: The dominant soils are Orthents, Psamments, Fluvents, Orthids, and Argids. Most of these soils 22 have a thermic temperature regime and an aridic moisture regime. A few have a hyperthermic or a mesic temperature regime. Torripsamments (Cajon, Pintura, Toquerville, and Rositas series), Torrifluvents (Coachella, Tobler, Hantz, Leeds, and Vint series), Salorthids (Land series), and Torriorthents (Isom and Ivins series) are in basins and valleys and on flood plains. Haplargids (Chuckwalla, Mohave, Renbac, and Bitter Springs series), Paleorthids (Las Vegas, Cave, Harrisburg, and Winkel series), Paleargids (Domino and Bermesa series), and Calciorthids (Hobog, Laverkin, Nickel, Sunrise, and Nikey series) are on older alluvial fans and terraces. Shallow Torriorthents (Cellar, House Mountain, Retriever, and St. Thomas series), shallow Haplustolls (Virgin Peak series), shallow Camborthids (Pulsipher series), and Torri¬ psamments (Moapa series) are in mountainous areas. Potential natural vegetation: This area supports thin stands of desert vegetation. Bursage, Joshua- tree, juniper, yucca, cactus, creosotebush, and Mormon-tea are major species. Numerous annual forbs and grasses grow during years of favorable moisture. Saltbush, saltgrass, alkali sacaton, and iodinebush grow on the alkali flats. Indian ricegrass, Joshua-tree, desert needlegrass, and galleta grow on sandy soils. 31—Imperial Valley California 9,420 km 2 (3,640 mi 2 ) Land use: Intensive irrigated agriculture is practiced in this area. Citrus fruit, dates, grapes, sugar beets, many kinds of vegetables, small grains, flaxseed, hay, and tame pasture grasses are grown. Many livestock are fattened each year in feedlots. Non- irrigated land is in desert vegetation that has only slight value as range. Maintaining a favorable salinity status in the root zone is a major concern of manage¬ ment. Rainfall is too low to leach salts from the soils, so all leaching must be accomplished with the use of irrigation water. Elevation and topography: Elevation ranges from 50 m below sea level to 200 m above sea level. This nearly level plain is broken by scattered steep-sided valleys and steep mesas. Climate: Average annual precipitation —50 to 100 mm. Average annual temperature —21 to 24°C. Aver¬ age freeze-free period —280 to 350 days. Water: Almost all water for agriculture comes from the Colorado River, but wells provide irrigation water locally. Soils: The dominant soils are Fluvents, Orthents, and Psamments. They are very deep and have a hyper¬ thermic temperature regime and an aridic moisture regime. Coarse to moderately fine textured Torri¬ fluvents (Coachella and Glenbar series), coarse to fine textured Torriorthents (Carrizo, Superstition, and Imperial series), and coarse textured Torri¬ psamments (Rositas and Myoma series) formed in recent alluvium and lacustrine deposits of the Colo¬ rado River. Potential natural vegetation: This area supports sparse stands of desert vegetation. Mesquite, arrow- weed, yucca, saltcedar, and cactus are dominant species. Numerous annual forbs and grasses grow during years of favorable moisture. 32—Northern Intermountain Desertic Basins Montana and Wyoming 21,210 km 2 (8,190 mi 2 ) Land use: More than one-half of this area is federally owned. The remainder is in farms and ranches. Most of the land is used for grazing. The range consists of desert shrubs and short grasses. About 5 percent of the area is irrigated. Most of the acreage is planted to alfalfa and other feed crops, but dry beans, malt barleys, sugar beets, and corn are important cash crops. Elevation and topography: Elevation ranges from 1,100 to 1,800 m. Piedmont plains and pediments slope from the mountains to the stream terraces of the Wind-Big Horn River system. In some places the plains are eroded to the clay shale bedrock, and there are areas of badland. Climate: Average annual precipitation —125 to 225 mm. Maximum precipitation is in spring and in fall. Average annual temperature —About 7°C. Average freeze-free period —120 to 140 days. Water: The low and erratic precipitation provides only a small amount of water. The Wind-Big Horn River and its tributaries bring irrigation water into the area from the bordering mountains. Deep artesian wells provide water for irrigation on the eastern side of the Big Horn Basin. Soils: The dominant soils are Argids. They are moder¬ ately deep to very deep and moderately fine textured. These soils have a mesic temperature regime, an aridic moisture regime, mixed mineralogy, and an argillic horizon. Haplargids (Griffy and Saddle series) are on piedmont plains and pediments over clay shale and sandstone. Torriorthents (Persayo series) and areas of rock outcrop are on dissected slopes. Torrifluvents (Youngston and Havre series) and Torriorthents (Apron series) are on recent alluvial fans and flood plains. Natrargids (Meeteetse series) are on alkaline clay shale. Potential natural vegetation: This area supports shrub-grass vegetation. Big sagebrush, gardner saltbush, rhizomatous wheatgrasses, Indian ricegrass, and needleandthread are dominant species. Black sage, gardner saltbush, and bluebunch wheatgrass are common on shallow soils on the uplands. 23 33—Semiarid Rocky Mountains Wyoming 11,000 km 2 (4,250 mi 2 ) Land use: One-fourth or more of this area is federally owned. The remainder is in ranches. Most of the land is used for grazing. The range consists of desert shrubs and short grasses. Open woodland is at high elevations in some mountains. Small irrigated tracts in isolated valleys are used mainly for hay. Elevation and topography: Elevation ranges from 1,800 to 3,100 m. Mountain ranges with steep slopes rise sharply from desert basins. Climate: Average annual precipitation —250 to 400 mm. Maximum precipitation is in spring and early in summer. Average annual temperature —7°C. Aver¬ age freeze-free period— Less than 120 days, decreas¬ ing with elevation. Water: Water is scarce. The low precipitation, small and intermittent streamflow, and scarcity of ground water seriously limit water developments. Soils: The dominant soils are Orthents. They are shallow to very deep and moderately coarse to mod¬ erately fine textured and have a frigid temperature regime, an aridic moisture regime, and mixed miner¬ alogy. Torriorthents (Crownest series), Haplargids (Cotha series), and areas of rock outcrop are on upland slopes. Torriorthents (Delphill and Patent series) are on pediments and alluvial fans at the base of the slopes. Potential natural vegetation: This area supports a grass-shrub vegetation. Columbia needlegrass, brome, rhizomatous wheatgrasses, and big sagebrush are the dominant species. Idaho fescue, Columbia needlegrass, black sagebrush, and scattered Rocky Mountain ju¬ niper are dominant on shallow soils. Lodgepole pine, ponderosa pine, and limber pine grow on upper mountain slopes. Clumps of aspen are in some moist pockets. 34—Central Desertic Basins, Mountains, and Plateaus Colorado, Wyoming, and Utah 122,350 km 2 (47,230 mi 2 ) Land use: Slightly more than one-half of this area is federally owned. The remainder is in ranches. Most of the land is used for sheep and cattle grazing. The range consists of desert shrubs and short grasses. Between 2 and 5 percent of the land, mostly along the few large streams, is irrigated. Hay and pasture are grown under irrigation. Elevation and topography: Elevation ranges from 1,900 to 2,200 m. Alluvial fans, piedmont plains, and pediments slope from the surrounding mountains to form broad intermountain basins. Climate: Average annual precipitation —175 to 300 mm. Maximum precipitation is in spring and fall. Average annual temperature —4 to 11°C. Average freeze-free period —80 to 100 days. Water: Water is scarce. Irrigation water is available along the few large streams that bring water into the area from adjoining mountains. Ground-water sup¬ plies are meager and little developed. Soils: The dominant soils are Orthents. They are shallow to very deep and medium textured to fine textured and have a frigid temperature regime, an aridic moisture regime, and mixed or montmorillonitic mineralogy. Torriorthents (Patent and Garsid series) and Haplargids (Diamondville and Fraddle series) are on piedmont plains, alluvial fans, and pediments. Torrifluvents are on flood plains. Shallow Torriorthents (Blazon and Haterton series) are on rough, broken slopes. Some Torriorthents (Elkol series) and Torri¬ fluvents (Laney series) have a high content of ex¬ changeable sodium. Potential natural vegetation: This area supports grass-shrub vegetation. Rhizomatous wheatgrasses, needleandthread, Indian ricegrass, and big sagebrush are the dominant species. Bluebunch wheatgrass, western wheatgrass, big sagebrush, and scattered Rocky Mountain juniper commonly grow on shallow soils on the uplands. 35—Colorado and Green River Plateaus Arizona, Colorado, and Utah 123,350 km 2 (47,630 mi 2 ) Land use: Approximately 90 percent of this area is rangeland. The range is grazed by sheep and cattle. About 1 percent of the area, along the valleys of the major streams, is irrigated cropland. Alfalfa, small grains for hay, and corn for silage are the chief crops. About 1 percent of the area in scattered small tracts on Indian reservations is dry-farmed, and corn is the chief crop. About 8 percent is juniper and pinyon- juniper woodland. Pfirewood and pinyon nuts are products of this woodland, which is also grazed by cattle and sheep. If the areas are overgrazed, juniper invades the grassland. Severe gullying and the lack of a dependable water supply are land use problems. Elevation and topography: In most places, eleva¬ tion is 1,300 to 1,500 m. Mt. Trumbull, on the north rim of the Grand Canyon, however, is 2,400 m high, and the Navajo Mountain, on the Utah-Arizona state line, is 3,200 m. In general, the surface consists of gently sloping to strongly sloping plains. Volcanic plugs that rise abruptly above the plains, steep scarps, or deeply incised canyons interrupt the plain surface. The Painted Desert, Vermillion and Echo Cliffs, Glen Canyon Recreational Area, and Canyon- lands National Park are included. Climate: Average annual precipitation —150 mm or less to about 350 mm at high elevations. About half of the precipitation falls from July through September; 24 April, May, and June are the driest months. Light snow falls in winter. Average annual temperature — 8 to 13°C. Average freeze-free period —110 to 180 days. Water: Water is scarce throughout the area. The Little Colorado River drains the largest segment of the area, but its flow is intermittent. Water is stored in small reservoirs for irrigation purposes, but supplies are often inadequate. Some irrigation water is obtained from erratic streamflow and in some localities from deep wells. Water from shallow wells is mostly highly mineralized and inadequate in quantity. Soils: The dominant soils are Orthents, Fluvents, and Psamments. They have a mesic temperature regime and an aridic moisture regime. Torriorthents (Moen- kopie, Claysprings, Aneth, and Winona series) and areas of rock outcrop are extensive. Large, actively eroded exposures of shale and sandstone (badland) include the Painted Desert and the Petrified Forest National Park. Deep, nearly level to gently sloping, well drained, moderately coarse textured to fine textured Torrifluvents (Trail, Ives, Tours, Jocity, and Navajo series) are on flood plains and low fans. Torripsamments (Sheppard series), sandy Cambor- thids, and Calciorthids (Mota and Whit series) are in the north. Potential natural vegetation: This area supports desert shrub and woodland vegetation. At high ele¬ vations, pinyon-juniper woodland and sagebrush have an understory of galleta, blue grama, black grama, and western wheatgrass. Galleta grass, alkali saca- ton, Indian ricegrass, bottlebrush squirreltail, and needlegrasses intermixed with fourwing saltbush and winterfat grow at lower elevations. Grease wood and shadscale are part of the plant community on salty soils. At low elevations, blackbrush is dominant on soils that formed in parent materials of sandstone and limestone. 36—New Mexico and Arizona Plateaus and Mesas Arizona and New Mexico 69,130 km 2 (26,690 mi 2 ) Land use: About one-fifth of this area is federally owned. An equal or larger proportion is set aside as Indian reservations. The remainder is in farms, ranches, or other private holdings. Most of the privately and publicly owned land is used for range. Less than 1 percent of the total area is cropland used for growing irrigated hay and pasture or for dry-farmed grain and hay. Elevation and topography: Elevation ranges from 1,500 to 2,300 m, but in a few isolated mountains it is more than 2,600 m. These plateaus and mesas have gentle slopes, but precipitous slopes are along valley walls and edges of the mesas. Climate: Average annual precipitation —250 to 325 mm in most of the area but 375 mm at higher elevations. About two-thirds of the precipitation falls from midsummer to early in autumn. Average an¬ nual temperature —9 to 12°C. Average freeze-free period —120 to 180 days. Water: Water is scarce because of the low precipitation and sparse streamflow. A small amount of water is available for irrigation along the major streams that flow into the area from surrounding mountains. Navajo Lake is near the northern border. Soils: Most of the soils are Argids and Orthents. They are well drained and fine textured to medium textured and have a mesic temperature regime, an aridic moisture regime, and mixed mineralogy. The nearly level to gently sloping Haplargids (Penistaja, Clovis, Fernando, Pankey, Silver, and Sedillo series) are on uplands, and the gently sloping to strongly sloping Haplargids are on piedmonts at the base of moun¬ tains. The gently sloping to strongly sloping Calciort hids (Harvey, Litle, and Las Lucas series) are on alluvial fans, and the gently sloping to rolling Calciorthids are on shale-controlled uplands. Shallow, gently sloping to moderately steep Torriorthents (Travessilla se¬ ries) are on sandstone-controlled uplands. The deep, gently sloping to hilly Torriorthents (Pojoaque and Chilton series) are on dissected uplands, and the deep, strongly sloping to rolling Torriorthents are on alluvial fans. Shallow Argiustolls (Cabezon, Encierro, and Bernal series) are on uplands of basalt and sed¬ imentary rocks. Haplustolls (Manzano and Prewitt series) and Torrifluvents (Lohmiller series) are on the stream deposits of valley floors and flood plains. Potential natural vegetation: Most of this area supports grassland vegetation. Indian ricegrass, blue grama, dropseed, and galleta are the major species. Alkali sacaton, fourwing saltbush, winterfat, and rabbitbrush grow in the valleys between mesas. Pinyon-juniper woodland is at the higher elevations and also on shallow 7 soils and escarpments. The understory is w'estern w'heatgrass, galleta, sideoats grama and, in some places, big sagebrush. 37—San Juan River Valley Mesas and Plateaus Arizona, Colorado, New Mexico, and Utah 13,350 km 2 (5,160 mi 2 ) Land use: About one-half of this area is in range of desert shrubs and short grasses. About 10 percent, mainly at higher elevations, is pinyon-juniper wood¬ land that provides some grazing. About one-third of the area is federally owned, some of which is grazed. About 2 percent is irrigated cropland in narrow 7 discontinuous bands along the San Juan River and its larger tributaries, and plans call for the irrigation of an additional 4 percent. Grain and hay growrn for livestock feed are the main crops, but fruits, vegeta¬ bles, and other cash crops are also grown. 25 Elevation and topography: Elevation ranges from 1,500 to 2,000 m. Gently sloping broad valleys and plains are bordered by deeply dissected bands of steep slopes and sharp local relief. Margins of mesas and a few isolated low mountain ranges are also steeply sloping. Climate: Average annual precipitation —175 to 250 mm. About one-half of the precipitation falls from midsummer to early in autumn. Average annual temperature— 10 to 12°C. Average freeze-free period —140 to 165 days. Water: The low precipitation and intermittent stream- flow provide a small amount of water for agriculture. A few major streams supply water for irrigation. Water from Navajo Lake is to be used for an irrigation project planned for the area. Ground water is scarce, of poor quality, and mostly untapped. Soils: Most of the soils are Orthents. They are well drained and medium textured and have a mesic temperature regime, an aridic moisture regime, and mixed mineralogy. Shallow, gently sloping to rolling Torriorthents (Farb and Chiptea series) are on dis¬ sected, shale- and sandstone-controlled uplands. Nearly level to gently sloping, loamy, deep Torriorthents (Turley, Fruitland, and Azfield series), Torrifluvents (Billings series), and Ustifluvents (Werlow series) are on side slopes and valley floors. Nearly level to gently sloping, loamy, deep Haplargids (Doak and Ship- rock series) and Camborthids (Kinnear and Avalon series) are on mesa tops. Sandy, deep, undulating to gently rolling Torripsamments (Sheppard series) are on dunelike uplands. Areas of badland and rock outcrop are conspicuous on the dissected uplands and on valley walls. Potential natural vegetation: This area supports desert shrub vegetation. Indian ricegrass, big sage¬ brush, fourwing saltbush, and galleta are major species. Shadscale, greasewood, alkali sacaton, and fourwing saltbush are on the bottom lands. Pinyon- juniper woodland, along with mountainmahogany, western wheatgrass, and galleta are at higher eleva¬ tions. Most of the western part of the area is grass¬ land on which Indian ricegrass, alkali sacaton, and sand dropseed are dominant. 39—Arizona and New Mexico Mountains Arizona, Colorado, New Mexico, and Utah 111,140 km 2 (42,910 mi 2 ) Land use: Most of this area is covered with timber of commercial quality, including an extensive stand of ponderosa pine. Lumbering is an important industry. This area, which constitutes the primary watershed for much of Arizona, contains numerous lakes and live streams and an abundance of wildlife. Recrea¬ tion, including hiking, camping, fishing, hunting, and skiing, is an important land use. At higher elevations the timbered areas grade to stands of pinyon and juniper, and at lower elevations they grade to chapar¬ ral and grassland. The woodland consists of relatively open stands; the understory is grass and browse. The woodland is used as range for summer grazing of cattle and sheep. Irrigated cropland is inextensive along the narrow bottoms of the live streams. Corn, alfalfa, small grains, and vegetables are the major crops and are used mostly on the farms where they are produced. In Utah, wheat and pinto beans are produced on dry cropland. Concerns of management include maintaining proper grazing distribution, con¬ trolling juniper that invades rangeland, and control¬ ling gullying. Wind and water erosion are hazards on dry cropland. Elevation and topography: In most places, eleva¬ tion ranges from 1,400 to 2,400 m, but it is 3,500 m on Baldy Mountain and 3,800 m on Humphreys Peak. This area is mostly very hilly and mountainous, but an upland plateau is dissected by many deep canyons. Climate: Average annual precipitation —275 to 900 mm, increasing with elevation. Average annual temperature— 5 to 15°C. In timbered areas at higher elevations the average is 7°C, and at lower eleva¬ tions it is 10°C. Average freeze-free period —less than 70 days at higher elevations to 170 days at lower elevations, averaging about 115 days. Water: This MLRA supplies water for much of the adjoining irrigated areas. Because more than one- half of the annual precipitation occurs in winter, there is a general deficiency of moisture during the growing season. Several of the larger streams and a few- of their larger tributaries maintain a yearlong flow. Much of this water is stored in reservoirs near or below the southern edge of the area and is used for irrigation and for municipal water supplies in the Central Arizona Basin and Range major land re¬ source area. Small natural and artificial lakes at higher elevations are used for fishing and other recreation. Annual runoff into all reservoirs is highly variable, and most of the smaller lakes and reservoirs are dry in some years. Ground water is limited and usually occurs at great depth. Soils: The dominant soils are Borolls, Boralfs, Ustolls, Ustalfs, Orthents, and Orthids. They have a cryic, frigid, or mesic temperature regime, depending mainly on elevation. Argiborolls (Brolliar, Sponseller, and Ess series) and Cryoborolls (Gordo and Tatiyee series) at the higher elevations formed in intrusive and extrusive volcanic materials, dominantly basalt. At lower elevations, Eutroboralfs (Dandrea, McVickers, Overgaard, and Hogg series), Ustorthents (Mirabal, Lockerby, and Telephone series), Haplustalfs (Jacks and Elledge series), Argiustolls (Showlow, Monticello, Northdale, and Roundtop series), Haplustolls (Tor- tugas and Ackman series), Calciorthids (Cibeque and Hovenweep series), and Glossoboralfs (Soldier series) 26 overlie schist, sandstone, shale, limestone, and old alluvium. Potential natural vegetation: This area supports alpine vegetation, conifer forests, chaparral, and grasses because of the broad elevation range. Such cushion plants as moss campion, kobresia, alpine timothy, and many low-growing forbs grow above timberline. Spruce-fir woodland characterizes the area below timberline. Aspen grows on sites that have not been disturbed by past fires. The under¬ story includes Thurber fescue, brome, bluegrasses, mountain muhly, Arizona fescue, lupine, aspen peavine, penstemons, and daisies. The major part of the area is a vast ponderosa pine forest. Common understory plants include bromes, junegrass, pine dropseed, wheatgrasses, mountain muhly, blue grama, sedges, and snowberry. Piny on-juniper woodland is at an elevation below 2,100 m. The understory is blue grama, tobosa, sideoats grama, and western wheat- grass. Below an elevation of about 1,800 m, turbinella oak, mountainmahogany, hollyleaf buckthorn, ceano- thus, and manzanita grow along with sideoats grama, blue grama, junegrass, longtongue muttongrass, squirreltail, and bluegrasses. 40—Central Arizona Basin and Range Arizona 47,130 km 2 (18,200 mi 2 ) Land use: Most of this area is desert that affords limited grazing during seasons of favorable moisture. Land under irrigation is used for growing cotton, alfalfa, barley, and other small grains. In places where water supplies are favorable, lettuce, carrots, cabbage, cauliflower, melons, other market vegeta¬ bles, and citrus are grown. Rapid urbanization around the larger communities is greatly reducing the acre¬ age of cropland. Land use problems include declining water tables and accumulation of salt in soils used for crops. Efficiently using the short water supply is a chief concern of management . Elevation and topography: Elevation ranges from 300 to 1,100 m, but in the mountains it is as high as 1,400 m. Many short, southeast-northwest-trending block-fault mountain ranges rise abruptly from the smooth or gently sloping valley floors. Valleys are filled to great depth with materials washed from the mountains. Climate: Average annual precipitation —125 to 300 mm. Precipitation falls mainly from July to Septem¬ ber and from December to March. Snow'fall is rare except at higher elevations. Average annual tempera¬ ture —18 to 22°C. Average freeze-free period —250 to 300 days. Water: Water for irrigation is stored in a reservoir system on the Salt River. Some water for irrigation is pumped from deep wells. The water generally is of good quality, but the ground-water table is dropping. No perennial streams originate or run through the area because the water of the larger drainages is impounded by reservoirs upstream from the culti¬ vated lands. Soils: The dominant soils are Orthids, Argids, Orthents, and Fluvents. They have a thermic and hyperthermic temperature regime and an aridic moisture regime. Shallow Camborthids (Lomitas series), Haplargids (Gachado and Lehmans series), Torriorthents (Cellar and House Mountain series), and areas of rock out¬ crop on hills and mountains make up about 50 percent of the area. Torrifluvents (Glenbar, Glendale, Gila, Gilman, Antho, Anthony, Vint, Vinton, Agua, Cashion, and Gadsden series) on low fans and flood plains are dominant in the valleys. Calciorthids (Laveen, Latene, Rillito, Rilloso, Coolidge, and Gunsight series), Haplargids (Mohall, Tremant, Pinamt, and Vecont series), Durorthids (Pinal series), Durargids (La Palma series), and Natrargids (Casa Grande series) also occur. Potential natural vegetation: This area supports desert shrub vegetation. The giant saguaro cactus is a major species. Bursage, desert wolfberry, ocotillo, cholla, desert saltbush, mesquite, brittlebush, bur- roweed, pricklypear, desert broom, and creosotebush are dominant desert shrubs. Bush muhly, Arizona cottontop, threeawns, and fluffgrass are understory plants. Winter annuals grow in places, depending on the amount of winter precipitation. Joshua-tree and littleleaf paloverde mixed with some honey mesquite and an understory of Mormon-tea, pricklypear, chol¬ la, ocotillo, desert saltbush, and such grasses as tridens, bush muhly, tobosa, Arizona cottontop, and desert needlegrass are on stony, rocky sites. At lower elevations, creosotebush, ironwood, mesquite, burroweed, and catclaw are associated with an un¬ derstory of threeawns and annuals such as red fes¬ cue, bluegrasses, fiddleneck, indianwheat, globemallow, and filaree. 41—Southeastern Arizona Basin and Range Arizona and New Mexico 45,560 km 2 (17,590 mi 2 ) Land use: Most of this area is used for grazing. Some land is under irrigation, and cotton, corn, alfalfa, small grains, and other farm crops are grown. In recent years, lettuce has been grown for the fall and spring markets. Many tracts of rangeland and crop¬ land are subdivided for community development. The main concern of management on rangeland is control¬ ling the distribution of grazing. (Invasion of brushy species and local gully erosion are symptoms of overgrazing.) Land use problems associated with cultivated land include declining water tables and a short supply of irrigation water. 27 Elevation and topography: Elevation ranges from 800 to 1,400 m in most places and from 1,500 m to 1,800 m in the mountains. On some peaks, however, elevation is 2,700 m, and on Mt. Graham in Arizona it is 3,300 m. This area consists of southeast-northwest- trending mountain ranges with relatively smooth valleys separating the mountains. In the vicinity of Wilcox Arizona, there is a closed basin, the bottom of which forms the Wilcox Playa. Climate: Average annual precipitation —275 to 375 mm, but as much as 900 mm at the higher elevations. More than half of the precipitation falls during July, August, and September. Snow falls occasionally in winter. Average annual temperature —13 to 17°C. Average freeze-free period —150 to 250 days. Water: None of the streams flow continuously, al¬ though they may have water in them for several months each year. There are no lakes or reservoirs of consequence. Water for irrigation generally is obtained by pumping ground water, and there has been a noticeable decrease in the ground-water level in the last several years. Water quality is generally satis¬ factory. Small artesian flows occur along parts of the San Pedro River. Soils: The dominant soils are Orthents, Ustolls, Argids, and Fluvents. They have a thermic temperature regime and mostly an aridic moisture regime. Shal¬ low Torriorthents (Cellar, House Mountain, and Tidwell series) and Haplustolls (Lampshire, Mabray, Witch, Faraway, Tortugas, and Barkerville series) and areas of rock outcrop on the hills and mountains make up approximately 40 percent of the area. In the valleys, Haplargids (White House, Bernardino, Sonoita, Caralampi, and Pinaleno series), soils having a high content of carbonates, including Calciustolls (Hathaway, Elfrida, Cogswell, and Kimbrough series), and Tomfluvents (Gila, Glendale, Anthony, Pima, Grabe, and Comoro series) are dominant. Other soils include Paleargids (Tubac series), Chromusterts (Bonita and Rimrock series), Natrustalfs (Crot series), Durorthids (Steward series), Natrargids (Gothard series), and Paleorthids (Cave series). Potential natural vegetation: This area supports forest, savanna, and desert shrub vegetation. Pine-oak woodlands are at higher elevations. Ponderosa pine, Douglas-fir, live oak, New Mexico locust, Mexican pinyon, buckbrush, and manzanita grow with an understory of muhlys, bluegrasses, sedges, pine dropseed, and squirreltail. Evergreen woodland sa¬ vannas are at intermediate elevations. Mexican blue oak, Emory oak, and turbinella oak are dominant species. Cone beardgrass, sideoats grama, blue grama, Texas bluestem, plains lovegrass, sprucetop grama, threeawns, and needlegrass characterize the under¬ story. Whitethorn, soaptree yucca, fourwing saltbush, mesquite, and ocotillo grow on drier soils at lower elevations. The understory consists of Rothrock grama, black grama, alkali sacaton, curly mesquite, plains bristlegrass, bush muhly, and lemongrass. 42—Southern Desertic Basins, Plains, and Mountains New Mexico and Texas 115,470 km 2 (44,580 mi 2 ) Land use: About one-third of this area is federally owned. Most of the remainder is in farms, ranches, or other private holdings. The federal land is mainly in New Mexico. Two-thirds or more of the total area is in range of low carrying capacity. Less than 1 percent is irrigated. Cotton, cantaloupes, and vegetables are the principal crops. Grain sorghum, alfalfa, and other feed and forage crops are also grown. Elevation and topography: Elevation ranges from 800 to 1,500 m in basins and valleys, but it is more than 2,600 m in the mountains. Broad desert basins and valleys are bordered by gently sloping to strongly sloping fans and terraces. Steep north-south-trending mountain ranges and many small mesas are in the western part. Climate: Average annual precipitation —200 to 325 mm. Maximum precipitation is from midspring to midautumn. Average annual temperature —13 to 18°C. A verage freeze-free period —200 to 240 days in most of the area but 180 days in the northern ends of the Pecos and Rio Grande valleys. Water: Scarce surface water and low precipitation are severe limitations to use of the area for range. The Rio Grande and Pecos Rivers and a few of their larger tributaries are the only perennial streams. Water for irrigation generally is obtained from these rivers or from wells. Ground water in deep valley fill provides water for domestic use and for livestock and in places for some irrigation. Soils: Most of the soils are Argids and Orthids. They are well drained and medium textured and have a thermic temperature regime, an aridic moisture re¬ gime, and mixed or carbonatie mineralogy. Deep and moderately deep Haplargids (Berino, Madurez, Mohave, Cacique, and Pyote series), Paleargids (Wickett and Douro series), and Calciorthids (Wink, Reaker, Hoban, Turney, Reagan, and Nickel series) are on uplands, piedmont plains, and dissected ter¬ races. Shallow Haplargids (Lehmans series), shallow Calciorthids (Lozier series), Ustolls (Ector series), and Toni orthents (Holloman series) are on bedrock- controlled uplands. Shallow Paleorthids (Simona, Upton, Conger, Blakeney, Delnorte, and Tencee series) are on mesas, uplands, and ten'aces. Deep and moderately deep Gypsiorthids (Yesum and Reeves series) are in closed basins. Camborthids (Mimbres series), Natrargids (Hondale series), and Ton’erts (Dalby and Verhalen series) are on basin floors. 28 Torrifluvents (Gila, Glendale, and Vinton series) are on the flood plains. Torripsamments (Bluepoint, Pen- well, Kermit, and Pintura series) are on hummocky sandy uplands. Potential natural vegetation: This area supports desert grass-shrub vegetation. Giant dropseed and mesa dropseed, along with scattered shrubs such as sand sagebrush and yuccas, grow on the sandier soils. Creosotebush, tarbush, catclaw, and javalinabush are on gravelly, calcareous foot slopes. Giant sacaton, vine-mesquite, desertwillow, brickellbush, and mes- quite grow in drainageways and depressions. Juni¬ per, pinyon, scattered ponderosa pine, and Douglas-fir are on upper mountain slopes. 29 E—ROCKY MOUNTAIN RANGE AND FOREST REGION 597,250 km 2 (230,600 mi 2 ) Rugged mountains are the dominant feature of this region, but there are some broad valleys and remnants of high plateaus. The average annual precipitation ranges from 500 to 1,025 mm in much of the region, but it is less than 250 mm in some valleys and 1,275 mm or more on some of the mountain peaks. The average annual temperature is generally 4 to 7°C, but it ranges from 2 to 10°C. The freeze-free period is 100 to 140 days in most valleys and basins, but it is 40 days or less in the high mountains where frost occurs every month of the year. Some of the highest mountains are covered by glaciers, and the ground is permanently frozen. The freeze-free period on foothills in the southern part is as long as 160 days. Ustolls, Ochrepts, and Ustalfs are the dominant soils in valleys and on lower mountain slopes. Ochrepts, Borolls, and Orthents are dominant on upper mountain slopes and crests. Orthents and areas of rock outcrop are extensive on steep mountain slopes, and Fluvents and Aquolls are in valleys. Grazing is the leading land use in the valleys and in the mountains, but lumbering is important in some of the forested mountain areas. Use of the land for recreation is important throughout this region. Irrigation is practiced in some of the valleys and dryfarming in others. Grain and forage for livestock are the main crops. Beans, sugar beets, peas, and seed crops are also grown in places where soils, climate, and markets are favorable. 43—Northern Rocky Mountains Idaho, Montana, Oregon, Washington, and Wyoming 282,650 km 2 (109,130 mi 2 ) Land use: Nearly all this area is federally owned and administered by the Forest Service, U.S. Depart¬ ment of Agriculture, and the Bureau of Land Man¬ agement, Department of the Interior. Most of the privately owned land is controlled by large commer¬ cial timber companies. All the forested areas are used as wildlife habitat, for recreation and watershed, and for timber production. Meadows on the upper moun¬ tain slopes and crests above timberline provide sum¬ mer grazing for livestock and big game animals. Mining is an important industry in Idaho and in western Montana. Dairy and livestock farms are important enterprises in the west. Less than 2 per¬ cent of the area is cropped. Forage, grain, peas, and a few other crops are grown in some valleys. Elevation and topography: Elevation is mainly 400 to 2,400 m, but it is almost 3,000 m on some mountain peaks. Some areas in Montana and Wyoming are at an elevation of 2,100 to 3,000 m, and mountain peaks are almost 4,300 m. High mountains having steep slopes and sharp crests are cut by narrow valleys, most of which have steep gradients. Lakes are com¬ mon, especially in glaciated areas. Climate: Average annual precipitation —Mainly 625 to 1,525 mm, increasing with elevation, but almost 375 mm in the western part of the area and almost 2,550 mm in high mountains. Most of the precipitation during fall, winter, and spring is snow. Summers are dry. Average annual temperature —2 to 7°C in most of the area, but it is 8°C or more at low elevations. Average freeze-free period —45 to 120 days, decreas¬ ing with elevation, and as long as 140 days in low valleys of Washington. Frost occurs every month of the year on high mountains; some peaks have a continuous cover of snow and ice. Water: Moderate precipitation and many perennial streams and lakes provide ample water. Streams and reservoirs supply water to adjoining MLRA’s for ir¬ rigation and other uses. Springs and shallow wells in the valleys provide water for domestic use and for live¬ stock. Elsewhere, ground-water supplies are small and mostly untapped. Soils: Most of the soils are Ochrepts and Andepts. They have a frigid or cryic temperature regime. Shallow to moderately deep, medium textured and moderately coarse textured Cry ochrepts (Jughandle and Holloway series) and Xerochrepts (Waits and Moscow series) are on mountain slopes. Cryandepts (Huckleberry, Truefissure, and Coerock series) are on ridges with thin layers of volcanic ash. Stony Cryorthents (Tamely series) and areas of rock out¬ crop are on peaks and ridges above timberline. Detailed soil survey information is lacking in most of the area. Potential natural vegetation: This area supports conifer forests. Forests of western white pine, ponderosa pine, lodgepole pine, western redcedar, western larch, hemlock, Douglas-fir, subalpine fir, and spruce are common. Alpine grasses, forbs, and shrubs and scattered stands of subalpine fir, spruce, and whitebark pine grow on high mountains of Mon¬ tana and Wyoming. 44—Northern Rocky Mountain Valleys Idaho, Montana, and Washington 32,320 km 2 (12,480 mi 2 ) Land use: Nearly all this area is in farms and ranches. As much as one-third of the land in some valleys is 30 irrigated. Potatoes, sugar beets, and peas are impor¬ tant cash crops, but a larger acreage is in hay, grain, and pasture for livestock feed. In places where precipitation is adequate, the land is dry-farmed to wheat. One-third to one-half of the area is range of native grasses and shrubs. Beef cattle and sheep are the principal livestock, but dairying is an important enterprise near the larger towns. Much of the area in northern Idaho is forested, and elsewhere many steep and stony soils are in woodland. These forests are of value to the lumber industry and are also grazed. Elevation and topography: Elevation ranges from 600 to as much as 2,100 m; the highest is in south¬ western Montana. The deep valleys bordered by mountains are mostly north-south trending. In the valleys, nearly level, broad flood plains are bordered by gently sloping to strongly sloping terraces and fans. In many places the valleys have been modified somewhat by glaciation, and in the north, lacustrine sediments cover much of the valley floors. Climate: Average annual precipitation —300 to 400 mm in most of the area, less than 250 mm in Montana, and 850 mm in northern Idaho. Precipitation is fairly evenly distributed throughout fall, winter, and spring but is low in summer. Most of the precipitation in winter is snow. Average annual temperature —4 to 8°C. Average freeze-free period —100 to 120 days in much of the area, but it is 80 days or less at the highest elevations and 130 days or more at the lowest. Water: Perennial streams flowing into the area from surrounding mountains are the principal source of water. The amount usually is adequate but depends on the snow accumulation in the mountains. Ground water is abundant in the deeper unconsolidated fill materials, and some is used for irrigation. Precipita¬ tion is adequate for some dryfarming at higher eleva¬ tions and throughout the area in northern Idaho. Soils: The dominant soils are mostly Orthids, Borolls, and Argids. They are medium textured to fine textured and mainly well drained and have a frigid or, at higher elevations, a cryic temperature regime. At the lower elevations, deep and moderately deep Calciorthids (Crago and Musselshell series), Haploborolls (Bitterroot and Grantsdale series), and Argiborolls (Martinsdale series) are on alluvial fans and terraces. Natrargids (Round Butte series) are on lacustrine fans and terraces, and Fluvents are on alluvial flood plains and low terraces. At the higher elevations, mostly deep, well drained to somewhat poorly drained Cryoborolls (Amsterdam, Bozeman, Bridger, and Gallatin series) are on alluvial terraces and fans, and Aquents and Aquepts are adjacent to drainageways and in undrained depressions. Potential natural vegetation: This area supports conifer forests and grassland vegetation. Bluebunch wheatgrass, rough fescue, Idaho fescue, and bearded wheatgrass are the major species of the grassland in the valleys and foothills. Douglas-fir, ponderosa pine, grand fir, western redcedar, western hemlock, pinegrass, common snowberry, mallow ninebark, and white spirea are the major forest species. 46—Northern Rocky Mountain Foothills Montana and Wyoming 52,070 km 2 (20,110 mi 2 ) Land use: About one-fifth of this area is federally owned. The remainder is in farms and ranches. One-half or more of the area is range of short and mid grasses and some shrubs. Many of the valleys are irrigated, but they make up only 1 or 2 percent of the total area. Grain and forage for livestock are the main crops, but potatoes, sugar beets, peas, and some other crops are grown in the warmer valleys. About one-fifth of this area, mainly along the northeastern side, is dry-farmed to wheat. Some of the highest hills are forested. Elevation and topography: Elevation ranges from 1,100 to 1,800 m in the north, increasing gradually to 1,800 or 2,400 m in the south and in central Wyoming. The rugged hills and low mountains are cut by many narrow valleys that have steep gradients. Broad flood plains and fans border a few of the major rivers. Climate: Average annual precipitation —Mainly 300 to 500 mm, but it is 750 mm at the highest elevations and 250 mm in some basins. In the north minimum precipitation is in spring, and in the south it is early in summer. Winter precipitation is snow. Average annual temperature —6 to 7°C. Average freeze-free period —Generally 90 to 125 days, but it is only 80 days at the highest elevations. Water: Precipitation is too low for good growth of crops in some parts of the area, but in others it is adequate for grain farming and forage production. The major rivers provide most of the water for irrigation, but small streams furnish local supplies. Ground water is abundant in the fill in some valleys, but in most of the area ground water is meager or is lacking. Soils: Soils of this area are mostly Borolls, Orthents, and Fluvents. They are medium textured to fine textured and mainly well drained and have a frigid temperature regime. Moderately deep to deep Argiborolls (Absarokee, Farnuf, and Savage series), Haploborolls (Winifred and Rottulee series), and Natriborolls (Adger series) are on sedimentary up¬ lands, alluvial fans, foot slopes, and terraces. Shallow Argiborolls (Sinnigam and Amherst series), Haplo¬ borolls (Castner series), and Ustorthents (Cabba and Wayden series) are on sedimentary uplands. Deep, nearly level to gently sloping Ustifluvents (Havrelon and Lohler series) are on flood plains and low alluvial 31 terraces. Soils in wooded areas are at higher eleva¬ tions where more rainfall is received. Potential natural vegetation: This area supports grass vegetation in the valleys and foothills and forest vegetation at higher elevations. Bluebunch wheatgrass, rough fescue, Idaho fescue, and western wheatgrass are the major grass species. Ponderosa pine, Rocky Mountain juniper, common snowberry, and skunkbush sumac are dominant species in for¬ ests. 47—Wasatch and Uinta Mountains Colorado, Idaho, Utah, and Wyoming 53,150 km 2 (20,520 mi 2 ) Land use: Less than one-third of this area is in farms and ranches. Most of the remainder is federally owned. There are several national parks and monu¬ ments and primitive areas. Some land is set aside as Indian reservations. Grassland and woodland are grazed in summer. Some dense forests are on moist sites. Recreation and mining are important land uses. A few valleys are irrigated; forage for livestock is the main crop, but a few other crops are grown. Elevation and topography: Elevation generally ranges from 1,500 to 2,700 m, but on some peaks it is 4,100 m. These strongly sloping to precipitous mountains have narrow crests and valleys. Some high plateaus have gently sloping tops and steep sides. The moun¬ tains are dissected by many streams, and lakes are common on mountain crests that have been glaciated. Climate: Average annual precipitation —Mainly 375 to 750 mm but as much as 1,025 mm on some mountain peaks. Precipitation is evenly distributed throughout the year. Much of the precipitation is snow. Average annual temperature —2 to 8°C, de¬ creasing with elevation. Average freeze-free period — Mainly 60 to 120 days, but there is no frost-free period on some high mountain peaks. Water: Streams, lakes, and ground water supply enough water for the range and forestry enterprises in most of the area. Perennial streams provide irrigation water in the few major valleys. Soils: Orthents, Fluvents, Aquolls, and Xerolls are common in the valleys. Ochrepts, Xerolls, Borolls, Boralfs, and Xeralfs are on mountain slopes. These soils have a frigid or cryic soil temperature regime and mixed, montmorillonitic, or carbonatic mineralo¬ gy. They formed in mixed parent materials of sedi¬ mentary and igneous rocks. Deep wet soils in the valley are Haplaquolls (Crooked Creek, Canburn, and Kovich series). Well drained Ustifluvents (Neto, Shupert, and Winetti series), Ustorthents (Podo and Ruko series), Xerorthents (Redcan series), and Calcixerolls (Calita and Lundy series) are in valleys. Palexerolls (Borvant series) are on old alluvial fans and low mountain foot slopes; they have a lime- cemented hardpan. On mountain slopes are shallow to deep Haploxerolls (Agassiz, Bradshaw, and Foxol series), Haploborolls (Brycan and Datino series), Argixerolls (Henefer, Smarts, and Wallsburg series), Argiborolls (Barfuss and LaPlatta series), and Palexerolls (Harkers, Goring, and Norcan series). In the high mountain areas are deep Paleborolls (Lucky Star, Elzinga, and Flygare series), Paleboralfs (Fitzgerald series), Cryoborolls (Bickmore, Daybell, and Dateman series), Cryoboralfs (Cliff, Duchesne, and Condie series), Cryochrepts (Scout, Lake Janee, and Marsell series), and Cry orthents (Mirrow Lake series). Potential natural vegetation: This area supports conifer, aspen, grasses, mountain shrub, and sage¬ brush-grass vegetation. Big sagebrush and bluebunch wheatgrass are dominant sagebrush-grass species. The zone above an elevation of about 4,000 m sup¬ ports alpine meadow. The conifers are Engelmann spruce, white fir, subalpine fir, Douglas-fir, lodgepole pine, and ponderosa pine. Numerous grasses and forbs grow under the aspen. Bluebunch wheatgrass, bearded wheatgrass, blue wildrye, mountain brome, several bluegrasses, and numerous forbs grow as an understory with Gambel oak, curlleaf and birchleaf mountainmahogany, snowberry, serviceberry, and chokecherry. 48A—Southern Rocky Mountains Colorado, New Mexico, Utah, and Wyoming 112,050 km 2 (43,260 mi 2 ) Land use: More than one-half of this area is federally owned. The remainder consists of farms, ranches, or other private holdings. The upper mountain slopes, below timberline, are forested. Grassland occurs above timberline at lower elevations and in valleys. Most of the grassland and much of the open woodland is grazed. Recreation, mining, and wildlife habitat are important 'and uses throughout this area. Small valleys are irrigated and used for growing hay and pasture for livestock. Elevation and topography: Elevation ranges from 2,300 to 4,300 m. These strongly sloping to precipi¬ tous mountains are dissected by many narrow stream valleys having steep gradients. In places the upper mountain slopes and crests are covered by snowfields and glaciers. High plateaus and steep-walled canyons are fairly common, especially in the west. Climate: Average annual precipitation —Generally 375 to 750 mm but as much as 1,025 mm or more on some of the higher mountains. Most of the precipitation falls in winter as snow 7 . Average annual temperature —0 to 7° C. Average freeze-free period —Generally less than 70 days. Water: Water from the streams and lakes is abundant, and ground water is plentiful. The lower valleys depend on streamflow from this area for irrigation w 7 ater. 32 Soils: Most of the soils are Boralfs. They are moder¬ ately deep, stony and very stony, and medium textured. They have an ustic or udic moisture regime, a cryic temperature regime, and mixed mineralogy. Cryo- boralfs (Peeler and Frisco series) are on timbered mountain slopes. Shallow Cryorthents (Crespin and Mine series) are on very steep grass- and shrub- covered breaks. Deep and moderately deep Cryoborolls (Woodhall and Carbol series) are on lower fans and valleys. Cryochrepts and Cryaquepts (Bottle and Vasquez series) and areas of rock outcrop are above timberline. Potential natural vegetation: This area supports forests on upper slopes, alpine tundra above timber- line, and shrub-grass vegetation at lower elevations. Grasses, sagebrush, and other shrubs grow on the lower slopes and in valleys. Lodgepole pine, aspen, Douglas-fir, and ponderosa pine are major trees of the lower forest. Engelmann spruce, subalpine fir, white fir, and limber pine intermingled with stands of aspen are typical on the mountain slopes. Willow, alder, and birch trees grow along streams. The timberline zone is characterized by stunted and wind- twisted limber pine, bristlecone pine, Engelmann spruce, and subalpine fir. Alpine grasses, herbaceous plants, and shrubs constitute the treeless alpine tundra. 48B—Southern Rocky Mountain Parks Colorado 20,110 km 2 (7,770 mi 2 ) Land use: About one-half of this area is federal land leased to ranchers for grazing of cattle and sheep. The remainder is privately owned ranches. Irrigated pastures and hayland adjacent to most of the rivers and streams provide most of the forage. Hay consists mainly of grasses and sedges and a small amount of clover. Grazing land is sparsely vegetated with grasses and shrubs and is low in production because of inadequate rainfall and low temperatures. Elevation and topography: Elevation ranges from 2,400 to 3,300 m. This area consists of nearly level to rolling mountain parks and valleys and a few narrow mountain ridges. Climate: Average annual precipitation —175 to 300 mm. About one-half of the precipitation falls as snow. Moisture is unevenly distributed within short dis¬ tances because of snowdrifts. Average annual temperature —1 to 7°C. Average freeze-free period — Generally less than 70 days. Water: Perennial streams originating from snowmelt in the adjacent high mountains furnish an abundance of water for irrigation of hay meadows in June and July. In August the streams are often short of water. Large reservoirs store w'ater for domestic, power, and irrigation uses outside the area. Soils: Most of the soils are Borolls. They are deep and moderately deep, very cobbly, and medium textured to coarse textured. They have an aridic or ustic moisture regime, a cryic temperature, and mixed mineralogy. Cryoborolls (Eyre and Bucklon series) formed in outwash and alluvium on the broad, grass- covered valley floors and slopes. Haplargids and Cryorthents on steeper slopes are primarily in residuum from sedimentary rocks. Potential natural vegetation: This area supports grass and grass-shrub vegetation. Big sagebrush, rabbitbrush, and winterfat are dominant shrubs. Arizona fescue, mountain muhly, sod-forming wheat- grasses, needlegrass, and bluegrasses are dominant grasses. 49—Southern Rocky Mountain Foothills Colorado and Wyoming 32,680 km 2 (12,620 mi 2 ) Land use: At least four-fifths of this area is in farms and ranches. Nearly all the remainder is federally owned. The grassland and woodland are grazed. Hay, pasture, and feed grains are growm in irrigated valleys, which make up less than 5 percent of the total area. A small acreage is dry-farmed to wheat. Elevation and topography: Elevation ranges from 1,700 to 2,400 m. These rugged hills and low moun¬ tains are in narrow bands along the eastern slopes of the Rocky Mountains. They are strongly dissected and in many places are crossed by large streams flowing eastward from the Rocky Mountains. In most places, local relief is about 100 m. Climate: Average annual precipitation —125 to 500 mm. Precipitation is low in winter, increases from spring to midsummer, and decreases in autumn. Av¬ erage annual temperature —4 to 10°C. Average freeze- free period —Generally 120 to 160 days, but it is shorter at higher elevations, especially in the north. Water: The major streams crossing the area provide irrigation water for narrow belts of cropland in their valleys, but elsewhere water is scarce. Soils: Most of the soils are Ustolls, Borolls, and Boralfs. They are mostly deep and have an ustic moisture regime, a mesic or frigid temperature regime, and mixed mineralogy. Deep loamy Argiustolls (Bresser series), Argiborolls (Peyton series), and Eutroboralfs are dominant. They formed mainly in locally transported sediments on the more smoothly sloping sites. Shal¬ low Haplustolls and Torriorthents are on steep and broken hill slopes. Potential natural vegetation: This area supports vegetation transitional between that of the grass¬ lands of the plains and the forests of the mountains. A broad belt of short grasses and shrubs (oak, moun- tainmahogany, antelope bitterbrush, and others) in¬ termingles with open stands of ponderosa pine, Douglas-fir, pinyon, and juniper on the hillsides and blue spruce, alder, narrowleaf cottonwood, birch, and willow along the streams. Gramas, needlegrasses, bluegrasses, and sod-forming wheatgrasses are the major grasses. 51—High Intermountain Valleys Colorado and New Mexico 10,060 km 2 (3,880 mi 2 ) Land use: Nearly one-half of this area is federally owned. The remainder is in farms and ranches. The Great Sand Dune National Monument is in this area. Desert shrubs and short grasses cover most of the land. About 25 percent of the area is irrigated cropland. Major crops are potatoes, malt barleys and other small grains, field peas, cool-season vege¬ tables, and hay. The native range is grazed in sum¬ mer, but it has a low carrying capacity. Elevation and topography: Elevation ranges from 2,100 to 2,700 m. Much of the area consists of nearly level to gently sloping old valley fill. Gently sloping to steep hills underlain by basalt are extensive in the south. Local relief is slight except in the south, where it is as much as 100 m. Climate: Average annual precipitation —150 to 500 mm, increasing from north to south. Most of the precipitation falls during the growing season. Aver¬ age annual temperature —4 to 10°C. Average freeze- free period —100 to 140 days. Water: The low precipitation in the north supports only a sparse cover of range plants, but rainfall in the south is adequate for a good cover of grass and sagebrush. Irrigation water is provided by the Rio Grande River and small reservoirs on intermittent streams flowing into the area from surrounding moun¬ tains. The Chama River is an important water source in the south. Wells that tap ground water in the deep valley fill are also an important source of water for irrigation and domestic use. Salinity is a problem in much of the area. Soils: Most of the soils are Argids. They are deep and moderately deep and coarse textured to medium textured. They have an aridic moisture regime, a frigid temperature regime, and mixed mineralogy. Deep loamy Haplargids (Graypoint and Asacio se¬ ries) are commonly underlain by sand or gravel formed in alluvium on valley floors and gentle slopes. Natrargids are extensive in the broader valleys. Mostly shallow Haploborolls and Torriorthents are on steeper slopes. Potential natural vegetation: This area supports desert shrub-grassland vegetation. Greasewood, rabbitbrush, fourwing saltbush, saltgrass, alkali sac- aton, wheatgrasses, sedges, and rushes are common at the lower elevations. Pinyon and juniper, Indian ricegrass, blue grama, needleandthread, wheatgrasses, and bluegrasses grow at higher elevations. Narrowleaf cottonwood grows along the major streams. 34 F—NORTHERN GREAT PLAINS SPRING WHEAT REGION 351,990 km 2 (135,900 mi 2 ) The fertile soils and the dominantly smooth topography of this region are favorable for agriculture, but the low precipitation and a short growing season severely limit the crops that can be grown. The average annual precipitation ranges from 250 to 550 mm. A large part of the precipitation falls during the growing season. The average annual temperature is 4 to 9°C in most of this region. The freeze-free period ranges from 100 to 155 days, increasing from north to south. Borolls and Aquolls are dominant soils. Borolls are on uplands, and Aquolls are in low wet areas and along streams. Aquolls are extensive in the Red River Valley in the eastern part of the region. Some of the Borolls have a high content of sodium, and some of the Aquolls have a high content of sodium and lime. Other important soils are Orthents on steep slopes and Ustolls in the southern part of the region. Spring wheat grown by dryfarming methods is the major crop. Other spring grains, flax, and hay are also grown. Potatoes, sugarbeets, soybeans, and corn are important crops in the Red River Valley. 52—Brown Glaciated Plain Montana 52,110 km 2 (20,120 mi 2 ) Land use: Nearly all this area is in farms and ranches. Level tracts, mostly in the west and making up almost one-half of the total area, are cropped. Spring wheat is the major cash crop, but feed grains and hay are also grown on most farms. Most of the land in the east is in range, but gently sloping soils are dry- farmed to wheat. Narrow discontinuous strips along the Milk River are irrigated. Feed grains, corn silage, hay, and tame pasture are grown on much of the irrigated land, and sugarbeets are an important cash crop. Elevation and topography: Elevation generally ranges from 600 to 1,400 m, increasing from east to west, but it is as much as 2,100 m in the Sweetgrass Hills. This glaciated plain is nearly level to gently rolling, but belts of steep slopes border some of the larger rivers. The Milk River has extensive flood plains, but flood plains along the other streams are narrow and discon¬ tinuous. Climate: Average annual precipitation —250 to 375 mm in most of the area and as much as 500 mm in the Sweetgrass Hills. Maximum precipitation is from spring through early summer. Precipitation in winter is snow. Average annual temperature —3 to 7°C. Average freeze-free period —100 to 130 days. Water: Most of the area depends on precipitation for water for both range and crops. The Milk River provides irrigation water to its flood plains and immediate adjacent land. On the uplands, water for livestock is stored in small reservoirs. The glacial drift yields a moderate amount of ground water that is hard but otherwise of good quality. Soils: Most of the soils are Borolls, Orthents, Argids, and Fluvents. These soils are medium textured to fine textured and well drained and have a frigid temperature regime. Deep, nearly level to strongly rolling Argiborolls (Scobey and Telstad series) are on glacial till plains. Shallow to deep, nearly level to steep Torriorthents (Lisam, Hillon, and Marias se¬ ries) are on shaly uplands, glacial till plains, and lacustrine terraces, fans, and foot slopes. Deep, nearly level to moderately sloping Natrargids (Absher and Thoeny series) are on alluvial fans and low terraces adjacent to drainageways and on glacial till plains. Deep, nearly level and undulating Paleargids (Phillips series) are on glacial till plains. Deep, nearly level Torrifluvents (Harlem and Havre series) are on flood plains and low terraces. Included with these soils are some soils in the Sweetgrass Hills. Wet or saline soils along streams or in seep spots are also included. Potential natural vegetation: This area supports grass¬ land vegetation. Bluebunch wheatgrass, needleand- thread, western wheatgrass, green needlegrass, and basin wildrye are dominant species. 53A—Northern Dark Brown Glaciated Plains Montana and North Dakota 30,740 km 2 (11,870 mi 2 ) Land use: Most of this area is in farms and ranches. Slightly more than one-half is cropland that is dry- farmed. Spring wheat is the chief crop, but flax, oats, and barley are grown on some farms. The more sloping soils are in range of native grasses. Elevation and topography: Elevation ranges from 600 to 900 m, increasing gradually from southeast to northwest. These gently undulating to rolling till plains include areas of kettle holes, kames, and moraines. Strongly rolling and steep slopes are adja¬ cent to major stream valleys. Climate: Average annual precipitation —300 to 350 mm. More than half of the precipitation falls during 35 the growing season. Winter precipitation is snow. Average annual temperature —3 to 5°C. Average freeze-free period —110 to 125 days. Water: In most years, moisture is inadequate for maximum crop production. The Missouri River is the only dependable source of water for irrigation; there¬ fore, only a small acreage is irrigated. There is a limited supply of ground water. In places, dug ponds are a source of water for livestock. Soils: Most of the soils are Borolls. They are deep, well drained, and medium textured and have a frigid temperature regime and mixed mineralogy. The nearly level and undulating Argiborolls (Williams and Bowbells series) are on till plains. The steeper Haploborolls (Zahl and Max series) are on uplands; others (Arnegard series) are on small fans and terraces. Very poorly drained Argiaquolls (Parnell series) and poorly drained Argialbolls (Tonka series) are in kettle holes. Potential natural vegetation: This area supports natural prairie vegetation characterized by western wheatgrass, needleandthread, green needlegrass, and blue grama. Little bluestem is an important species on sloping and thin soils. Prairie cordgrass, northern reedgrass, and slim sedge are important species on wet soils. Western snowberry, stiff goldenrod, echinacea, and prairie rose are commonly interspersed throughout the area. 53B—Central Dark Brown Glaciated Plains North Dakota and South Dakota 44,980 km 2 (17,370 mi 2 ) Land use: Most of this area is in farms and ranches, and about two-thirds is cropland that is dry-farmed. Spring wheat is the chief crop, but flax, oats, barley, and alfalfa are grown on many farms. The more sloping soils are in range of native grasses. Elevation and topography: Elevation ranges from 500 to 600 m, increasing gradually from southeast to northwest. These nearly level to rolling till plains include areas of kettle holes, kames, moraines, and small glacial lakes. Moderately steep and steep slopes are adjacent to major stream valleys. Climate: Average annual precipitation —350 to 425 mm. More than half of the precipitation falls during the growing season. Winter precipitation is snow. Average annual temperature —1 to 7°C. Average freeze-free period —110 to 130 days. Water: In most years moisture is inadequate for maxi¬ mum crop production. The Missouri River is the only dependable source of water for irrigation; therefore, only a small acreage is irrigated. There is a limited supply of ground water. In places, ponds are a source of water for livestock. Soils: Most of the soils are Borolls. They are deep, well drained, and medium textured and have a frigid temperature regime and mixed mineralogy. The nearly level and undulating Argiborolls (Williams and Bowbells series) are on till plains. Haploborolls (Zahl and Max series) are on steeper uplands. The nearly level to gently sloping Natriborolls (Noonan and Niobell se¬ ries) are scattered on till plains. Very poorly drained Argiaquolls (Parnell series) and poorly drained Argialbolls (Tonka series) are in kettle holes. Potential natural vegetation: This area supports natural prairie vegetation characterized by western wheatgrass, needleandthread, green needlegrass, and blue grama. Little bluestem is an important species on sloping and thin soils. Prairie cordgrass, northern reedgrass, and slim sedge are important species on wet soils. Western snowberry, stiff goldenrod, echinacea, and prairie rose are commonly interspersed throughout the area. 53C—Southern Dark Brown Glaciated Plains South Dakota 13,870 km 2 (5,350 mi 2 ) Land use: Most of this area is in farms and ranches, and slightly more than half is cropland that is dry- farmed. Winter wheat is the chief cash crop. Corn, grain, sorghum, oats, and alfalfa are grown on many farms. The more sloping soils are in range. Elevation and topography: Elevation ranges from 400 to 700 m. These nearly level to gently rolling till plains include many areas of potholes. Moderately steep and steep slopes are adjacent to major valleys. Climate: Average annual precipitation —425 to 475 mm. More than half of the precipitation falls during the growing season. Precipitation in winter is snow. Average annual temperature —7 to 9°C. Average freeze-free period —130 to 150 days. Water: In most years, moisture is inadequate for maximum crop production. The Missouri River is the only dependable source of water for irrigation; there¬ fore, irrigated cropland is mostly confined to a nar¬ row band along its valley. There is a limited supply of ground water. Most water for livestock comes from dug ponds. Soils: Most of the soils are Ustolls. They are deep, well drained, and medium textured and have a mesic temperature regime and mixed mineralogy. The nearly level to moderately sloping Argiustolls (Highmore, Eakin, and Glenham series) are on uplands, and other Argiustolls (Mobridge and Onita series) are in swales. Natrustolls (Cavo, Demky, and Jerauld series) also are on uplands. Ustorthents (Betts series) are on the steeper parts of the landscape, and Natraquolls (Hoven series) are in upland depressions. Potential natural vegetation: This area supports natural prairie vegetation. Western wheatgrass, blue grama, needleandthread, and green needlegrass are dominant species. Little bluestem and prairie sandreed are important species on steeper sites. Western 36 snowberry and prairie rose are commonly interspersed thoughout the area. 54—Rolling Soft Shale Plain Montana, North Dakota, and South Dakota 58,100 km 2 (22,430 mi 2 ) Land use: Nearly all this area is in farms and ranches. In most places agriculture is a combination of live¬ stock production and cash grain farming. About three-fifths of the area is in native grasses and shrubs that are grazed. The less sloping soils, making up about one-third of the total area, are dry-farmed. Wheat, other small grains, feed grains, hay, silage corn, and flax are the principal crops. Small tracts on the bottom land along the Missouri River and a few of its larger tributaries are irrigated. Elevation and topography: Elevation is 500 m in the east and gradually slopes to about 1,100 m in the west. This moderately dissected rolling plain is un¬ derlain by soft calcareous shale, siltstone, and sand¬ stone. Maximum local relief is about 100 m but is considerably less in most of the area. Buttes, badland, and moderately steep and steep slopes are adjacent to major valleys. The northern and eastern parts have a glacially modified topography and in some places are covered by thin layers of glacial drift. Climate: Average annual precipitation —325 to 450 mm. Most of the precipitation falls during the grow¬ ing season. Precipitation in winter is snow. Average annual temperature —4 to 7°C. Average freeze-free period —110 to 135 days. Water: In most years the supply of moisture is inade¬ quate for maximum crop production. Water for irri¬ gation is available in quantity only from the Missouri River and a few of its larger tributaries. Water for livestock is stored in small reservoirs on uplands. A small area of sand and gravel yields moderate quanti¬ ties of ground water. Ground water is scarce or is lacking in areas underlain by shale. Soils: Most of the soils are Borolls. They are moder¬ ately deep and deep, well drained and moderately well drained, and loamy and clayey. These soils have a frigid temperature regime and mixed mineralogy. The nearly level to rolling Haploborolls (Vebar and Chama series) and Argiborolls (Morton series) are on sedimentary uplands. The more sloping, shallow Ustorthents (Cabba series) and Ustipsamments (Flasher series) are on sedimentary uplands. The nearly level and gently sloping Natriborolls (Rhoades and Belfield series) are on sedimentary uplands and alluvial fans and terraces. The nearly level to gently sloping Argiborolls (Williams and Vida series) are on till-mantled sedimentary uplands in the northern and eastern parts of the area. Ustochrepts (Cherry se¬ ries) and Ustorthents (Lambert series) are on fans, terraces, and foot slopes. Potential natural vegetation: This area supports natural prairie vegetation. Western wheatgrass, blue grama, needleandthread, and green needlegrass are dominant species. Prairie sandreed and little blue- stem are important species on the very shallow soils. Buffaloberry, chokecherry, and prairie rose are com¬ mon in draws and narrow valleys. 55A—Northern Black Glaciated Plains North Dakota 32,240 km 2 (12,450 mi 2 ) Land use: Nearly all this area is in farms and ranches, and about 80 percent is cropland that is dry-farmed. Cash-grain wheat production is the principal enter¬ prise on many farms, but other cash grains, feed grains, hay, flax, and sunflowers also are grown. The more sloping and thinner or sandy soils are in native range. About 3 percent of this area is forested. Elevation and topography: Elevation ranges from 300 to 700 m, increasing from east to west. These mostly nearly level to undulating till plains include areas of kettle holes, kames, and moraines. Also in the area are glacial lake plains and some steep slopes adjacent to streams. Climate: Average annual precipitation —375 to 450 mm. More than half of the precipitation falls during the growing season. Precipitation in winter is snow. Average annual temperature —3 to 4°C. Average freeze-free period —100 to 120 days. Water: In most years precipitation is inadequate for maximum crop production. The few perennial streams are widely spaced and are little used for irrigation. Water for livestock is stored in ponds and small reservoirs on individual farms and ranches. Ground water is plentiful in glacial drift, but the water is hard. Sandstone underlying part of the area yields large quantities of highly mineralized artesian water, but the shale yields very little water. Soils: Most of the soils are Borolls and Aquolls. They are deep, well drained to poorly drained, and sandy, loamy, and clayey and have a frigid temperature regime and mixed mineralogy. The nearly level and undulating Haploborolls (Barnes, Svea, Gardena, and Hecla series) are on till plains and glacial lake plains. Very poorly drained Argiaquolls (Parnell series) and Argialbolls (Tonka series) are in kettle holes. The sloping to steep Haploborolls (Buse series) are on till plains. Argiborolls (Bottineau and Kelvin series) are on till plains in the forested areas. Potential natural vegetation: This area supports natural prairie vegetation characterized by western wheatgrass, needleandthread, green needlegrass, and blue grama. Little bluestem is an important species on sloping and thin soils. Prairie cordgrass, northern reedgrass, big bluestem, and slim sedge are impor¬ tant species on wet soils. Western snowberry and prairie rose are commonly interspersed throughout 37 the area. A small part of the area can support forest vegetation characterized by oak and aspen. 55B—Central Black Glaciated Plains North Dakota and South Dakota 52,480 km 2 (20,260 mi 2 ) Land use: Nearly all this area is in farms and ranches, and about 70 percent is cropland that is dry-farmed. Cash-grain wheat production is the principal enter¬ prise on many farms. Other small grains, feed grains, hay, flax, and sunflowers are also grown. About one-fourth of the area, consisting of the more sloping and thinner soils, is native range and some woodland. Elevation and topography: Elevation ranges from 300 to 600 m, increasing from east to west. Most of this area is nearly level to undulating till plains that include areas of kettle holes, kames, and moraines. Glacial lake plains and some steep slopes are adjacent to streams. Climate: Average annual precipitation —400 to 500 mm. More than half of the precipitation falls during the growing season. Precipitation in winter is snow. Average annual temperature —4 to 7°C. Average freeze-free period —120 to 140 days. Water: In most years precipitation is inadequate for maximum crop production. Perennial streams are few and widely spaced and are little used for irriga¬ tion. Water for livestock is stored in ponds and small reservoirs on individual farms and ranches. Ground water is plentiful in glacial drift, but the water is hard. Sandstone underlying part of the area yields large quantities of highly mineralized artesian water, but the shale yields very little water. Soils: Most of the soils are Borolls. They are deep, well drained and moderately well drained, and sandy to clayey and have a frigid temperature regime and mixed mineralogy. The nearly level and undulating Haploborolls (Barnes, Svea, Emrick, Heimdal, and Aastad series) and Argiborolls (Forman series) are on till plains. The nearly level Haploborolls (Gardena and Hecla series) and Natriborolls (Aberdeen series) are on glacial lake plains. The sloping to steep Haploborolls (Buse series) are on till plains. Very poorly drained Argiaquolls (Parnell series) are in kettle holes. Potential natural vegetation: This area supports natural prairie vegetation characterized by western wheatgrass, needleandthread, green needlegrass, and blue grama. Little bluestem is an important species on sloping and thin soils. Prairie cordgrass, northern reedgrass, big bluestem, and slim sedge are impor¬ tant species on wet soils. Western snowberry and prairie rose are commonly interspersed throughout the area. 55C—Southern Black Glaciated Plains South Dakota 20,240 km 2 (7,810 mi 2 ) Land use: Nearly all this area is in farms and ranches, and about 70 percent is cropland that is dry-farmed. Corn, small grains, and alfalfa are the principal crops. Grain sorghum is also grown. About one- fourth of the area, consisting of the steeper sloping soils, is in native range and tame pasture. Elevation and topography: Elevation ranges from 400 to 600 m. Most of the area is nearly level to undulating till plains with potholes and moraines. Steep slopes are adjacent to the major streams. Climate: Average annual precipitation —450 to 525 mm. More than half of the precipitation falls during the growing season. Precipitation in winter is snow. Average annual temperature —7 to 9°C. Average freeze-free period —130 to 155 days. Water: In most years precipitation is inadequate for maximum crop production. Perennial streams are few and widely spaced and are little used for irriga¬ tion. Water for livestock is stored in ponds and small reservoirs on individual farms and ranches. Sand¬ stone underlying part of the area yields large quan¬ tities of highly mineralized artesian water, but the shale yields very little water. Water from reser¬ voirs on the Missouri River is used for irrigation on the adjacent upland soils. Soils: Most of the soils are Ustolls. They are deep, well drained and moderately well drained, and sandy to clayey. These soils have a mesic temperature regime and mixed mineralogy. The nearly level to moder¬ ately sloping Argiustolls (Houdek and Prosper se¬ ries), Haplustolls (Clarno, Ethan, and Bonilla series), and Natrustolls (Dudley, Jerauld, and Stickney se¬ ries) are on till plains. Ustorthents (Betts series) occupy the steeper parts of the landscape, and Argialbolls (Tetonka series) are in upland depres¬ sions. Potential natural vegetation: This area supports natural prairie vegetation characterized by western wheatgrass, green needlegrass, needleandthread, and porcupinegrass. Big bluestem is an important species on soils with restricted drainage. Prairie cordgrass, northern reedgrass, and western wheatgrass are dominant on the poorly drained and very poorly drained soils. 5(i—Red River Valley of the North Minnesota, North Dakota, and South Dakota 41,230 km 2 (15,920 mi 2 ) Land use: Nearly all this area is in farms and ranches, and about 80 percent is cropland that is dry-farmed. Important cash crops are spring wheat, soybeans, potatoes, sugar beets, and corn. Some oil-producing crops and edible beans are grown. On some farms, 38 feed grains and forage for dairy cattle are the princi¬ pal crops. Nearly 10 percent of the area in the northeast is wooded. Elevation and topography: Elevation is 300 m, decreasing gradually to 200 m in the north. This nearly level glacial lake plain is bordered on the east by outwash, gravelly beaches, and dunes. Climate: Average annual precipitation —475 to 550 mm. More than half of the precipitation falls during the growing season. Precipitation in winter is snow. Average annual temperature —2 to 7°C, decreasing from south to north. Average freeze-free period —105 to 135 days. Water: Efficient use of water is a major concern of management. In years of normal precipitation, mois¬ ture is sufficient for commonly grown crops. In some places drainage systems are needed so that farming operations can be started when the temperature is favorable. Soils: Most of the soils are Aquolls. They are deep, somewhat poorly drained and poorly drained, and sandy to clayey and have a frigid temperature re¬ gime. Calciaquolls (Bearden, Hegne, Glyndon, and Ulen series), Haplaquolls (Fargo series), and Hap- loborolls (Gardena and Embden series) are on the glaciolacustrine plains. Potential natural vegetation: This area supports natural prairie vegetation characterized by little blue- stem, big bluestem, switchgrass, and indiangrass. Bur oak, American basswood, American elm, eastern cottonwood, green ash, and willows grow in drain- ageways. Shrubs include American plum, common chokecherry, skunkbush sumac, and western snow- berry. 39 G—WESTERN GREAT PLAINS RANGE AND IRRIGATED REGION 564,490 km 2 (217,950 mi 2 ) This section of the Great Plains is rolling upland. The soils are underlain by clay shale, siltstone, soft sandstone, and (locally) thick alluvium. The average annual precipitation ranges from 275 to 600 mm but fluctuates widely from year to year. The average annual temperature ranges from 7°C in the north to 16°C in the south. The freeze-free period ranges from 100 days in the north to 200 days in the south. Ustolls are dominant throughout much of the region, but Argids are common in the west and in the south. Orthents on dissected slopes, Psamments in sandy areas, and Fluvents on flood plains are also extensive. Usterts in heavy clays are important locally. The major part of this region is in range. Some wheat is dry-farmed, mainly along the eastern margin. Irrigation, particularly sprinkler, is increasingly practiced. Feed grain for livestock is the principal crop grown on the irrigated land. Potatoes, sugar beets, corn, and vegetables are important locally. 58A—Northern Rolling High Plains, Northern Part Montana and Wyoming 105,620 km 2 (40,780 mi 2 ) Land use: Most of this area consists of privately owned ranches. The remainder is federally owned. Most of it is in native grasses and shrubs grazed by cattle and sheep. The rest is mainly dry-farmed to wheat. Narrow strips of land along the Yellowstone River and its main tributaries are irrigated. Sugar beets, alfalfa, other hay crops, and corn for silage are the principal crops. Some of the land is in tame pasture. The upper slopes and tops of some of the higher buttes and mountains are open woodland. Elevation and topography: Elevation generally ranges from 900 to 1,800 m, increasing from east to west and from north to south, but in a few mountains it is as high as 2,100 m. These dissected plains are underlain by shale, siltstone, and sandstone. Slopes are mostly gently rolling to steep, and wide belts of steeply sloping badland border a few of the larger river valleys. Local relief is mainly in meters to tens of meters. In places, flat-topped, steep-sided buttes rise sharply above the general level of the plains. Climate: Average annual precipitation —300 to 500 mm in most of the area and as much as 750 mm in the mountains, but it fluctuates widely from year to year. Maximum precipitation is in spring and early in autumn. Precipitation in winter is snow. Average annual temperature —4 to 7°C. Average freeze-free period —120 to 140 days. Water: The low and erratic precipitation is the princi¬ pal source of water for agriculture. Water for live¬ stock is stored in small reservoirs, but supplies are inadequate for significant irrigation. Irrigation water in quantity is available only along the Yellowstone River and one or two of its larger tributaries. Ground water is scarce in most of the area, but locally sand and gravel deposits and coal beds yield small to moderate amounts. Soils: Most of the soils are Orthents, Orthids, Argids, Borolls, and Fluvents. They are medium textured to fine textured, shallow to deep, and mainly well drained. Most of these soils have a frigid temperature regime, but soils in some wide river valleys, such as the Yellowstone River Valley, have a mesic tempera¬ ture regime. The nearly level to steep Torriorthents (Lisam, Cabbart, and Lambeth series), Camborthids (Yamac, Lonna, and Cambeth series), Calciorthids (Crago and Cargill series), Haplargids (Bonfri se¬ ries), Natrargids (Absher series), and Argiborolls (Tanna, Ethridge, and Evanston series) are on sedi¬ mentary uplands, fans, terraces, and foot slopes. The nearly level Torrifluvents (Havre and Glendive se¬ ries) are on flood plains and low stream terraces. Potential natural vegetation: This area supports grassland vegetation. Western wheatgrass, bluebunch wheatgrass, green needlegrass, and needleandthread are dominant species. In the eastern part of the area, little bluestem replaces bluebunch wheatgrass as the dominant species. 58B—Northern Rolling High Plains, Southern Part Montana and Wyoming 50,810 km 2 (19,620 mi 2 ) Land use: More than two-thirds of this area is in ranches. Most of the remainder is federally owned. Nearly 80 percent of the area is in native grasses and shrubs grazed by cattle and sheep. Gently sloping deep soils, making up about 4 or 5 percent of the area, are dry-farmed to wheat. Narrow strips of land along the Tongue, Powder, and Platte Rivers and some of their tributaries are irrigated. Alfalfa, other hay crops, and feed grains are the principal crops. Some tracts are in tame pasture. The upper slopes and tops of some of the higher buttes and mountains are open woodland. Elevation and topography: Elevation generally ranges from 900 to 1,800 m, increasing gradually from north 40 to south, but in a few buttes it is as high as 2,100 m. These dissected plains are underlain by shale and sandstone. Slopes are mostly gently rolling to steep, and wide belts of steeply sloping badland border a few of the larger river valleys. Local relief is mainly in tens of meters. In places, flat-topped, steep-sided buttes rise sharply above the general level of the plain. Climate: Average annual precipitation —300 to 475 mm in most of the area but it fluctuates widely from year to year. Maximum precipitation is in spring and early in autumn. Precipitation in winter is snow. Average annual temperature —7 to 9°C. Average freeze-free period —100 to 130 days. Water: The low and erratic precipitation is the princi¬ pal source of water for agriculture. Water for live¬ stock is stored in small reservoirs, but supplies are inadequate for significant irrigation. Irrigation water in quantity is available only along the major rivers and some of their larger tributaries. Ground water is scarce in most of the area, but in places, sand and gravel deposits and coalbeds yield small to moderate amounts. Soils: Most of the soils are Orthents, Orthids, Argids, and Fluvents. They are moderately coarse textured to fine textured and mainly well drained and have a mesic temperature regime. The nearly level to steep, shallow 7 to deep Torriorthents (Kim, Thedalund, Samsil, Shingle, and Tassel series) and the nearly level to steep, moderately deep to very deep Haplargids (Cushman, Olney, Terry, and Vona series) are on sedimentary uplands. The nearly level to moderately sloping, moderately deep to very deep Camborthids (Zigweid and McRae series) and Paleargids (Bidman and Briggsdale series) are on alluvial fans, foot slopes, and terraces. The nearly level, deep Torri- fluvents (Haverson, Glenberg, and Bankard series) are on flood plains and low stream terraces. Potential natural vegetation: This area supports grassland vegetation. Rhizomatous wheatgrasses, green needlegrass, needleandthread, blue grama, and threadleaf sedge are dominant species on deep soils. Bluebunch wheatgrass and little bluestem are major species on shallow soils on hills and ridges. Basin wildrye, green needlegrass, rhizomatous wheat- grasses, and shrubs are dominant along bottom land and streams. Big sagebrush is the dominant shrub. 58C—Northern Rolling High Plains, Northeastern Part North Dakota 8,400 km 2 (3,240 mi 2 ) Land use: Most of this area is in ranches, and more than 80 percent is rangeland. Cow-calf operations are the principal livestock enterprise. Elevation and topography: Elevation ranges from 600 to 1,000 m. This area consists mainly of badland and moderately steep to steep slopes along the Little Missouri River and its tributaries. The Killdeer Moun¬ tains are also in this area. Climate: Average annual precipitation —350 to 400 mm. More than half the precipitation falls during the growing season. Precipitation in winter is snow. Average annual temperature —4 to 6°C. Average freeze-free period —110 to 120 days. Water: In most years, the supply of moisture is inade¬ quate for maximum crop production. The Little Mis¬ souri River is the principal source of surface water. Ground water is scarce or is lacking in areas under¬ lain by shale. Water for livestock is stored in ponds. Soils: Most of the soils are Orthents. They are shallow and well drained to excessively drained and have a frigid temperature regime and mixed mineralogy. The moderately steep to very steep Torriorthents (Cabbart series) and Torripsamments (Fleak and Zeona series) and areas of badland are on strongly dissected sedimentary uplands. Potential natural vegetation: This area supports natural prairie vegetation characterized by western wheatgrass, blue grama, little bluestem, and prairie sandreed. Rocky Mountain juniper, green ash, and quaking aspen are important species on some north¬ facing slopes. Silver sagebrush is common on bottom lands. 58D—Northern Rolling High Plains, Eastern Part North Dakota and South Dakota 10,000 km 2 (3,860 mi 2 ) Land use: More than four-fifths of this area is in ranches. Most of the remainder is state and federally owned. Most of the area is in native grasses and shrubs grazed by cattle and sheep. Gently sloping, deep and moderately deep soils, making up 10 to 15 percent of the area, are dry-farmed to wheat and alfalfa. Some tracts are in tame pasture. The upper slopes and tops of some of the higher buttes are open woodland. Elevation and topography: Elevation ranges from 700 to 1,000 m, increasing gradually from east to west. These dissected plains are underlain by shale and sandstone. Slopes are mostly gently rolling to steep. Local relief is mainly between 25 and 100 m. In places flat-topped, steep-sided buttes rise sharply above the general level of the plain. Climate: Average annual precipitation —325 to 375 mm in most of the area, but it fluctuates widely from year to year. Maximum precipitation is in spring and early in summer. Precipitation in winter is snow. Average annual temperature —4 to 7°C. Average freeze-free period —120 to 130 days. Water: The low and erratic precipitation is the princi¬ pal source of water for agriculture. Water for live¬ stock is stored in small ponds or dugouts. Some wells provide water for livestock. 41 Soils: Most of the soils are Orthents, Orthids, Argids, and Borolls. They are medium textured to fine textured and mainly well drained and have a frigid tempera¬ ture regime. Nearly level to steep, shallow Torri- orthents (Blackhall and Cabbart series) and nearly level to steep, moderately deep Camborthids (Twi¬ light series) are on uplands. Nearly level to moder¬ ately sloping, deep and moderately deep Natrargids (Absher, Archin, Bullock, and Parchin series) are on alluvial fans, terraces, and uplands. Nearly level to strongly rolling, moderately deep and deep Argiborolls (Assinniboine, Evanston, and Marmarth series) are on uplands. Nearly level to rolling Torripsamments (Tusler and Zeona series) are on uplands. Torrifluvents (Glendive, Hanly, and Havre series) are on flood plains and low stream terraces. Potential natural vegetation: This area supports natural mixed prairie vegetation characterized by western wheatgrass, green needlegrass, blue grama, and buffalograss. Little bluestem and sideoats grama grow on shallow soils. The upper slopes and tops of some of the higher buttes are in open ponderosa pine woodland. Silver and big sagebrush grow on clayey soils in the west. 60A—Pierre Shale Plains and Badlands Nebraska, South Dakota, and Wyoming 23,600 km 2 (9,110 mi 2 ) Land use: Practically all this area is in farms and ranches. Most of it is in native grasses and is used for grazing livestock. Some small nearly level to moder¬ ately sloping tracts are farmed to winter wheat or are used for producing feed crops for livestock. The Badlands National Monument is a large tourist at¬ traction. Elevation and topography: Elevation is generally 800 to 1,100 m on uplands but ranges to 1,300 m. These shale plains have long, smooth slopes and are mostly gently sloping to strongly sloping. Along drainages and streams, slopes are moderately steep to steep. The Badlands consist of eroded walls and escarpments, small grass-covered tableland and mesas, and basins in which there are scattered eroded buttes. Slopes range from nearly level to very steep. This area is cut by many drainages and gullies. Climate: Average annual precipitation —300 to 400 mm. Most of the precipitation falls during the grow¬ ing season. Precipitation in winter is mainly snow that usually is accompanied by high winds that cause much drifting. Average snowfall is about 60 to 90 cm. Average annual temperature —7 to 9°C. Average freeze-free period —130 to 150 days. Water: Because of the limited precipitation, production of cultivated crops is marginal. Most of the soils are moist or wet early in spring and are deficient in moisture during much of the growing season. Water for livestock comes mainly from runoff that flows into dams. Few places have shallow-water wells for do¬ mestic use. Soils: Most of the soils are Orthids. They are moder¬ ately deep and deep and fine textured and have a mesic temperature regime and montmorillonitic min¬ eralogy. Nearly level to moderately sloping Cambor¬ thids (Kyle, Pierre, Swanboy, and Winler series) are on shale uplands. Shallow Torriorthents (Ennings, Lismas, Midway, and Samsil series) are on steeper slopes. Nearly level to gently undulating, deep and moderately deep, medium textured Argiustolls (Manter, Nunn, Satantz, Tuthill, Keith, and Richfield series) are on terraces and uplands. Shallow Torrior¬ thents (Epping, Imlay, and Orella series) and Camborthids (Bufton and Conata series) are in the Badlands. Torrifluvents (Glenberg, Haverson, and Lohmiller series) are on the bottom land of major streams. Potential natural vegetation: This area supports natural mixed prairie vegetation characterized by western wheatgrass, green needlegrass, blue grama, and buffalograss. Little bluestem and sideoats grama grow on the shallow soils. Big bluestem grows along streams, especially where an effective water table is present. Sand sagebrush grows on sandy soils and silver sagebrush on clayey soils in the west. The eroded walls and escarpments of the Badlands are devoid of vegetation. 60B—Pierre Shale Plains, Northern Part Montana 5,600 km 2 (2,160 mi 2 ) Land use: Practically all this area is in farms and ranches. Most of it is rangeland used for grazing livestock. Some small nearly level to moderately sloping tracts are farmed to winter wheat or are used for growing feed crops for livestock. Elevation and topography: Elevation ranges from 900 to 1,000 m on uplands. These shale plains have long, smooth, gentle to strong slopes. Slopes along drainageways and streams are moderately steep to steep. Climate: Average annual precipitation —300 to 350 mm. Most of the precipitation falls during the grow¬ ing season. Precipitation in winter is mainly snow, which usually is accompanied by high winds that cause much drifting. Average annual temperature —6 to 7°C. Average freeze-free period —110 to 125 days. Water: Because of the limited precipitation, the grow¬ ing of cultivated crops is marginal. Most of the soils are moist or wet early in spring and are deficient in moisture during much of the growing season. Water for livestock comes mainly from runoff that flows into dams. Soils: The dominant soils are Orthids and Orthents. They are moderately deep and deep and fine textured 42 and have a frigid temperature regime and montmoril- lonitic mineralogy. Nearly level to moderately slop¬ ing Camborthids (Abor, Bascovy, and Bickerdyke series) are on shaly uplands. Shallow Torriorthents (Dilts, Lisam, and Yawdim series) are on steeper slopes. Torrifluvents (Harlem series) are on the bottom land of major streams. Potential natural vegetation: This area supports natural mixed prairie vegetation characterized by western wheatgrass, green needlegrass, and blue grama. Little bluestem and sideoats grama grow on shallow soils. 61—Black Hills Foot Slopes South Dakota and Wyoming 8,400 km 2 (3,240 mi 2 ) Land use: Most of this area is in farms and ranches. Native grass is used mainly for livestock grazing. Some of the less sloping parts are farmed mainly to alfalfa and small grains for livestock feed. Ponderosa pine grows in some parts marginal to the Black Hills. Elevation and topography: Elevation is mainly 900 to 1,200 m but ranges to 1,700 m. Slopes are mostly hilly to steep. Drainages are well defined. Climate: Average annual precipitation —375 to 450 mm. Most of the precipitation falls during the grow¬ ing season. Average snowfall in winter is 60 to 100 cm. Average annual temperature —6 to 9°C. Average frost-free period —110 to 140 days. Water: Crop production is marginal because of the limited precipitation. Most of the soils suitable for cultivation are dry during much of the growing season. Domestic water is provided mostly by flow¬ ing streams, shallow wells, and springs. Soils: Most of the soils are Orthents. They are deep to shallow and fine textured to medium textured and have a mesic temperature regime. The medium textured soils have mixed mineralogy, and the fine textured soils have montmorillonitic mineralogy. Loamy Torriorthents (Butche, Canyon, Enning, Nevee, and Spearfish series) are on the steeper landscapes and clayey Torriorthents (Grummit series) on the smoother landscapes. Eutroboralfs (Lakoa and Maitland se¬ ries) are on the edge of the Black Hills. The nearly level to moderately sloping, deep Haplustolls (Tilford series) and Argiustolls (Vale series) are in areas in the “redbed valley.” Potential natural vegetation: This area supports open grassland, forest, and savanna vegetation. The grassland is characterized by little and big bluestem, green needlegrass, western wheatgrass, and needle- andthread. Ponderosa pine grows in scattered open forest stands. Bur oak grows throughout the area, and in places it grows in nearly pure stands. Quaking aspen and eastern hophombeam are scattered through¬ out the forests. Scattered green ash and American elm grow along with big bluestem along stream bottoms. 62—Black Hills South Dakota and Wyoming 9,200 km 2 (3,550 mi 2 ) Land use: Most of this area is in the Black Hills National Forest. The Black Hills area, an important tourist attraction, is used for mining, recreation, and hunting. Small farms and ranches, rural homes, and summer homes on small acreages are scattered throughout. Some timber is harvested. Small ranches and farms depend on the Black Hills National Forest for summer grazing. Elevation and topography: Elevation is mainly 1,100 to 2,000 m, but it is 2,200 m on Harney Peak. Slopes range from moderate on some of the high plateaus to very steep along drainageways and on peaks and ridges. Narrow valleys are mostly gently sloping to strongly sloping. Climate: Average annual precipitatioyi —450 to 650 mm. Precipitation in winter is mostly snow that ranges from about 150 cm at lower elevations to as much as 360 cm at higher elevations. Average annual temperature —3 to 7°C. Average freeze-free period —80 to 130 days. Water: Precipitation, perennial streams, springs, and shallow wells provide adequate water for domestic use. In most years soil moisture is adequate for normal plant growth. Soils: Most of the soils are Boralfs. They have a frigid or cryic temperature regime and montmorillonitic mineralogy. Eutroboralfs (Citadel series), Haploborolls (Paunsaugunt series), and Eutrochrepts (Vannocker series) are at lower elevations, and Cryoboralfs are at higher elevations. Potential natural vegetation: This area supports open to dense forest vegetation. Ponderosa pine is the dominant species. Black Hills spruce grows at higher elevations and along major drainageways. Paper birch and quaking aspen are on sites that have been burned over by wildfire. Kentucky bluegrass, poverty oatgrass, Richardson needlegrass, and Can¬ ada wildrye are common under open forest stands. 63A—Northern Rolling Pierre Shale Plains South Dakota 29,610 km 2 (11,430 mi 2 ) Land use: Most of this area is in farms and ranches. Urban expansion is limited. The area is used mainly for livestock production and cash-grain farming. Al¬ falfa, sorghum, and hay are the principal crops grown for livestock feed. Winter wheat is the main cash crop. Dry-farming soils not suited to cultivation is destroying the native grassland. 43 Elevation and topography: Elevation ranges from 400 to 500 m on the bottom land of the Missouri River to 500 to 900 m on the shale plain uplands. The areas that are cropped are mainly at elevations of about 500 to 800 m. These areas are nearly level to rolling and have long smooth slopes and a well-defined dendritic drainage system. River and creek valleys have smooth floors and steep walls. Climate: Average annual precipitation —375 to 475 mm. Most of the precipitation falls during the grow¬ ing season. Precipitation in winter is mostly snow. Average annual temperature —7 to 9°C. Average freeze-free period —130 to 160 days. Water: In most years precipitation is inadequate for maximum plant growth. The reservoirs on the Mis¬ souri River are prominent features on the eastern border. There are few shallow-water developments, and most water for livestock comes from surface runoff that flows into dams or from deep artesian flows. Soils: Most of the soils are Ustolls and Orthents. They are fine textured and very fine textured and have a mesic temperature regime and montmorillonitic min¬ eralogy. The nearly level to rolling, well drained, moderately deep and deep Haplustolls (Promise and Boyd series), Argiustolls (Millboro and Reliance se¬ ries), Camborthids (Swanboy series), and Ustochrepts (Boro, Lakoma, and Labu series) are on uplands. Shallow Ustorthents (Okaton and Sansarc series) are on the steeper slops. Poorly drained Haplaquolls (Rolls series) are in upland depressions. Potential natural vegetation: This area supports a transition between mixed and true prairie vegeta¬ tion. Green needlegrass, western wheatgrass, needle- andthread, porcupinegrass, little bluestem, and big bluestem are the major species. The bluestems and sideoats grama are dominant on the thin and shallow soils. Bur oak, buffaloberry, and prairie rose are common on slopes along the major streams. 63B—Southern Rolling Pierre Shale Plains South Dakota and Nebraska 28,400 km 2 (10.970 mi 2 ) Land use: Most of this area is in farms and ranches. Urban expansion is limited. The area is used mainly for livestock production and cash-grain farming. Al¬ falfa, sorghum, and hay are the principal crops grown for livestock feed. Winter wheat, grain sorghum, and corn are the main cash crops. Elevation and topography: Elevation ranges from 400 to 500 m on the bottom land of the Missouri River to 400 to 600 m on the shale plain uplands. The areas that are cropped are mainly at elevations of about 500 m. These areas are nearly level to rolling and have long smooth slopes and a well-defined dendritic drain¬ age system. Rivers and creek valleys have smooth floors and steep walls. Climate: Average annual precipitation —475 to 600 mm. Most of the precipitation falls during the grow¬ ing season. Precipitation in winter is mostly snow. Average annual temperature —8 to 10°C. Average freeze-free period —135 to 160 days. Water: In most years precipitation is inadequate for maximum plant growth. The reservoirs on the Mis¬ souri River are prominent features on the eastern border. There are few shallow-water developments, and most water for livestock comes from surface runoff that flows into dams or from deep artesian flows. Soils: Most of the soils are Ustolls and Orthents. They are fine textured and very fine textured and have a mesic temperature regime and montmorillonitic min¬ eralogy. Nearly level to rolling, well drained, moder¬ ately deep and deep Haplustolls (Opal and Promise series), Camborthids (Pierre, Kyle, and Swanboy series), and Ustochrepts (Lakoma series) are on uplands. Shallow Ustorthents (Okaton and Sansarc series) and Torriorthents (Samsil series) are on the steeper slopes. Poorly drained Haplaquolls (Rolls series) are in upland depressions. Well drained Argiustolls (Canning and Ree series) are on isolated high terraces along rivers and creeks. Ustifluvents (Munjor series) and Torrifluvents (Glenerg and Haverson series) are on the bottom land of major streams. Potential natural vegetation: This area supports mixed prairie vegetation. Western wheatgrass, green needlegrass, and blue grama are the major species. Little bluestem and sideoats grama are dominant on the shallow soils. Buffaloberry, skunkbush sumac, and prairie rose are common on steep slopes along the major streams. 64—Mixed Sandy and Silty Tableland Nebraska, South Dakota, and Wyoming 28,400 km 2 (10,970 mi 2 ) Land use: Most of this area is in ranches and farms. About three-fifths of the area is rangeland grazed primarily by livestock. The scenic Pine Ridge, an escarpment extending in a general east-west direc¬ tion in the north-central part of the area, has grassed areas and pine trees of commercial value. Nearly one-third of the area is cropland. South of Pine Ridge, the major enterprise is cash-grain farming, and winter wheat is the main crop. In other parts of the area, feed and forage for livestock are the main crops. Corn and sugar beets are irrigated crops in places where the supply of water is adequate and the soils are suitable. Elevation and topography: Elevation ranges from 900 to 1,200 m, increasing gradually from east to 44 west. The nearly level to gently sloping tableland south of the narrow, steep-walled valleys of Pine Ridge has the highest elevation. The topography north of the Pine Ridge escarpment is strongly sloping but becomes less sloping as distance from the escarpment increases. Local relief is mainly in me¬ ters, but at Pine Ridge relief is in tens of meters. Climate: Average annual precipitation —375 to 450 mm. Maximum precipitation is during the freeze-free period. Precipitation in winter is snow. Average annual temperature —7 to 9°C. Average freeze-free period —About 140 days. Water: Most of the area depends on the rather low and erratic precipitation for water. Ground water is scarce and of poor quality in most of the area. Locally, mainly south of Pine Ridge, underground sand and gravel yield moderate to large quantities of good- quality water. Soils: Most of the soils are Ustolls. They are medium textured and formed in loess or in alluvium. They have a mesic temperature regime and mixed miner¬ alogy. The nearly level to strongly sloping, deep Argiustolls (Alliance, Kadoka, Keith. Manter, Rich¬ field, and Rosebud series) are on uplands. The nearly level to steep, deep Haplustolls (Bridget series) are on foot slopes. Shallow Torriorthents (Canyon, Epping, Keota, and Tassel series) are on ridges and sides of upland drainageways. Deep sandy Torripsamments (Valent series) are in eolian sand deposits. Potential natural vegetation: This area supports a mixture of short, mid, and tall grasses. Blue grama, western wheatgrass, threadleaf sedge, sideoats grama, little bluestem, prairie sandreed, switchgrass, sand bluestem, and needleandthread are the major spe¬ cies. On Pine Ridge, these plants grow in association with ponderosa pine, eastern redcedar, western snowberry, skunkbush sumac, common chokecherry, and rose. 65—Nebraska Sand Hills Nebraska and South Dakota 56,810 km 2 (21,930 mi 2 ) Land use: Nearly all this area is in large ranches, most of which is in native grass grazed by livestock. Tracts along the streams and subirrigated valleys are used largely for hay, and the rolling hills and dry valleys are grazed. Use of sprinkler irrigation has increased in recent years. Corn is the principal irrigated crop. Elevation and topography: Elevation ranges from 600 to 1,200 m, increasing gradually from east to west. Most of this area consists of rolling to steep, irregular sand dunes stabilized by grass vegetation and of narrow elongated, nearly level to gently sloping valleys between the sand dunes. Sand dunes and narrow valleys commonly extend for several miles in a northwest-southeast direction. There are many scattered small, level depressions. Streams are few, but there are many small permanent and inter¬ mittent lakes. The height of the dunes ranges from meters to tens of meters. Climate: Average annual precipitation —425 to 575 mm. About three-fourths of the precipitation falls from midspring to midautumn. Precipitation in win¬ ter is snow. Average annual temperature —9 to 11°C. Average freeze-free period —140 to 150 days. Water: Precipitation is the source of water for range vegetation. The many small lakes, ponds, and a few streams provide water for livestock and for domestic requirements. Ground water is abundant and of good quality. In most places, water is available for irriga¬ tion. Soils: Most of the soils are Psamments. They are deep, sandy soils that formed in eolian sand. They have a mesic temperature regime, an ustic moisture regime, and mixed mineralogy. Excessively drained Usti- psamments (Valentine series) are on stabilized sand dunes. Well drained Haplustolls (Dunday series) are in the dry valleys. Somewhat poorly drained Haplustolls (Elsmere series) are in subirrigated valleys. Poorly drained and very poorly drained Haplaquolls (Gannett and Loup series) are in depressions between the dunes and along the bottom land of larger streams. Potential natural vegetation: This area supports mid and tall grass plant communities. Little blue¬ stem, sand bluestem, prairie sandreed, switchgrass, indiangrass, sand lovegrass, and needleandthread are major species on uplands. Big bluestem, switch- grass, indiangrass, prairie cordgrass, and various sedges and rushes grow on sites having a high water table. 66—Dakota-Nebraska Eroded Tableland Nebraska and South Dakota 12,400 km 2 (4,800 mi 2 ) Land use: Most of this area is in native grasses that are grazed by cattle. Some of the smoother parts of the area are used for growing crops, mainly corn, forage and grain sorghum, and alfalfa for livestock feed. In a few cultivated sections, winter wheat is grown as a cash crop. Elevation and topography: Elevation ranges from 600 to 900 m. The higher parts of the tableland are nearly level to moderately sloping, but steeper sec¬ tions are on the sides of ridges and drainageways. Drainages are well defined except in some undulating areas where eolian sandy materials mantle the bed¬ rock. Climate: Average annual precipitation —450 to 550 mm. Most of the precipitation falls during the grow¬ ing season. Precipitation in winter is mainly snow that ranges from about 60 to 100 cm. Average annual 45 temperature —8 to 10°C. Summers are hot, and win¬ ters are cold. Average freeze-free period —130 to 160 days. Water: The limited precipitation makes farming a risk, and maximum crop production is not expected in most years. The Niobrara River is the only perennial stream. Throughout most of the area, shallow water is available in quantities sufficient for livestock and domestic uses. Most soils are deficient in moisture during much of the latter part of the growing season. Soils: Most of the soils are Ustolls. They are moder¬ ately deep and deep, well drained and moderately well drained, and medium textured and moderately coarse textured. These soils have a mesic tempera¬ ture regime, an ustic moisture regime, and mixed mineralogy. The nearly level to sloping Argiustolls (Holt, Kadoka, Paka, Reliance, and Tuthill series) and Haplustolls (Anselmo and Vetal series) are on uplands. The moderately steep to steep Ustorthents (Okaton series) and Torriorthents (Tassel series) are on the sides of draws, on high ridges, and along drainageways. Deep sandy Haplustolls (Doger, Dunday, and Elsmere series) and Ustipsamments (Valentine series) are in areas of eolian deposits. Ustifluvents (Inavale series) and Fluventic Haplustolls (Cass series) are along the drainages. Potential natural vegetation: This area supports mixed prairie vegetation. Little bluestem, prairie sandreed, green needlegrass, and needleandthread are dominant species. Sideoats grama and plains muhly are important species on the shallow soils. Leadplant and prairie rose grow on the sides of draws. 67—Central High Plains Colorado, Nebraska, and Wyoming 74,410 km 2 (28,730 mi 2 ) Land use: Most of this area is in farms and ranches, but land near Denver and other cities along the western edge is being converted to urban use. About three-fifths is in range of native short and mid grasses grazed by cattle and sheep. About one-fourth is dry-farmed to wheat and other grains. An exten¬ sive acreage is irrigated. Corn, alfalfa, sugar beets, and vegetables are the major irrigated crops. Wet soils on flood plains are in meadows used for hay or pasture. Elevation and topography: Elevation ranges from 1,100 to 1,800 m, increasing gradually from east to west. These undulating to rolling plains have been moderately dissected by streams. Steep slopes bor¬ der the valleys of the larger streams and also the edges of isolated mesas. The dunes bordering some of the valleys have rolling to hilly irregular topogra¬ phy. Local relief is mainly in meters to tens of meters. Climate: Average annual precipitation —325 to 425 mm. Maximum precipitation is in midspring and late in autumn. Average annual temperature —7 to 10°C in most of the area, increasing to 13°C in the extreme south. Average freeze-free period —120 to 160 days in most of the area but as long as 180 days in the extreme south. Water: Water for range vegetation and dryfarming is provided by the low and erratic precipitation. In much of the area, sand and gravel yield adequate quantities of ground water for livestock and for domestic and other uses. In areas where shale bed¬ rock is near the surface, ground water is scarce and commonly of poor quality. Irrigation water is obtained mostly from the larger rivers, but locally wells pro¬ vide some irrigation water. Soils: Most of the soils are Ustolls and Argids. They are deep and medium textured and fine textured and have mixed or montmorillonitic mineralogy. They have an aridic moisture regime that is borderline to ustic and a mesic temperature regime. The nearly level to gently sloping, fine Paleustolls (Weld and Platner series) and loamy Haplargids (Fort Collins and Vona series) on uplands formed in eolian and alluvial materials under a cover of grass. Torriorthents, Haplustolls, and Argiustolls are the major included soils. Potential natural vegetation: This area supports short and mid grass prairie vegetation. Blue grama with pricklypear, buffalograss, western wheatgrass, threeawn, and sand dropseed are the major species. Cottonwood is common along the major drainage- ways. 69—Upper Arkansas Valley Rolling Plains Colorado 34,000 km 2 (13,130 mi 2 ) Land use: Nearly all this area is in farms and ranches. Almost three-fourths is in native short grasses used for grazing. Flood plains and terraces along the Arkansas River, making up 5 to 10 percent of the area, are irrigated. Alfalfa, sugar beets, grain sor¬ ghum, melons, seed crops, corn, small grains, onions, and other vegetables are the chief crops. Land that is flooded frequently and soils that are strongly affected by salts are used for grazing. Between 5 and 10 percent of the area is dry-farmed. Winter wheat, dry beans, and grain sorghum are the main crops. Elevation and topography: Elevation ranges from 1,100 to 1,900 m, increasing gradually from east to west. In many places, these undulating to rolling shale plains are mantled by loess or windblown sand, alluvium, and outwash. Wide bands of steep slopes border several of the larger tributaries of the Arkan¬ sas River. Local relief is mostly less than 25 m but is as much as 50 m in some of the rough broken areas. 46 Climate: Average annual precipitation —250 to 375 mm, but it fluctuates widely from year to year. Maximum precipitation is from midspring through late autumn. Average annual temperature —10°C. Average freeze-free period —140 to 160 days. Water: The low and erratic precipitation is the source of water for range vegetation. The Arkansas River and one or two of its larger tributaries provide water for irrigation along their valleys. In much of the area, ground water in the deeper sand and gravel provides water for livestock and for domestic uses, and locally it provides some water for irrigation. Ground water is scarce in a large part of the area where shale is near the surface. Soils: Most of the soils are Argids. They are deep and medium textured to fine textured. These soils have mixed or montmorillonitic mineralogy, an aridic mois¬ ture regime that is marginal to ustic, and a mesic temperature regime. The nearly level to gently slop¬ ing Haplargids (Baca, Wiley, and Olney series) are extensive on uplands. They formed in loess and local eolian deposits under short grass vegetation. Also extensive are shallow and moderately deep Torri- orthents that formed mainly on sedimentary rocks without a loess cover. Potential natural vegetation: This area supports short grass prairie vegetation. Blue grama with galleta, cholla, threeawn, ring muhly, and alkali sacaton are the major species. Cottonwood is com¬ mon along the major streams. Stony and rocky soils support a mixed stand of pinyon and juniper with understory species similar to those in nearby openings and grasslands. 70—Pecos-Canadian Plains and Valleys Colorado and New Mexico 84,830 km 2 (32,750 mi 2 ) Land use: Most of this area is in farms, ranches, or other private holdings. About 10 percent is federally owned. More than three-fourths of the area is in range, and cattle and sheep grazing is the principal enterprise. Some of the northern and eastern slopes of the high mesas in the north are covered by forest vegetation, but the total forested area is small. About 3 percent of the area is cropland. In places where moisture supplies are favorable, mainly in the west and north, the deeper soils are dry-farmed. Beans, small grains, and grain sorghum are the principal crops. Some hay is also grown, and some land is in pasture. Small tracts in some of the valleys and on the uplands are irrigated with water from wells and from reservoirs. Forage crops and feed grains are the principal crops. Elevation and topography: Elevation ranges from 1,200 to 2,100 m, increasing gradually from southeast to northwest, but it is 2,400 m on a few mesas and mountains. Most of these dissected high plains are gently sloping to rolling, but bands of steep slopes and rough broken land border the stream valleys. A few isolated mountains, mesas, and canyon walls have steep to very steep slopes. Valley floors are mostly narrow and cut by stream channels. Local relief is mainly in meters but is as much as 100 m in some of the rough broken areas. Climate: Average annual precipitation —300 to 400 mm, but it fluctuates widely from year to year. Maximum precipitation is from late in spring to early in autumn. Average annual temperature —10 to 16°C. Average freeze-free period —135 to 200 days, decreas¬ ing from southeast to northwest. Water: Water is scarce throughout the area because of the low and erratic precipitation and the few peren¬ nial streams. Ground water in deep sand and gravel in the north and from limestone in the southern two-thirds of the area provides water for domestic use and for livestock, and locally it provides water for irrigation. Ground water is scarce in areas where shale and sandstone are near the surface. Soils: Most of the soils are Orthids, Argids, and Ustolls. They are well drained and moderately fine textured to moderately coarse textured and have mixed mineralogy. In the north and in the west, these soils have a mesic temperature regime and in the south and in the east a thermic temperature regime. They have an ustic or aridic moisture re¬ gime. Deep Calciorthids (Harvey, Dean, Quay, and San Jon series on upland alluvial fans and Bascom series on uplands) are nearly level to strongly slop¬ ing. Shallow Calciorthids (Pinon series) on low lime¬ stone ridges and hills are strongly sloping to moder¬ ately steep. Deep Haplargids (Penistaja, Clovis, Witt, Tapia, Redona, and Canez series) on uplands are nearly level to undulating. Deep Camborthids (La Fonda, La Lande, and Ima series) on upland alluvial fans are level to moderately sloping. Argiustolls are deep (Rednun, La Brier, and Torreon series) and moderately deep (Carnero series) in depressions and on uplands and shallow (Bernal series) on mesa tops and upland ridges. Haplustolls are deep (Manzano and Colmor series) on valley floors and alluvial fans and shallow (Apache and Laporte series) on uplands. Shallow Calciustolls (Deama and Ector series) on limestone hills and ridges are strongly sloping to moderately steep. Paleorthids (Pastura and Blakeney series) and Paleargids (Douro series) are on uplands. Moderately sloping to steep, shallow Torriorthents (Travessilla and Penrose series) are on ridges, and deep Torriorthents (Lacita and Otero series) are on valley floors and uplands. Torrerts (Montoya series) are on valley floors. Potential natural vegetation: This area supports plains grassland vegetation that is dominantly short and mid grasses. Blue grama is the dominant species. 47 Western wheatgrass is the associated species in the northern part of the area. Lesser amounts of blue grama in association with black grama, galleta, New Mexico feathergrass, and a variety of shrubs, half shrubs, and forbs characterize the southern part. Scattered juniper and pinyon with an understory of sideoats grama, bottlebrush squirreltail, and western wheatgrass grow on shallow soils and in escarp¬ ments. Ponderosa pine grow T s on north and east slopes of the high mesas. 48 H—CENTRAL GREAT PLAINS WINTER WHEAT AND RANGE REGION 575,720 krrr (222,280 mi 2 ) The soils, topography, and climate in this region are more favorable for agriculture than those in the Great Plains to the north and west. A longer freeze-free season in the Central Great Plains permits a greater variety of crops to be grown. The average annual precipitation is 500 to 750 mm in much of this region but ranges from 375 to 900 mm, increasing from northwest to southeast. More rain falls during the summer than during the other seasons. The average annual temperature is 10 to 18°C, increasing from north to south. The freeze-free period is 170 to 180 days in most of this region but ranges from 140 to 240 days, increasing in length from north to south. Ustolls are the dominant soils. Orthents on steep slopes, Psamments in deep sands, and Fluvents on flood plains are common throughout the region. Cash-grain farming is the major agricultural enterprise on most of the better soils, and wheat is the principal crop. In the northern part along the Platte River, corn and alfalfa are grown extensively under irrigation. In the south, where the freeze-free period exceeds 200 days, cotton is grown extensively under irrigation. Irrigation water is obtained from wells. Steeply sloping, shallow, and sandy soils are used for range. 71—Central Nebraska Loess Hills Nebraska 26,220 km 2 (10,120 mi 2 ) Land use: Nearly all this area is in farms and ranches, and almost two-fifths is dry-farmed. About one-half of the area is in native grasses used for grazing. Winter wheat, grain sorghum, and alfalfa are the major dry-farmed cash crops. Between 5 and 10 percent of the area, consisting of flood plains and terraces along the Platte River and its larger tribu¬ taries, is irrigated. Corn, alfalfa, and seed crops are the principal irrigated crops. Alfalfa is commercially grown in the Platte River Valley. Vegetables are commercially grown on some of the mixed sandy and silty soils. Elevation and topography: Elevation ranges from 500 to 800 m, increasing from east to west. Nearly level to gently sloping loess-mantled narrow ridgetops are separated by steep slopes bordering drainage- ways. Some stream valleys have nearly level flood plains and large stream terraces. Nearly level soils on high stream terraces are in the southern part of the area in the Platte River Valley. Local relief is in meters to tens of meters. Climate: Average annual precipitation —500 to 625 mm. Most of the precipitation falls from spring through autumn, but the maximum is from late in spring to early in summer. Average annual tem¬ perature —About 11 to 12°C. Average freeze-free pe¬ riod —150 to 160 days, increasing from west to east. Water: In most of the area, the low erratic precipita¬ tion is the source of water for crops and native grasses. The larger rivers provide water for irriga¬ tion along their valleys. In much of the area, good- quality ground water is abundant for domestic and livestock needs and is used locally for irrigation. Gravity irrigation is practiced extensively on bottom lands and stream terraces of the Platte River and other larger streams. Soils: Most of the soils are Ustolls. They are deep silty soils that formed in loess. They have a mesic temper¬ ature regime, an ustic moisture regime, and mixed mineralogy. The nearly level to strongly sloping Argiustolls (Holdrege series) are extensive on ridgetops. Steep, silty Ustorthents (Coly series) are on breaks along drainageways. Argiustolls (Hall se¬ ries) and Haplustolls (Hord series) are on stream terraces. Ustifluvents (Hobbs series) are extensive on flood plains. Fine sandy loam Haplustolls (Anselmo series) are in the zone transitional to the Sand Hills. Potential natural vegetation: This area supports short, mid, and tall grass plant communities on the uplands. Big bluestem, little bluestem, switchgrass, indiangrass, sideoats grama, blue grama, and west¬ ern wheatgrass are major species on silty soils. Needleandthread, prairie sandreed, sand bluestem, little bluestem, and blue grama are major species on sandy soils. 72—Central High Tableland Colorado, Kansas, and Nebraska 77,220 km 2 (29,810 mi 2 ) Land use: Nearly all this area is in farms and ranches, and three-fifths or more is cropland. This is a major dryfarming area. Winter wheat is the main cash crop, but large acreages are planted to other small grains, grain sorghum, alfalfa, and other hay crops. Many crops are grown on the narrow bands of irrigated land along the Platte, Republican, and Arkansas Rivers. Corn, grain sorghum, and sugar beets are grown extensively on the nearly level uplands where ground water is used for irrigation. One-third or more of the area, consisting of hilly and steep slopes bordering drainageways, is in native grasses and shrubs used for grazing. 49 Elevation and topography: Elevation ranges from 800 to 1,200 m, increasing from east to west. On this smooth loess-mantled tableland, slopes are mostly nearly level to gently rolling, but the major valleys are bordered by steep slopes. The Arkansas and Platte Rivers and a few of their larger tributaries have broad level flood plains and terraces. The local relief on uplands is in meters, but valleys are tens of meters below the general level of the upland. Climate: Average annual precipitation —400 to 525 mm, but it fluctuates widely from year to year. Maximum precipitation is from late in spring through early autumn. Precipitation in winter is snow that ranges from about 40 cm annually in the south to 90 cm in the north. Average annual temperature —10 to 14°C. Average freeze-free period —140 to 185 days, increasing from northwest to southeast. Water: The low and erratic precipitation is the source of water for dryland crops and pastures on uplands. Irrigation water obtained from the Arkansas, Repub¬ lican, and Platte Rivers is used along the valleys of these rivers. In most of the area, good-quality ground water is adequate for domestic and livestock needs and is used locally for irrigation. Ground water is scarce in areas where shale is near the surface. Soils: Most of the soils are Ustolls. They are well drained and medium textured and moderately fine textured. They have a mesic temperature regime, an ustic moisture regime, and mixed or montmorillonitic mineralogy. On loess-mantled uplands, well drained Argiustolls (Keith, Kuma, Rago, and Richfield se¬ ries) are in nearly level and gently sloping areas, Haplustolls (Ulysses series) in gently sloping and moderately sloping areas, and Torriorthents (Colby series) in steeper areas. Torriorthents (Canyon se¬ ries) and Ustorthents (Canlon series) are shallow over caliche and are on the steeper and more broken slopes. Torripsamments (Valent series), on hummocky and duned eolian sands, are associated with Argiustolls (Haxtun series) and Haplustolls (Anselmo series). Haplustolls (Bridgeport, McCook, and Duroc series) are on flood plains and terraces. Potential natural vegetation: This area supports a short grass prairie vegetation. Blue grama and buffalograss are the dominant species. Sideoats grama, blue grama, hairy grama, and little bluestem grow’ on the steeper dissected areas. 73—Rolling Plains and Breaks Kansas and Nebraska 59,260 km 2 (22,880 mi 2 ) Land use: Nearly all this area is in farms, and about three-fifths is dry-farmed cropland. Winter wheat and grain sorghum are the major crops in much of the area, but corn is important in the north. Feed grains and hay are other major crops. About 2 percent of the area, mostly narrow bands of bottom land and ter¬ races along the Republican and Platte Rivers and their major tributaries, is irrigated. Corn, alfalfa, small grains, and hay are the principal crops grown on irrigated land, but some potatoes and vegetables are grown. One-third or more of the area is in native grasses used for grazing. Elevation and topography: Elevation ranges from 500 to 900 m, increasing from east to west. These dissected plains have broad undulating to rolling ridgetops and hilly to steep valley sides. The valleys generally are narrow, but the Republican River and its larger tributaries have broad flood plains and terraces. Local relief is in meters to tens of meters. Climate: Average annual precipitation —500 to 625 mm. Maximum precipitation is from midspring to early in autumn. Precipitation in w’inter is snow that ranges from about 45 cm annually in the south to 60 cm in the north. Average annual temperature —10 to 13°C. Average freeze-free period —150 to 180 days, increasing from northwest to southeast. Water: In most of the area, the moderate and erratic precipitation is the source of w T ater for crops and pasture. The Republican and Platte Rivers and their larger tributaries provide w y ater for irrigation along their valleys. Abundant supplies of ground water for irrigation and other uses are obtained from deep w r ells in the north. Ground w r ater is scarce in the south where shale and limestone are near the sur¬ face. Soils: Most of the soils are Ustolls. They are deep, well drained, and medium textured and moderately fine textured. These soils have a mesic temperature re¬ gime, an ustic moisture regime, and mixed and montmorillonitic mineralogy. The nearly level to mod¬ erately sloping Argiustolls (Harney and Holdrege series) are on loess-mantled uplands. Haplustolls (Uly series) and Ustorthents (Coly series) are on adjacent steeper slopes. Gently sloping and moder¬ ately sloping Haplustolls (Wakeen series) and Pellu- sterts (Bogue series) are moderately deep over shale on the more strongly dissected uplands. Haplustolls (Hord, McCook, and Roxbury series) and Ustifluvents (Hobbs and Munjor series) are on flood plains and terraces. Potential natural vegetation: This area supports natural prairie vegetation. Little bluestem, big blue- stem switchgrass, western wheatgrass, and sideoats grama characterize the vegetation on loamy soils. Blue grama, buffalograss, and western wheatgrass characterize the vegetation on clayey soils on up¬ lands. 74—Central Kansas Sandstone Hills Kansas 12,210 km 2 (4,710 mi 2 ) Land use: Most of this area is in farms, more than one-half of which is cropland. Winter w’heat is the principal crop. Grain sorghum, hay, small grains, and corn are other important crops. Some land along the 50 large rivers is irrigated. The crops grown in non- irrigated areas are also grown under irrigation, but more corn and less wheat is grown under irrigation. About one-third of the area is in native grasses grazed by cattle. Elevation and topography: 400 to 500 m, increasing from east to west. Local relief on this undulating to hilly dissected plain is in tens of meters. The larger rivers have wide flood plains and terraces, but the small streams have narrow bottom lands. Climate: Average annual precipitation —625 to 700 mm. Most of the precipitation falls from spring through autumn, but the maximum is in midsummer. Annual snowfall averages about 50 cm. Average annual temperature —12 to 13°C. Average freeze-free period —170 to 180 days. Water: If moisture is carefully conserved, the moder¬ ate precipitation generally is adequate for crops and pasture. The larger streams can supply water for irrigation, but most of them have not been used for this purpose. Ground water is adequate to meet domestic and livestock needs in most of the area and is used locally for irrigation. Ground water is scarce in the east where shale is near the surface. Soils: Most of the soils are Ustolls. They are shallow to deep and medium textured and moderately fine- textured. They have a mesic temperature regime, an ustic moisture regime, and mixed and montmorillonitic mineralogy. The nearly level and gently sloping, well drained and moderately well drained Argiustolls are on loess-mantled uplands (Crete, Smolan, and Longford series) and on side slopes and foot slopes in dissected areas (Lancaster and Geary series). The moderately steep and hilly, shallow Haplustolls (Hedville series) are over sandstone on uplands. Ustifluvents (Hobbs series) are on flood plains of the smaller streams. Haplaquolls (Solomon series) and Haplustolls (Sutphen, Roxbury, and New Cambria series) are on bottom lands of major streams. Potential natural vegetation: This area supports mid and tall grasses. Little bluestem, big bluestem, switchgrass, sideoats grama, and western wheatgrass are major species. 75—Central Loess Plains Kansas and Nebraska 34,840 km 2 (13,450 mi 2 ) Land use: Nearly all this area is in farms, about two-thirds of which is cropland. Hard winter wheat and grain sorghum are the main cash crops, but large acreages are planted to other small grains and hay. Corn is a major cash crop in the north. Most of the corn is irrigated by water from wells or canals. About one-fourth of the land is rangeland or pastureland grazed by beef cattle. Elevation and topography: Elevation ranges from 500 to 600 m, increasing from east to west. Most of these nearly level to gently rolling plains are mantled by loess, but the part south of central Kansas is underlain by unconsolidated sediments, soft sand¬ stone, and shale. The present drainage pattern cuts into the upper loess mantle and in places exposes the older Loveland loess. Stream valleys are mostly narrow and are not deeply incised. Relief is in meters to tens of meters. Climate: Average annual precipitation —625 to 750 mm. Maximum precipitation is from midspring to midautumn. The low winter precipitation is snow. Average annual temperature —10 to 14°C, increasing from north to south. Average freeze-free period —160 to 190 days. Water: The moderate but somewhat erratic precipita¬ tion is the source of water for grain crops, native grasses, and pasture. In the northwest, the Platte River supplies some water for irrigation. Ground water that is hard but otherwise of good quality is abundant in the sand and gravel underlying part of the area. Adequate quantities of ground water are available for irrigation in the northern part. Ground water is scarce in areas where shale and clay are near the surface. Soils: Most of the soils are Ustolls. They are deep silty soils that formed in loess. They have a mesic temper¬ ature regime, an ustic moisture regime, and mixed mineralogy. Argiustolls (Hastings, Geary, Holder, Holdrege, and Crete series in the north and Irwin, Ladysmith, and Geary series in the south) are the dominant soils on uplands. Argiustolls (Hall series) are on stream terraces of major streams or rivers. Argiaquolls (Butler series), Argialbolls (Fillmore se¬ ries), and Pellusterts (Goessel series) are associated soils in level areas and in depressions. Strongly sloping to steep Ustorthents (Coly series) formed in loess. Ustifluvents (Hobbs series) are on flood plains, and Haplustolls (Hord series) are on stream terraces. Shallow, strongly sloping to steep Haplustolls (Kipson series) formed in material weathered from shale. Potential natural vegetation: This area supports mid and tall grass plant communities. Big bluestem, little bluestem, switchgrass, indiangrass, and sideoats grama characterize the vegetation on silty upland soils. These grasses and western wheatgrass are on bottom lands and in upland basins. 76—Bluestem Hills Kansas and Oklahoma 19,400 km 2 (7,490 mi 2 ) Land use: Nearly all this area is in farms and ranches, about three-fifths of which is in native grasses grazed by beef cattle. Nearly one-fifth of the area, consisting mainly of the deeper soils in valleys and on some of the uplands, is cropland. Some winter wheat is grown as a cash crop. Other small grains, grain sorghum, alfalfa, and other hay are the major crops. These crops are also grown on small irrigated areas along the Arkansas River. 51 Elevation and topography: Elevation ranges from 300 to 500 m. These dissected limestone and shale uplands have narrow divides and narrow steep-sided valleys. Only a few large streams have a significant area of flood plain. Local relief is commonly in meters or tens of meters. Climate: Average annual precipitation —750 to 900 mm. Maximum precipitation is from midspring through early autumn. Annual snowfall averages 35 to 50 cm. Average annual temperature —12 to 16°C. Average freeze-free period —170 to 190 days but slightly more than 200 days in the south. Water: The moderate precipitation provides water for pastures and crops. Much of the water for livestock is stored in small reservoirs and ponds. In the lime¬ stone areas, shallow wells yield moderate quantities of good-quality water, but very little is available in areas underlain by shale. Water from deep wells is highly mineralized. Soils: Most of the soils are Ustolls. They are shallow to deep, medium textured to fine textured soils that are stony in some places. These soils have an ustic moisture regime, a mesic (Kansas) or thermic (Okla¬ homa) temperature regime, and mixed mineralogy. Well drained and moderately well drained, nearly level to moderately sloping Argiustolls (Irwin, Labette, and Ladysmith series) and Natrustolls (Dwight se¬ ries) are on clay-mantled uplands that in some places are covered by thin loess. Shallow and moderately deep Haplustolls (Sogn and Clime series) are on steeper slopes underlain by limestone and shale. Moderately sloping Argiustolls (Florence'series) in cherty limestone are on narrow divides and on side slopes of broader ridges. Haplaquolls (Osage series) and Hapludolls (Ivan and Verdigris series) are on flood plains, and Argiudolls (Reading series) and Haplustolls (Muir series) are on terraces. Potential natural vegetation: This area supports tall grass prarie vegetation. Bigbluestem, indiangrass, switchgrass, and little bluestem are dominant spe¬ cies. Little bluestem and big bluestem grow on the shallow soils. 77—Southern High Plains Kansas, New Mexico, Oklahoma, and Texas 126,780 km 2 (48,950 mi 2 ) Land use: Almost all this area is in farms and ranches. More than two-fifths, consisting of breaks along the Canadian and Cimarron Rivers and their larger trib¬ utaries and areas of sandy soils in the southwest, is range of native grasses and shrubs grazed by beef cattle. About one-third of the area, the smooth uplands, is dry-farmed to winter wheat, grain sor¬ ghum, and cotton. Nearly one-fifth of the area is irrigated. Wheat and grain sorghum are the major crops south of the Canadian River. Other major crops grown in places where irrigation water is available include soybeans, corn, alfalfa, and vegetables. Elevation and topography: Elevation ranges from 800 to 2,000 m, increasing gradually from southeast to northwest. These smooth high plains are gently sloping, but along the major rivers, breaks are very steep. The deep sand in the southwest has an irregu¬ lar dune topography. Local relief is in meters, but the major valleys are tens of meters below the general level. Climate: Average annual precipitation —375 to 550 mm, but it fluctuates widely from year to year. Maximum precipitation is from late in spring through autumn. The low precipitation in winter is mainly snow. Average annual temperature —13 to 17°C. Av¬ erage freeze-free period —130 to 220 days, increasing from north to south and from west to east. Water: The moderately low and erratic precipitation is the source of water for dry-farmed crops and for range. Perennial streams are few; they fluctuate widely in flow from year to year and are little used for irrigation. Sand and gravel throughout the cen¬ tral and northern parts of the area yield an abun¬ dance of ground water. Irrigation water is obtained from wells, but in the central and southern parts withdrawals exceed recharge, and the water table is gradually declining. Some areas formerly irrigated are now dry-farmed. Soils: Most of the soils are Ustolls and Ustalfs. They are deep, fine, and medium textured and coarse textured. These soils have a mesic or thermic tem¬ perature regime, an ustic moisture regime, and mixed or carbonatic mineralogy. The level to gently sloping Paleustolls (Pullman, Olton, Acuff, Sherm, Gruver, Texline, and Dumas series), Argiustolls (Richfield series), Paleustalfs (Amarillo, Dallam, Rickmore, and Spurlock series), and Haplustalfs (Dalhart series) are the principal soils on the uplands. Calciustolls (Portales and Dioxice series), Haplustolls (Ulysses series) and Paleustolls (Mansker, Conlen, Sunray, and Estacado series) are dominant on ridges and on the more sloping parts. Haplustolls (Bippus, Humbarger, and Spur series) are on young valley floors and flood plains of the streams. Pellusterts (Randall and Ness series) are in clayey playa lake basins. Shallow Calciorthids (Potter series), Paleorthids (Pastura se¬ ries), and Torriorthents (Travessilla series) are on the steep slopes and in the breaks. Paleustalfs (Patricia, Springer, and Brownfield series), Haplargids (Triomas, Faskin, and Jalmar series), Ustipsamments (Tivoli series), and Torripsamments (Penwell series) are deep sandy soils in the southwest. Loamy, shallow to moderately deep soils in the southwest are Calciustolls (Kimbrough series), Paleustolls (Lea, Slaughter, and Stegall series), Paleustalfs (Arvana series), Paleorthids 52 (Blakeney and Conger series), and Paleargids (Douro and Sharvana series). Potential natural vegetation: This area supports a short grass community characterized by blue grama and buffalograss. Mid grasses such as sideoats grama grow on the more open soils and breaks. Tall grasses such as sand bluestem, little bluestem, and indiangrass grow mixed with shinnery oak and sand sagebrush on the sandy soils. A wide range of perennial forbs grow on the sandier soils and are characterized by dotted gayfeather, pitchersage, sagewort, bushsunflower, and daleas. 78—Central Rolling Red Plains Kansas, Oklahoma, and Texas 130,370 km 2 (50,340 mi 2 ) Land use: About 60 percent of this area is rangeland, and 35 percent is cropland. The rest of the area is urban land, woodland, or pasture. Nearly all the area is in farms or ranches. Most rangeland is in the west, but some is throughout the area. Ranges and pas¬ tures are grazed mainly by beef cattle. Winter wheat and grain sorghum are the major cash crops grown throughout the area. Cotton is an important crop south of the Cimarron River; alfalfa and peanuts are important locally. The crops grown under irrigation are also grown in nonirrigated areas. Soil erosion is a major concern of management if the soils are culti¬ vated or if range and pasture are overgrazed. Elevation and topography: Elevation ranges from 500 to 900 m, increasing gradually from east to west. On these dissected plains, the broad divides are nearly level to gently sloping, but slopes are short and steep in the valleys. In places the valleys are bordered by a rolling to steep irregular dune topog¬ raphy. Local relief is mainly in meters, but a few of the larger valleys are tens of meters or more below the general level of the plain. In southwestern Okla¬ homa, the Wichita Mountains are as much as 300 m above the surrounding plains. Climate: Average annual precipitation —500 to 750 mm, increasing from west to east. Maximum precipi¬ tation is in spring, and the minimum is in winter. Snowfall ranges from 25 cm in the north to 10 cm in the south. Average annual temperature —14 to 18°C. Average freeze-free period —185 days to 230 days. Water: The moderate but somewhat erratic precipita¬ tion supplies water for range and crops. Small ponds on individual farms provide water for livestock. Some larger ponds on individual farms are used for flood control, recreation, irrigation water, or water for livestock. A few large ponds and reservoirs are a source of municipal water and irrigation water. Riv¬ ers are a potential source of water for irrigation. Water in .some of the larger rivers is highly mineral¬ ized. The deep sand and gravel in valleys yield some ground water. In sloping areas where the underlying sandstone and shale are near the surface, ground water is scarce. Soils: The major soils are Ustolls, Ustalfs, and Ochrepts. They have a thermic temperature regime, an ustic moisture regime, and mixed mineralogy. The nearly level to gently sloping, well drained and moderately well drained, deep Argiustolls (Abilene, Carey, and St. Paul series), Paleustolls (Hollister, Rotan, Sagerton, and Tillman series), and Natrustolls (Foard series) are on uplands. The Ustalfs mainly are deep and sandy or loamy and have a loamy subsoil. They have a thermic temperature regime and mixed mineralogy. The nearly level to undulating or rolling, well drained, deep Haplustalfs (Devol and Grandfield series) and Paleustalfs (Miles, Springer, Wichita, Winters, and Nobscot series) are on uplands. The gently sloping to moderately steep Ustochrepts (Dill, Enterprise, Hardeman, Obaro, Quinlan, Vernon, and Woodward series) are on uplands. Ustifluvents (Clairemont, Lincoln, Mangum, Yomont, and Yahola series) are minor soils on flood plains. Potential natural vegetation: This area supports mid and tall grasses. Sand bluestem, little bluestem, and sand sagebrush are dominant on the coarse- textured soils. Little bluestem, gramas, and associated grasses and forbs grow on the finer textured soils. 79—Great Bend Sand Plains Kansas 10,770 km 2 (4,160 mi 2 ) Land use: Nearly all this area is in farms and ranches, and more than two-thirds is cropland. Cash-grain farming is the principal enterprise. Hard winter wheat is the major crop, but grain sorghum and alfalfa are also grown. About one-fifth of the land, consisting of sandy soils and steeply sloping areas, is in native grasses grazed by beef cattle. Elevation and topography: Elevation ranges from 500 to 800 m. These undulating to rolling plains have a deep mantle of windblown sand and sandy outwash materials. Local relief is mainly in meters. Climate: Average annual precipitation —525 to 700 mm. Maximum precipitation is from late in spring through early autumn. The annual snowfall averages from 35 to 50 cm. Average anmial temperature —13 to 14°C. Average freeze-free period —180 to 190 days. Water: The source of water for crops and pasture is the moderate but somewhat erratic precipitation. Along the northern edge, the Arkansas River is a potential source of irrigation water but currently is little used for this purpose. Deep sand yields an abundance of good-quality ground water for domestic use, live¬ stock, irrigation, and other purposes. Soils: Most of the soils are Ustalfs. They are deep, coarse textured and moderately coarse textured soils that have a thermic temperature regime and an udic moisture regime. Sandy Haplustalfs (Pratt series) and loamy Haplustalfs (Attica series) are on broad undulating to hummocky plains. Ustipsamments (Tivoli series) are on steeper hummocks and dunes. The nearly level and gently undulating, loamy Argiustolls (Farnum and Naron series) are on slopes. The nearly level Argiaquolls (Carwile series) in depressions and in areas with no defined drainage pattern are moder¬ ately extensive throughout the area. Haplustolls on flood plains (Waldeck, Zenda, and Lesho series) and terraces (Canadian series) are along major streams. Potential natural vegetation: This area supports tall grass prairie vegetation. Sand bluestem, little bluestem, switchgrass, and indiangrass are major species. Sand bluestem, little bluestem, and giant sandreed grow on sandy dunes. 80A—Central Rolling Red Prairies Kansas, Oklahoma, and Texas 52,700 km 2 (20,350 mi 2 ) Land use: About 40 percent of this area is rangeland, and 40 percent is cropland. About 20 percent of the area is urban land, woodland, or pasture or is used for other purposes. Nearly all the area is in farms or ranches. Most cropland is in the north, but some is throughout the area. Winter wheat is the major cash crop. Alfalfa, cotton, grain sorghum, peanuts, and soybeans are important crops locally. The range and pasture are grazed mainly by beef cattle, but locally there are some dairy cattle. Soil erosion is a major concern of management if the soils are intensively cultivated or range and pasture are overgrazed. Elevation and topography: Elevation ranges from 300 to 500 m, increasing gradually from east to west. On this dissected plain, the divides are undulating to gently rolling and the valley sides are hilly and steep. Flood plains of large streams are wide and level and are less dissected by stream channels than those to the west. Local relief is mainly in meters. Climate: Average annual precipitation —625 to 900 mm. Maximum precipitation is in spring and the minimum in winter. Annual snowfall ranges from 30 cm in the north to 10 cm in the south. Average annual temperature —14 to 18°C. Average freeze-free period —190 to 230 days. Water: The moderate and somewhat erratic precipita¬ tion is the source of water for crops and pasture. Several large rivers that cross the area from west to east are potential sources of irrigation water but currently are little used for this purpose. Small ponds on individual farms provide flood control, recreation, irrigation water, or water for livestock. A few large ponds and reservoirs are a source of municipal water and are also used for recreation. In areas where the valleys have deep sand and gravel, shallow wells provide moderate quantities of water for domestic use and for livestock. Ground water is scarce and generally is highly mineralized in sloping areas where the underlying sandstone and shale are near the surface. Soils: The major soils are Ustolls. They are loamy or clayey and have a thermic temperature regime, an ustic moisture regime, and mixed mineralogy. The nearly level to sloping, well drained or moderately well drained, deep or moderately deep Argiustolls (Anocon, Grant, Pond Creek, Tabler, Shellabarger, and Stoneburg series) and Paleustolls (Bethany, Kirkland, and Renfrow series) are on uplands. The nearly level to steep, well drained, shallow to deep Haplustolls (Minco, Nash, and Lucien series) are on uplands. The nearly level, well drained or moderately well drained, deep Haplustolls (Miller, Port, and Reinach series) are on flood plains and low terraces. Minor soils include deep Haplustalfs (Bluegrove, Grainola, Pratt, and Steedman series) on uplands and Ustifluvents (Gaddy, Clairemont, and Yahola series) and Udifluvents (Gracemont and Gracemore series) on flood plains. Potential natural vegetation: This area supports mixed prairie vegetation. Woody trees and shrubs are in the major drainageways. Indiangrass, big bluestem, switchgrass, and little bluestem are domi¬ nant species on the deeper soils and in the valleys. Little bluestem usually is dominant on the uplands and on shallow soils. SOB—Texas North-Central Prairies Texas 25,500 km 2 (9,850 mi 2 ) Land use: Nearly all this area is in ranches and farms. More than 80 percent is native range, pasture, or scrub oak forest. About 15 percent of the area is cropland. Most grassland is grazed by beef cattle. Some rangeland is also grazed by sheep and goats. Valleys, bottom land, and outwash areas of deep soils are farmed to wheat, oats, cotton, and grain sor¬ ghum. Hunting leases for deer, quail, and wild tur¬ key are an important source of income in the area. The major concern of management is controlling woody brush that encroaches on the grassland. Elevation and topography: Elevation ranges from 200 to 700 m. These dissected limestone, sandstone, and shale uplands have broad undulating divides and narrow steep-sided valleys. Only a few large, through- flowing streams have significant flood plains. Relief is mainly in meters, but the large valleys are tens of meters below the adjacent uplands. Climate: Average annual precipitation —550 to 750 mm. Maximum precipitation is in spring and in fall. Summer moisture deficit ranges from 200 to 275 mm. Average annual temperature —18 to 19°C. Average freeze-free period —214 to 240 days. 54 Water: The moderate but somewhat erratic rainfall is the source of water for crops and range. Summer droughts are common. The larger rivers, such as the Brazos and Colorado Rivers, flow most of the year, but local streams flow intermittently. There are several large lakes and numerous flood-detention reservoirs in the area. Some rural residents depend on community systems supplied from lakes for water; others depend on private lakes for water. Livestock water comes from streams or ponds. Ground water is scarce. Soils: Most of the soils are Ustolls, Usterts, Ustalfs, and Ochrepts. These soils are well drained and mod¬ erately well drained, somewhat stony, and medium textured to fine textured. They have a thermic temperature regime, an ustic moisture regime, and mixed or montmorillonitic mineralogy. Very shallow to moderately deep Calciustolls (Talpa, Lueders, Kavett, Tarrant, and Valera series), Ustorthents (Yates series), and Argiustolls (Tarpley and Speck series) are on limestone plateaus or cuestas. Deep Chromusterts (Leeray series) and Haplustolls (Nukrum series) are in valleys at the base of cuesta scarps. Shallow and moderately deep Ustochrepts (Owens and Throck series) are on scarps and shaly uplands. Shallow to deep Haplustalfs (Callahan series), Rho- dustalfs (Exray series), and Paleustalfs (Bonti and Truce series) are on hills and ridges and are underlain by interbedded sandstone and shale. Shallow Cal¬ ciustolls (Cho and Mereta series) and deep Calciustolls (Nuvalde and Rowena series), Chromusterts (Reap series), and Pellusterts (Roscoe series) are on ancient alluvium and outwash. Paleustolls (Sagerton series), Paleustalfs (Winters and Wichita series), and Hap¬ lustalfs (Thurber series) are on outwash and stream terrace deposits. Deep Haplustolls (Elandco, Deleon, Frio, and Gowen series) and Ustifluvents (Bunyan, Yahola, Clairemont, and Lincoln series) are on young¬ er stream deposits on flood plains. Potential natural vegetation: This area supports savanna vegetation. The potential vegetation is rather uniform throughout the area despite the wide varia¬ tion in soils. Little bluestem, indiangrass, big blue- stem, sideoats grama, hairy grama, and Texas wintergrass are the dominant grass species. Post oak and blackjack oak, sumacs, bumelias, and elm are the dominant woody species. There also are numerous perennial forbs, including Maximilian sunflower, heath aster, bushsunflower, and Engelmann-daisy. 55 I—SOUTHWEST PLATEAUS AND PLAINS RANGE AND COTTON REGION 175,990 km 2 (67,950 mi 2 ) This region is in the warmer part of the southern Great Plains. Moderate precipitation is accompanied by high temperatures, and precipitation effectiveness is low. The average annual precipitation is 500 to 750 mm throughout most of the region, but it ranges from 375 to 900 mm. Generally, much of the precipitation falls in spring and in autumn. The average annual temperature ranges from 16 to 22°C. The freeze-free period ranges from 210 to more than 325 days, increasing in length from north to south. Freeze-free years are common in the extreme southern part of the region. The major soils on uplands are Argids and Orthids in the west and Ustalfs, Ustolls, and Usterts in the east. Ustolls and Usterts are especially prominent in the southeast. Shallow Orthents are on uplands throughout the region. Soil temperatures generally are higher than 22°C south of the Edwards Plateau. Slopes range from steep to nearly level. Range is the dominant land use in most of this region, but wheat, grain sorghum, and other small grains are grown in places where soils, topography, and moisture supply are favorable. Cotton grown under irrigation is important in the southeast. Citrus fruits and winter vegetables are grown along the lower Rio Grande Valley area. 81—Edwards Plateau Texas 96,770 km 2 (37,370 mi 2 ) Land use: Most of this area is range. Local tracts are cultivated, and a few are irrigated; the source of water is ground water and streams. The range is grazed by beef cattle, sheep, goats, and wildlife. Hay, pasture, and small grain for grazing are the principal crops. Pecan orchards are on flood plains. Irrigated cotton and grain sorghum are grown local¬ ly. Hunting leases for deer, quail, mourning dove, wild turkey, and javelina are an important source of income. The major concern of management is control¬ ling brush that invades the grasslands. Elevation and topography: Elevation ranges from 200 to 500 m on valley floors. On hills and in plateaus it ranges from 400 to 1,200 m, increasing gradually from east to west. Valleys are narrow to broad and have gently sloping to steep walls and smooth to undulating floors. Hills are sloping to very steep. Plateaus are broad and nearly level to undulating. Climate: Average annual precipitation— 375 to 750 mm. About three-fourths of the precipitation falls during the growing season. Average annual tem¬ perature— 18 to 20°C. Average freeze-free period— 230 to 270 days. Water: In the western part rainfall is adequate for range grasses but inadequate for cultivated crops, and in the central and eastern parts rainfall is mar¬ ginal for both. High temperatures and high evapora¬ tion and transpiration rates in summer limit crop production. Only a few rivers and streams flow throughout the year. Deep wells provide some water for irrigation and livestock and for domestic needs. Soils: Most of the soils are Ustolls. They are stony and moderately fine textured and fine textured. These soils have a thermic temperature regime, an ustic moisture regime, and carbonatic or montmorillonitic mineralogy. Very shallow and shallow, gently sloping to sloping Calciustolls (Ector and Tarrant series) are on limestone hills. Shallow and moderately deep, nearly level to gently sloping Calciustolls (Kavett and Valera series) are on plateaus. Deep, nearly level Chromusterts (Tobosa and Anhalt series) occur on broad limy outwash plains and broad plateaus. Shal¬ low, gently sloping to steep Ustochrepts (Brackett series) are on hills of marl and chalk. Haplustolls (Frio and Rioconcho series) are on the younger stream deposits of valley floors. Potential natural vegetation: This area supports a plant community ranging from desert shrub vegeta¬ tion in the west to a mixed oak savanna with tall and mid grasses in the east. Mid and short grasses and an abundance of low-growing woody plants characterize the vegetation in the west. Oaks in association with mid and tall grasses grow in the central and eastern parts. The savanna ranges from nearly open grass¬ lands with scattered trees to oak stands interspersed with grasses. Forbs are in great abundance through¬ out the Edwards Plateau. 82—Texas Central Basin Texas 5,500 km 2 (2,120 mi 2 ) Land use: Most of this area is range. Small acreages are cultivated, and a few are irrigated from ground water. The range is grazed mainly by beef cattle, sheep, and wildlife. Grain sorghum, cotton, peanuts, and small grain for grazing are the principal crops. In a few places, land formerly used for crops is now used as pasture or is reverting to range. Hunting leases for deer, quail, mourning dove, and wild turkey are an important source of income. Fishing camps and other water-based recreation also contribute to the 56 economy. The major concern of management is con¬ trolling brush that invades the grasslands. Elevation and topography: Elevation ranges from 200 to 300 m on valley floors, but on hills and plateaus it ranges from 300 to 400 m. The broad valleys have moderately sloping walls and smooth to undulating floors. The hills are moderately sloping to steep, and the plateaus are broad and gently sloping to undulat¬ ing. Climate: Average annual precipitation —625 to 750 mm. About three-fourths of the precipitation falls during the growing season. Average annual tempera¬ ture— 18 to 20°C. Average freeze-free period^- 210 to 270 days. Water: The rainfall is adequate for range grasses but is marginal for crops because of extended high tempera¬ tures and high evaporation and transpiration rates during the summer. Only a few rivers and large streams flow throughout the year, and irrigation from these sources is limited. Deep wells provide water for some irrigation. Shallow and deep wells and ponds provide water for livestock and for domes¬ tic needs. Soils: Most of the soils are Ustalfs. They are somewhat gravelly and moderately coarse textured and have a thermic temperature regime, an ustic moisture re¬ gime, and mixed mineralogy. Deep and moderately deep, nearly level to gently sloping Paleustalfs (Pedemales and Castell series) occur on limy outwash and gneiss. Shallow and moderately deep, gently sloping to sloping Haplustalfs (Click and Oben series) occur in areas underlain by granite and sandstone. Ustochrepts (Keese series) are on the steeper slopes underlain by granite, and Ustorthents (Nebgen se¬ ries) are on the steeper slopes underlain by sand¬ stone. Shallow to moderately deep, undulating Haplustolls (Harper series) and Argiustolls (Rumple series) are on uplands underlain by limestone. Potential natural vegetation: This area supports a mixed oak savanna vegetation of live oak, post oak, and blackjack oak with tall and mid grasses such as little bluestem, sideoats grama, indiangrass, and switchgrass, sand and plains lovegrass, green sprangle- top, purpletop, pinhole bluestem and plains bristlegrass. Such forbs as orange zexmania, bushsunflower, Engelmann-daisy, and trailing ratany grow through¬ out the area. A mid grass community with scattered individual or groves of live oak and post oak grows on the shallow and more droughty soils. Major grass species on these sites are sideoats grama, meadow dropseed, pinhole bluestem, Arizona cottontop, vine- mesquite, Texas wintergrass, and little bluestem. 83A—Northern Rio Grande Plain Texas 20,900 km 2 (8,070 mi 2 ) Land use: Most of the area is range, but large acre¬ ages are cultivated. The range is grazed mainly by beef cattle and wildlife. Grain sorghum, cotton, corn, flax, and small grain for grazing are the main crops. Local areas are irrigated. Hunting leases for deer, quail, and mourning dove are an important source of income. The major concern of management is con¬ trolling the brush and cactus that invade the grass¬ lands. Elevation and topography: Elevation ranges from 25 m in the southeast to 200 m in the northwest. These plains are nearly level but smooth hills and valleys are gently rolling. The valleys are narrow to broad. The hills are mostly in the east. Climate: Average annual precipitation —625 to 750 mm. Most of the precipitation falls during the grow¬ ing season. Average annual temperature —21 to 22°C. Average freeze-free period —260 to 310 days. Water: Rainfall is adequate for range grasses but mar¬ ginal for cultivated crops. High temperatures and high evaporation and transpiration rates limit crop production. The Nueces River and deep wells pro¬ vide water for irrigation. Deep wells and ponds provide water for livestock and for domestic use. Soils: Most of the soils are Ustalfs. They are deep and moderately coarse textured and coarse textured. These soils have a hyperthermic temperature re¬ gime, an ustic moisture regime, and mixed mineralo¬ gy. Ustolls are also extensive. Gently sloping to undulating Paleustalfs (Floresville, Miguel, Webb, and Wilco series) are on plains. Nearly level to gently sloping Argiustolls (Clareville and Elmendorf series) and Calciustolls (Knippa series) are in broad valleys. Gently sloping to rolling Calciustolls (Olmos and Pettus series) are on hills. Potential natural vegetation: This area supports open grassland with scattered mesquite, live oak, and other trees. Little bluestem, sideoats grama, lovegrass tridens, fourflower trichloris, Arizona cottontop, plains bristlegrass, and other mid grasses are dominant on the deeper soils. A number of forbs, including orange zexmania, catclaw sensitivebrier, western indigo, and bushsunflower grow on these soils. Open grassland with scattered low-growing brush, such as guajillo, blackbrush, elbowbush, and kidney wood, characterize the shallower soils. Ari¬ zona cottontop, sideoats grama, green sprangletop, and twoflower trichloris are dominant mid grasses on these soils. 83B—Western Rio Grande Plain Texas 23,470 km 2 (9,060 mi 2 ) Land use: Most of this area is range grazed by beef cattle and wildlife. Grain sorghum, small grain, cot¬ ton, and improved pasture are the principal crops. Small grain is mostly grazed for winter pasture. Hunting leases for deer, quail, mourning dove, wild turkey, and javelina are an important source of 57 income. The major concern of management is control¬ ling brush and cactus that invade the native grass¬ lands. Locally, saline and alkali soils are a land use problem. Elevation and topography: Elevation ranges from 50 m in the southeast to 300 m in the northwest. Much of this plain is gently undulating and somewhat dissected by intermittent drainageways. Climate: Average annual precipitation —425 to 525 mm. Maximum precipitation is during the growing season. Average annual temperature —21 to 22°C. Average freeze-free period— 260 to 290 days. Water: Rainfall is adequate for the growth of range grasses. In most years it is inadequate for cropland because of saline soils, high temperatures, and high evaporation and transpiration rates. The Rio Grande is the major perennial stream; other rivers flow intermittently. Locally, deep wells and ponds pro¬ vide water for livestock, domestic use, and irrigation. Soils: Most of the soils are Usterts and Torrerts. They are deep, fine textured saline soils that have montmorillonitic mineralogy. Also extensive are Ustolls and Orthids that have been mixed mineralogy. These soils have a hyperthermic temperature regime and an ustic or aridic moisture regime. Nearly level to gently sloping Pellusterts (Montell and Monteola series) are on plains over clayey marine sediments. Gently undu¬ lating Torrerts (Catarina series) are on plains in the southwestern part of the area. Nearly level Haplustolls (Dant series) and Calciustolls (Elindio series) are on broad plains in the northern part. Shallow and grav¬ elly Calciustolls (Jimenez and Olmos series) are on ridges and small hills. Nearly level to gently undulat¬ ing Calciorthids (Copita and Pryor series) are on plains over marine sediments. Potential natural vegetation: This area supports open grassland with scattered shrubs. Mid grasses such as alkali sacaton, twoflower trichloris, pink pappusgrass, white tridens, whiplash pappusgrass, and vine-mesquite are dominant on deep, clayey soils. Guayacan, spiny hackberry, desert yaupon, and fourwing saltbush are the principal shrubs. Bundle- flower, bushsunflower, Texas varilla, and other forbs make up a minor but significant part of the plant communities. The more gravelly soils support semiopen grassland vegetation of mid grasses interspersed with low-growing shrubs. Guajillo, blackbrush, and kidneywood are the principal shrubs. Arizona cottontop, sideoats grama, pink pappusgrass, pinhole bluestem, green sprangletop, and tanglehead are the dominant grasses. Several species of forbs grow on these soils, mainly bushsunflower, orange zexmania, snoutbeans, daleas, and gauras. 83C—Central Rio Grande Plain Texas 23,470 km 2 (9,060 mi 2 ) Land use: Most of this area is range grazed by beef cattle and wildlife. Grain sorghum, cotton, and small grain for grazing are the main crops. Local areas are irrigated. Hunting leases for deer, wild turkey, quail, mourning dove, javelina, and exotic game animals are an important source of income. The major con¬ cern of management is controlling brush and cactus that invade the grasslands. Elevation and topography: Elevation ranges from 25 m in the east to 200 m in the northwest. This plain is nearly level to gently undulating and is weakly dissected by intermittent drainageways. Climate: Average annual precipitation —525 to 650 mm. Maximum precipitation is during the growing season. Average annual temperature —21 to 23°C. Average freeze-free period —280 to 325 days. Water: Rainfall is adequate for the growth of range grasses, but crop yields are limited by periods of moisture stress caused by high temperatures and high evaporation and transpiration rates. Deep wells and ponds provide water for irrigation, livestock, and domestic use. Soils: Most of the soils are Ustalfs. They are moder¬ ately deep to deep and moderately coarse textured and coarse textured and have mixed mineralogy. Ustolls are also extensive. These soils have a hyperthermic temperature regime and an ustic mois¬ ture regime. Gently undulating Paleustalfs (Nueces and Sarita series) are on sandy eolian plains. Nearly level to gently sloping Paleustalfs (Delfina and Delmita series) are on loamy eolian plains in the central and eastern parts of the area. Nearly level to gently undulating Haplustalfs (Brennan and Comitas series) are on loamy eolian plains in the central and western parts. Gently sloping to gently undulating Calciustolls (Hidalgo and Olmos series) and Haplustolls (Tordia series) are on plains underlain by ancient marine sediments. Nearly level to gently undulating Orthids (Copita, Randado, and Zapata series) are on plains in the western part of the area. Potential natural vegetation: This area supports prairie vegetation with a few scattered trees and shrubs. Major species on soils with deep, fine sand surfaces are tall and mid grasses such as seacoast bluestem, indiangrass, crinkleawn, and tanglehead and an abundant variety of perennial legumes and forbs. Species commonly growing on soils on loamy eolian plains in the central and eastern parts of the area are mid grasses such as Arizona cottontop, fourflower thichloris, tanglehead, plains lovegrass, and pinhole bluestem. Many forbs and low-growing shrubs, including condalias, vine ephedra, and guajillo, grow with these grasses. 831)—Lower Rio Grande Valley Texas 6,600 km 2 (2,550 mi 2 ) Land use: Most of this area is cropland or improved pasture that is extensively irrigated, but large acre- 58 ages are in range. Major crops are cotton, grain sorghum, citrus, onions, cabbage, and other truck crops. The range is mainly grazed by beef cattle and wildlife. Hunting leases for quail, white-winged dove, and mourning dove are an important source of in¬ come. Major land use problems are saline soils and inadequate subsurface drainage on cropland. Elevation and topography: Elevation ranges from sea level in the east to about 200 m in the northwest, but is mainly less than 100 m. Much of the area is nearly level. Drainageways are shallow and have low gradients. Climate: Average annual precipitation —425 to 700 mm. Maximum precipitation is during the growing season. Average annual temperature —22 to 23°C. Average freeze-free period —300 to 330 days. Water: Rainfall is adequate for the growth of range grasses. It is low in the western and central parts of the area and marginal in the eastern. High tempera¬ tures and high evaporation and transpiration rates limit crop production. The Rio Grande, the only perennial stream, provides water for irrigation. Lo¬ cally, deep wells and ponds provide water for live¬ stock, domestic use, and irrigation. Soils: Most of the soils are Ustalfs. They are deep, moderately fine textured and fine textured soils that formed in alluvial sediments. They have a hyperthermic temperature regime, an ustic moisture regime, and mixed mineralogy. Ustolls having mixed mineralogy are also extensive. Nearly level to gently sloping Paleustalfs (Delfina and Nueces series) are on plains in the northeast. Nearly level to gently undulating Haplustalfs (Brennan, Duval, and Hebbronville se¬ ries) are on plains in the west. Nearly level to gently sloping Calciustolls (Hidalgo and Raymondville se¬ ries) are on plains in the central and eastern parts of the area. Nearly level Ustifluvents (Camargo, Rio Grande, and Zalla series) are on flood plains along the Rio Grande. Potential natural vegetation: This area supports open mid grass prairie vegetation with scattered woody plants and some perennial forbs and legumes on upland soils. Twoflower and fourflower trichloris, plains bristlegrass, and lovegrass tridens are among the dominant grasses. Desert yaupon, spiny hack- berry, and blackbrush are major woody plants. Tall and mid grasses such as switchgrass, giant sacaton, fourflower trichloris, big sandbur, little bluestem, and southwestern bristlegrass are dominant on the savanna plant communities on bottom lands. Hack- berry and elms are major woody plants. Forbs are important but minor components of the plant com¬ munities. 59 j—SOUTHWESTERN PRAIRIES COTTON AND FORAGE REGION 145,120 km 2 (56,030 mi 2 ) This region consists of prairies and savannas in eastern Texas, in south-central Oklahoma, and in southeastern Kansas. The average annual precipitation ranges from 625 to 1,150 mm. The average annual temperature ranges from 15 to 22°C, and the freeze-free period is 190 to 280 days. Ustalfs, Ustolls, and Usterts are the dominant soils. Ustalfs are on the upland savannas, and Ustolls and Usterts are in the praries. The prairies are intensively farmed. Cotton, grain sorghum, wheat, other feed grains, and hay are important crops. The more sloping savannas are used mainly for grazing. Locally, peanuts and watermelons are important crops. 84A—Cross Timbers Kansas, Oklahoma, and Texas 27,400 km 2 (10,580 mi 2 ) Land use: Nearly all this area is in farms and ranches. About 40 percent is rangeland, 30 percent woodland, 15 percent pastureland, and almost 15 percent crop¬ land. The rest is used for urban development and for other purposes. All the rangeland, woodland, and pastureland is grazed by beef cattle, but locally there are some dairy cattle. Small grains, grain sorghum, cotton, alfalfa, and other hay crops are important in much of the area. Large acreages of peanuts, tree fruits, and vegetables are grown in the south. Elevation and topography: Elevation ranges from 300 to 400 m, but along the Red River it is 200 m. Ridgetops on these rolling to hilly uplands are nearly level to strongly rolling and narrow to moderately broad. Stream valleys are narrow 7 and have steep gradients. Local relief is mostly a few 7 tens of meters, but the large valleys are 50 m or more below 7 the adjacent uplands. Climate: Average annual precipitation —625 mm in the west to 900 mm in the east. Maximum precipitation is in spring, and the minimum is in winter. Snowfall ranges from 30 cm in the north to 10 cm in the south. Average annual temperature —15 to 17°C. Average freeze-free period —190 to 240 days. Water: The moderate and somewhat erratic rainfall is the source of w 7 ater for range and crops. Large reservoirs provide water for cities and towrns and for recreation or flood control. Farm ponds are a major source of w 7 ater for livestock. In most of the area, shallow 7 wells supply water for domestic use, but ground w r ater is scarce in places w'here sandstone and shale are near the surface. Soils: The major soils are Ustalfs and Ochrepts. They have a thermic temperature regime and an ustic moisture regime. The Ustalfs are loamy and have a loamy or clayey subsoil and siliceous or mixed miner¬ alogy. Well drained, very gently sloping, undulating to sloping or hummocky, moderately deep to deep Haplustalfs (Dougherty, Konawa, Stephenville, and Weatherford series) are on uplands. Well drained and moderately well drained, very gently sloping to steep or rolling, deep Paleustalfs (Chaney, Demona, Duffau, Eufaula, Nimrod, Niotaze, and Windthorst series) are on uplands. Ochrepts are shallow and loamy and have siliceous mineralogy. Well drained to somewhat excessively drained, very gently sloping, shallow Ustochrepts (Darnell series) are on ridge crests and steep valley slopes. Well drained, deep, nearly level Ustifluvents (Bunyan, Pulaski, and Pulexas series) and somew 7 hat poorly drained, nearly level, deep Udifluvents (Tribbey series) are on flood plains. Potential natural vegetation: This area supports an open stand of trees w 7 ith an understory of mid and tall grasses, forbs, and low 7 woody plants. Post oak and blackjack oak are the dominant tree species. Big bluestem, little bluestem, indiangrass, sunflower, and lespedezas are the major species in the herba¬ ceous understory. 84B—West Cross Timbers Oklahoma and Texas 15,050 km 2 (5,810 mi 2 ) Land use: Most of this area is in farms and ranches. About 85 percent is native grass pasture, improved grass pasture, or noncommercial oak forests that are used for grazing. Most of the pastureland, rangeland, and woodland is grazed by beef cattle, but dairy cattle are important in some places. In general, the acreage of cropland is decreasing, and that of improved pasture is increasing. About 14 percent of the area is farmed to peanuts, grain sorghum, small grains, or forage sorghum. Improved bermudagrass and other hay crops are important. Locally, peaches, apples, pecans, and vegetables are important crops. About 1 percent of the area is used for urban devel¬ opment and for other purposes. Elevation and topography: Elevation is mainly 300 to 400 m, but along the Red River it is about 200 m. These uplands are nearly level to rolling and are moderately dissected. Land in the north has a higher average slope gradient and is gullied. Land in the south is nearly level to undulating and has been 60 affected more by soil blowing. Stream valleys are narrow and have steep gradients. Local relief is mostly several meters. Climate: Average annual precipitation —625 to 875 mm, decreasing east to west. Maximum precipitation is in spring and in fall. Average precipitation during the frost-free period is about 500 to 600 mm. The summer moisture deficit ranges from about 175 to 250 mm. Average annual temperature —17 to 19°C. Average freeze-free period —225 to 240 days. Water: The moderate and somewhat erratic rainfall is the source of water for pasture and crops. Shallow wells for supplemental irrigation are common in the south, but the availability and quantity of water varies greatly. Farm ponds are a major source of water for livestock. Local streams have intermittent flow. A few large reservoirs provide water for cities and towns and for recreation and irrigation. In most of the area, shallow wells supply water for domestic use, but ground water is scarce in places where sandstone and shale are near the surface. Soils: Most of the soils are Ustalfs. They are well drained and moderately well drained, medium textured and coarse textured. These soils have a thermic temperature regime, an ustic moisture regime, and mixed or siliceous mineralogy. Deep, nearly level to undulating Paleustalfs (Windthorst, Duffau, Eufaula, and Konsil series) and nearly level to undulating, deep to moderately deep Haplustalfs (Chaney, Demona, Nimrod, Patilo, and Pedernales series) and deep, nearly level to undulating Haplustalfs (Cisco series) occur on uplands in the south. Ustifluvents (Bunyan, Energy, and Pulexas series) and Haplustolls (Elandco and Lamkin series) are on the narrow flood plains. Potential natural vegetation: This area supports savanna vegetation. Tall grass is interspersed with trees and underbrush. Little bluestem, purpletop tridens, indiangrass, switchgrass, big bluestem, sand lovegrass, post oak, blackjack oak, elm, coralberry, greenbrier, and elbowbush are dominant species. Engelmann-daisy, Maxmilian sunflower, and trailing wildbean are among the numerous perennial forbs. 84C—East Cross Timbers Texas 5,790 km 2 (2,240 mi 2 ) Land use: Most of this area is in farms and ranches, but sizable acreages in the central section are rap¬ idly being converted to urban uses. About 80 percent of the rural land is in improved pasture, native grass pasture, or noncommercial oak forest vegetation and is grazed by beef cattle. About 10 percent of the area is farmed to peanuts, small grain, forage sor¬ ghums, and fruit and vegetable crops. In general, the acreage of cropland is decreasing, and that ol im¬ proved pasture and urban development is increasing. Elevation and topography: Elevation is about 200 m. Extensive gently sloping to rolling uplands are moderately dissected. Sloping to rolling sandstone- capped hills and ridges rise prominently above the surrounding uplands. Stream valleys are narrow and have steep gradients. Local relief is mostly from 1 to 10 or 15 m. Climate: Average annual precipitation —875 to 1,000 mm. Maximum precipitation is in spring and in fall. Average precipitation during the frost-free period is about 600 to 650 mm. The summer moisture deficit ranges from about 125 to 200 mm. Average annual temperature —17 to 19°C. Average freeze-free period —227 to 250 days. Water: The moderate and somewhat erratic rainfall is the major source of water for pasture and crops. Large reservoirs provide water for cities and towns and for recreation. Farm ponds are a major source of water for livestock. In most of the area, shallow wells supply water for domestic use. A few small irrigation wells supply a very limited quantity of water. Local streams have intermittent flow. Soils: Most of the soils are Ustalfs. They are well drained and medium textured and coarse textured. These soils have a thermic temperature regime, an ustic moisture regime, and mixed, siliceous, or montmorillonitic mineralogy. Shallow to moderately deep Haplustalfs (Rayex series) and Paleustalfs (Birome series) are on sandstone-capped hills and ridges. Moderately deep to deep, gently sloping to sloping Paleustalfs (Aubrey, Birome, Callisburg, Crosstell, Gasil, and Konsil series) are on uplands. Deep, gently sloping Paleustalfs (Silstid and Heaton series) and Quartzipsamments (Arenosa series) are on sandy uplands. Haplustolls (Gowen series) and Ustifluvents (Pulexas and Bunyan series) occupy narrow flood plains. Potential natural vegetation: This area supports oak savanna vegetation with a tall grass understory. Little bluestem, purpletop tridens, indiangrass, switchgrass, big bluestem, post oak, blackjack oak, elm, coralberry, American beautyberry, bumelia, greenbrier, and elbowbush are some of the dominant species. Engelmann-daisy, lespedezas, and trailing wildbeans are among the numerous perennial forbs. 85—Grand Prairie Oklahoma and Texas 31,650 km 2 (12,220 mi 2 ) Land use: Most of this area is in farms and ranches, but urbanization is increasing in the central and southern parts. More than 40 percent is native rangeland, and about 15 percent is improved pasture. Beef cattle are the principal livestock, but dairy cattle and sheep are important in the central and southern parts. About 25 percent of the area, includ¬ ing valleys, bottom lands, and the deeper soils on 61 uplands, is cropland. Oats, wheat, grain sorghum, forage sorghum, cotton, corn, and hay are the princi¬ pal crops. Native pecan orchards are common along the flood plains. Deer and wild turkey hunting leases are an important source of income in the south. Elevation and topography: Elevation is 200 to 400 m but ranges from 400 to 500 m on some of the high peaks in the southwest and in the Arbuckle Moun¬ tains in the north. The area consists of a gently rolling to hilly, dissected limestone plateau and of the low, rugged Arbuckle Mountains. Stream valleys are shallow and narrow in their upper reaches but deepen and broaden near the eastern edge of the area. Steep slopes border the valleys of larger streams and are along the side slopes of flat-topped plateaus and in most of the Arbuckle Mountains. Relief is mainly several meters, but the large valleys are about 50 m below the adjacent uplands. Climate: Average annual precipitation —700 to 1,025 mm. Maximum precipitation is in spring and in fall. More than half of the precipitation falls during the frost-free period. Average annual temperature —17 to 21°C. Average freeze-free period —200 to 260 days. Water: The moderate but somewhat erratic rainfall is the source of water for crops, pasture, and range. The large rivers flow all year. Several large lakes and flood-detention reservoirs are potential sources of water for irrigation but are little used for this pur¬ pose now. Deep ground water is abundant, and many springs and wells are throughout the area. Soils: Most of the soils are Ustolls, Usterts, and Ochrepts. They are well drained and moderately well drained and moderately fine textured and fine textured. They have a thermic temperature regime, an ustic moisture regime, and montmorillonitic, mixed, or carbonatic mineralogy. Moderately deep to deep, nearly level to gently sloping Pellusterts (San Saba, Branyon, and Slidell series) and Chromusterts (Crawford and Sanger series) are on uplands, in upland valleys, and on ancient stream terraces. Shal¬ low to moderately deep, gently sloping Calciustolls (Purves, Bolar, and Denton series) are on the smooth uplands. Very shallow to shallow, gently rolling to hilly, mostly stony or gravelly Haplustolls (Aledo and Eckrant series), Calciustolls (Tarrant, Purves, and Doss series), and Argiustolls (Speck and Tarpley series) are on limestone ridges and plateaus. Shallow, gravelly, or stony Ustochrepts (Brackett series) and Calciustolls (Real series) are on the steeper side slopes of the plateaus. Deep, well drained Haplustolls (Krum series), Argiustolls (Blanket series) and Calciustolls (Venus and Lewisville series) are on outwash in the valleys and along stream terraces. Deep, well drained Haplustolls (Frio, Bosque, and Gowen series) are on flood plains. Deep Argiustolls (Durant series), Paleudolls (Newtonia series), and Haplustalfs (Normangee series) are on smooth up¬ lands in the north. Shallow, stony Haplustolls (Kiti series) and areas of rock outcrop occur on the Arbuckle Mountains in the north. Potential natural vegetation: This area supports prairie vegetation with widely scattered live oak trees. Little bluestem, indiangrass, big bluestem, and switchgrass are typical species. Little bluestem, sideoats grama, tall grama, and scattered shrub live oak and juniper trees characterize the natural vege¬ tation on the very shallow soils and along escarp¬ ments. 86—Texas Blackland Prairie Texas 47,860 km 2 (18,480 mi 2 ) Land use: Nearly all this area is in farms, but urban development is increasing. About 40 percent of the area is cropland, about 45 percent improved pasture or rangeland, and the remainder urban areas or narrow strips of woodland along streams. Cotton and grain sorghum are the major cash crops. Other principal crops are small grain, corn, soybeans, and johnsongrass and other hay crops. Wheat and soy¬ beans are important local crops in the north, and corn is an important crop in the south. Native pecan orchards are common along the flood plains. The present trend is toward a decrease in cropland on the more sloping and eroded soils and an increase in pasture. Beef cattle are the principal livestock. Elevation and topography: Elevation ranges from 100 to 200 m, increasing gradually from south to north and from east to west. The area is mostly a nearly level to gently rolling dissected plain. Nearly level to gently sloping uplands merge into narrow valleys that have more sloping valley walls. Large rivers that cross the area have broad but shallow valleys. Significant tracts of hilly land are along the Austin chalk escarpment near the western side of the area. Relief is mainly from 1 to 10 m. Climate: Average annual precipitation —750 to 1,150 mm. Maximum precipitation is in spring and in fall. Average precipitation during the frost-free period is about 600 to 650 mm. Average annual temperature —17 to 21 °C. Average freeze-free period —230 to 280 days. Water: In most years the moderate rainfall is adequate for crops and pastures, but summer droughts that reduce crop yields are common. The large rivers flow all years. Many large lakes and small flood-detention reservoirs provide municipal water supplies and rec¬ reation facilities and help to control flooding. Small farm ponds on individual farms are an important source of water for livestock. Ground water is scarce throughout the area, but in a few places small quanti¬ ties of water are obtained from wells. Soils: Most of the soils are Usterts, Ustolls, Aqualfs, and Ustalfs. They are well drained to somewhat 62 poorly drained and medium textured to fine textured. These soils have a thermic temperature regime, an ustic or aquic moisture regime, and montmorillonitic, mixed, or carbonatic mineralogy. Moderately deep to deep, nearly level to gently sloping Pellusterts (Houston Black, Branyon, Dalco, Leson, and Burleson series) are on uplands, in valleys, and on stream terraces. Moderately deep to deep, gently sloping to sloping Chromusterts (Heiden, Ferris, and Vertel series) are on eroded uplands. Shallow to moderately deep, gently sloping to moderately steep Haplustrolls (Austin and Stephen series) and very shallow, gently sloping to moderately steep Ustorthents (Eddy series) are on uplands along the Austin chalk escarpment. Deep, nearly level to gently sloping Calciustolls (Lewisville and Venus series) and Haplustolls (Krum series) are in valleys and on stream terraces. Deep, nearly level to sloping Albaqualfs (Mabank series), Ochraqualfs (Wilson series), and Paleustalfs (Crockett series) are on uplands. Somewhat poorly drained Pelluderts (Trinity and Kaufman series), Haplaquolls (Tinn se¬ ries), and moderately well drained Chromusterts (Ovan series) are on flood plains. Potential natural vegetation: This area supports true prairie vegetation in which little bluestem is dominant. Indiangrass, big bluestem, switchgrass, and eastern gamagrass are major species. Many forbs grow in the area. Along major rivers and tributaries, the plant community is a savanna. Oak, elm, cotton¬ wood, hackberry, and pecan produce a 30-percent canopy. Sedges, Virginia and Canada wildrye, rustyseed paspalum, beaked panicum, switchgrass, indiangrass, little and big bluestem, eastern gamagrass, and vine-mesquite are major herbaceous species. Tickclover, trailing wildbean, lespedezas, and gay- feather are common forbs. 87—Texas Claypan Area Texas 13,510 km 2 (5,210 mi 2 ) Land use: Most of this MRLA is in farms. Urban use is inextensive but is expanding in a few places. Most of the farmland is used for pasture and range; some of the pasture was formerly cropped. About half is in improved grasses that are fertilized. Much of the rangeland has been overgrazed. The remaining acreage is in native and annual grasses. The cropland is used principally for grain sorghum, but cotton, corn, pea¬ nuts, hay, and truck crops are important in some places. About a third of the farmland is in wood- lots. Elevation and topography: Elevation ranges from 50 to 200 m. The Claypan Area is a nearly level to sloping plain. Dissected sites are steeper along entrenched river and creek valleys. Valleys of large streams are shallow, and the wide flood plains are bordered by nearly level terraces. Climate: Average annual precipitation —750 to 1,075 mm. Maximum precipitation is in winter and in spring, and the minimum is in summer and in au¬ tumn. Average annual temperature —18 to 22°C, in¬ creasing from north to south. Average freeze-free period —240 to 280 days. Water: The moderate precipitation is the major source of water for crops and pasture. Rainfall in summer is erratic, and in most years crop yields are reduced by a lack of moisture. A few large reservoirs on major streams provide municipal water and also serve as recreation facilities. Water for farm use comes from ponds and wells. Soils: Most of the soils are Ustalfs. They are deep, medium textured and moderately coarse textured soils that have a slowly or very slowly permeable clayey subsoil. They have a thermic temperature regime, an ustic moisture regime, and montmorillonitic mineralogy. Moderately well drained, nearly level and gently sloping Paleustalfs (Axtell and Tabor series) and poorly drained Albaqualfs (Arol, Falba, and Lufkin series) are on the uplands. Interspersed in many places are well drained and moderately well drained Paleustalfs (Tremona, Catilla, Straber, Patilo, Padina, and Silstid series) that have a thick sandy surface. Pelluderts (Kaufman and Trinity series), Pellusterts (Burleson series), Haplustolls (Ships se¬ ries), and Hapludolls (Pledger series) are on flood plains and clayey terraces along the Trinity and Brazos Rivers. Potential natural vegetation: The climax plant com¬ munity in this area is oak savanna. Little bluestem is dominant on all sites except those that are poorly drained. Little bluestem and beaked panicum are dominant in poorly drained areas. Indiangrass, brownseed paspalum, beaked panicum, switchgrass, and big bluestem grow throughout the area. The area also supports a wide variety of forbs, legumes, shrubs, and woody vines such as dayflower, spiderwort, bundleflower, lespedezas, sensitivebrier, hackberry, hawthorn, yaupon, elbowbush, greenbrier, and hon¬ eysuckle. Some mixed pine-hardwood forests are in the southwest and in the east. Hardwood forests of oak, elm, pecan, and other species grow on the wet bottom lands. 63 K—NORTHERN LAKE STATES FOREST AND FORAGE REGION 277,100 km~ (106,990 mi 2 ) Soils poorly suited to cultivation and a short cool growing season severely limit agriculture in this region. The a\ eiage annual precipitation ranges from 500 to 825 mm. Maximum rainfall occurs during the growing season. The average annual temperature is 2 to 7°C, and the freeze-free period ranges from 95 to 145 days. The more or less freely drained Boralfs are the dominant soils. Aqualfs and Aquepts are on wet uplands and in depressions. Psamments and Orthods (mainly in the northeast) are on sand plains. Histosols are in wet low areas and in bogs. A large part of this region is forested, and lumbering and recreation are the principal uses. Mining is a major industry in all parts of the region except in the east. Forage and some grains grown for dairy cattle and other livestock are the mam crops in the farmed areas. Locally, potatoes and vegetables for canning are important crops 57—Northern Minnesota Gray Drift Minnesota 21,440 km 2 (8,280 mi 2 ) Land use: About 50 percent of this area is in farms, and most of the remainder is in timber. A large part of the timber is in a national forest. There are many lakes, and water-based recreation is a significant enterprise. The farms usually are small and are used mainly for growing forage and feed grain for live¬ stock. Sunflowers, wheat, and other cash crops are grown on some farms, mainly in the western part of the area. Elevation and topography: Elevation ranges from 300 to 500 m. The rolling glacial moraine and associated outwash has short, choppy, and complex slopes. Relief varies as much as 25 to 50 m within a short distance. Lakes are common. Climate: Average annual precipitation —525 to 675 mm. About 350 to 450 mm of precipitation falls during the growing season. Snowfall ranges from 100 to 125 cm. Average annual temperature —3 to 6°C. Average freeze-free period —100 to 120 days. Water: The abundant supply of surface and ground water meets all present needs of the area. Many lakes provide ample opportunity for recreation. Soils: Most of the soils are Boralfs. Aqualfs and Fibrists are in wet places and in depressions. The soils are deep and medium textured and have a frigid temper¬ ature regime and mixed mineralogy. Well drained and moderately well drained, nearly level to sloping Eutroboralfs (Nebish, Waukon, and Warba series) are on uplands. Ochraqualfs (Shooker series) are on level sites. Borofibrists (Brophy series) and Sphag- nofibrists (Waskish series) formed in organic materi¬ als in depressions. Potential natural vegetation: This area supports forest vegetation. Aspen, northern hardwoods, white spruce, blackberry, blue cohosh, and false-Solomons- seal grow on the finer textured soils. Bur oak, red pine, jack pine, wintergreen, roses, and big bluestem grow on the sandy soils. 88—Northern Minnesota Glacial Lake Basins Minnesota 31,010 km 2 (11,970 mi 2 ) Land use: More than 80 percent of this area is forested and is used mainly for lumbering and recreation. The remainder is used for growing feed grains and forage for beef and dairy cattle. Some grass and legume seed are produced as a cash crop. An adverse climate and poorly drained soils severely limit use of the land for agriculture. Elevation and topography: Elevation ranges from 300 to 400 m. This area is nearly level. At one time it was occupied by broad glacial lakes. Climate: Average annual precipitation —500 to 675 mm. About 350 to 450 mm fall during the growing season. In most years, snowfall ranges from 102 to 127 cm. Average annual temperature —3 to 5°C. Average freeze-free period— 95 to 105 days. Water: Ample water supplies meet the present needs of the area. There are a few large lakes and major streams. Soils: Most of the soils are Aqualfs, Boralfs, Saprists, and f ibrists. The mineral soils are deep and medium textured to fine textured and have a frigid tempera¬ ture regime and mixed mineralogy. Well drained and moderately well drained, level and gently sloping Eutroboralfs (Baudette and Taylor series) and poorly drained Ochraqualfs (Indus and Spooner series) are in lacustrine materials. Borosaprists (Rondeau and Cathro series) and Sphagnofibrists (Wasish series) formed in organic residues in the wetter depressional parts of the area. Potential natural vegetation: This area supports swamp and forest vegetation. Black spruce and vary¬ ing mixtures of tamarack, northern white-cedar, and black ash are in conifer swamps. Low shrubs, mosses, and herbaceous plants such as Labradortea ledum, leatherleaf, creeping snowberry, marshmarigold, sedges, and sphagnum mosses are in bog swamps. The mineral soils support species such as quaking aspen, balsam fir, northern hardwoods, mountain maple, glossy buckthorn, skunk currant, and sweet white violet. 90—Central Wisconsin and Minnesota Thin Loess and Till Minnesota and Wisconsin 55,750 km 2 (21,530 mi 2 ) Land use: Except for the state and national forests and some Indian reservations, nearly all this area is in farms. Slightly more than one-fourth is cropland used mainly for growing feed grains and forage for dairy cattle. Potatoes, sweet corn, and canning peas are important cash crops. Other vegetables and fruits are grown locally. About one-sixth of the area is pasture and native grasses. Most of the remainder is forested, mainly farm woodlots and state and na¬ tional forests. Forested areas are used for pulp and timber production and for recreation. Controlling erosion on steep slopes and improving drainage on wet soils are the principal concerns of management. Elevation and topography: Elevation ranges from 300 to 500 m. Locally, the level to rolling till plains are mantled by loess. The topography is irregular; there are nearly level outwash plains and lacustrine basins, low hills and ridges, and many lakes and organic deposits in basins. Local relief is mainly a few meters, but some hills rise more than 50 m above the adjacent lowlands. Climate: Average annual precipitatioji —625 to 750 mm. Most of the precipitation falls during the grow¬ ing seasQp. Winter precipitation is mainly snow. Average annual temperature —4 to 7°C. Average freeze-free period —120 to 140 days. Water: The moderate precipitation generally is ade¬ quate for crops and pasture, but in dry years crops on sandy soils are damaged by a lack of moisture. Most of the wet lowland soils need to be drained for good crop and forage production. Ground water is abun¬ dant in deep glacial drift deposits but scarce in areas where the drift is thin. The many lakes and streams are also sources of water. Soils: Most of the soils are Boralfs. They are moder¬ ately deep to deep and medium textured and have a frigid temperature regime and mixed mineralogy. Well drained and moderately well drained, nearly level to moderately sloping Glossoboralfs (Santiago, Otterholt, Spencer, and Antigo series), somewhat poorly drained, nearly level to moderately sloping Glossaqualfs (Almena and Withee series), and nearly level to moderately sloping Ochraqualfs (Freer se¬ ries) in loess-mantled drift are on outwash and till plains. Ochraqualfs (Marshfield series), Glossaqualfs (Auburndale series), Haplaquepts (Cable and Rib series) and Haplaquolls (Adolph series) are the lower lying wet mineral soils. Borosaprists (Seeleyville and Lupton series) and Borohemists (Rifle and Green¬ wood series) in the deeper depressions formed in organic residue from plants. Udipsamments (Plainfield, Menahga, and Friendship series) are on the sandy outwash plains. Udifluvents are on the flood plains of rivers and streams. Potential natural vegetation: This area supports natural stands of mixed northern hardwood forest vegetation on the medium textured soils. Oak, maple, white ash, elm, and basswood are dominant species. Natural stands of jack, red, and white pine grow on the sandy soils. Pioneer species of aspen, paper birch, and cherry are on the uplands; spruce and larch are in the depressions. Growing in some parts of the west are prairie vegetation characterized by little and big bluestem and scattered oak trees. 91 —Wisconsin and Minnesota Sandy Outwash Minnesota and Wisconsin 52,780 km 2 (20,380 mi 2 ) Land use: About 90 percent of this area is in farms. About 10 percent, mostly in Wisconsin, is state and federally owned. Nearly one-third of the area is cropland. Feed grains and forage for livestock are the main crops, but truck crops are also important. Potatoes and canning crops such as snap beans, peas, and corn are commonly grown under irrigation. Cran¬ berries are grown on some wet soils. About one-tenth of the area is forested and used mainly for pulp and timber production. These forested areas and associated lakes and streams provide recreation facilities. Con¬ trolling soil blowing and conserving moisture on sandy soils, improving drainage on wet soils, and maintaining soil fertility are major concerns of man¬ agement. Elevation and topography: Elevation is about 300 m. Topography ranges from uniformly level areas in some places to irregular nearly level and gently rolling areas. In Minnesota many lakes are in basins and depressions. Local relief throughout the area is mostly from 1 to 10 m. Climate: Average annual precipitation —About 625 mm in Minnesota and 750 to 825 mm in Wisconsin. Most of the precipitation falls during the growing season. Precipitation in winter is snow. Average annual temperature —4 to 7°C. Average freeze-free period —125 to 145 days. Water: In years of normal precipitation, the moderate precipitation is inadequate for crops and pasture on sandy soils. In years of little or no precipitation, crop yields are seriously reduced. Irrigation is widely used for high-value crops. The wet lowland soils need to be drained for good crop production. Ground water is abundant in the glacial deposits. Soils: Most of the soils are Psamments. They are deep and coarse textured and have mesic and frigid tem¬ perature regimes and mixed mineralogy. Well drained 65 and moderately well drained, nearly level and rolling Udipsamments (Plainfield, Coloma, Brems, Menahga, and Zimmerman series) and somewhat poorly drained, nearly level and rolling Udipsamments (Morocco and Meehan series) are on sandy outwash plains or on sandy till uplands. Humaquepts (Newton series) and Haplaquolls (Isanti series) are underlain by sandy drift on wet lowlands. Borosaprists (Seeleyville and Lupton series) and Borohemists (Rifle and Green¬ wood series) in deeper depressions formed in organic residue from plants. Nearly level and gently rolling Argiudolls (Dakota series), Hapludolls (Dickman, Burkhardt, Sparta, and Dickinson series), and Hapludalfs (Tell, Meridian, and Wyocena series) formed on outwash and till uplands that have a loamy cover¬ ing over the sandy drift. Udifluvents are on flood plains of rivers and streams. Potential natural vegetation: This area supports oak-pine forest vegetation. Mixed forest stands of pin oak and jack pine grow on coarse textured upland soils. Big and little bluestem and scattered trees are in prairie openings. Loamy upland soils support oak-hickory forest vegetation. Sedge meadows, spruce and larch, and aspen and jack pine grow on low wetlands. 92—Superior Lake Plain Michigan, Minnesota, and Wisconsin 4,950 km 2 (1,910 mi 2 ) Land use: More than three-fourths of this area is forested, nearly all of which is privately owned and used for timber production and for recreation. Be¬ tween 5 and 10 percent is cropland. Feed grains and hay for dairy cattle and other livestock are the principal crops. Locally, potatoes and small fruit are important cash crops. Only 1 or 2 percent of the land is pasture. Elevation and topography: Elevation ranges from 200 to 300 m, increasing gradually from the lakeshore inland. Some rocky knobs, hills, and low mountains make up part of this nearly level lake plain. Local relief on the lake plain is only a meter or two, but the adjoining hills and mountains rise sharply 25 m to more than 100 m above the plains. Climate: Average annual precipitatiom-625 to 875 mm. Maximum precipitation is in midsummer and the lowest in midwinter. Precipitation in winter is snow. Average annual temperature— 3 to 6°C. Average freeze-free period— Less than 100 days to 140 days, decreasing from the lakeshore inland. Water: Precipitation is adequate for crops and pasture. Level areas of wet soils need to be drained for good growth of crops. There are few inland lakes, but much of the area has access to Lake Superior for recreation. Soils: The dominant soils are Boralfs and Orthods. They are deep and moderately deep and fine textured to moderately coarse textured. These soils have a frigid temperature regime and mixed or illitic miner¬ alogy. Well drained to somewhat poorly drained Eutroboralfs (Ontonagon, Rudyard, and Watton se¬ ries) formed in clayey and loamy lacustrine sediments and glacial till. Well drained Haplorthods (Michagamme series) formed in glacial drift over bedrock, and Fragiorthods (Gogebic, Iron River, and Munising series) formed in loamy glacial till. Associated soils are Haplaquepts (Pickford series) and Haplaquods (Tula series). Potential natural vegetation: This area supports for¬ est vegetation of broadleaf deciduous and needleleaf evergreen trees. Sugar maple, yellow birch, American beech, and hemlock are the dominant tree species. White spruce, balsam fir, paper birch, and red maple commonly grow on the wetter soils. 93—Superior Stony and Rocky Loamy Plains and Hills Michigan, Minnesota, and Wisconsin 56,080 km 2 (21,650 mi 2 ) Land use: More than four-fifths of this area is forested, about half of which is privately owned, and half consists of county, state, or national forests. Lumber¬ ing, mining, and recreation are important. Only about 10 percent of the area is cropland or pasture. Feed grains and forage for dairy cattle and other livestock are the main crops. In places potatoes are an important cash crop. Cranberries are grown on wet soils in some parts of Wisconsin. Some soils are too stony or too rocky to be used for crops. A short growing season, improving drainage on wet soils, and maintaining fertility are the principal concerns of management. Elevation and topography: Elevation ranges from 300 to 600 m, but on a narrow strip bordering the Great Lakes it is about 200 m. These undulating to rolling glacial drift plains are bordered on the north by high hills. Local relief is mainly a few meters to several tens of meters. In many places the hills rise 100 or 200 m above the adjacent lowlands. Many small lakes and some large lakes are in this area. Climate: Average annual precipitation —750mm. About two-thirds of the precipitation falls during the grow¬ ing season. Precipitation in winter is snow. Average annual temperature—2 to 6°C. Average freeze-free period —80 to 140 days, decreasing with increasing elevation and from the Great Lakes inland. Water: The moderate precipitation generally is ade¬ quate for crops and pasture, but in years of little or no precipitation, crops on sandy soils are damaged by a lack of moisture. Most of the soils on wet lowlands need to be drained for good crop and forage produc¬ tion. Ground water is abundant in deep glacial depos¬ its but scarce in areas where the drift is thin. The lakes and streams are additional sources of water. 66 Soils: Most of the soils are Orthods. They are moder¬ ately deep to deep, somewhat stony, and medium textured. These soils have a frigid temperature re¬ gime, an udic moisture regime, and mixed mineralo¬ gy. Moderately well drained and well drained Fragiorthods, which have a fragipan, (Munising, Gogebic, Wakefield, and Iron River series) and Haplorthods (Goodman and Stambaugh series) are on outwash plains and uplands. Nearly level Haplaquepts (Cable series) are on lowlands. Borosaprists (Seelye- ville, Loxley, and Carbondale series) and Borohemists (Rifle, Greenwood, and Spalding series) are in deeper depressions. They formed in plant residue. Sandy Haplorthods (Vilas, Kalkasa, and Rubicon series) formed in sandy drift scattered throughout the area. Areas of stony land and rock land are on some of the steeper slopes, knobs, and hills. Potential natural vegetation: The upland soils in this area support natural stands of mixed northern hardwood and pine forest vegetation. Sugar maple, yellow birch, hemlock, white pine, and red pine are the dominant species. The lowland areas support natural stands of spruce and larch forest vegetation or sphagnum moss bogs. Aspen, paper birch, and cherry are pioneer species on the upland soils. 94A—Northern Michigan and Wisconsin Sandy Drift Michigan, Minnesota, and Wisconsin 39,920 km 2 (15,410 mi 2 ) Land use: About a third of this MLRA consists of national and state forests; another third is in small privately owned holdings. There are a few large hold¬ ings. The forests are used mainly for lumbering and recreation. Forage and feed grains for dairy cattle and other livestock are the principal crops. In places potatoes are an important cash crop, and other vegetables and fruit are also grown. Cranberries are grown on lowland soils in Wisconsin. Elevation and topography: Elevation ranges from 200 m along the lakeshores to more than 500 m in the central part. Belts of morainic hills make up part of this broad glacial-drift plain. Much of the area is nearly level to gently rolling, and local relief is only a few meters, but in the morainic areas local relief ranges from several meters to more than 100 m. Climate: Average annual precipitation —675 to 850 mm. Precipitation is fairly evenly distributed in late spring through early autumn. Minimum precipitation is in winter; winter precipitation is mainly snow. Average annual temperature —4 to 7°C. Average freeze-free period —120 to 140 days along the lake- shores, but in some low areas it is as short as 80 days. Water: Because of the moderate precipitation, mois¬ ture must be carefully managed to insure that enough water is available for crops and pasture grown on the sandy soils. The wet soils on lowlands must be drained before they can be used for field crops and tame pasture commonly grown in the area. Ground water is abundant in the deep glacial drift that covers nearly all the area. Many large and small lakes are used extensively for recreation. Soils: Most of the soils are Orthods or Saprists. They have a frigid temperature regime, and the mineral soils have mixed mineralogy. Deep, coarse textured, and moderately coarse textured Haplorthods (Kalkaska, Vilas, Rubicon, Emmett, and Montcalm series) formed in sandy or loamy glacial drift. The associated very poorly drained Borosaprists (Carbondale, Lupton, and Tawas series) formed in organic materials in depressions. Also important in the area are Udi- psamments (Grayling and Omega series) on outwash plains, Psammaquents (Roscommon series) and Haplaquods (Au Gres and Kinross series) in flat, wet areas, and Eutroboralfs (Nester, Kawkawlin, and Rudyard series) and Haplaquepts (Pickford and Sims series) on moraines, till plains, and lake plains. Potential natural vegetation: This area supports for¬ est vegetation of broadleaf deciduous and needleleaf evergreen trees. Jack pine, red pine, and bigtooth aspen are the dominant tree species on the more sandy soils. Sugar maple, yellow birch, American beech, and hemlock are dominant on the moist sites. Tamarack, black spruce, and northern white-cedar are dominant on the wet soils. 94B—Michigan Eastern Upper Peninsula Sandy Drift Michigan 15,170 km 2 (5,860 mi 2 ) Land use: About 5 percent of this MLRA is cropland; most of the rest is forested. More than half of the forest land is in national and state forests. Most of the remaining forest land is in small holdings, but there are a few large holdings. The forests are used mainly for lumbering and recreation. Forage and feed grains for dairy cattle and other livestock are the principal crops. Elevation and topography: Elevation ranges from 200 to 300 m, increasing gradually from the shores of the Great Lakes inland. This broad glacial-drift plain consists of some broad swampy areas. Much of this area is nearly level to gently rolling, and local relief is only one or two meters. Climate: Average annual precipitation —725 to 850 mm. Precipitation is fairly evenly distributed from late spring through early autumn. Minimum precipitation is in winter; precipitation in winter is mainly snow. Average annual temperature —4 to 6°C. Average freeze-free period —90 to 155 days. Water: Because of the moderate precipitation, mois¬ ture must be carefully managed to insure that enough water is available for crops and pasture grasses grown on the sandy soils. The wet soils on lowlands 67 must be drained before they can be used for field crops and tame pasture grasses commonly grown in the area. Ground water is abundant in the deep glacial drift. Soils: Most of the soils are Orthods, Saprists, or Hemists. They have a frigid temperature regime, and the mineral soils have mixed mineralogy. Deep, coarse textured and moderately coarse textured, well drained and moderately well drained Haplorthods (Kalkaska, Rubicon, Emmet, Onaway, and Longrie series) and Fragiorthods (Trenary series) formed in sandy or loamy glacial drift. The associated very poorly drained Borosaprists (Carbondale, Lupton, and Tawas series) and Borohemists (Greenwood and Rifle series) formed in organic materials in depres¬ sions. Also important in the area are Eutroboralfs (Rudyard and Ontonagon series) and Haplaquepts (Pickford and Munuscong series) on moraines, till plains, and lake plains and Psammaquents (Roscommon series) and Haplaquods (Au Gres series) on flat, wet sites. Locally Eutrochrepts (Detour series) and Haploborolls (Johnswood series) are important on till plains and glacial lake benches. Potential natural vegetation: This area supports for¬ ests of broadleaf deciduous and needleleaf evergreen trees. Sugar maple, paper birch, balsam fir, hem¬ lock, yellow birch, and American beech are the dominant tree species. Jack pine, red pine, and white pine are major species on the more sandy soils. Black spruce, northern white-cedar, and tamarack are domi¬ nant on the wetter soils. 68 L—LAKE STATES FRUIT, TRUCK, AND DAIRY REGION 193,780 km 2 (74,820 mi 2 ) The soils and climate in this region are favorable for agriculture. Typically, the land surface is a nearly level to gently sloping glaciated plain. The average annual precipitation ranges from 675 to 925 mm, but it is 1,150 mm in the extreme eastern part. Precipitation is fairly evenly distributed throughout the year. In most of the region, the average annual temperature is 6 to 11°C. The freeze-free season generally is 130 to 180 days, but it is as long as 200 days in narrow belts adjacent to the Great Lakes. The dominant well drained soils in this region are Udalfs in the southern part and Boralfs in the northern part. Aqualfs and Aquepts are the dominant wet soils throughout the region. The sandy soils are Psamments and Orthods. Histosols are in low wet areas and in bogs. This region has a wide variety of agricultural enterprises. Dairy farming is important. Canning crops, corn, soft winter wheat, beans, and sugar beets are among the leading crops. Fruits, especially sour cherries, are important in a narrow belt adjacent to the Great Lakes. Much of the cropland near the larger cities is being subdivided and developed for urban uses. 95A—Northeastern Wisconsin Drift Plain Michigan and Wisconsin 15,760 km 2 (6,090 mi 2 ) Land use: More than 90 percent of this MLRA is in farms, nearly 60 percent of which is cropland. Feed grains and hay are the chief crops. Much of the grain is fed to dairy cattle and other livestock on the farms where it grows. Canning crops, fruits, and specialty crops are important. The rest of the land in farms is about equally divided between tame pasture and farm wood- lots. Less than 5 percent of the MLRA is used for urban development. Recreation is an important land use, especially along the major streams and on sites bordering Green Bay and Lake Michigan. Controlling erosion on the steeper slopes and improving drainage on wet soils are primary concerns of management. Elevation and topography: Elevation ranges from 200 to 400 m. Locally, the nearly level to rolling till plains are mantled by silt. Nearly level outwash plains and lacustrine basins, low hills, and ridges are throughout the area. Some lakes and bogs are in basins. Local relief is mainly several meters, but some hills rise more than 50 m above the adjacent lowlands. Climate: Average annual precipitation —700 to 750 mm. About two-thirds of the precipitation falls dur¬ ing the growing season. Winter precipitation is mainly snow. Average annual temperature —6 to 8°C. Aver¬ age freeze-free period —120 to 160 days; the longest period is in the south and in a narrow belt along Lake Michigan. Water: The moderate precipitation generally is ade¬ quate for crops and pasture, but in years of little or no precipitation, crops on sandy soils are damaged by a lack of moisture. Most of the wet soils on lowlands need to be drained for good crop and forage produc¬ tion. Ground water is plentiful in deep glacial drift deposits except in areas where the drift is clayey. Lakes and streams are additional sources of water. Soils: Most of the soils are Udalfs. They are moder¬ ately deep to deep and medium textured and fine textured. These soils have a mesic temperature re¬ gime, an udic moisture regime, and mixed mineralo¬ gy. Well drained and moderately well drained, nearly level to sloping Hapludalfs (Kewaunee, Hortonville, and Theresa series) and Argiudolls (Hochheim series) and somewhat poorly drained, nearly level to sloping Hapludalfs (Manawa and Symco series) are on till plains. In the north, moderately deep to deep, me¬ dium textured and moderately coarse textured Orthods, which have a frigid temperature regime and mixed mineralogy, are dominant. Well drained and moder¬ ately well drained, gently undulating to sloping Haplorthods (Onaway, Emmet, and Longrie series) and Eutroboralfs (Underhill series) and somewhat poorly drained, gently undulating to sloping Eutro¬ boralfs (Solona series) are on till plains. Haplaquepts (Angelica and Ensley series) in loamy drift and Haplaquolls (Poygan series) in clayey and silty drift are on the lower lying wet mineral sites. Borosaprists (Seeleyville, Lupton, Cathro, and Carbondale series) and Borohemists (Rifle series) that formed in organic residue from plants are in the deeper depressions. Potential natural vegetation: The upland soils in this area support natural stands of mixed northern hardwoods and pine forest vegetation. Sugar maple, oak, white ash, elm, yellow birch, white and red pine, and American beech are the principal species. Low¬ land areas support both mixed hardwood and conifer forest vegetation. Elm, soft maple, black ash, and northern white-cedar are major species. 69 95B—Southern Wisconsin and Northern Illinois Drift Plain Illinois and Wisconsin 28,530 km 2 (11,020 mi 2 ) Land use: More than 90 percent of this MLRA is in farms, 65 percent of which is cropland. Feed grains and forage for livestock are the chief crops. Much of the feed grain and forage is fed to dairy cattle and other livestock on the farms where they are grown, but cash-grain farming is also important. Canning crops, potatoes, fruits, and other specialty crops are important, especially around urban centers. The rest of the land in farms is about equally divided between tame pasture and farm woodlots. Urban areas, mostly in the south and east, make up the rest of the MLRA. Recreation is becoming important. Some of the better farmland is increasingly used for urban development. Controlling erosion on slopes and improving drainage on wet soils are the major concerns of management. Elevation and topography: Elevation ranges from 200 to 300 m. This area consists of a glaciated plain with belts of morainic hills and ridges and nearly level outwash terraces. Drumlins (long steep-sided oval hills) are a prominent feature in the north- central part. Local relief is mainly a few meters, but the moraines, drumlins, and bedrock escarpments rise 25 to 100 m above the adjacent lowlands. Climate: Average annual precipitation —750 to 825 mm. About two-thirds of the precipitation falls dur¬ ing the growing season. Precipitation in winter is mainly snow. Average annual temperature —7 to 9°C. Average freeze-free period —140 to 170 days, decreas¬ ing from south to north and from Lake Michigan shore inland. Water: The moderate precipitation generally is ade¬ quate for crops and pasture, but in years of little or no precipitation, some crops on coarse textured soils are damaged by a lack of moisture. Many of the fine textured soils need water management practices that facilitate tillage and harvesting operations. Poorly drained soils must be drained for good production of cultivated crops. Ground water is abundant in the underlying drift; sandy and gravelly drift yields the largest amount. Sandstone and limestone bedrock formations below the glacial drift are good sources of water. Lake Michigan and the many inland lakes and streams are additional sources of water for domestic use and for recreation. Soils: Most of the soils are Udalfs. They are moder¬ ately deep to deep and medium textured. These soils have a mesic temperature regime, an udic moisture regime, and mixed mineralogy. Moderately well drained and well drained Hapludalfs (Miami, McHenry, Fox Ozaukee, and Theresa series) formed in loamy glacial drift, commonly with a thin silt mantle, on nearly level to sloping relief. Moderately deep, medium textured Argiudolls (Pair, Plano, Saybrook, Ringwood, and Hochheim series) are associated soils on the same landforms. Haplaquolls (Will and Pella series) and Argiaquolls (Brookston, Westland, Sebewa, and Mussey series) formed in medium textured material on the lowlands. Udipsamments (Plainfield, Oakville, and Chelsea series) are on some of the sandy sites. Udifluvents (Junear and Arenzville series) and Hapludolls (Radford series) are in silty sediments on flood plains. Potential natural vegetation: This area supports hardwood forest and prairie vegetation. The upland soils support natural stands of oak, sugar maple, and hickory forests and natural prairie characterized by little and big bluestem. Scattered oak and hickory trees grow in many of the prairies. Lowland areas support sedge and grass meadows and mixed stands of hardwood and conifer forests. Elm, ash, cottonwood, soft maple, and white cedar are the major species in the lowland forests. 96—Western Michigan and Northeastern Wisconsin Fruit Belt Michigan and Wisconsin 10,650 km 2 (4,110 mi 2 ) Land use: In Michigan about 60 percent of the area is forested, mainly farm woodlots; about 25 percent is cropland; and 10 percent or more consists of state and national forests and parks. In Wisconsin about 30 percent of the area is forested. Most of the remainder is cropland, and about 10 percent is native and tame pasture. Forage and feed grains for dairy cattle are the major crops, but fruits and specialty crops are also grown and are of great economic importance. This is one of the major areas of production of cherries in the United States. Recreation is an important land use, especially on sites bordering Lake Michigan and Green Bay. Controlling soil blowing and water ero¬ sion, conserving moisture, and improving drainage on wet soils are the principal concerns of manage¬ ment. Elevation and topography: Elevation ranges from 200 to 300 m. This area consists mostly of rolling to hilly moraines and beach ridges, but there are some nearly level plains and bedrock-controlled ridges. Local relief is mainly several meters, but in places, hills rise more than 50 m above the adjacent low¬ lands. Much of the area rises sharply from the lakeshore to the adjoining hilltops. Climate: Average annual precipitation —675 to 750 mm. Most of the precipitation falls during the grow¬ ing season. Precipitation in winter is snow. Average annual temperature —6 to 8°C. Average freeze-free period —135 to 170 days, increasing from north to south and decreasing from the lakeshore inward. Water: In years of normal precipitation, moisture is adequate for crops, but in years of little or no 70 precipitation, yields are reduced because of a lack ol moisture, especially on the sandy soils and in areas where bedrock is at a shallow depth. Ground water is abundant in the deep sandy and loamy drift areas. Fissures in the limestone bedrock in Wisconsin are also a good source of water. Lake Michigan, Green Bay, and numerous inland lakes are an additional source of water. Soils: Most of the soils are Orthods or Boralfs. They are moderately deep to deep and medium textured to coarse textured. These soils have a frigid tempera¬ ture regime, an udic moisture regime, and mixed mineralogy. Well drained Haplorthods (Montcalm, Kalkaska, Rubicon, Emmet, Onaway, and Longrie series) in loamy or sandy textured glacial drift are dominant. Well drained Eutroboralfs (Kolberg se¬ ries) in thin loamy glacial drift over lime rock are important in Wisconsin. In Michigan, well drained and moderately well drained Eutroboralfs (Nester series) and somewhat poorly drained Eutroboralfs (Kawkawlin series) formed in deep glacial drift. Udipsamments (Grayling series) formed in deep sands. Haplaquepts (Ensley and Ruse series), Haplaquods (Kinross and Au Gres series), and Psammaquents (Roscommon series) formed in sandy and loamy ma¬ terials in low-lying areas. Borosaprists (Carbondale, Lupton, Cathro, and Seelyeville series) formed from organic remains of plants in the deeper depressions. Potential natural vegetation: This area supports forest vegetation consisting of broadleaf deciduous and needleleaf evergreen trees. Sugar maple, yellow birch, beech, and hemlock are the dominant tree species. Jack pine, red pine, and white pine are dominant on the more sandy soils. Lowland soils support both mixed hardwood and conifer forests. Elm, soft maple, black ash, and white cedar are the major lowland species. 97 —Southwestern Michigan Fruit and Truck Belt Michigan 5,960 km 2 (2,300 mi 2 ) Land use: Nearly four-fifths of this MLRA is in farms, slightly more than half of which is cropland. Fruits, especially peaches and grapes, are grown extensively near the Lake Michigan shore. Many other fruits, vegetables, and melons are also grown. Forage and feed grains for dairy cattle and other livestock are important crops. Some land is in permanent pasture, but most of the farmland that is not cultivated is in woodlots. A large part of the area that is not in farms is in state forests and parks, and about 5 percent is used for urban development. Elevation and topography: Elevation is about 200 m, but some hills are 300 m. This area consists of a nearly level glacial-drift plain and scattered, gently to strongly rolling morainic hills. Local relief is only a few meters in most places, but in the rolling areas local relief is 25 to 50 m. Climate: Average annual precipitation —825 to 925 mm. Precipitation is fairly evenly distributed through¬ out the year, but it is slightly greater late in spring and early in summer and is lower in midwinter. Precipitation in winter is snow. Average annual temperature —9 to 10°C. Average freeze-free period —160 to 180 days, decreasing from west to east. Water: In years of normal precipitation, moisture is adequate for crops, but in years of little or no precipitation, yields are reduced by a lack of mois¬ ture. Most of the fine textured soils need artificial drainage to insure that tillage operations are not delayed in spring and in fall. Wet areas must be drained for good growth of crops. The deep glacial deposits yield an abundance of ground water for domestic, municipal, and industrial uses. The many small lakes in this area are used extensively for boating, fishing, and other recreation. Soils: Most of the soils are Udalfs. They are deep, moderately coarse textured and coarse textured. These soils have a mesic temperature regime, an udic moisture regime, and mixed mineralogy. Well drained Hapludalfs (Oshtemo and Spinks series) that formed in loamy or sandy glacial drift are dominant. Associated soils are Udipsamments in deep sand (Oakville se¬ ries) and Ochraqualfs (Blount series) and Hapludalfs (Miami and Morley series) in loamy glacial till. Medisaprists (Houghton series) are in depressions throughout the area. Potential natural vegetation: This area supports broadleaf deciduous forest vegetation. Bitternut hick¬ ory, shagbark hickory, white oak, red oak, black oak, American beech, and sugar maple are the dominant tree species. White ash, red maple, quaking aspen, and black cherry are extensive on the wet sites. 98—Southern Michigan and Northern Indiana Drift Plain Illinois, Indiana, and Michigan 60,050 km 2 (23,190 mi 2 ) Land use: About three-fourths of this MLRA is in farms; much of the remainder is used for urban develop¬ ment, and a small acreage is in state forests and parks. More than one-half of the area is cropped. Corn, other feed grains, and hay for dairy cattle and other livestock are the major crops. Soft winter wheat and dry beans are important cash crops, and fruits and vegetables are grown in many places where the soils and markets are favorable. Less than 10 percent of the area is permanent pasture, and most of the rest of the farmland is in small woodlots. Elevation and topography: Elevation ranges from 200 to 300 m, but some hills are more than 300 m. This broad glaciated plain is deeply mantled by till and outwash. Much of the area is nearly level to 71 gently rolling, and local relief is a few meters. Belts of morainic hills, however, have stronger slopes, and relief is as much as 25 to 50 m or more. Climate: Average annual precipitation —750 to 925 mm. Precipitation is fairly evenly distributed through¬ out the year, but it is slightly higher late in spring and early in summer. Average annual temperature —8 to 9°C. Average freeze-free period —mainly 140 to 150 days but is 160 days in the southwest. Water: In much of the area, the moderate precipitation is adequate for crops, but conserving moisture in the coarse textured soils is a major concern of manage¬ ment. Ground water is abundant in the deep glacial drift. Many small and medium-size lakes and many perennial streams are additional sources of water. The lakes are used extensively for recreation. Soils: Most of the soils are Udalfs or Aqualfs. They are deep, medium textured and moderately coarse textured. These soils have a mesic temperature re¬ gime, an udic or aquic moisture regime, and mixed mineralogy. In the south, well drained Hapludalfs (Miami, Hillsdale, Riddles, Fox, and Oshtemo series) and somewhat poorly drained Ochraqualfs (Conover series) that formed in loamy glacial drift are domi¬ nant. Associated soils are Argiaquolls (Brookston series) and Haplaquolls (Colwood, Gilford, Maumee, and Granby series) on flats; rolling, excessively drained to moderately well drained Udipsamments (Plainfield and Oakville series); and nearly level and gently sloping, moderately well drained and somewhat poorly drained Udipsamments (Brems and Morocco series). In the south, well drained and moderately drained Hapludalfs (Marlette and Perrington series), some¬ what poorly drained Hapludalfs (Ithaca series), and poorly drained Ochraqualfs (Capac series) in loamy glacial till are dominant. Associated soils are Hap- laquepts (Parkhill series) and Psammaquents (Kingsville series). Medisaprists (Houghton, Palms, Adrian, and Edwards series) are in depressions throughout the area. Haplorthods are of local importance in the northwest. Potential natural vegetation: This area supports broadleaf deciduous forests. Bitternut hickory, shag- bark hickory, white oak, red oak, black oak, sugar- maple, and beech are the dominant tree species. Red maple, white oak, and American basswood are exten¬ sive on the wetter soils. 99—Erie-Huron Lake Plain Indiana, Ohio, and Michigan 35,780 km 2 (13,810 mi 2 ) Land use: Nearly nine-tenths of this MLRA is in farms, about two-thirds of which is cropland. Cash crops are important. Corn, winter wheat, soybeans, and hay are the major crops, but sugar beets and canning crops also are important. Some fruit and truck crops are grown on the coarse textured soils. Dairying is an important enterprise on some farms near the larger cities. The remaining farmland is used for permanent pasture and for other purposes, but most of it is in small farm woodlots. About 10 percent of the area is used for urban development. Elevation and topography: Elevation is about 200 m, increasing gradually from the lakeshore inland. Local relief on most of this nearly level broad lake plain is only a few meters, but some beach ridges and low moraines rise several meters above the general level. Climate: Average annual precipitation —700 to 875 mm. Precipitation is fairly evenly distributed through¬ out the year, but it is slightly higher late in spring and early in summer. Average annual temperature —7 to 11°C. Average freeze free period —140 to 160 days. Water: In most years the moderate precipitation pro¬ vides enough water for crops. Many of the soils require artificial drainage before they can be used for crops, and even the better drained soils need some drainage to insure that tillage operations are not delayed in spring and in fall. The abundant ground water meets domestic and municipal needs in much of the area. The Great Lakes supply water for large cities, are major transportation arteries, and are used for recreation. Soils: Most of the soils are Aqualfs or Aquepts. They are deep and fine textured to coarse textured. These soils have a mesic temperature regime, an aquic moisture regime, and mixed or illitic mineralogy. The dominant soils are somewhat poorly drained to very poorly drained Ochraqualfs (Nappanee and Hoytville series) and poorly drained and very poorly drained Haplaquepts (Lenawee and Toledo series) that formed in lacustrine and glacial drift. Associated soils are Haplaquolls (Belleville, Colwood, Granby, and Wauseon series), Udipsamments (Tedrow series), and Hapludalfs (Kibbie, Selfridge, and Metea series). Somewhat poorly drained Ochraqualfs (Shebeon series) and poorly drained Haplaquepts (Kilmanagh series), along with associated Haplaquolls (Tappan series) and some Haplaquods (Wixom and Arkona series), are in the “thumb” area of Michigan. Potential natural vegetation: This area supports broadleaf deciduous forests. Bitternut hickory, shag- bark hickory, white oak, red oak, and black oak are dominant. Red maple, white ash, American bass¬ wood, and quaking aspen are dominant on the wetter soils. 100—Erie Fruit and Truck Area New York, Ohio, and Pennsylvania 4,260 km 2 (1,640 mi 2 ) Land use: Slightly more than two-thirds of this MLRA is in farms, about a third of which is cropland and the rest about equally divided between pasture and 72 woodland. Small areas, however, are used for rural residences and for other purposes. The cropland is used for vineyards, orchards, small fruits, canning crops, and truck crops. Dairying is an important enterprise, especially near the larger cities. A large part of the area not in farms is used for urban development, major highways, and railroads. Parks occupy a sizable acreage. Elevation and topography: Elevation is about 220 m, increasing gradually from the lakeshore inland. This nearly level to gently sloping plain is underlain mainly by lacustrine sediments and partly by glacial till. Low beach ridges are a prominent feature. Local relief is mainly a few meters, but in some places along the lakeshore there are steep wave-cut cliffs. Climate: Average annual precipitation —750 to 900 mm. Precipitation is evenly distributed throughout the year. Heavy snowfall is common in winter. Aver¬ age annual temperature —10 to 11°C. Average freeze- free period —Mainly 160 to 180 days, but it is 200 days in a narrow belt in Ohio. Water: In most years precipitation is adequate for crops except for those on the coarse textured soils. Supplemental irrigation water for high-value fruit and vegetable crops is obtained from wells or from the Great Lakes. The wetter soils must be drained before they can be used for crops, and even the better drained soils benefit from drainage. The abun¬ dant ground water meets domestic, industrial, and municipal needs in much of the area, but some of the larger cities obtain water from the Great Lakes. The Great Lakes also provide transportation and are used extensively for recreation. Soils: Most of the soils are Aquepts and Aqualfs. They are medium textured to fine textured and have a mesic temperature regime, an aquic moisture re¬ gime, and illitic mineralogy. Very poorly drained, nearly level Haplaquepts (Conneaut and Allis series) formed in a mantle of lake-deposited silty material, and the underlying medium textured glacial till. Somewhat poorly drained, nearly level to gently sloping Fragiaquepts (Wallington series) formed in stratified, lake-laid loamy material. Poorly drained, nearly level to gently sloping Ochraqualfs (Mahoning series) formed in moderately fine textured glacial till. Well drained, moderately well drained, and some¬ what poorly drained, nearly level to moderately steep Hapludalfs (Kibbie, Sisson, and Tuscola series) formed in stratified, lake-laid deposits that generally have a silty and sandy texture. Potential natural vegetation: This area supports mixed oak, mixed mesophytic, and beech forests. The mixed oak forests consist of white oak, black oak, northern red oak, and some scarlet oak, shagbark hickory, bitternut hickory, pignut hickory, and mock- ernut hickory. Broadleaf and other deciduous species occur in the mesophytic forest in equal proportions. Among the dominant species in the beech forests are American beech, sugar maple, red oak, white ash, and white oak. Other dominant species are American basswood, shagbark hickory, black cherry, and, more rarely, cucumbertree. 101—Ontario Plain and Finger Lakes Region New York 32.790 km 2 (12,660 mi 2 ) Land use: Most of this area is in farms. About one-half of the acreage is cropland used mainly for hay, corn, and small grains associated with dairy operations. Cash crops, including canning and truck crops, wheat, and dry beans, are also produced. Orchard crops are important locally, particularly near Lake Ontario. Vineyards are common near some of the Finger Lakes. About one-third of the area is forested, mostly in farm woodlots. Urban uses account for about 14 percent of the area and are expanding around the larger cities, such as Buffalo, Rochester, and Syracuse. Elevation and topography: Elevation is 100 to 400 m, increasing gradually from the shores of the Ontario and Oneida Lakes to the Allegheny Plateau, the southern border of the area. Most of the area is a nearly level to rolling plain. Low remnant beach ridges are commonly interspersed with a relatively level lake plain in the north. Drumlins (long, narrow, steep-sided, cigar-shaped hills) are prominent in an east-west belt in the center of the area. The Finger Lakes area consists of a gently sloping to rolling till plain. Local relief is mostly a few meters, but the larger drumlins and many valley sides rise 25 to 100 m above the adjacent lowlands or valley floors. Streams generally flow 7 northward, but the Mohaw r k River flows eastward. Climate: Average annual precipitation —900 to 1,150 mm, increasing from west to east. Precipitation is evenly distributed throughout the year. Snowfall is heavy in winter. Average annual temperature —7 to 10°C. Average freeze-free period —Mainly 140 to 160 days, but it is 180 days in a narrow belt along Lake Ontario. Water: In most years the moderate precipitation is adequate for crops, but in years of little or no precipitation yields are reduced by a lack of moisture. The Finger Lakes, Lake Ontario, streams, farm ponds, and wells are potential sources of irrigation water for high-value crops. Ground water is abun¬ dant in most areas. It is close to the surface through¬ out much of the year in the lowlands, w 7 hich extend across the northern part of the area. Lake Ontario and many of the larger lakes provide opportunities for recreation. The New 7 York State Barge ( anal, traversing the area from east to w'est, is an important transportation artery. Soils: Most of the soils are Udalfs. They are deep, 73 medium textured and moderately fine textured. These soils have a mesic temperature regime, an udic mois¬ ture regime, and mixed mineralogy. Well drained and moderately well drained, undulating to moder¬ ately sloping Hapludalfs formed in high lime glacial till (Honeoye, Cazenovia, and Hilton series) and lacustrine sediments (Collamer, Schoharie, and Galen series). Nearly level to gently sloping, somewhat poorly drained Ochraqualfs (Appleton and Niagara series) are extensive in low areas. Poorly drained and very poorly drained Haplaquepts (Canadaigua and Lamson series) formed in lacustrine sediments and are common at the lowest elevations in the northern part of the area. Hapludalfs (Palmyra and Wampsville series) formed in calcareous outwash deposits, and moderately deep tills (Aurora and Lairdsville series) are prominent locally but are of small extent. Well drained and moderately well drained Eutrochrepts (Hamlin and Teel series) formed in alluvial deposits along streams. Potential natural vegetation: This area supports forest vegetation, particularly hardwoods. The po¬ tential forest types are elm-ash-red maple or beech- birch-sugar maple in varying proportions. Other spe¬ cies associated with these types include basswood, hemlock, white pine, black cherry and some species of upland oak. Northern whitecedar, red maple, black ash, and aspen grow on the wet soils. Cattails and mosses grow on the organic soils and on other extremely wet sites. 74 M—CENTRAL FEED GRAINS AND LIVESTOCK REGION 725,500 km 2 (280,110 mi 2 ) Fertile soils and a favorable climate make this one of the outstanding grain-producing regions of the world. The average annual precipitation is 625 to 900 mm in much of the region but ranges from 500 mm in the extreme northwest to 1,150 mm along the eastern and southern fringe. Somewhat more than half the precipitation falls during the growing season. The average annual temperature ranges from 6 to 13°C. The freeze-free period is 140 to 180 days in most of the region, but it is as short as 130 days along the northern fringe and as long as 235 days in the extreme southwest. , Udolls and Udalfs are the dominant well drained soils, and Aqualfs and Aquolls are the dominant wet soils. Some of the Udalfs and Aqualfs in the eastern part of the region have a fragipan. Fluvents are along streams, and Orthents are on strongly sloping sites. Corn, soybeans, oats, and other feed grains are the chief crops. Hay, winter wheat, and many other crops are also grown. Much of the grain is fed to beef cattle and hogs on the farms where it is grown. A large amount, however, is shipped to other regions for livestock feed, exported to foreign countries, or processed for food and industrial uses. 102A—Rolling Till Prairie Minnesota and South Dakota 38,600 km 2 (14,900 mi 2 ) Land use: Most of this area is in farms, and about 70 percent is cropland. The area is used primarily for crops grown for sale or for feeding livestock. Corn, soybeans, alfalfa, flax, spring wheat, and oats are the principal crops. Wooded sections generally are nar¬ row bands along streams and rivers or are shelterbelts around farmsteads. Recreation is an important land use around the many natural lakes in the northern part of the area. Elevation and topography: Elevation ranges from 300 to 400 m on lowlands to 400 to 500 m on uplands. Isolated highs on the Prairie Coteau in northern South Dakota are about 600 m. The nearly level to rolling topography has many depressions and ill- defined drainages. Steeper slopes are on the sides of drainage ways and in breaks adjacent to some of the larger tributaries. Climate: Average annual precipitation —500 to 600 mm. Half or more of the precipitation falls during the growing season. Precipitation in winter is mostly snow. Average annual temperature —6 to 9°C. Av¬ erage freeze-free period —120 to 140 days. Water: Precipitation is the principal source of moisture for crops. In many years it is inadequate for maxi¬ mum production. Shallow wells in glacial deposits and small ponds are the principal sources of water for livestock. Many natural lakes are in the north, and many of the larger ones are used for recreation. Soils: Most of the soils are Borolls. They are deep and loamy and silty and have a frigid temperature regime and mixed mineralogy. The nearly level to rolling Haploborolls (Aastad, Barnes, Buse, Kranzburg, and Svea series) and Argiborolls (Forman and Peever series) are on till uplands. Poorly drained Argiaquolls (Parnell series) and Haplaquolls (Quam series) are in upland depressions. Potential natural vegetation: This area supports true prairie vegetation characterized by big and little bluestem, porcupinegrass, and green needlegrass. Needleandthread and prairie dropseed are important species on the steeper soils. Prairie cordgrass com¬ monly grows in wet areas. 102 B—Loess Uplands and Till Plains Iowa, Minnesota, South Dakota, and Nebraska 43,790 km 2 (16,910 mi 2 ) Land use: Most of this area is in farms, and about 70 percent is cropland. The area is used primarily for crops grown for sale or for feeding livestock. Corn, soybeans, grain sorghum, alfalfa, and oats are the principal crops. Wooded sections generally are nar¬ row bands along streams and rivers or are shelterbelts around farmsteads. Irrigation is increasingly prac¬ ticed in areas where water supplies are available. Urban development is expanding around some of the larger cities. Elevation and topography: Elevation ranges from 300 to 400 m on the Missouri River bottom land to 400 to 500 m on uplands. The loess uplands are character¬ ized by long smooth slopes and well-defined drain¬ ages. The till plains are mostly nearly level to gently rolling and have many depressions and ill-defined drainages. Steeper slopes are on the sides of drain- ageways and in breaks adjacent to some of the larger tributaries. Climate: Average annual precipitation —500 to 650 mm. Half or more of the precipitation falls during the growing season. Precipitation in winter is mainly snow that averages about 62 to 102 cm. Average annual temperature—' 9 to 11°C. Average freeze-free period —135 to 165 days. 75 Water: Precipitation is the principal source of moisture for crops, but in some years it is inadequate for maximum production. Shallow wells are the principal source of water for domestic and livestock needs. Water for irrigation is available along some of the major rivers and the larger tributaries. Soils: Most of the soils are Ustolls. They are deep and silty and loamy and have a mesic temperature re¬ gime, an ustic moisture regime, and mixed mineralo¬ gy. Well drained, nearly level to moderately sloping Haplustolls (Belfore, Moody, and Nora series) are on loess uplands, and Ustorthents (Crofton series) are on the steeper parts of the landscape. Other well drained, nearly level to moderately sloping Haplustolls (Clarno, Egan, Ethan, and Wentworth series) are on sites in the till plains, and Ustorthents (Betts series) are on the steeper slopes. Poorly drained Argialbolls (Tetonka series), Argiaquolls (Worthing series), and Haplaquolls (Whitewood series) are in upland de¬ pressions. Fluvaquents (Albaton series), Haplaquolls (Lamo and Luton series), and Udifluvents (Haynie series) are dominant on the stream valley floors and bottom land of the Missouri River. Potential natural vegetation: This area supports true prairie vegetation characterized by big and little bluestem, indiangrass, porcupinegrass, and green needlegrass. Needleandthread and prairie dropseed are important species on the steeper soils. Prairie cordgrass usually grows in the wet areas. 103—Central Iowa and Minnesota Till Prairies Iowa and Minnesota 71,990 km 2 (27,800 mi 2 ) Land use: Nearly all this area is in farms, and about three-fourths is cropland. The proportion of cropland is highest in the southern part of the area. Corn, soybeans, and other feed grains are major crops. Some cropland is used for hay. Dairy farming is an important enterprise in the north. Between 10 and 15 percent of the area is permanent pasture. Narrow bands of woodland on steep slopes border stream valleys, and some of the wet bottom land is also forested. About 5 percent of the area is used for urban development, and a similar proportion is used for other purposes. Elevation and topography: Elevation ranges from 300 to 400 m. Most of this area is a nearly level to gently rolling till plain, but some morainic hills are in the east. Relief is mainly a few meters, but some major valleys are 50 m or more below the adjoining uplands. Climate: Average annual precipitation —625 to 850 mm. Two-thirds or more of the precipitation falls during the freeze-free period. Average annual temperature —6 to 9°C, decreasing to 4°C in the northwest. Average freeze-free period —130 to 160 days. Water: The moderate precipitation is adequate for crops, but in years of low rainfall yields are reduced. Ground-water supplies are adequate for domestic, livestock, and municipal needs. Some natural lakes and ponds and a few artificial reservoirs provide water and recreation. Soils: Most of the soils are Udolls, Udalfs, Aqualfs, and Aquolls. They are deep and medium textured and moderately fine textured and have a mesic tempera¬ ture regime and mixed mineralogy. Well drained and moderately well drained, nearly level to sloping Hapludolls (Clarion and Nicollet series) and Hapludalfs (Kelkenny, Lester, and Le Sueur series) are on uplands. Poorly drained Haplaquolls (Webster, Marna, Madelia, and Canisteo series) and Ochraqualfs (Lerdal series) are on level and slightly depressed surfaces. Potential natural vegetation: This area supports natural prairie vegetation characterized by little blue- stem, indiangrass, and switchgrass. Little bluestem, indiangrass, and needlegrass grow on sandy, droughty soils. Little bluestem, sideoats grama, blue grama, and scattered trees and shrubs of bur oak, juniper, and sumac grow on very shallow soils. 104—Eastern Iowa and Minnesota Till Prairies Iowa and Minnesota 22,640 km 2 (8,740 mi 2 ) Land use: Nearly all this area is in farms, and about 80 percent is cropland. Corn, soybeans, other feed grains, and hay are the major crops. Less than 10 percent is pasture. A similar proportion is wooded, mainly on wet bottom land and on steep slopes bordering stream valleys. Raising and feeding hogs and beef cattle and dairying are important enterprises. Many of the wet soils require artificial drainage for good growth of field crops commonly grown in the area. Erosion is a hazard on sloping soils. Elevation and topography: Elevation ranges from 300 to 400 m. This nearly level to gently sloping till plain mainly has local relief of a few meters. The streams have narrow and shallow valleys in their upper reaches, and only in the east is there much dissection. Climate: Average annual precipitation —700 to 850 mm. More than two-thirds of the precipitation falls during the growing season. Precipitation in winter is mainly snow. Average annual temperature —6 to 9°C. Average freeze-free period —140 to 160 days. Water: Precipitation is generally adequate for crops, but in years of little or no precipitation yields are reduced. Ground water is adequate for livestock, domestic, and municipal needs. Soils: Most of the soils are Udolls, Udalfs, and Aquolls. 76 They are deep and medium textured and moderately fine textured and have a mesic temperature regime and mixed mineralogy. Moderately well drained and well drained, gently sloping Hapludolls (Kenyon and Ostrander series), Argiudolls (Dinsdale series), and Hapludalfs (Racine and Renova series) are on up¬ lands. Somewhat poorly drained, nearly level or gently sloping Hapludolls (Floyd and Klinger series) and poorly drained, nearly level or gently sloping Haplaquolls (Clyde series) are in concave areas on the uplands. Well drained Hapludolls (Waukegan series) and poorly drained Haplaquolls (Marshan series) are on stream terraces. Moderately well drained Hapludolls (Spillville series) and Haplaquolls (Coland series) are on bottom lands. Potential natural vegetation: This area supports prairie vegetation. Big bluestem and indiangrass are dominant on the well drained soils on the rolling slopes. Switchgrass, prairie cordgrass, and prairie dropseed are better adapted to the somewhat poorly drained soils. Switchgrass, sedges, and rushes grow in poorly drained draws or valleys. Common cattails grow on swampy sites. Little bluestem, porcupinegrass, and sand lovegrass grow on sandy, rocky, dry sites. Forbs such as clovers, phlox, sunflower, gayfeather, and goldenrod grow on the better soils. Roundhead lespedeza, spiderwort, and flowering spurge grow on the droughty soils. Loosestrife, bedstraw, milkweed, and tickclovers are water-tolerant species that grew on wet soils. 105—Northern Mississippi Valley Loess Hills Illinois, Iowa, Wisconsin, and Minnesota 57,520 km 2 (22,210 mi 2 ) Land use: Nearly all this area is in farms, but only about two-fifths is cropland. Feed grains and forage for dairy cattle and other livestock are the principal crops. About one-fifth of the area is permanent pasture. Nearly one-third, mainly the more sloping parts, consists of farm woodlots used for commercial timber production and for farm products. The Missis¬ sippi River and major tributaries provide opportunities for recreation. Controlling erosion on sloping lands and protecting lowlands from stream overflow are the principal concerns of management. Elevation and topography: Elevation ranges from 200 m on the valley floors to 400 m on the highest ridges. The sloping to hilly uplands are dissected by both large and small tributaries of the Mississippi River. Bottom land along all streams is narrow. Some ridgetops are broad and have undulating slopes. Local relief is mainly several meters to several tens of meters. Climate: Average annual precipitation —750 to 900 mm. Two-thirds or more of the precipitation falls during the freeze-free period. Average annual temperature—7 to 10°C. Average freeze-free period —140 to 160 days. Water: In most years the moderate precipitation is adequate for crops and forage, but in years of little or no precipitation, yields on thin soils over bedrock are reduced. Ground water is abundant in outwash de¬ posits in the valleys, but the amount varies on the uplands. The supply of ground water in areas under¬ lain by sandstone and limestone generally is moder¬ ate. The many springs, streams, and farm ponds are additional sources of water. Soils: Most of the soils are Udalfs. They are moder¬ ately deep and deep and medium textured. These soils have a mesic temperature regime, an udic moisture regime, and mixed mineralogy. Well drained Hapludalfs (Fayette, Dubuque, Seaton, Gale, Nordness, and Norden series) that formed in a loess mantle over bedrock or in glacial till are dominant. Nearly level to gently sloping Argiudolls (Tama, Dodgeville, Rich- wood, and Dakota series) and Hapludolls (Muscatine series) are on benches and broad ridgetops. Hapludolls (Frontenac, Brodale, and Bellechester series) are on steep slopes bordering the major valleys. Well drained Udifluvents (Dorchester, Chaseburg, and Arenzville series) are along stream bottoms. Quartzipsamments (Boone series) are on steep slopes, and nearly level Udipsamments (Plainfield and Gotham series) are on stream benches. Steep, stony, and rocky soils are also common in the area. Potential natural vegetation: The upland soils sup¬ port natural hardwood forest vegetation. Oak, hicko¬ ry, and sugar maple are the dominant species. Big and little bluestem and scattered oak trees grow on some sites. The lowland soils support mixed hard¬ wood forest vegetation. Elm, cottonwood, river birch, ash, silver maple, and willow are the dominant spe¬ cies. Sedge and grass meadows and scattered trees grow on some lowland sites. 106—Nebraska and Kansas Loess-Drift Hills Kansas and Nebraska 27,090 km 2 (10,460 mi 2 ) Land use: Nearly all this area is in farms, and between one-half and three-fourths is cropland. Wheat and corn are important cash crops, but a large acreage of grain sorghum, soybeans, and alfalfa and other hay crops are grown. Most of the grain and hay is fed to livestock on the farms where they are grown. About one-fourth of the area is pasture or range. Cropland is more extensive on the less sloping soils that formed in loess. Pastures of native grasses are more exten¬ sive on strongly sloping to steep soils that formed in glacial till. Pastures of introduced grasses and leg¬ umes are on the better soils, but native grasses are 77 common on the more sloping shallow soils. Native woodland is confined to narrow bands bordering drainageways and streams and on some nearly level, wet soils on bottom lands. Elevation and topography: Elevation ranges from 300 to 500 m, increasing from east to west. In most places this dissected glacial-drift plain is mantled by thick loess. Ridgetops are broad and smooth, and slopes are nearly level to strongly sloping. Stream valleys are bordered by relatively narrow bands of hilly to steep slopes. Valley floors are narrow except along one or two of the larger tributaries of the Missouri River. Local relief is mainly several meters, but some of the larger valleys are 25 to 50 m or more below the level of the adjacent uplands. Climate: Average annual precipitation —750 to 925 mm, increasing from northwest to southeast. About three-fourths of the precipitation falls from late in spring through early autumn. The scant precipitation in winter is mainly snow. Average annual temper¬ ature —About 13°C. Average freeze-free period — 160 to 190 days. Water: Precipitation is generally adequate for crops, but in years of little or no precipitation yields are reduced by a lack of moisture. Locally, small areas along some of the perennial streams are irrigated. On most farms, shallow wells in glacial drift supply water for domestic and livestock needs. Small ponds and reservoirs are other important sources of water for livestock. In some places, deep wells provide water. Soils: Most of the soils are Udolls. They are deep and have a mesic temperature regime, an udic moisture regime, and mixed mineralogy. Silty Argiudolls (Sharpsburg series) and Hapludolls (Marshall and Monona series) are well drained, nearly level to moderately steep soils on loess-mantled ridgetops and upper side slopes. Loamy Argiudolls (Burchard, Pawnee, and Shelby series) are gently sloping to moderately steep soils that formed in glacial till. Nearly level to gently sloping Argiudolls (Wymore and Grundy series) have a clayey subsoil and formed in loess; they are on uplands. Udorthents (Ida and Steinauer series) are on steep upland slopes. Hapludolls (Kennebec series) and Haplaquolls (Colo and Wabash series) are on bottom lands. Potential natural vegetation: This area supports grassland vegetation characterized by mid and tall grasses. Big bluestem, little bluestem, switchgrass, indiangrass, porcupinegrass, and sideoats grama are dominant species on silty upland soils. Clayey soils on the uplands support a similar plant community but have a higher percentage of switchgrass and some wildrye. Green ash, hackberry, oak, boxelder, black walnut, and maple trees grow along streams and intermittent drainageways. 107—Iowa and Missouri Deep Loess Hills Iowa, Kansas, Nebraska, and Missouri 53,810 km 2 (20,770 mi 2 ) Land use: Most of this area is in farms, and about 60 percent is cropland. Corn, soybeans, and hay are the principal crops. About 20 percent of the area is permanent pasture. About 10 percent, mainly in narrow belts of steep slopes bordering stream valleys and wet bottom land, is forested. Raising beef cattle and feeding beef cattle and hogs are important enter¬ prises on many farms. The hazard of erosion is severe on the upland soils. Controlling flooding and sedi¬ mentation on bottom lands are concerns of manage¬ ment. Elevation and topography: Elevation ranges from 200 m along the Missouri River flood plain in the south to 500 m on the highest ridgetops in the north. This rolling to hilly, loess-mantled plain is intricately dissected. Small valleys have narrow flood plains, but the larger valleys have broad floors. Local relief is mainly several meters to more than 50 m. Climate: Average annual precipitation —625 to 925 mm. Two-thirds or more of the precipitation falls during the freeze-free period. The low precipitation in winter is mainly snow. Average annual tempera¬ ture —7 to 13°C, increasing from north to south. Average freeze-free period —150 to 190 days, increas¬ ing from north to south. Water: The moderate precipitation and abundant streamflow' are important sources of water. Ground water is abundant in deep outwash in valleys but is less plentiful on the uplands. The Missouri River is a major transportation artery and is also used for recreation. Soils: Soils of the uplands are mainly Udolls. Orthents are also extensive. They are deep and medium textured and moderately fine textured and have a mesic temperature regime, an udic moisture regime, and mixed minerology. Well drained, gently sloping to rolling Hapludolls (Galva, Marshall, and Monona se¬ ries) and gently sloping to rolling, somewhat poorly drained, Argiudolls (Higginsville series) are on loess- mantled uplands. Somewhat poorly drained, nearly level to gently sloping Hapludolls (Primghar series) and poorly drained, nearly level to gently sloping Haplaquolls (Marcus series) are on loess-mantled uplands. Somewhat excessively drained and well drained, strongly sloping to very steep Udorthents (Hamburg and Ida series) are in thick loess and on uplands. Well drained Hapludalfs (Knox series) are in narrow bands on slopes where moisture is favorable for growth of forest vegetation. Moderately well drained, moderately sloping to steep Argiudolls are on side slopes in clay loam glacial till. Well drained and moderately well drained Udifluvents (Haynie 78 and McPaul series) and Hapludolls (Keg, Kennebec, and Salix series), somewhat poorly drained or poorly drained Fluvaquents (Onawa and Albaton series), and poorly drained or very poorly drained Haplaquolls (Colo, Luton, and Wabash series) formed in alluvium and are extensive on bottom lands. Potential natural vegetation: This area supports tall prairie grasses. Big bluestem, indiangrass, and switchgrass are major species. Little bluestem and sideoats grama grow well on the steep soils adjacent to the Missouri River. Trees grow throughout the area. Eastern cottonwood, American elm, honeylocust, sycamore, and black walnut are common tree species on the bottom lands. Basswood, red oak, white oak, and shagbark hickory grow on protected upland slopes. Bur oak and bitternut hickory are well adapted to the steep slopes. 108—Illinois and Iowa Deep Loess and Drift Illinois, Iowa, and Missouri 79,790 km 2 (30,800 mi 2 ) Land use: Nearly all this area is in farms, and about 80 percent is cropland. Corn, soybeans, and other feed grains grown extensively on the less sloping soils are sold as cash crops. In areas where slopes are strong, more of the land is used for hay and pasture and more of the grain is fed to livestock on farms where it is grown. About 10 percent of the area is in intro¬ duced and native grasses. Making up about 5 percent are narrow bands of forest on steep valley sides and wet bottom land. About 5 percent is used for urban development and other purposes. Conservation prac¬ tices are used to reduce erosion, flooding, and sedi¬ mentation. Elevation and topography: Elevation ranges from 200 m on the lowest valley floors to 300 m on the highest uplands, increasing gradually from east to west. Much of this dissected loess-mantled glacial plain is rolling to hilly, but some of the broad uplands far from the large streams are level to undulating. The smaller streams have narrow valley floors, but the large streams have broad flood plains. Local relief is mainly several meters to 25 or 50 m, but the upland flats have relief of only 1 or 2 m. Climate: Average annual precipitation —750 to 900 mm. Two-thirds or more of the precipitation falls during the freeze-free period. The low precipitation in winter is mostly snow. Average annual tempera¬ ture —8 to 12°C. Average freeze-free period —160 to 180 days. Water: The favorably distributed moderate precipita¬ tion and the many perennial streams are important water sources. Ground water is abundant in the glacial drift that underlies much of the area. The Mississippi River and a few large tributaries are transportation arteries and are used for recreation. Soils: Most of the soils are Udolls. They are deep, medium textured soils that formed mainly in loess. These soils have a mesic temperature regime, an udic moisture regime, and montmorillonitic or mixed min¬ eralogy. Somewhat poorly drained, nearly level Argiudolls (Flanagan, Ipava, and Mahaska series) and Hapludolls (Muscatine series) and poorly drained nearly level Haplaquolls (Drummer and Sable se¬ ries), and Argiaquolls (Taintor and Virden series) are on uplands. Well drained and moderately well drained Argiudolls (Sharpsburg, Shelby, and Tama series) are gently sloping to strongly sloping. Well drained Hapludalfs (Fayette, Seaton, Clinton, and Hickory series) on the steep slopes of valley sides make up only 10 to 15 percent of the total area. Somewhat poorly drained Hapludolls (Lawson series), well drained Hapludolls (Huntsville series), and moderately well drained Udifluvents (Nodaway series) are in silty alluvium on the flood plains. Poorly drained and very poorly drained Haplaquolls (Colo and Zook series) are in clayey alluvium on the flood plains. Potential natural vegetation: When this area was settled, it supported tall grass prairie vegetation. The present potential for natural vegetation is unclear. Forest vegetation consisting of black oak, white oak, bur oak, shagbark hickory, and some walnut grows on the steep slopes of valley sides. Silver maple, elm, and ash grow on flood plains. 109—Iowa and Missouri Heavy Till Plain Iowa and Missouri 37,110 km 2 (14,330 mi 2 ) Land use: Nearly all this area is in farms, and about 55 percent is cropland. Corn, soybeans, other feed grains, and hay are the principal crops. About 25 percent of the area is in introduced and native grasses, and about 10 percent is woodland. Beef cattle and swine are important sources of income on many farms. Conservation practices are used to reduce erosion, flooding, and sedimentation. Elevation and topography: Elevation ranges from 200 m in the lowest valleys to 300 m on the highest ridges. This dissected till plain has a thin mantle of loess. Slopes are mostly rolling to hilly but some broad ridgetops are nearly level to undulating. The slopes bordering major stream valleys are steep. A few large rivers have nearly level broad valley floors. Local relief is mainly several meters to 25 or 50 m, but the upland flats and valley floors have local relief of only 1 or 2 m. Climate: Average annual precipitation —825 to 1,025 mm. About two-thirds of the precipitation falls dur¬ ing the freeze-free period. The low precipitation in winter is snow. Average annual temperature —10 to 13°C. Average freeze-free period —160 to 180 days. Water: In most years the favorably distributed moder¬ ate precipitation provides enough water for crops. 79 The many small perennial streams and a few large streams are additional sources of water but are little used for these purposes. Ground-water supplies are small and undependable. The stream flow fluctuates severely and frequently. Soils: Most of the soils are Udolls. They are deep and have a medium textured surface layer and a fine textured subsoil. They have a mesic temperature regime, an udic moisture regime, and montmorillonitic mineralogy. Somewhat poorly drained, nearly level to moderately sloping Argiudolls (Haig series) and Ochraqualfs (Kilwinning, Kniffin, and Pershing se¬ ries) and nearly level to moderately sloping, poorly drained, Argialbolls (Edina series), are on upland divides on loess-covered till plains. Somewhat poorly drained, gently sloping to strongly sloping Argiudolls (Adair, Lagonda, and Lamoni series) and poorly drained, gently sloping to strongly sloping Argiaquolls (Clarinda series) are on convex side slopes with a thin mantle of loess or pedisediment over glacial till. Well drained and moderately well drained, moderately sloping to steep Argiudolls (Shelby series) and Hapludalfs (Armster, Armstrong, Gara, Keswick, and Lindley series) are on side slopes on clay loam glacial till. Moderately well drained Hapludolls (Kennebec and Lawson series) and Udifluvents (Nodaway series) are on silty alluvium flood plains. Poorly drained and very poorly drained Haplaquolls (Chequest, Colo, Zook, and Wabash series) and some¬ what poorly drained Argialbolls (Vesser series) are on clayey alluvium flood plains. Potential natural vegetation: This area supports grassland vegetation. Big bluestem, indiangrass, lit¬ tle bluestem, and switchgrass are the major species. The natural drainageways and the lowland soils in¬ terspersed throughout the area support forest vege¬ tation. Oak and hickory species are dominant. Most of the native grasses have disappeared because of cultivation and overgrazing. Naturalized bluegrass is prevalent on noncultivated areas. 110—Northern Illinois and Indiana Heavy Till Plain Illinois, Indiana, and Wisconsin 26,350 km 2 (10,170 mi 2 ) Land use: Most of this area is in farms, but about 25 percent in the north, consisting of Chicago and its suburbs, is used for urban development. Some land formerly used for crops is rapidly becoming urban¬ ized. Farmed areas are used mainly for cash-grain crops. Corn and other feed grains are the principal crops. Woodland occupies less than 5 percent of the area and is mainly on wet flood plains, on steeply sloping valley sides, and on morainic ridges. Control¬ ling wetness, ehosion, flooding, and sedimentation are major concerns of management in both urban and farm areas. Elevation and topography: Elevation is about 200 m, increasing gradually from Lake Michigan south. Streams have cut shallow valleys in much of this nearly level to gently sloping glaciated plain. Local relief is a few meters. Climate: Average annual precipitation —750 to 900 mm. About two-thirds of the precipitation falls dur¬ ing the freeze-free period. Precipitation in winter is snow. Average annual temperature —9 to 11°C. Av¬ erage freeze-free period —About 160 days, but it is 180 days in a narrow belt along Lake Michigan. Water: In most years, the favorably distributed mod¬ erate precipitation is adequate for crops. Abundant ground water in the glacial drift meets domestic and municipal needs in much of the area. The large cities in the north depend on Lake Michigan for water. A few large perennial streams are potential sources of water but are little used for this purpose. Soils: Most of the soils are Udolls, and some are Aquolls. They are deep and moderately deep, fine, moderately fine, and medium textured and have a mesic temperature regime and mixed or illitic miner¬ alogy. Well drained, gently sloping and moderately sloping Argiudolls (Saybrook and Varna series) are on the thinly loess-covered glacial till uplands. Some¬ what poorly drained Argiudolls (Elliott, Swygert, and Clarency series) are nearly level or gently slop¬ ing. Poorly drained Haplaquolls (Ashkum, Bryce, and Drummer series) are on flats and in depressions. Very poorly drained Medisaprists (Houghton and Lena series) are in wet depressions, but they are not extensive. On outwash underlain by silt, sand, and gravel are loamy, well drained and moderately well drained Argiudolls (Plano, Proctor, and Warsaw se¬ ries), somewhat poorly drained Arguidolls (Brenton and Elburn series), and well drained Hapludalfs (Fox series). Well drained and moderately well drained, gently sloping to strongly sloping Hapludalfs (Morley and Miami series) are on uplands covered by a thin mantle of glacial till; somewhat poorly drained Ochraqualfs (Blount series) are associated soils in nearly level areas. Potential natural vegetation: When this area was settled, about 60 percent of the total acreage supported prairie vegetation. The present potential for natural vegetation in prairie sections of the area is unknown. Cattails, bulrushes, and common reed grow on or¬ ganic soils in marshes. A few bogs support tamarack, pitcherplant, sundew, cranberry, leatherleaf, win- terberry, and dwarf birch. Ill—Indiana and Ohio Till Plain Illinois, Indiana, Ohio, and Michigan 84,980 km 2 (32,810 mi 2 ) Land use: More than 90 percent of this area is in farms, and about 80 percent is cropland. Corn, soy¬ beans, other feed grains, and hay for livestock are the principal crops. Dairying is an important enter¬ prise near cities, and truck and canning crops are 80 grown extensively on sites where the soils and mar¬ kets are favorable. Small acreages of permanent pasture and small farm woodlots make up the rest of the farmland. Elevation and topography: Elevation ranges from 200 to 300 m, increasing gradually from west to east. This gently sloping glacial till plain is broken in places by hilly moraines, kames, and outwash terraces. Relief is mainly a few meters, but in places, hills rise as much as 25 m above the adjoining plains. The few large streams commonly have narrow and shallow valleys. Climate: Average annual precipitation —900 to 1,025 mm. Half or more of the precipitation falls during the freeze-free period. The low precipitation in winter is mostly snow. Average annual temperature —10 to 13°C. Average freeze-free period —155 to 180 days. Water: The favorably distributed moderate precipita¬ tion is adequate for crops in years of normal precipi¬ tation, but in some years yields are reduced by drought. Ground water in glacial deposits is the principal source of water for domestic, industrial, and municipal uses. A few large streams, mainly tributar¬ ies of the Ohio River, are potential sources of water but are little used for this purpose. A few lakes in the western part of the area are widely used for recrea¬ tion. Soils: Most of the soils are Udalfs and Aqualfs. They are deep and medium textured to fine textured and have a mesic temperature regime, an aquic or udic moisture regime, and mixed or illitic mineralogy. They formed in calcareous loamy glacial till, which is mantled by loess in the southern part of the area. The dominant soils are gently sloping to moderately slop¬ ing, moderately well drained or well drained Hapludalfs (Cardington, Miami, Miamian, Morley, and Russell series) and nearly level, somewhat poorly drained Ochraqualfs (Blount, Crosby, and Fincastle series). Argiaquolls (Brookston and Pewamo series), Hap- laquolls (Drummer series), and Medisaprists (Palms and Houghton series) are on flats and in depressions. Nearly level to moderately sloping Hapludalfs (Fox and Ockley series) are on terraces and outwash plains. Potential natural vegetation: This area supports hardwood forest vegetation. White oak, pin oak, yellow-poplar, sweetgum, and northern red oak grow on the wetter soils. White oak, yellow-poplar, sweetgum, northern red oak, American beech, sugar maple, and white ash are major species on the better drained soils. 112—Cherokee Prairies Kansas, Missouri, and Oklahoma 59,410 km 2 (22,940 mi 2 ) Land use: Nearly all this area is in farms, and about one-half is cropland. Winter wheat, soybeans, corn, grain sorghum, other feed grains, and hay are the major crops. Some cotton is grown in a few counties in Oklahoma. About one-third of the area is in pasture grasses and legumes; native grasses grow on the more sloping parts. About one-tenth of the area, the steeper valley slopes and some of the wet bottom land, is woodland. The acreage of woodland in Kansas is considerably less than that in Missouri and in Oklahoma. Elevation and topography: Elevation ranges from 100 to 400 m. These gently sloping to rolling dis¬ sected plains are underlain by sandstone, shale, and limestone. The northern part has a thin mantle of loess. Even though the area is thoroughly dissected, local relief is in meters, and large valleys are about 25 m below the adjacent uplands. Climate: Average annual precipitation —900 to 1,050 mm. Maximum precipitation is from late in spring through autumn. Annual snowfall ranges from about 12 cm in the south to 45 cm in the north. Average annual temperature —13 to 17°C. Average freeze- free period —190 to 235 days. Water: In many years the moderate precipitation is adequate for crops and pasture, but in some years summer droughts reduce crop yields. In much of the area, shallow wells are the principal source of water for domestic use and for livestock, but small ponds and reservoirs on individual farms are increasingly important sources of water for livestock. Deep wells, especially in limestone areas, also provide water. Soils: Most of the soils are Aqualfs and Udolls. They are shallow to deep and medium textured and moder¬ ately fine textured. These soils have a thermic tem¬ perature regime, an aquic or udic moisture regime, and mixed mineralogy. Somewhat poorly drained nearly level and gently sloping Albaqualfs (Parsons and Taloka series), Argiaquolls (Woodson series), and Argialbolls (Hartwell series) are on clay-mantled uplands. Moderately well drained and well drained, gently sloping and sloping Paleudolls (Dennis and Okemah series), Hapludalfs (Barden and Liberal series), and Argiudolls (Bates and Eram series) are on uplands underlain by silty and sandy shale and sandstone. Well drained, gently sloping Argiudolls (Lula and Catoosa series) are underlain by limestone and are on uplands; shallower and more stony Argiudolls (Clareson series), Haplustolls (Shidler series), and Hapludolls (Coweta and Collinsville series) are on steeper slopes of limestone, sandstone, and loamy shale. Gently sloping to moderately sloping clayey Argiudolls (Summit series) are underlain by clayey shale and clay beds and are on foot slopes. Haplaquolls (Osage series), Hapludolls (Verdigris and Wynona series), and Ochraqualfs (Hepler series) are on the flood plains of most streams. Potential natural vegetation: The western part of this area supports tall grass prairie vegetation. Big bluestem, little bluestem, indiangrass, and switchgrass are the dominant species. The eastern part and the 81 valleys in the western part support natural vegeta¬ tion characterized by trees. Red oak, white oak, and shagbark hickory are major species. Islands of tall grass prairie vegetation are common. 113—Central Claypan Areas Illinois and Missouri 28,570 km 2 (11,030 mi 2 ) Land use: Nearly all this MLRA is in farms, and about 60 percent is cropland. Corn, soybeans, other feed grains, and hay for cattle and other livestock are the main crops. About 10 percent is in permanent introduced and native grasses. An additional 20 percent, mainly on the steeper slopes and on wet bottom land, is forested. About 5 percent is used for urban devel¬ opment; the remainder is used for miscellaneous pur¬ poses. Wetness is the major land use problem. Elevation and topography: Elevation ranges from 200 to 300 m in Missouri and is about 200 m in Illinois, increasing gradually from south to north in both states. This MLRA consists of nearly level to gently sloping silt-mantled old till plains. Stream valleys are shallow, and most of them are narrow. Local relief is mainly a few meters. Climate: Average annual precipitation —About 1,025 mm. About 60 percent of the precipitation falls during the freeze-free period. Average annual temperature —13°C. Average freeze-free period —180 to 190 days. Water: In most years the moderate precipitation is adequate for crops. Small to moderate quantities of water are available from ground water. A few large perennial streams are potential sources of water, but they are little used for this purpose. Most of the soils are somewhat poorly drained to poorly drained, and claypans prevent effective artificial drainage on most of them. Soils: Most of the soils are Aqualfs. They have a deep, medium textured surface layer and a fine textured and moderately fine textured subsoil. These soils have a mesic temperature regime, an aquic moisture regime, and montmorillonitic mineralogy. In areas in Missouri are nearly level, poorly drained Albaqualfs (Putnam series) and gently sloping, somewhat poorly drained Ochraqualfs (Mexico and Leonard series). On some sites in Illinois are nearly level Albaqualfs (Cisne, Cowden, and Wynoose series). Somewhat poorly drained, nearly level and gently sloping Hapludalfs (Bluford and Hoyleton series) and moder¬ ately well drained, nearly level and gently sloping Fragiudalfs (Ava series) are on loess-covered old till plains. Well drained and moderately well drained, moderately sloping to steep Hapludalfs (Armstrong, Gara, Keswick, Lindley, and Weller series in Mis¬ souri and Hickory series in Illinois) are on side slopes. Fluvaquents (Belknap, Piopolis, and Westerville series) and Udifluvents (Sharon series) are in silty alluvium. Haplaquolls (Wabash series) are in clayey alluvium on narrow flood plains of small extent. Potential natural vegetation: When this MLRA was settled, most of the level upland soils supported tall grass prairie vegetation characterized by big bluestem, indiangrass, prairie dropseed, and switch- grass. The present potential for natural vegetation on the level upland soils is unknown. Forests of post oak, swamp white oak, blackjack oak, and pin oak grow on poorly drained soils. White oak, shingle oak, black oak, hickory, white ash, basswood, sugar maple, elm, and walnut grow on the better drained soils. Silver maple, willows, cottonwood, sycamore, elm, pin oak, white oak, hickory, and ash grow on flood plains. 114—Southern Illinois and Indiana Thin Loess and Till Plain Illinois, Indiana, and Ohio 34,880 km 2 (13,470 mi 2 ) Land use: Nearly all this area is in farms, but only about 50 percent is cropland. Corn, soybeans, other feed grains, and hay for dairy cattle and other livestock are the principal crops. Some tobacco is grown as a cash crop in Indiana and in Ohio. About 20 percent of the area is forested, much of which con¬ sists of small farm woodlots but some is in large holdings. Most of the remaining farmland is pasture. About 5 percent of the area, mainly along the Ohio River, is used for urban development or for industrial purposes. Conservation practices are used to reduce erosion, sedimentation, and flooding. Elevation and topography: Elevation ranges from 100 m on valley floors to 400 m on ridgetops. The ridgetops increase gradually in elevation from west to east. This dissected old glacial till plain has a moderately thick mantle of loess. Most of the ridgetops are narrow, but some are broad. Ridge slopes and valley sides are steep. Local relief on the ridgetops is in meters, but stream valleys are tens of meters below the adjoining uplands. Climate: Average annual precipitation —900 to 1,150 mm. Maximum precipitation is in spring and early in summer, and the minimum is from midsummer through autumn. Average annual temperature —12 to 14°C. Average freeze-free period —180 to 200 days. Water: In most years the moderate precipitation is adequate for crops, but yields are reduced occasion¬ ally by droughts. In most of the area ground water is adequate for domestic, industrial, and municipal needs, but ground water is scarce in places where shale is near the surface. Many small streams are potential sources of water, but they are little used for this purpose. Soils: Most of the soils are Aqualfs. They are deep and medium textured and have a mesic temperature regime, an aquic moisture regime, and mixed miner- 82 alogy. Poorly drained Ochraqualfs (Clermont series) are on broad flat uplands in Indiana and in Ohio. Somewhat poorly drained, nearly level and gently sloping Hapludalfs (Bluford series), Glossaqualfs (Vigo series), and Fragiaqualfs (Avonburg series) are on slopes. Moderately well drained and well drained, gently sloping to strongly sloping Fragiudalfs (Ava, Cincinnati, and Rossmoyne series) are on side slopes. Well drained Hapludalfs (Hickory series) are on steeper slopes of the glacial till uplands. Well drained, shallow Hapludolls (Fairmount series) formed in shaly limestone materials and are on valley sides near the Ohio-Indiana state line. Well drained Udifluvents (Haymond series) and somewhat poorly drained Fluvaquents (Belknap, Bonnie, and Wakeland series) are in silty alluvium on relatively narrow flood plains. Potential natural vegetation: This area supports hardwood forest vegetation. Pin oak, white oak, shingle oak, hickory, sweetgum, and black oak are dominant on the wetter sites. White oak, black oak, red oak, hickory, yellow-poplar, ash, sugar maple, and black walnut grow on the better drained sites. Honeylocust is dominant on soils that formed in shaly limestone materials. Silver maple, cottonwood, sycamore, pin oak, elm, and sweetgum grow along rivers and streams. Black walnut is an abundant species on deep, well drained soils on some small flood plains. 115—Central Mississippi Valley Wooded Slopes Indiana, Illinois, and Missouri 60,860 km 2 (23,500 mi 2 ) Land use: Nearly all this area is in farms, and about 40 percent is cropland. Feed grains and hay for livestock are the principal crops, but grape vineyards and peach and apple orchards are important in some places. About 35 percent of the area is forested, which includes some national forests. Most of the remainder of the farmland is in permanent pasture and native grasses. The hazards of erosion and sedi¬ mentation are severe in urban areas near St. Louis and other cities and on the farmland. Elevation and topography: Elevation ranges from 100 m on the main valley floors to 300 m on the ridgetops. This dissected glacial till plain has rolling narrow ridgetops and hilly to steep ridge slopes and valley sides. The small streams have narrow valleys and steep gradients. The major rivers have nearly level broad flood plains. Valley floors are tens of meters below the adjoining hilltops. Climate: Average annual precipitation —900 to 1,150 mm. About two-thirds of the precipitation falls dur¬ ing the freeze-free period. The maximum is in spring and early in summer and the minimum from mid¬ summer through autumn. Average annual tempera¬ ture —12 to 14°C. Average freeze-free period —180 to 200 days, increasing from north to south. Water: In most years precipitation is adequate for the crops commonly grown, but in some years yields are reduced by drought. Ground water is the source of water for domestic and livestock needs on farms. The Mississippi, Missouri, and Ohio Rivers are major transportation arteries and are also used for recrea¬ tion. Soils: Most of the soils are Udalfs. They are deep and medium textured to moderately fine textured and have a mesic temperature regime, an udic moisture regime, and mixed mineralogy. Well drained and moderately well drained Hapludalfs (Alford, Fayette, Menfro, Muren, Weller, and Winfield series) are in silty loess; other Hapludalfs (Gara, Hickory, Keswick, and Lindley series) are in glacial till; and still others (Bloomfield and Princeton series) are in sandy aeolian material. Well drained and moderately well drained Fragiudalfs (Grenada, Hatton, and Hosmer series) are on ridgetops in silty material. Well drained, cherty Paleudalfs (Goss series) weathered from cherty limestone. Somewhat excessively drained shallow Hapludolls (Gasconade series) are on steep slopes. Udifluvents (Eel, Genesee, Haymond, Nodaway, and Sharon series), Fluvaquents (Piopolis, Shoals, and Wakeland series), Haplaquolls (Beaucoup, Darwin, and Wabash series), and Hapludolls (Leta series) are on flood plains. Potential natural vegetation: This area supports a forest flora consisting mainly of oak and hickory species. 83 N—EAST AND CENTRAL FARMING ANI) FOREST REGION 612,230 km 2 (236,380 mi 2 ) This borderland region between the north and the south includes the Appalachian mountains, valleys, and dissected plateaus and the Ozarks. The average annual precipitation is 1,025 to 1,275 mm in much of the region but ranges from 900 mm along the western edge to 1,525 mm or more in some of the higher mountains in the east. The average annual temperature is 9 to 17°C. The freeze-free period is 180 to 200 days in a large part of the region but ranges from about 140 days in the northeast to as long as 240 days in some of the valleys in the south. Udults and Udalfs on uplands are the most extensive soils. The Udults are on deeply weathered stable landforms. Fluvents along streams are not extensive, but they are cropped intensively throughout the region. Ochrepts are extensive on mountain slopes and on dissected plateaus. Udalfs and Udolls are in limestone valleys and basins, but their total area is small. Small general farms are characteristic of much of the region, but large dairy and livestock farms are on the more favorable soils. Corn, soybeans, small grains, and hay are the chief crops. Tobacco is an important cash crop, especially in the eastern two-thirds of the region. Steeply sloping land, nearly one-half of the region, is mainly forests used for both recreation and timber production. A large part of the Nation’s coal is mined in this region. 116A—Ozark Highland Arkansas, Missouri, and Oklahoma 69,810 km 2 (26,950 mi 2 ) Land use: About 70 percent of this area is forests or woodland, most of which is in large holdings, national forests, or farm woodlots. About 20 percent is pas¬ ture, mainly of introduced grasses and legumes. About 10 percent is cropland. Corn, feed grains, and hay for dairy cattle and other livestock are the principal crops. Orchards, vineyards, and truck crops are important on some of the more friable deep soils. Summer droughts and steep slopes are major land use problems. Elevation and topography: Elevation ranges from 200 to 500 m. These sharply dissected limestone plateaus have narrow rolling ridgetops that break sharply to steep side slopes. Valleys are narrow and have steep gradients, especially in the upper reaches. Local relief is in meters to tens of meters. Climate: Average annual precipitation —1,025 to 1,225 mm. Maximum precipitation is in spring and early in summer, and the minimum is in midsummer. Average annual temperature —13 to 16°C. Average freeze-free period —180 to 200 days. Water: The moderate precipitation is adequate for crops and pasture. On most farms shallow wells or springs supply water for domestic needs and for livestock, but deep wells are required for large quantities. Water from deep wells is of good quality but is hard. Small ponds on many individual farms provide some water for livestock, and a few large reservoirs are used for flood control and for recrea¬ tion. Soils: Most of the soils are Udults and Udalfs. They are deep, medium textured to fine textured, cherty soils that weathered from limestone. They have a mesic temperature regime, an udic moisture regime, and siliceous or mixed mineralogy. Somewhat excessively drained to well drained Paleudults (Clarksville, Coulstone, Macedonia, Noark, and Poynor series) and Paleudalfs (Peridge and Goss series) are on ridges and side slopes. Moderately well drained, nearly level to moderately steep Fragiudults (Captina and Nixa series) are on slopes. Somewhat excessively drained, shallow Hapludolls (Gasconade series) and areas of rock outcrop are on steep, dissected land¬ scapes. Udifluvents (Midco and Elsah series) on flood plains and Hapludalfs (Razort and Secesh series) on terraces are in stream valleys. Fine textured Hapludults (Agnos and Gassville series), Paleudalfs (Gepp se¬ ries), and Paleudults (Doniphan series) also occur. Potential natural vegetation: This area supports oak-hickory and oak-hickory-pine forests. Oak-hickory- pine forests are more dominant in the east. Glades, openings having bedrock outcrops or that are shallow to bedrock, support a more herbaceous vegetation consisting primarily of indiangrass, little bluestem, and dropseeds. Glades are more common in the south¬ west. 116B—Ozark Border Missouri 35,470 km 2 (13,690 mi 2 ) Land use: About 40 percent of this area is cleared of timber and brush and is cultivated. Forage and grain are grown as feed for beef, dairy cattle, and other livestock. Corn, soybeans, sorghum, small grain, grass, alfalfa, and other legumes are the major crops. About 35 percent of the area consists of forests or woodland, most of which is in farm woodlots and large holdings. About 25 percent is permanent pas¬ ture of introduced grasses and legumes. Summer 84 droughts and susceptibility of the soils to erosion are major land use problems. Elevation and topography: Elevation ranges from 200 to 500 m. These broad limestone ridges and remnants of plateaus have gently sloping to moder¬ ately sloping tops and strongly sloping to steep side slopes. The stream valleys are narrow to moderately wide and have relatively steep gradients. Local dif¬ ferences in elevation range from 1 to 10 meters. Climate: Average annual precipitation —975 to 1,225 mm. Maximum precipitation is in spring and early in summer, and the minimum is in midsummer. Average annual temperature —13 to 16°C. Average freeze-free period —180 to 200 days. Water: In many years the moderate precipitation is adequate for crops and pastures, but summer droughts of sufficient severity and duration to reduce crop yields are common. On most farms shallow wells or springs supply water for domestic needs and for livestock, but deep wells are required for large quantities. Water from deep wells is of good quality but is hard. Small ponds on many individual farms provide some water for livestock, and a few large reservoirs are used for flood control and for recrea¬ tion. Soils: Most of the soils are Udalfs or Udults. They are moderately deep, medium textured to fine textured, cherty, limestone soils that are partly covered with a thin mantle of loess. They have a mesic temperature regime, an udic moisture regime, and siliceous or mixed mineralogy. Well drained, nearly level to moderately sloping Fragiudalfs (Hobson, Lebanon, Viraton, and Wilderness series), poorly drained, nearly level to moderately sloping Fragiaqualfs (Bado and Gerald series), and well drained Fragiudults (Captina and Nixa series) are on the broad tops of upland ridges. Well drained Hapludalfs (Barco, Bardley, and Bolivar series) are also on upper parts of ridgetops and side slopes on the uplands, and well drained Paleudalfs (Eldon and Goss series) and Paleudults (Clarksville series) are on the steeper and lower parts of side slopes and hillsides. Well drained, nearly level Hapludolls (Cedargap series) and Udi- fluvents (Elsah and Sharon series) are on bottom lands. Well drained Hapludalfs (Ashton, Razort, and Waben series) and Paleudalfs (Britwater series) oc¬ cupy stream terraces. Potential natural vegetation: This area supports oak-hickory savanna vegetation. It is a transitional area between oak-hickory forests and bluestem prai¬ ries. Big bluestem, little bluestem, indiangrass, and switchgrass are the dominant grassland species. The forests and grasslands are interspersed. The oak- hickory forests are more common on north slopes and on deeper soils and the grasslands on south slopes and on soils with low available moisture capacity. 117—Boston Mountains Arkansas, and Oklahoma 14,930 km 2 (5,770 mi 2 ) Land use: About 76 percent of this MLRA is forested, mainly in farm woodlots but large tracts in Arkansas are national forests. About 16 percent is grazing land, 6 percent is cropland, and 2 percent is used for miscellaneous purposes. Small grains and hay crops for livestock are the main crops. Peach and apple orchards are important locally. Pastures are mostly of tame grasses and legumes but native grasses grow on the prairie outliers in the west. Elevation and topography: Elevation ranges from 200 m on the lowest valley floors to 800 m on the highest ridge crests. Ridgetops of these deeply dis¬ sected sandstone and shale plateaus are narrow and rolling. Valleys are narrow and steep sided and have steep gradients. Local relief is in tens of meters. Climate: Average annual precipitation —1,150 to 1,325 mm. Maximum precipitation is in spring and in fall, and the minimum is in midsummer. Average annual temperature —14 to 17°C. Average freeze-free period —180 to 205 days. Water: The moderately high precipitation is adequate for crops and pastures. Shallow wells are the princi¬ pal source of water for domestic use. Small ponds on individual farms provide water for livestock, and springs are numerous on the mountainsides and in the valleys. Deep wells are needed for moderate to large quantities of ground water. Large reservoirs on a few of the major streams are sources of municipal water and also provide flood control and recreation. Soils: The major soils are Udults. They are stony and nonstony and medium textured. These soils have a thermic temperature regime, an udic moisture re¬ gime, and siliceous or mixed mineralogy. Well drained, shallow and moderately deep Hapludults (Mountainburg and Linker series) are on ridgetops, benches, and upper slopes. Well drained, deep Paleudults (Nella series) and Hapludults (Enders series) are on the middle and lower slopes and in concave interledge positions. Udifluvents (Ceda series) and Hapludults (Spadra series) are on stream flood plains, and Fragiudults (Leadvale and Taft series) and Hapludults (Pickwick series) are on terraces in the valleys. Potential natural vegetation: This area supports hardwood forests. The primary overstory species are red oak, white oak, and hickory. Shortleaf pine and eastern redcedar are important on disturbed sites, on shallow soils, and on south or west slopes. Big bluestem, switchgrass, indiangrass, and little blue¬ stem are important understory species under medium to open forest canopy. Broadleaf uniola, longleaf uniola, wildryes, and low panicums are important species under heavy canopy. 85 118—Arkansas Valley and Ridges Arkansas and Oklahoma 27,250 km 2 (10,520 mi 2 ) Land use: About 57 percent of this MLRA is forested. About one-third of the wooded area is federally owned, and most of the other two-thirds consists of farm woodlots. Twenty-six percent of the MLRA is grazed land, 11 percent is cropland, and 6 percent is used for miscellaneous purposes. Most of the cropland is in the less sloping valleys areas, but some is on flat mountain tops. Small grains and hay are the major crops. Soybeans are an important crop on the Arkan¬ sas River bottom land. Orchards, vineyards, and vegetable crops are important locally. Pastures on the bottom land of small streams and throughout cleared parts of the uplands consist of a mixture of tame and native grasses and legumes. Elevation and topography: Elevation ranges from 100 m on the lowest valley floors to 900 m on some mountain tops. These ridges and valleys are under¬ lain by slightly folded to level beds of sandstone and shale. Ridge slopes are steep; most crests are narrow and rolling, but some are broad and flat. The inter¬ vening valleys are broad and smooth. Local relief is in meters in the valleys and on the flat ridgetops. The ridges and mountains rise sharply tens of meters above adjacent valleys. Climate: Average annual precipitation —1,125 to 1,275 mm. Maximum precipitation is in spring and in autumn. Average annual temperature —16 to 17°C. Average freeze-free period —200 to 240 days. Water: The moderate precipitation generally is ade¬ quate for crops and pasture. On the uplands, water for domestic use comes mainly from shallow wells and water for livestock from small ponds on individual farms. In the valleys, springs, shallow wells, small ponds, and perennial streams provide water for most uses. Deep wells yield large quantities of hard water, but in areas of shale bedrock ground water is scarce. Soils: The major soils are Udults. They are stony and nonstony and medium textured. These soils have a thermic temperature regime, an udic moisture re¬ gime, and siliceous or mixed mineralogy. Well drained, shallow and moderately deep Hapludults (Mountainburg and Linker series) are on ridgetops, benches, and upper slopes. Well drained, deep Hapludults (Enders series) and Paleudults (Nella series) are on middle and lower slopes and in concave interledge positions. Fragiudults (Leadvale, Taft, and Cane series) are in the valleys. Udifluvents (Roxana series), Udipsam- ments (Crevasse series), Haplaquolls (Roellen se¬ ries), and Hapludalfs (Gallion series) are minor soils along the Arkansas River, and Dystrochrepts (Barling series) and Hapludults (Spadra and Pickwick series) are minor soils on terraces along smaller streams. Potential natural vegetation: This area supports hardwood forests. The primary overstory species are red oak, white oak, and hickory. Shortleaf pine is important on disturbed sites, on shallow soils, and on sites having a south or west aspect. Big bluestem, switchgrass, indiangrass, and little bluestem are important understory species under medium to open forest canopy. Broadleaf uniola, longleaf uniola, wildryes, and low panicums are important species under heavy canopy. 119—Ouachita Mountains Arkansas and Oklahoma 24,640 km 2 (9,510 mi 2 ) Land use: About 76 percent of this MLRA is forested, about one-fourth of which, mainly in Arkansas, is federally owned. Some is in large holdings, but much of it is in farm woodlots. Lumbering, wood-using in¬ dustries, and recreation are important throughout the area. Seventeen percent of the MRLA is grazing land, about 5 percent is cropland, and 2 percent is used for miscellaneous purposes. Forage and small grains are the major crops. Pastures are largely a mixture of tame grasses and legumes, but on some small prairie outliers in the west pastures are of native grasses. Elevation and topography: Elevation ranges from 100 m on the lowest valley floors to 800 m on the highest mountain peaks. These steep mountains are underlain by folded and faulted shale, slate, quartz¬ ite, sandstone, and chert. Most of the stream valleys are narrow and have steep gradients, but wide terraces and flood plains border the Ouachita River in western Arkansas. Local relief is in tens of meters to more than 300 meters. Climate: Average annual precipitation —1,225 to 1,425 mm, decreasing to 900 mm along the western edge. Precipitation is fairly evenly distributed through¬ out the year, but the maximum is in spring and early in autumn. Average annual temperature —16 to 17°C. Average freeze-free period —200 to 240 days. Water: The high precipitation, perennial streams, and reservoirs provide abundant water. Several large reservoirs for water storage and flood control are also used for recreation. In the valleys, small ponds, springs, and shallow wells are the main sources of water for domestic use and for livestock. Soils: The major soils are Udults. They are stony and nonstony and medium textured. These soils have a thermic temperature regime, an udic moisture re¬ gime, and siliceous or mixed mineralogy. Well drained, shallow and moderately deep Hapludults (Townley, Pirum, and Sherwood series) are at the higher eleva¬ tions and on steeper slopes. Well drained, deep and moderately deep Hapludults (Carnasaw, Pirum, and Sherwood series) are on the gentle slopes of ridgetops, benches, and foot slopes. Dystrochrepts (Ouachita series) and Ochraquults (Amy series) on flood plains 86 and Hapludults on terraces in the valleys are minor soils. Potential natural vegetation: This area supports hardwood-pine forests. The primary overstory spe¬ cies are southern red oak, black oak, white oak, and hickories. Pine constitutes as much as 40 percent of the cover—shortleaf pine on the uplands and loblolly pine on the lower lying alluvial soils. Switchgrass, little bluestem, and indiangrass are the primary grass species in the understory. Prairie cordgrass, plumegrass, low panicums, sedges, and rushes are present in smaller amounts. 120—Kentucky and Indiana Sandstone and Shale Hills and Valleys Indiana and Kentucky 30,990 km 2 (11,970 mi 2 ) Land use: Most of this area consists of small and medium-size farms. A large part in Indiana is in the Hoosier National Forest; some large tracts belong to coal mining companies. About 40 percent of the area is cropland, but the acreage varies widely from county to county, depending largely on the topogra¬ phy. Corn, soybeans, and wheat are the major crops, but tobacco is important in some parts. About 40 percent of the area is in forests of mixed hardwoods, but forest products are important in only a few parts of the area. About 17 percent is pasture used mostly for beef cattle. Urban development is minor. Stabiliz¬ ing strip mine spoil is a major concern of manage¬ ment. Elevation and topography: Elevation ranges from 100 m on the Ohio River flood plain to about 200 m on the higher ridges. Local relief generally is 50 to 100 m between ridgetops and the flood plains of local streams. The area is mostly hilly with broad undulating ridgetops on major divides. The flood plains and terraces of the Ohio River and its tributaries are nearly level to sloping. Climate: Average annual precipitation —1,175 mm. About 525 mm falls during the growing season. The variable snowfall averages 25 cm. Average annual temperature —14°C. Average freeze-free period —185 days. Water: Water is abundant in most of the area. In most years precipitation is adequate for crops. In some years, however, droughts reduce yields, and in oth¬ ers, too much rainfall delays planting or interferes with harvesting operations. The large streams and constructed lakes supply most of the urban water, and waterlines supply much of the water to nearby rural communities. Large quantities of ground water are available in the valley of the Ohio River and its major tributaries, but only small quantities are lo¬ cally available throughout the rest of the area. Soils: Most of the soils are Udalfs. They are medium textured and moderately fine textured. These soils have a mesic temperature regime, an udic moisture regime, and mixed mineralogy. They formed in loess and in residuum from sandstone, shale, and siltstone. Fragiudalfs (Grenada and Zanesville series), which have a fragipan, and Hapludalfs (Wellston and Frondorf series) are the dominant soils on ridgetops and side slopes. Fragiudults (Tilsit series) and Hapludults (Gilpin series) are in the northern part of the area. Hapludolls (Huntinton series), Eutrochrepts (Nolin series), and Fluvaquents (Melvin series) are loamy soils on flood plains of major streams. Haplaquepts (Karnak series) are clayey soils in slack water areas. Dystrochrepts (Cuba series), Udifluvents (Haymond series), and Fluvaquents (Stendal and Wakeland series) are loamy soils on flood plains of local origin. Hapludalfs (Wheeling series) and Fragiudalfs (Otwell series) are loamy soils on terraces of the major streams. Potential natural vegetation: This area supports oak-hickory forest vegetation on the rolling plateau. Coves and cooler slopes support mixed hardwood vegetation of beech, supar maple, yellow-poplar, white ash, and red and white oak. Eastern redcedar often grows on the shallower limestone soils. Such bottom land hardwoods as cottonwood, cherry bark oak, pin oak, Shumard oak, sweetgum, and swamp white oak are on flood plains. 121—Kentucky Bluegrass Indiana, Kentucky, and Ohio 29,490 km 2 (11,390 mi 2 ) Land use: Most of this area consists of small and medium-size farms. Urbanization is minor except near Louisville, Lexington, and Cincinnati. About 30 percent of the area is cropland, but the acreage varies widely from county to county, depending largely on the topography. Corn, hay, and tobacco are the major crops. About 45 percent of the area is pasture grazed mostly by beef cattle, but dairying and horse farms are important in some places. About 20 percent is mixed hardwood forest vegetation, but wood products are not important. Elevation and topography: Elevation ranges from about 200 m on the Ohio River flood plain to about 300 m on the higher ridges near Lexington. The topography ranges from highly dissected hills that have local relief of about 50 to 100 m to undulating broad upland plains that have local relief of about 25 m. Climate: Average annual precipitation —About 1,125 mm. About one-half of the precipitation falls during the growing season. The variable snowfall averages about 37 cm. Average annual temperature —About 13°C. Average freeze-free period —About 180 days. Water: Water is abundant in most of the area. In most years, precipitation is adequate for crops, but in some years, yields are reduced by droughts. The large 87 streams and constructed lakes supply most of the water in urban areas, and waterlines supply much of the water in nearby rural communities. Farm ponds, wells, and cisterns are the major sources of water in other rural communities. Large quantities of ground water are available in the valley of the Ohio River and its major tributaries, but only small quantities are locally available throughout the rest of the area. Soils: Most of the soils are Udalfs. They are fine textured and moderately fine textured and have a mesic temperature regime, an udic moisture regime, and mixed mineralogy. The dominant great groups are Hapludalfs (Eden and Lowell series), Paleudalfs (Maury and Crider series), Fragiudalfs (Nicholson series), and Hapludolls (Fairmount series). These soils formed in residuum from limestone or from thin bedded shale, siltstone, and limestone and in loess over residuum on hillsides, ridgetops, and upland plains. They are generally moderately deep to very deep, but the Fairmount soils are shallow. Loamy Hapludolls (Huntington series), Eutrochrepts (Nolin series) and Fluvaquents (Newark series) are on flood plains. Loamy Hapludalfs (Wheeling and Elk series) and Fragiudalfs (Otwell series) are on stream ter¬ races. Potential natural vegetation: This area supports mixed hardwood forest vegetation, generally on the better sites. Chinkapin oak, bur oak, blue ash, Shumard oak, white ash, hackberry, American elm, black walnut, black cherry, black locust, and Kentucky coffeetree are important species. Eastern redcedar is dominant on the drier slopes and on abandoned farmland. 122—Highland Rim and Pennyroyal Alabama, Indiana, Tennessee, and Kentucky 52,640 km 2 (20,320 mi 2 ) Land use: Most of this area consists of small and medium-size farms. Urbanization is relatively small. Extensive forests are on the deeply dissected hills surrounding the Nashville Basin and along the west¬ ern edge joining the Coastal Plain. Elsewhere, the forests consist mostly of small farm woodlots. Hay and pasture for beef cattle are the principal crops. Corn and soybeans, grown mostly on narrow strips of bottom land and on upland fiats, are important local¬ ly. Tobacco, especially burley, is an important cash crop. Elevation and topography: Elevation is 200 to 300 m, ranging from about 100 m along the deepest valley floors to about 400 m on the crest of isolated hills. The area is greatly diversified with low rolling hills, upland flats, and narrow valleys. Steep slopes occur where the encircled Nashville Basin cuts into the area and along the western edge bordering the Coastal Plain. Elsewhere, except for steep walls and hillsides along deeply cut stream channels, the topog¬ raphy is predominantly gently rolling to strongly rolling with a few interruptions by broad upland flats and shallow basins. In many places the land surface is pitted by limestone sinks. Climate: Average annual precipitation —1,125 to 1,375 mm. Maximum precipitation is in winter and early in spring, and the minimum is in fall. Average annual temperature —13 to 16°C, decreasing from south to north. Average frost-free period —180 to 205 days, decreasing from south to north. Water: In most years, precipitation is adequate for crops, but in some years, yields are reduced by short dry periods early in summer. The numerous peren¬ nial streams and lakes supply abundant water to much of the area. Several medium to large lakes constructed by the U.S. Corps of Engineers provide flood control, power production, recreation, and water for municipalities. In some parts where surface water is scarce, the water comes mainly from wells, large springs, and farm ponds. In many places, waterlines from metropolitan areas extend far into the country¬ side. Soils: Most of the soils, southward from about the Kentucky-Tennessee border, are Udults that have a thermic temperature regime, an udic moisture re¬ gime, and siliceous and kaolinitic mineralogy. Udalfs and Udulfs of mesic temperature regime, udic mois¬ ture regime, and mixed mineralogy are dominant in Kentucky and in Indiana. The soils generally are very deep to cherty limestone and strongly acid and highly leached and have a subsoil rich in clay. In the southern part, well drained, cherty Paleudults (Baxter, Bodine, and Fullerton series) are on hillsides, and moderately well drained Fragiudults (Dickson and Sango series) are on upland flats. Fragiaquults (Guthrie series) are in small basins and depressions, and Dystrochrepts (Ennis and Lobelville series) are in narrow strips of bottom land. In the northern part, well drained Paleudults (Baxter and Frederick series) are on hill slopes, well drained Paleudalfs (Crider and Pembroke series) are on broad smooth areas capped with loess, and moderately well drained Fragiudults and Fragiudalfs (Bedford, Nicholson, and Lawrence series) are on upland flats. On the narrow strips of bottom land are mainly Hapludolls (Huntington series), Udifluvents (Haymond series), and Eutro¬ chrepts (Nolin series). In the extreme northernmost part in Indiana, a sizable area is underlain by shale, sandstone, and limestone; loamy-skeletal Dystrochrepts (Weikert and Berks series) and Hapludults (Gilpin series) are on the slopes, and Hapludalfs (Wellston series) and Fragiudalfs (Zanesville series) are on upland flats capped with loess. Potential natural vegetation: This area supports oak-hickory forests. Yellow-poplar is common on the deeper soils. Understory plants include a variety of grasses, forbs, vines, and shrubs. Little bluestem and broomsedge are dominant grass species. 88 123—Nashville Basin Tennessee 15,680 km 2 (6,060 mi 2 ) Land use: The densely populated Nashville Basin consists mostly of small and medium-size farms. Much farmland has been converted to residential use and to small estate-type farms, particularly around Nashville. Hay, pasture, and some grain for beef cattle and dairy cattle are the principal crops. Small acreages of burley tobacco, cotton, and soybeans are grown. Some large rocky sites, commonly called “Glady Land,” are in redcedar forest or in redcedar-deciduous brush. Elevation and topography: Elevation is about 200 m, but isolated hills rise to an elevation of 300 to 400 m. Some of the more deeply cut stream channels are as low as 200 m above sea level. Most of the outer part of the Basin is deeply dissected and consists of steep slopes between narrow rolling ridgetops and narrow valleys. The inner part of the Basin is predominantly undulating and rolling. In many places the land surtace is deeply pitted by limestone sinks, and outcrops of limestone rock are almost every¬ where. Climate: Average annual precipitation —About 1,275 mm. Maximum precipitation is in midwinter and early in spring, and the minimum is in autumn. Average annual temperature —14 to 16°C. The tem¬ perature varies little throughout the Basin. Average freeze-free period —192 days. Water: The moderately high precipitation generally provides adequate moisture for crops and pasture, but in some years, short periods of drought in sum¬ mer reduce pasture and crop yields. Permanent streams and lakes are an important source of water. The Cumberland River has dams for flood control, power production, navigation, and recreation. Ground water from wells and springs is an important source of water for domestic use and for livestock. Farm ponds are used to supplement the water supply, especially in places where surface water is scarce because of limestone sinks. Soils: Udalfs are the most extensive soils in the Basin, but Udults occupy a large acreage. These soils have a thermic temperature regime, an udic moisture re¬ gime, and a clayey subsoil. Well drained, fine textured Hapludalfs are on hillsides in the outer or phosphatic part of the Basin (Mimosa and Hampshire series) and on low hills in the inner part (Tablott series). Well drained Paleudalfs (Lomond and Cumberland series) occupy a sizable acreage in the inner part of the Basin where there are deposits of alluvium or of alluvium and loess. Dark brown loamy, cherty Hapludults (Dellrose series) are on steep, deeply dissected hills that extend around the rim of the Basin. A small acreage of Rendolls (Gladeville series) in the inner Basin, where the rock is at or near the surface, is commonly called “Glady Land.” Hapludolls (Arrington, Lynnville and Egam series) and Haplaquolls (Roellen and Godwin series) are on the inextensive bottom lands. Outcrops of limestone are common. Potential natural vegetation: This area supports oak-hickory stands. Yellow-poplar grows on the north¬ ern slopes, and eastern redcedar and cedar-hardwood stands grow on the limestone glades and rocky, clayey sites. Understory vegetation includes many grasses, forbs, vines, and shrubs. Broomsedge blue- stem is the dominant grass species. 124—Western Allegheny Plateau Ohio and Pennsylvania 19,040 km 2 (7,350 mi 2 ) Land use: Most of this area consists of farms, but about one-fourth is used for other purposes. About one-fifth is cropland. Hay and feed grains for live¬ stock are the principal crops, and fruits and vegeta¬ bles are important locally. About one-fifth is pasture. Two-fifths is forested, about half of which consists of farm woodlots and about half state and national forests and large commercial holdings. Strip mining of coal is an important industry in the north, but only a small part of the total area is strip mined. Elevation and topography: Elevation ranges from 200 m on the lowest valley floors to 400 m at the highest ridgetops. The dissected sandstone plateau has narrow level valley floors, rolling ridgetops, and hilly to steep ridge slopes. Local relief is about 50 to 100 m. Climate: Average annual precipitation —1.025 to 1,150 mm. Precipitation is evenly distributed except for a slight maximum late in spring and a minimum late in autumn. Average annual temperature —9 to 13°C. Average freeze-free period— Mainly 140 to 160 days, but it is 180 days along the southern edge. Water: The moderate precipitation and many perennial streams supply an abundance of water. Shallow wells and springs are the principal sources of water for domestic and livestock uses. Deep ground water is abundant but is highly mineralized. Reservoirs on many streams provide water for industrial and mu¬ nicipal use for most of the cities in the area and also for some cities in adjoining areas. Soils: Most of the soils are Ochrepts, Udults, and Udalfs. They have mixed mineralogy, a mesic tem¬ perature regime, and an udic moisture regime. They are on sloping to steep sites and are well drained to moderately well drained. Medium textured, gravelly to very gravelly Dystrochrepts (Muskingum and Dekalb series) formed in residuum derived from acid sand¬ stone interbedded with siltstone and shale. Moder¬ ately fine textured Hapludults (Gilpin, Trappist, and Latham series) formed in residuum derived from acid siltstone, shale, and some sandstone. Moderately fine textured to fine textured Hapludalfs (Guernsey, Keene, 89 and Upshur series) formed in residuum derived mostly from clay, shale, and siltstone. Potential natural vegetation: This area supports a mixed oak forest vegetation. White oak, black oak, northern red oak, and some scarlet oak are dominant species. Shagbark hickory, bitternut hickory, pignut hickory, and mockernut hickory are also included. Oak, blackgum, flowering dogwood, sassafras, Vir¬ ginia pine, pitch pine, and shortleaf pine occur mostly on the ridgetops. 125—Cumberland Plateau and Mountains Alabama. Kentucky, Tennessee, Virginia, and West Virginia 63,840 km 2 (24,640 mi 2 ) Land use: Most of this area consists of small and medium-size farms. An extensive acreage in Ken¬ tucky is in the Daniel Boone National Forest, and some large tracts are owned by coal and timber companies. Urbanization is minor. About 80 percent of the area is forests of mostly mixed hardwoods. Lumber is an important product. About 8 percent of the area is cropland. Corn, hay, and tobacco are the major crops. About 8 percent is pasture used mostly for beef cattle. Stabilizing strip-mined areas is a major concern of management. Elevation and topography: Elevation ranges from 200 m on the Ohio River flood plain to about 300 m on nearby ridgetops, gradually rising to near the Virginia-Kentucky border,where local flood plains are about 500 m, and higher mountains are about 1,200 m. The highly dissected landscape is largely a series of long steep side slopes between narrow ridgetops or crests and narrow stream flood plains. Climate: Average annual precipitation —1,175 mm; about 525 mm falls during the growing season. The variable snowfall averages about 50 cm. Average annual temperature— 13°C. Average freeze-free pe¬ riod —175 days. Water: Water is abundant in most of the area. In most years precipitation is adequate for crops, but in some years yields are reduced by droughts. The large streams and constructed lakes supply most of the urban water. Farm ponds, wells, and cisterns are sources of water in rural communities. Large quanti¬ ties of ground water are available in the valley of the Ohio River and its major tributaries, but only small quantities are locally available in the rest of the area. Soil: Most of the soils are Udults. Thay are medium textured to fine textured. These soils have a mesic temperature regime, an udic moisture regime, and mixed or siliceous mineralogy. Hapludults (Shelocta, Jefferson, Clymer, Gilpin Latham, Lily, and Hartsells series) and Fragiudults (Tilsit series) on side slopes and ridges formed in loamy hillside colluvium or residuum. Medium textured, very gravelly Dystro- chrepts (Dekalb, Berks, and Calvin series) are on upper side slopes and ridges. Loamy Dystrochrepts (Pope series) and Fluvaquents (Bonnie series) are on flood plains. Loamy Hapludults (Allegheny series) and Fragiudults (Monongahela series) are on stream terraces. Potential natural vegetation: This area supports a variety of woody and herbaceous plant communities. Mixed hardwood forest vegetation is in coves and on north- and east-facing slopes. Yellow-poplar, beech, black walnut, basswood, red and white oaks, hemlock, and buckeye are among the 20 or more tree species. Oak-hickory communities, shortleaf pine, pitch pine, and Virginia pine are on ridges and on south- and west-facing slopes. Willows, sycamore, sweetgum, and river birch grow on flood plains. 126—Central Allegheny Plateau Ohio, Pennsylvania, and West Virginia 50,770 km 2 (19,600 mi 2 ) Land use: Most of this area consists of farms, but less than one-half of the area consists of income-producing farms. The farm income is predominantly from beef cattle and dairy farms associated with hay, grass¬ land, and cultivated crops. About one-half of the area is forested, and the sale of timber is important in some parts. Urban expansion, including industrial and residential developments, is increasing along the Ohio River and major tributaries. Much of the crop¬ land has been converted to this purpose. Large acreages are owned or leased for strip mining of coal. Elevation and topography: Elevation ranges from 200 m on the lowest valley floors to 400 m or more at the highest ridgetops. The dissected plateau is under¬ lain mainly by horizontal bedded sandstone, siltstone, and shale and a few layers of limestone. The narrow, level valleys and narrow, sloping ridgetops are separated by long, steep to very steep side slopes. Relief locally is about 100 m. Climate: Average annual precipitation —900 to 1,150 mm. Precipitation is somewhat unevenly distributed. The maximum is in midsummer and the minimum in autumn and early in winter. Annual snowfall ranges from less than 90 cm to more than 127 cm. Average annual temperature —4 to 13°C. Average freeze-free period— 120 to 170 days. Water: Water from springs, wells, farm ponds, reser¬ voirs, and cisterns is plentiful. Large quantities of ground water can be obtained from deep wells, but the water generally is highly mineralized. Improved environmental practices are helping solve the prob¬ lem of stream pollution from coal mine and other industrial wastes. Soils: Most of the soils are Udalfs, Udults, and Ochrepts. They are mostly well drained and moderately well drained, moderately deep and deep, medium and fine textured soils on uplands. They have a mesic temper¬ ature regime, an udic moisture regime, and mixed 90 mineralogy. Sloping to steep Hapludalfs (Westmore¬ land, Culleoka, Upshur, and Guernsey series) formed in material weathered from lime-influenced siltstone, shale, and fine grained sandstone. Sloping to very steep Hapludults (Gilpin series) and Dystrochrepts (Berks and Dekalb series) formed in material weath¬ ered from acid sandstone, siltstone, and shale on uplands. Potential natural vegetation: This area supports deciduous forest vegetation. White oak, red oak, black oak, hickory, and associated upland hardwoods are major species. Scarlet oak, chestnut oak, and hickory, along with scattered Virginia pine, shortleaf pine, and white pine, grow on dry ridges and on the shallower soils. Yellow-poplar, black walnut, red oak, red maple, and other species requiring much moisture grow in sheltered coves, on foot slopes, and on north-facing slopes. 127—Eastern Allegheny Plateau and Mountains Maryland, Pennsylvania, and West Virginia 43,680 km 2 (16,870 mi 2 ) Land use: Most of this area consists of farms; about 8 percent is cropland. Corn, small grains, and forage for dairy and beef cattle are the principal crops. Other important crops include potatoes and soybeans. Dairy, beef, and poultry farms are important enter¬ prises. About 3 percent of the area is hardwood forests, most of which is privately owned, although there are large blocks of state forest and game lands and national forests. About 6 percent consists of urban areas and disturbed land, including strip mines. Stabilizing and revegetating strip-mined areas and controlling acid drainage water from coal mines are major concerns of management. Elevation and topography: Elevation ranges from 300 m in the lowest valleys to 600 to 800 m over much of the plateau top; mountains in the southeast are 1,100 to 1,400 m. This deeply dissected plateau terminates in a high escarpment in the east. Steep slopes are dominant, but level to gently rolling pla¬ teau remnants are conspicuous in the north. Local relief is mainly about 100 m, but some mountain peaks in the south rise 300 m or more above the plateau or adjacent valleys. Climate: Average annual precipitation—1,025 to 1,425 mm. Maximum precipitation is in spring and in summer, and the minimum is in fall. Precipitation averages 550 to 825 mm during the growing season. The average snowfall ranges from 90 cm in the south to more than 227 cm in the north. Average tempera¬ ture —7 to 11°C. Average freeze-free period —110 to 160 days. The shorter growing seasons occur at the higher elevations and in the north. Water: Water from springs, wells, farm ponds, reser¬ voirs, and streams is plentiful. The major rivers include the Youghiogheny, North Branch of the Potomac, West Branch of the Susquehanna, and the Allegheny. Several large reservoirs include Deep Creek Lake, Youghiogheny River Reservoir, and Alle¬ gheny Reservoir. Ground water is plentiful, although well yields are highly variable in the sandstone and shale bedrock. Soils: Most of the soils are Ochrepts, Udults, and Aquults. They have a mesic temperature regime, an udic or aquic moisture regime, and mixed mineralo¬ gy. Nearly level to steep Dystrochrepts (Calvin, Dekalb, and Hazleton series), Hapludults (Clymer, Gilpin, and Wharton series), and Fragiudults (Cookport series) formed in material weathered from acid sand¬ stone, siltstone, and shale on the plateau and on the upper mountain slopes. The Dystrochrepts are me¬ dium textured and very gravelly. The Udults are medium textured to fine textured. Nearly level to gently sloping, medium textured Dystrochrepts (Pope and Philo series) of lesser extent formed in alluvium along streams and are susceptible to periodic stream overflow. Somewhat poorly drained, fine textured, nearly level to sloping Ochraquults (Cavode series) formed in material weathered from shale on the plateau or along the foot slopes. Potential natural vegetation: This area supports a mixed hardwood forest vegetation. Oak, black cher¬ ry, yellow-poplar, maple, and other associated hard¬ woods are the principal species at lower elevations. White pine, Virginia pine, and black walnut also grow but are of lesser extent. Red spruce, hemlock, birch, and maple species grow on the high mountain soils. Sugar maple, black cherry, and red oak com¬ monly grow at intermediate elevations. 128—Southern Appalachian Ridges and Valleys Alabama, Georgia, Tennessee, Virginia, and West Virginia 69,430 km 2 (26,810 mi 2 ) Land use: Most of this area consists of small and medium-size farms. About 40 percent is forests of mixed hardwoods, most of which, except for a few wooded mountain ridges, are in small farm woodlots. A large acreage in Virginia is in the George Washing¬ ton and Thomas Jefferson National Forests. Hay, pasture, and some grain for beef cattle and dairy cattle are the principal crops. Burley tobacco is the important cash crop in the southern two-thirds of the area (excluding Georgia). Some cotton is grown south of Chattanooga. Small acreages of corn and soybeans are grown throughout the area, mainly on narrow strips of bottom land and on adjacent low terraces. Elevation and topography: Elevation ranges from 200 m near the southern end to more than 600 m in Central Virginia. Some isolated linear mountain ridges rise to nearly 1,500 m above sea level. The area is highly diversified. It consists of many parallel ridges, 91 narrow intervening valleys, and large bodies of low, irregular hills. The ridges and valleys often have a difference in elevation of 200 m. The western side of the area is dominantly hilly to very steep and is rougher and much steeper than the eastern side, much of which is rolling and hilly. Climate: Average annual precipitation —925 to 1,400 mm. Maximum precipitation is in midwinter and in midsummer, and the minimum is in autumn. Average annual temperature— 13 to 16°C. Average freeze-free period —170 to 210 days. Water: Precipitation generally is adequate for crops and for other needs. Short dry periods early in summer occasionally reduce crop yields. Permanent streams, originating in the mountainous regions on either side, carry water to nearly all parts of the area. Several dams, constructed by the Tennessee Valley Authority on the Tennessee River and its major tributaries, provide flood control, navigation, power production, and recreation. Shallow wells, supplemented locally by springs and ponds, are im¬ portant sources of water for farmstead use. Soils: Most of the soils are Udults and, to a lesser extent, Ochrepts. They have an udic moisture regime and a thermic or mesic temperature regime. The soils dominantly are well drained, strongly acid, and highly leached and have a clay-enriched subsoil. They range from shallow on the sandstone and shale ridges to very deep in the valleys and on the large limestone formations. Paleudults (Dunmore, Decatur, Dewey, Frederick, and Fullerton series, commonly cherty) are on the numerous and extensive areas underlain by limestone that traverse the region in a southwest- northeast direction. Hapludults (Sequoia series) are dominant in the valleys underlain by acid shale. Steep, shallow to moderately deep, shaly and stony Dystrochrepts (Muskingum, Weikert, Wallen, Litz, Lehew, and Calvin series) are on the sides of the steep ridges. Shallow, shaly Eutrochrepts (Dandridge and Whitesburg series) are on the shale formation that extends along the eastern side of the area. Hapludolls (Huntington and Staser series) and Eutrochrepts (Chagrin. Hamblen, Lobdell, Sullivan, and Lindside series) occupy the narrow strips of bottom land. The proportion of poorly drained soils, mainly Aquepts and Aquults, is very small. Potential natural vegetation: This area supports hardwood or mixed hardwood-pine forest vegetation. The deeper soils support good oak-hickory stands. The shallower soils, mostly on southern and western slopes, support pine or oak-pine types. Understory vegetation is also reflected by aspect. Little bluestem is the dominant grass species. 129—Sand Mountain Alabama and Georgia 17,540 km 2 (6,770 mi 2 ) Land use: This area is about 70 percent woodland, 18 percent cropland, and 9 percent pastureland. About 3 percent is used for coal mining, urban development, or other purposes. About 83 to 88 percent of the woodland is privately owned, 10 to 15 percent indus¬ try owned, and about 2 percent federally owned. Timber production is mostly in the southern half of the area. Poultry production is the major farm enter¬ prise. Corn, cotton, and vegetables are the major cash crops. Controlling erosion on soils that are cropped is the primary concern of management. Pastures are grazed mainly by beef cattle and are important disposal areas for poultry wastes. Elevation and topography: Elevation ranges from 100 to 400 m, but a few mountaintops are as high as 500 m. The area is deeply dissected and consists mainly of a series of rather narrow valleys, steep escarpments, and broad plateaus that are underlain by sandstone and shale. Valley floors are commonly about 100 m below adjacent plateau summits. Climate: Average annual precipitation —1,300 to 1,400 mm. Precipitation is somewhat unevenly distributed. The maximum is in midwinter, decreasing gradually from spring to autumn and increasing slightly in midsummer. Average annual temperature— 16 to 17°C. Average freeze-free period —Mainly 200 to 210 days but ranges to 240 days in some valleys. Water: In most years, precipitation is adequate for crops and pastures. Droughts are short and infre¬ quent. Streams, springs, and ponds provide water for livestock. Deep wells provide an adequate supply of water for most domestic and municipal uses. Most streams flow intermittently and are often dry in summer and in autumn except after rainstorms. A few large reservoirs are in the area. Soils: The dominant soils are Udults and Ochrepts. They have an udic moisture regime, a thermic tem¬ perature regime, and mixed mineralogy. They are over sandstone and shale and are mostly moderately fine textured to fine textured. Moderately deep, nearly level to steep Hapludults (Hartsells, Linker, and Townley series) are on broad plateaus, ridgetops, mountaintops, or upper side slopes. Deep Hapludults (Enders series) and Fragiudults (Wynnville series) are on some of the more level upland sites. Shallow, gravelly and very gravelly, nearly level to steep Dystrochrepts (Hector and Montevallo series) are on narrow upper valley slopes and ridgetops. Areas of rock outcrop are common on these sites. Deep Hapludults (Albertville series) and Paleudults (Allen series) are on lower side slopes and terraces. Potential natural vegetation: This area supports mixed oak-pine forest vegetation. Shortleaf pine, loblolly pine, sweetgum, yellow-poplar, red oaks, and white oaks are the major overstory species. Dogwood and redbud are major midstory species. Japanese honeysuckle, greenbrier, low panicums, bluestems, and native lespedezas are understory species. 92 130—Blue Ridge Georgia, Maryland, North Carolina, Pennsylvania, Tennessee, and Virginia 47,030 km 2 (18,160 mi 2 ) Land use: Two-thirds or more of the area is forested. About a fifth of the area consists of national parks and forests. The acreage of parkland and forests is much higher in Georgia and in Tennessee. Parts of the area are popular resort and recreation sites. About one-tenth of the area is cropland, mainly on small farms in valleys and coves, and one-sixth is pasture. Corn and hay are the chief crops, but small grains, potatoes, and many kinds of fruits and vege¬ tables are also grown. Tobacco is an important crop in some places. Most of the farms are part-time enterprises, and the occupants earn a large part of their livelihood elsewhere. Elevation and topography: Elevation ranges from 300 m in the lower valleys and on foot slopes to more than 2,000 m in the mountains along the Tennessee- North Carolina boundary, decreasing gradually both north and south from this high point. The rugged mountains have steep slopes, sharp crests, and nar¬ row valleys. Stream dissection is deep and intricate. Major streams and their tributaries flow through gorges and gaps of the mountains. Broad valleys and basins with rolling hills are extensive throughout the area. Local relief is 100 to more than 1,000 m. Climate: Average annual precipitation —Mainly 1,025 to 1,275 mm but as much as 2,025 mm on the highest peaks in the south. Precipitation is somewhat unevenly distributed. The maximum is in midsummer and in midwinter and the minimum in autumn. Precipitation is 900 to 1,025 mm in the Asheville basin and in similar protected areas. Average annual tempera¬ ture —10 to 16°C. Average freeze-free period —150 to 220 days, decreasing with increasing elevation and from south to north. It is sharply reduced on elevated peaks. Water: Springs and shallow wells provide domestic water, but the ground water yield from wells is generally small. Water for livestock comes largely from springs and perennial streams, though some farm ponds have been built recently. In the southern two-thirds of the area, the major rivers have many dams that are used for flood control, electric power production, and recreation. Soils: The dominant soils are Ochrepts and Udults. They are moderately deep and deep and medium textured. These soils have a mesic temperature re¬ gime, an udic moisture regime, and mixed mineralo¬ gy. Dystrochrepts (Ashe, Ditney, Sylico, Brookshire, Ranger, and Ramsey series) and Hapludults (Edneyville and Saluda series) are the principal soils on steep slopes of lower mountains. Hapludults (Fannin, Evard, and Porters series) are on the rolling foothills. Hapludults (Tusquittee series) and Haplumbrepts (Spivey series) formed from colluvium on foot slopes and coves. Boulders and outcrops of bedrock are conspicuous but inextensive on mountain slopes. Haplumbrepts (Burton series) are dominant at higher elevations. In the broad valleys, extensive Hapludults (Brevard, Fannin, Hayesville, Clifton, and Saluda series) are associated with Rhodudults (Rabun and Dyke series) over mafic rocks on rolling hills. Dystrochrepts (Comus and Codorus series) along the many narrow streams are frequently flooded unless protected. Potential natural vegetation: This area supports Appalachian oak forest vegetation. White pine-hemlock, chestnut oak, white oak-red oak-hickory, northern red oak-basswood-white ash, yellow-poplar-white oak-northern red oak, and loblolly pine-shortleaf pine are important cover types. Dogwood, hornbeam, pawpaw, sassafras, persimmon, greenbrier, leath- erwood, mountain-laurel, rhododendron, and witchhazel are included in the understory vegetation. Red spruce and balsam fir grow at higher elevations. 93 O—MISSISSIPPI DELTA COTTON AND FEED GRAINS REGION 116,080 km 2 (44,820 mi 2 ) This region consists of flood plains and low terraces of the Mississippi River south of its confluence with the Ohio River. The average annual precipitation ranges from 1,150 to 1,650 mm. The average annual temperature ranges from 14 to 21°C. The freeze-free period ranges from 200 to 340 days, increasing in length from north to south. Aquepts, Aqualfs, Aquents, Udolls, and Udalfs are extensive. Many of the soils require drainage if they are used for crops. Most of the soils throughout the region are poorly drained. If artificially drained, they are highly productive for many crops. Soybeans, cotton, corn, and hay are grown throughout the region. Rice in Arkansas and Louisiana and sugarcane in Louisiana are important crops locally. The wettest areas that are not artifically drained remain in forests, which are important for hardwood timber production and wildlife habitat. 131—Southern Mississippi Valley Alluvium Arkansas, Mississippi, Missouri, and Tennessee 93,600 km 2 (36,140 mi 2 ) Land use: Most of this area is in farms. About 55 percent is cropland, 35 percent woodland, and 7 percent pasture. About 3 percent is used for miscel¬ laneous purposes. Cropland makes up about three- fourths of the acreage in the north and less than one-fourth in the south. The proportion of forest land varies inversely with that planted to crops; the proportion of pasture is a little higher in the south. This is an important cash-crop area. Soybeans, cot¬ ton, and wheat grown by highly mechanized methods are the major crops throughout the area. Corn is an important crop in Missouri. Rice is an important crop in Arkansas, Louisiana, and Mississippi, and sugar¬ cane is important in southern Louisiana. Controlling surface water and artificially draining the wet soils are major concerns of management. Elevation and topography: Elevation is at sea level in the south and increases gradually to about 200 m in the north. The area consists of level to gently sloping broad flood plains and low terraces. Most of the area is flat. The only noticeable slopes are sharp terrace scarps and natural levees that rise sharply to several meters above adjacent bottom lands or stream chan¬ nels. Swamps are significant in the extreme southern part in Louisiana. Climate: Average annual precipitation —1,150 to 1,650 mm, increasing from north to south. In most of the area maximum precipitation is in winter and early in spring, decreasing gradually to a minimum in autumn. Along the Gulf Coast, maximum precipita¬ tion is in midsummer and early in autumn. Snowfall is negligible. Average annual temperature —14 to 21°C, increasing from north to south. Average freeze-free period —200 to 340 days, increasing from north to south. Water: Precipitation, streamflow, and aquifers supply moderate to large quantities of potable ground water. The Mississippi River crosses the area from north to south, and many of its tributaries also cross the area. Oxbow lakes and bayous are extensive throughout. Potable ground water is not available in extreme southern Louisiana. Soils: The dominant soils are Aquepts, Aqualfs, Aquents, Udolls, and Udalfs. They are deep, medium textured and fine textured soils that have an udic or aquic moisture regime, a thermic temperature regime, and mostly montmorillonitic or mixed mineralogy. Fine textured Haplaquepts (Alligator, Perry, Portland, Sharkey, and Tunica series), Hapludolls (Desha, Bowdre series), and Ochraqualfs (Jackport series), and medium textured Fluvaquents (Commerce, Mhoon, and Convent series), Natraqualfs (Foley series), Ochraqualfs (Dundee, Amagon, and Hebert series), and Hapludalfs (Dubbs, Bosket, and Rilla series) occupy backswamp areas and older natural levees. Minor soils include moderately coarse textured Dystrochrepts (Beulah series) and Udifluvents (Rob- insonville series), medium textured Fluvaquents (Gideon series), fine textured Hydraquents (Barbary series), and organic Medisaprists (Maurepas series). The Hydraquents and Medisaprists are in the extreme southern part in Louisiana. Potential natural vegetation: This area supports deciduous bottom land forest vegetation. Willow oak, water oak, Nuttall oak, swamp white oak, sweetgum, water tupelo, baldcypress, native pecans, and hicko¬ ries are the principal species. Black willow, eastern cottonwood, sycamore, sugarberry, and green ash are dominant on the more recent soils. Switchgrass, eastern gamagrass, little bluestem, indiangrass, Flor¬ ida paspalum, plumegrass, sedges, and rushes are the dominant understory species. 94 P—SOUTH ATLANTIC AND GULF SLOPE CASH CROPS, FOREST, AND LIVESTOCK REGION 688,050 km 2 (265,660 mi 2 ) This region consists of the gently sloping to rolling southern Piedmont and upper Coastal Plain. The average annual precipitation ranges from 1,025 to 1,525 mm. Precipitation is considerably higher in midsummer than in the rest of the year. The average annual temperature is 16 to 20°C in most of the region but is as low as 14°C in some of the higher parts and as high as 21°C in the extreme southeast. The freeze-free period is 200 days or more in most of the region but is as long as 290 days in the southernmost part. Udults are the dominant soils. Udalfs are less extensive in places where texture is clayey or the soils are on erosional surfaces. Ochrepts and Udalfs, which formed in limy materials, occur in parts of the region. Aquents, Fluvents, and Ochrepts are on flood plains and on low terraces. Forests are important throughout this region and are the major land use in most areas. Cotton, soybeans, small grains, and corn are the main crops grown. Tobacco and peanuts are important locally. Pastures are also important and in some places are the main land use. Dairying is an 133A—Southern Coastal Plain Alabama, Florida, Georgia, Mississippi, North Carolina, South Carolina, Tennessee, and Virginia 285,050 km 2 (110,060 mi 2 ) Land use: This area is about 69 percent woodland, 17 percent cropland, and 11 percent pastureland. About 3 percent of the area is used for rangeland, urban development, or other purposes. The woodland is 65 to 75 percent privately owned and 25 to 35 percent industry owned. A small percentage is federally owned. Timber production is important. Cash crops include soybeans, corn, peanuts, and cotton. Major vegetable crops, melons, tobacco, and pecans are important in some parts. Recently, livestock farming has increased. Pastures are used mostly for beef cattle, but some dairy cattle and hogs are raised. Controlling soil erosion and improving drainage on low wetland areas are major concerns of manage¬ ment. Elevation and topography: Elevation ranges from 25 to 200 m, increasing gradually from the lower Coastal Plain northward. The area is strongly dis¬ sected into nearly level and gently undulating valleys and gently sloping to steep uplands that are under¬ lain by unconsolidated sand, silt, and clay. Stream valleys generally are narrow in their upper reaches but become broad and have widely meandering stream channels as they approach the coast. Local relief is mainly a few meters, but in some of the more deeply dissected areas relief is 25 to 50 m. Climate: Average annual precipitation —1,025 mm in the north to 1,525 mm in the south. Minimum precipi¬ tation is in autumn throughout the area. In the east maximum precipitation is in midsummer, and in the west it is in winter and in spring. Average annual temperature —16 to 20°C, increasing from north to south. Average freeze-free period —200 to 280 days, increasing from north to south. Water: Precipitation, perennial streams, and ground important enterprise locally. water provide an abundance of water. Domestic water supplies are obtained mainly from shallow wells and water for livestock from perennial streams and small farm ponds. In most places, one or more aquifers provide ample ground water for municipal and industrial uses. The many perennial streams have the potential for supplying water for municipal use, human consumption, and farming but have been little used for these purposes. A few large reservoirs are available for recreation and other uses. Soils: The dominant soils are Udults. They are deep and have a thermic temperature regime, an udic moisture regime, a loamy or sandy surface layer, and a loamy or clayey subsoil. Well drained and moder¬ ately well drained, nearly level to strongly sloping Paleudults (Bama, Bowie, Dothan, Malbis, Norfolk, Orangeburg, Red Bay and Ruston series) are on uplands. Well drained gently sloping to steep Hap- ludults (Cahaba, Cuthbert, Kirvin, Luverne, Saffell, and Sweatman in the south and Suffolk, Emporia, Rumford, Kenansville, and Craven in the north) are on uplands. Associated with these soils in less sloping areas are the moderately well drained and somewhat poorly drained, loamy Fragiudults (Ora, Bourne, Pheba, and Savannah series), Fragiudalfs (Dulac and Providence series), Paleudults (Clarendon and Golds¬ boro series) and the well drained to moderately well drained, clayey Paleudults (Angie, Faceville, Green¬ ville, Marlboro, and Shubuta series). Other well drained, nearly level to steep Paleudults (Darco, Fuquay, Lucy, Troup, and Wag-ram series), which have a thick sandy surface layer, are on uplands. Less extensive but locally important soils are the nearly level to moderately steep Quartzipsamments (Alaga, Kershaw, and Lakeland series) on uplands (mostly in the south), Paleudalfs (Atwood, Boswell, Millwood, and Susquehanna series) and Glossaqualfs (Aldine, Caddo, Guyton, Mollville, Waller, and Wrightsville series) (in the southwest), Paleudalfs 95 (Lexington series) on some loess-capped hilltops in the north-central part of the area, and nearly level Ochraquults (Amy, Myatt, Rembert, and Weston series), Albaquults (Cantey and Leaf series), and Paleaquults (Byars, Coxville, Pantego, and Plummer series) on low wetland. Bottom land soils include Udifluvents (Colling, Iuka, and Ochlockonee series), Fluvaquents (Bibb, Falaya, Mantachie, and Waverly series), and Dystroehrepts (Chenneby and Ouchita series). Potential natural vegetation: This area supports mixed oak-pine forest vegetation. Loblolly, longleaf, slash, and shortleaf pines; sweetgum; yellow-poplar; and red and white oaks are major overstory species. Dogwood, gallberry, and farkleberry are major un¬ derstory species. Common sweetleaf, American holly, greenbrier, southern bayberry, little bluestem, Elliott bluestem, threeawn, grassleaf goldaster, native lespedezas, and low panicums are other understory species. 133B—Western Coastal Plain Arkansas, Louisiana, Oklahoma, and Texas 140,640 km 2 (54,300 mi 2 ) Land use: Most of this area is in farms. Between one-half and three-fourths is forest and woodland. A few large tracts are owned by large corporations and the federal government (national forests), and lum¬ ber and pulp wood production is important. Land that is cleared is used mostly for pasture and hay crops. About one-sixth is used for cropland. Common crops grown are corn, grain sorghum, oats, soy¬ beans, peanuts, rice, and vegetable crops. Elevation and topography: Elevation ranges from 25 to 200 m, increasing from south to north. This area is a gently to strongly sloping dissected coastal plain. Local relief is in meters. Climate: Average annual precipitation —1,025 to 1,350 mm, increasing from northwest to southeast. Maximum precipitation is in spring and early in summer, and the minimum is late in summer and in autumn. Average annual temperature —16 to 20°C. Average freeze-free period —200 to 270 days, increas¬ ing from north to south. Water: Precipitation, perennial streams, and ground water generally provide an abundance of water. Even though summer rainfall is generally adequate, droughts are common. There is a summer moisture deficit of 50 to 150 mm. The wet soils need to be drained before they can be used for crops. A few large reservoirs on major streams provide municipal water supplies and also serve as recreation sites. Water for farm use comes from ponds and wells. Soils: Most of the soils are Udults. They are deep, moderately coarse textured and coarse textured. These soils have a moderately coarse textured to fine textured subsoil, a thermic temperature regime, an udic moisture regime, and siliceous or mixed miner¬ alogy. Moderately well drained Paleudults (Bowie, Felder and Malbis series), well drained Paleudults (Briley, Lilbert, Darco, Ruston, Shubuta, and Smithdale series), well drained Hapludults (Kirvin and Cuthbert series), moderately well drained Hapludults (Sacul series), moderately well drained Hapludalfs (Woodtell and Cadeville series), well drained Paleudalfs (Nacogdoches and Bernow series), well drained Hapludalfs (Kisatchie series), somewhat poorly drained Albaqualfs (Anacoco series), and somewhat excessively drained Paleudults (Eustis series) are on uplands. Fluvaquents (Mantachie, Boggy, and Nahatche series), Udifluvents (Iuka, Oklared, and Severn se¬ ries), Eutrochrepts (Marietta and Redlake series), and Glossaqualfs (Guyton series) are along major streams that drain the area. Most of the soils are weathered from sandstone and shale. Potential natural vegetation: This area supports pine-hardwood forest vegetation. Loblolly pine and shortleaf pine grow with sweetgum, southern red oak, white oak, flowering dogwood, and post oak. American beautyberry, greenbrier, hawthorns, berry vines, and others make up the woody understory. Little bluestem and pinhole bluestem are the domi¬ nant herbaceous species. Other major grasses include beaked panicum, longleaf uniola, spike uniola, and yellow indiangrass. Many species of low-growing panicums and paspalums and perennial forbs such as tickclovers, lespedezas, wildbean, and several com¬ posites contribute significantly to the total annual yield. 134—Southern Mississippi Valley Silty Uplands Arkansas, Kentucky, Louisiana, Mississippi, and Tennessee 51,410 km 2 (19,850 mi 2 ) Land use: Most of this area is in farms; a small acreage is federally owned. About 35 percent of the area is cropland, but the proportion varies greatly from county to county, depending on the soils and the topography. This is largely a cash-crop area. Cotton, corn, soybeans, and wheat are major crops, but rice is important locally in Arkansas and in Louisiana, and strawberries are important in Louisiana. Feed grains and forage are grown on dairy farms. About 16 percent of the area is in pasture or hay. About 46 percent is in forest of mixed pine and hardwoods. Lumber is the major forest product, and some pulp- wood is harvested. The present trend is toward the conversion of the pasture and forest to cropland. About 3 percent of the area is used for urban devel¬ opment or other purposes. There is an increase in urban development near the metropolitan areas. Elevation and topography: Elevation ranges from 25 to 100 m. The sharply dissected plains have a thick loess mantle that is underlain by unconsolidated 96 sand, silt, and clay, mainly of marine origin. Valley sides are hilly to steep, especially in the west. The intervening ridges are mostly narrow and rolling, but some of the interfluves between the upper reaches of the valleys are broad and flat. Stream valleys are narrow in the upper reaches but broaden rapidly downstream and have wide, flat flood plains and meandering stream channels. Local relief is mainly several meters to 25 or 50 m. Climate: Average annual precipitation —1,150 to 1,525 mm, increasing from north to south. Maximum precipitation is in winter and in spring, decreasing gradually through summer to autumn except for a moderate increase in midsummer. Average annual temperature —16 to 20°C, increasing from north to south. Average freeze-free period —200 to 280 days, increasing from north to south. Water: Precipitation and ground water are abundant. On the uplands shallow wells, cisterns, ponds and rural water systems are the main sources of water for domestic use and livestock. Shallow wells provide small quantities of water, but deep wells in underly¬ ing sand and gravel yield large quantities. Most steams are small and flow intermittently. They flow most of the time in winter and in spring but only during and immediately after storms in summer and in autumn. Soils: Most of the soils are Udalfs. They are deep, medium textured soils that have a thermic tempera¬ ture regime, an udic moisture regime, and mixed mineralogy. Well drained, nearly level to very steep Hapludalfs (Memphis series) are on uplands. Moder¬ ately well drained, nearly level to strongly sloping Fragiudalfs (Grenada and Loring series) are on ridgetops, side slopes, and terraces. Somewhat poorly drained Fragiudalfs (Calloway series) and poorly drained Udifluvents (Morganfield and Vicksburg se¬ ries), moderately well drained Udifluvents (Adler and Collins series), and somewhat poorly drained Fluvaquents (Falaya series) are on flood plains. In the east where the loess mantle thins, well drained Paleudalfs (Lexington series), moderately well drained Fragiudalfs (Dulac and Providence series), well drained Hapludults (Brandon and Silerton series), and well drained Paleudults (Smithdale series), all of which are gently sloping to steep, are on ridgetops and side slopes. Well drained Dystrochrepts (Ariel series), moderately well drained Udifluvents (Collins series), moderately well drained Dystrochrepts (Oaklimeter series), and somewhat poorly drained Fluvaquents (Falaya and Gillsburg series) are on the flood plains. Potential natural vegetation: This area supports hardwood and pine forest vegetation. Cherrybark oak and Shumard oak are widely distributed. Yellow- poplar, white ash, cottonwood, and black walnut are important species on the flood plains. Loblolly and shortleaf pines are on a wide variety of sites, mainly the eroded soils of the uplands and ridges. Other hardwood species that commonly grow in this area are w T hite oak, basswood, sweetgum, water oak, American elm, blackgum, sycamore, sassafras, south¬ ern red oak, chinkapin oak, American beech, and hickory. 135—Alabama, Mississippi, and Arkansas Blackland Prairie Alabama, Arkansas, and Mississippi 21,550 km 2 (8,320 mi 2 ) Land use: In Alabama and Mississippi, this area is about 58 percent woodland, 26 percent pastureland, and 14 percent cropland. The small outlier in Arkan¬ sas is about 40 percent pastureland, 33 percent woodland, and 25 percent cropland. Most soil areas have been disturbed, and only small remnants of the former prairie vegetation remain. About 2 percent of the area is used for urban development or for other purposes. Soybeans are the major crop, but corn, small grains, and cotton are also grown. Pastures are used mainly for beef production, but in some places dairying is an important industry. The woodland is about 75 to 80 percent privately owned, and about 20 to 25 percent is owned by industry. This is not a very productive woodland area. Controlling soil erosion and infestation of Johnsongrass on soils that are cultivated are major concerns of management. Elevation and topography: Elevation ranges from 25 to 100 m. Some of the more prominent valley floors are less than 25 m, and a few' ridgetops exceed 100 m. Valley floors, side slopes, and ridgetops are under¬ lain by clay, marl, and chalk. Local relief is mainly a few meters. Climate: Average annual precipitation —1,225 to 1,425 mm. Maximum precipitation is early in winter, in spring, and in midsummer; the minimum is in autumn. Average annual temperature —16 to 18°C, decreasing from south to north. Average freeze-free period —220 to 260 days. Water: Precipitation and perennial streams are impor¬ tant sources of water, but ground water from moder¬ ately deep and deep wells is the principal source for both domestic and municipal uses. Ponds provide water for livestock, and locally they are used for recreation. A few large reservoirs are available for recreation and other uses. Soils: The dominant soils are Ochrepts and Udalfs. They are fine textured and have a thermic tempera¬ ture regime, an udic moisture regime, and mont- morillonitic or carbonatic mineralogy. They are mainly moderately deep to deep over soft limestone or chalk and typically shrink, swell, and crack. Well drained Eutroehrepts (Sumter series) and moderately well drained to poorly drained Hapludalfs (Oktibbeha and Vaiden series), all of w'hich are nearly level to gently sloping and strongly sloping, are on w’ide ridgetops 97 and narrow side slopes. Shallow Udorthents (Demopolis series) occur locally but are of small extent. Moder¬ ately well drained to poorly drained, nearly level to gently sloping Haplaquepts (Leeper series) and Chromuderts (Terouge series), Hapludolls (Catalpa series), and Pelluderts (Eutaw and Trinity series) are on bottom land and in low upland areas. The outer perimeter of the area is intermittently ringed with moderately well drained to somewhat poorly drained Paleudalfs (Boswell and Susquehanna series) and moderately well drained and well drained Hapludults (Saucul and Saffell series). Potential natural vegetation: This area supports deciduous hardwood forest vegetation. Red oak, white oak, sweetgum, and blackgum are the dominant overstory species. Eastern redcedar, dogwood, and osage orange are major midstory species. Japanese honeysuckle, greenbrier, little bluestem, native lespedezas, plumegrass, low panicums, sedges, and rushes are the dominant understory species. 136—Southern Piedmont Alabama, Georgia, North Carolina, South Carolina, and Virginia 161,430 km 2 (62,330 mi 2 ) Land use: Most of this area is in small farms, but a sizable acreage is controlled by woodland companies. Land adjacent to major cities is used for residences and associated urban development. Although most of the land was once cultivated, much has reverted to mixed stands of pine and hardwoods. Most of the open land is pasture, but some crops, such as soy¬ beans, small grain, corn, cotton, wheat, and, to a lesser extent, tobacco, are grown. Dairy cattle and poultry are important locally. Elevation and topography: Elevation ranges from 100 to 400 m. Drainage patterns are well defined. Streams have dissected the original plateau, leaving narrow to fairly broad upland ridgetops and short slopes adjacent to the major streams. The valley floors generally are narrow and make up about 10 percent or less of the land area. The associated stream terraces are minor. Climate: Average annual precipitation —1,150 to 1,400 mm. Precipitation is evenly distributed through¬ out the year, but the lowest is in autumn; snowfall is light. Average annual temperature —14 to 18°C. Av¬ erage freeze-free period —205 to 235 days. Water: Precipitation, perennial streams, and lakes provide an abundance of water. Ground-water sup¬ plies are relatively small, but shallow and deep wells are the principal sources of water for domestic use. Small farm ponds are an important source of water for livestock. Soil: The dominant soils are Udults. They have a clayey or loamy subsoil, a thermic temperature re¬ gime, an udic moisture regime, and kaolinitic, mixed, or oxidic mineralogy. Well drained very gently slop¬ ing to gently sloping Hapludults (Cecil, Madison, and Appling series) and Paleudults (Davidson series) are on uplands. Well drained Hapludults, Rhodudults, Dystrochrepts, and Hapludalfs (Pacolet, Cecil, Gwin¬ nett, Louisa, Louisburg, and Wilkes series) are on the steeper slopes. In some localities, these soils contain coarse fragments. Dystrochrepts (Chewacla series), Udifluvents (Congaree and Cartecay series), and Fluvaquents (Wehadkee series) are in alluvial deposits. Potential natural vegetation: The uplands generally support hardwood and pine forest vegetation. Loblolly pine, slash pine, white oak, red oak, gum, yellow- poplar, and sycamore are principal species; pine is dominant on eroded sites. Hardwoods or mixed stands of pine and hardwoods are on slightly eroded soils and stream flood plains. Dogwood, honeysuckle, pinehill bluestem, briars, and other grasses and forbs charac¬ terize the understory. 137—Carolina and Georgia Sand Hills Georgia, North Carolina, and South Carolina 22,680 km 2 (8,760 mi 2 ) Land use: Most of this area is in farms; about one-sixth is federally owned and used for military posts and as training areas. Small acreages are used for urban development or for other purposes. About 80 percent is forest of pine and scrub oaks. Pulpwood and some lumber are the principal forest products. About 15 percent of the area is cropland, and about 5 percent is pasture. Corn and cotton are the principal crops. Most of the farms are part-time or subsistence farms. Elevation and topography: Elevation ranges from 50 to 200 m, increasing gradually from south to north. The area is a dissected rolling to hilly upland. In many of the more dissected sites, there are stablized dunes, resulting in very irregular slopes. Local relief is mainly several meters, but a few hills are 25 to 50 m above adjacent areas. Climate: Average annual precipitation —1,150 to 1,275 mm. Maximum precipitation is in midsummer, and the minimum is in autumn. Average annual temperature —17 to 18°C. Average freeze-free period —220 to 240 days. Water: Precipitation, perennial streams, and ground water supply an abundance of water. The kind and amount of plant growth is severely limited by low moisture in the rapidly permeable soils that are dominant in this area. Soils: The dominant soils are Psamments and Udults. They have a thermic temperature regime and an udic moisture regime. Deep, sandy Quartzipsamments (Lakeland and Kershaw series) and Paleudults (Blanton and Troup series) are on rolling to hilly slopes where the upper sandy strata are thick. Fragiudults (Blaney and Vaucluse series), Paleudults (Dothan and Fuquay series), and Hapludults (Pelion series) occur where 98 the upper sand strata are thinner and underlain by more clayey materials. Psammaquents (Osier series) and Humaquepts (Rutlege series) are on very poorly drained sites along drainageways. Potential natural vegetation: This area supports pine-oak forest vegetation. Longleaf pine is the dom¬ inant species. Turkey, blackjack, bluejack, and sand live oaks are included. Little bluestem, panicums, pineland threeawn, and associated grasses and forbs make up the ground cover vegetation. 138—North-Central Florida Ridge Florida 3,400 km 2 (1,310 mi 2 ) Land use: Most of this area is in farms, but some large holdings are used exclusively for forestry. Pasture makes up about one-fourth of the area; the remainder is mainly cropland. Corn, peanuts, tobacco, soybeans, vegetables, and melons are major crops. Some hay and feed grains are grown for livestock. More than one-half of the area is forested. Pulpwood and lumber are the principal forest products. Elevation and topography: Elevation ranges from 25 to 50 m. The sand-mantled limestone upland has an irregular, gently rolling topography. Many lime¬ stone sinks, some filled with water, dot the area. There are a few streams. Local relief is a few meters to about 10 m. Climate: Average annual precipitation —1,300 to 1,400 mm. Maximum precipitation is in summer, and the minimum is in winter and late in autumn. Aver¬ age annual temperature —20 to 21°C. Average freeze- free period —280 to 290 days. Water: The abundant rainfall and ground water are the principal sources of water. Shallow and deep wells provide water for domestic use, for livestock, and for irrigation. The many lakes and ponds are used for recreation. Soil: The dominant soils are Udults and Psamments. They have a thermic temperature regime and an udic moisture regime. Well drained and somewhat poorly drained Paleudults (Blanton and Albany series) have thick sandy layers over a loamy subsoil. Excessively drained and moderately well drained Quartzipsamments (Alpin and Chipley series) are sandy throughout. Well drained, sandy Hapludalfs (Archer series), which have a clayey subsoil, and poorly drained sandy Haplaquods (Mascotte and Leon series), which have a weakly cemented layer, are less extensive. Potential natural vegetation: This area supports open pine and oak forest vegetation. Longleaf pine and turkey oak are dominant trees. Several bluestem species, indiangrass, and several threeawn species are the dominant ground cover. Hairy panicum and many sedges are scattered throughout the area. Legumes and many annual forbs are in this area. 99 R—NORTHEASTERN forage and forest region 314,540 km 2 (121,440 mi 2 ) This cool, humid region consists of plateaus, plains, and mountains. The average annual precipitation ranges from 750 to 1,325 mm. In most of the region more than one-half of the precipitation falls during the freeze-free season. The average annual temperature is 3 to 11°C. The freeze-free period generally is 110 to 160 days but ranges from 80 days in the higher mountains to as long as 200 days in some areas along the Atlantic coast. Ochrepts and Orthods are the dominant soils. They commonly have a fragipan. Udalfs formed in limy parent material. They also have a fragipan but are less extensive than the Orchrepts and Orthods. Aqualfs, Aquepts, and Histosols occur in the lowlands and in depressions. Fluvents on flood plains are of small extent but are important for many uses. Stoniness and steep slopes are limitations to use of many of the soils. Most of the land in this region, especially the steeper areas, is forested. Significant amounts of lumber and pulpwood are produced. Locally, Christmas trees and maple syrup are important forest products. Forage and grains for dairy cattle are the principal crops. In places where markets, climate, and soils are favorable, fruits, tobacco, potatoes, and vegetables are important crops. Wildlife habitat and recreation are important land uses. 139—Eastern Ohio Till Plain Ohio and Pennsylvania 15,030 km 2 (5,800 mi 2 ) Land use: About three-fourths of the area is in farms, one-fifth is urbanized, and the remainder is used for other purposes. About one-third is cropland. Feed grains and forage for dairy cattle are the main crops in the west. Similar crops are grown in the east, where there are many part-time farms and many rural residences. Slightly more than 10 percent is pasture. About one-fifth is hardwood forest, mainly in farm woodlots. Some large holdings are used for watershed protection. Elevation and topography: Elevation ranges from 200 to 300 m, increasing gradually from north to south. The gently to strongly rolling dissected glaci¬ ated plateau is underlain mostly by sandstone and siltstone. Stream valleys are narrow and are not deeply incised. In places, the interfluves are broad and nearly level. Local relief is about 2 to 15 m. Climate: Average annual precipitation —900 to 1,025 mm. Precipitation is fairly evenly distributed through¬ out the year, but it is slightly higher in spring and early in summer and lowest in winter. Precipitation in winter is mostly snow. Average annual tempera¬ ture —About 10°C. Average freeze-free period — About 160 days. Water: Precipitation, perennial streams, and ground water provide an abundance of water. Shallow and deep wells are the main sources of water for domestic use and municipal supplies. On many farms, small artificial ponds provide water for livestock and sup¬ plemental irrigation and are also used for recreation. Large reservoirs on perennial streams provide water for several of the large cities. Soils: Most of the soils are Udalfs and Aqualfs. They have a mesic temperature regime, an udic or aquic moisture regime, and mixed or illitic mineralogy. They are medium textured to fine textured and formed from glacial till. Included is a distinct, rela¬ tively small area of Udults in more acid till. Well drained and moderately well drained, gently sloping to moderately steep Fragiudalfs (Canfield, Rittman, and Wooster series) are on uplands. Somewhat poorly drained, gently sloping Ochraqualfs (Mahoning se¬ ries) are on uplands. Poorly drained and somewhat poorly drained, nearly level to gently sloping Fragia- qualfs (Sheffield and Ravenna series) are on uplands. Well drained, gently sloping to moderately steep Fragiudults (Hanover series) are on uplands. Potential natural vegetation: This area supports mostly beech forest vegetation. American beech, sugar maple, red oak, white ash, and white oak are the dominant species. American basswood, shagbark hick¬ ory, black cherry, and cucumbertree also are includ¬ ed. American beech and suger maple are dominant on poorly drained local flatland. Mixed mesophytic oak- sugar maple and oak forest grows locally. 140—Glaciated Allegheny Plateau and Catskill Mountains New Jersey, New York, Pennsylvania, and Ohio 70,540 km 2 (27,240 mi 2 ) Land use: Much of this area is in farms, but a large acreage is in second and third growth forests of oak and northern hardwoods. Urban use is expanding in some places. The Catskills are used mainly for recre¬ ation. Hay, pasture, and some grain for dairy cattle are the principal crops. Locally, potatoes are an important crop on the plateau tops, and poultry, fruits, and truck crops are produced in many of the narrow valleys. Abandoned or idle land common in the steeper areas is reverting to grasses, weeds, shrubs, and trees. Elevation and topography: Elevation is 200 to 300 m on valley floors, 500 to 600 m at the plateau surface, and 1,100 m or more in parts of the Catskills. The top of the dissected plateau is broad and nearly 100 level to moderately sloping. The narrow valleys have steep walls and smooth floors. The Catskills in the east have steep slopes. Climate: Average annual precipitation —750 to 1,025 mm. Precipitation is mostly snow. Average annual temperature —8 to 10°C. Average freeze-free period —110 to 160 days. Water: Precipitation and perennial streams and lakes provide an abundance of water. The Finger Lakes are a conspicuous feature along the northern border. Soils that have a fragipan are too wet in winter and in spring and are deficient in moisture during much of the growing season. Soils: Most of the soils are Ochrepts. They are moder¬ ately deep to deep, somewhat stony, and medium textured. These soils have a mesic temperature re¬ gime, an udic moisture regime, and mixed mineralo¬ gy. Nearly level to moderately sloping, moderately well drained Fragiochrepts (Mardin and Wellsboro series) and somewhat poorly drained Fragiaquepts (Volusia and Moms series) are on till-mantled up¬ lands. Shallower and more stony Dystrochrepts (Lordstown and Oquaga series) are on steeper sites. Deep, well drained Dystrochrepts (Chenango series) are on outwash in the valleys. Dystrochrepts (Barbour series) and Eutrochrepts (Tioga and Chagrin series) are on the younger stream deposits of valley floors. Hapludalfs (Howard and Palmyra series) in limy outwash materials are conspicuous locally but of small extent. Potential natural vegetation: This area supports forest vegetation, particularly hardwood species. Beech-birch-maple and elm-ash-red maple are poten¬ tial forest types. Oak species increase from east to west, particularly in areas of shallow and dry soils. In places, conifers, such as white pine, are important. Aspen, hemlock, northern white-cedar, and black ash grow on the wetter soils. In some parts of the area, sugar maple has potential economic significance. 141—Tughill Plateau New York 3,080 km 2 (1,190 mi 2 ) Land use: Most of this area is forested with mixed hardwoods and conifers. Part of the forested land is abandoned cropland that has reverted to forest vege¬ tation. Pulpwood, saw logs, Christmas trees, and maple syrup are the principal forest products. Less than one tenth of the area is cropland. Forage and some feed grains grown for dairy cattle are the main crops. Sizable acreages have reverted to unproductive brush and weeds. Urbanization is insignificant in this area. Elevation and topography: Elevation ranges from 300 m along the lower margins to 600 m at the plateau top. This plateau is underlain by sandstone. It is nearly level to gently sloping across the top, and hilly to steep around the margins. Local relief is a few meters to about 25 m, but the bordering lowlands are about 100 m below the plateau top. Streams flow off the plateau in several directions. Climate: Average annual precipitation —900 to 1,025 mm. Precipitation is evenly distributed throughout the year. Snowfall is heavy from late in autumn to early in spring. In some places, the total snowfall is as much as 355 cm. Average annual temperature —4 to 7°C. Average freeze-free period —110 to 135 days. Water: Precipitation and perennial streams provide an abundance of water. Shallow and deep wells supply water for domestic use and for livestock. There are few natural ponds or lakes, but ground water is close to the surface in many areas. Dense fragipans in most of the soils perch ground water for extended periods during winter and spring. The water resources avail¬ able are little used. Soils: Most of the soils are Orthods or Aquods. They are deep, stony, and medium textured. These soils have a frigid temperature regime, an udic or aquic moisture regime, mixed mineralogy, and a fragipan. They formed in glacial till derived primarily from acid sandstone. Well drained and moderately well drained Fragiorthods (Worth and Empeyville series) are on undulating to moderately sloping landscapes. Associated in lower areas are nearly level to gently sloping, poorly drained Fragiaquods (Westbury series). Very poorly drained Humaquepts (Tughill series) are ex¬ tensive in flats and in depressions. A few large deeper and wetter depressions contain Borohemists (Rifle series). Haplorthods (Colosse and Adams se¬ ries) in sandy outwash deposits are prominent locally but are of small extent. Potential natural vegetation: This area supports northern hardwood forest vegetation. The beech- birch-sugar maple type is of primary importance. Sugar maple is of particular economic significance. The elm-ash-red maple type also has potential in some parts of the area. Red spruce, balsam fir, and white pine can be expected in mixed stands. Early succession vegetation includes high and low bush blueberry and aspen-birch forest types. As succes¬ sion approaches climax, sugar maple, beech, and hemlock increase in importance. Eastern hemlock, white spruce, American elm, black ash, and red maple grow on the wetter soils. A moss-Labrador tea-fern vegetation grows on extremely wet, organic soils. 142—St. Lawrence-Champlain Plain New York and Vermont 14,260 km 2 (5,510 mi 2 ) Land use: Most of this area is in farms or forests; only about 6 percent is used for urban development or for other purposes. About one-fourth is cropland, and less than one-tenth is pasture. Hay for dairy cattle is 101 the principal crop, but some small grain and corn are grown for silage. Potatoes are an important cash crop in some places, and a few apple orchards are on the slopes along Lake Champlain, but the total acreage of these crops is small. About one-half of the area is forested with northern hardwoods and conifers. Saw logs and pulpwood are the main forest products. Christmas trees and maple syrup are produced in some localities. Elevation and topography: Elevation ranges from 25 to 300 m, increasing gradually from the St. Lawrence River southward and from Lake Champlain to the east and the west. Rivers and streams have cut relatively deep but narrow valleys across the nearly level to undulating marine and glacial plain. Local relief is usually only a few meters, but glacial till ridges, till plains, and some outwash terraces rise 5 to 25 m above the adjacent plain. Climate: Average annual precipitation —About 900 mm. Precipitation is evenly distributed throughout the year. Snowfall is heavy from late in autumn to early in spring. Average annual temperature —4 to 7°C. Average freeze-free period —120 to 140 days but about 160 days in a narrow belt around Lake Champlain. Water: Precipitation, numerous perennial streams, and ground water provide an abundance of water. Deep wells in the glacial drift yield moderate quantities of water. The ground water in areas underlain by limestone is highly mineralized. Nearly level areas, mainly of heavy textured marine and lake-laid sedi¬ ments, have ground water close to the surface during part of the year. The St. Lawrence Seaway, which forms the northern border of the area, and Lake Champlain are important transportation arteries and are also used extensively for recreation. Soils: The dominant soils are Aqualfs and Ochrepts. They are deep and fine textured and medium textured. These soils have a mesic temperature regime, an udic or aquic moisture regime, and illitic or mixed miner¬ alogy. At the lowest elevations, nearly level, poorly drained and somewhat poorly drained Ochraqualfs (Covington and Kingsbury series) and poorly drained and very poorly drained Haplaquepts (Livingston series) are in clayey marine and lake-laid sediments. Some sizable areas of these heavy textured deposits have a thin sandy mantle, and poorly drained to somewhat poorly drained Haplaquepts (Swanton se¬ ries) and moderately well drained Eutrochrepts (Elmwood series) occur in these areas. Associated on the same landscape are well drained and moderately well drained Eutrochrepts (Grenville and Hogansburg series) on low ridges of calcareous glacial till. The soils of the higher till plains grade from a mesic temperature regime to a frigid temperature regime, and the dominant ones are moderately well drained and well drained Fragiorthods (Empeyville and Worth series), well drained Dystrochrepts (Charlton series) and somewhat poorly drained Fragiaquods (Westbury series). The glacial drift in these gently sloping to rolling areas is moderately stony and is derived mainly from acid sandstone. Well drained Haplorthods (Colton and Adams series) in sandy glacial outwash and aeolian deposits are also fairly extensive. Areas of rock outcrop are prominent features in the western part of the area. Potential natural vegetation: This area supports hardwood forest vegetation. The beech-birch-sugar maple forest type is the dominant climax species. Basswood, American elm, maple species, white ash, black cherry, and white pine are included in this forest type. The aspen-birch type, earlier in succes¬ sion, is economically important. Species such as east¬ ern hemlock, red maple, American elm, and spruce have potential on wet soils. 143—Northeastern Mountains Maine, Massachusetts, New Hampshire, New York, and Vermont 101,760 km 2 (39,290 mi 2 ) Land use: More than 90 percent of this area is forested with northern hardwoods, spruce, and fir. Wood for lumber and pulp for the paper industry are the principal products. Most of the remaining area con¬ sists of isolated farms or of small residential devel¬ opments or is used for recreation. Much of the area of the Adirondacks in New York is in a state park. Although most of the area in New England is privately owned, some large acreages are in national forests, state forests, or state parks. This area is widely used for year-round recreation. Most farming is a part- time enterprise. Erosion on logging roads and ski trails is a potentially serious land use problem. Elevation and topography: Elevation ranges from 300 to 1,200 m, but a few isolated peaks are more' than 1,500 m, and some of the valleys, especially in northeastern Maine, are less than 300 m. The moun¬ tains and foothills are commonly rounded; are under¬ lain by granite, anorthosite, gneiss, schist, and slate; and are thinly mantled by glacial till. Many glacially broadened valleys have glacial outwash deposits and contain numerous swamps and lakes. Mountain and foothill slopes are moderately steep to very steep, and valleys are nearly level to sloping. Climate: Average annual precipitation —875 to 1,325 mm. More precipitation falls in summer than in winter. Heavy snowfalls are common in winter. Av¬ erage annual temperature —3 to 7°C. Average freeze- free period —80 to 130 days. Water: Precipitation, perennial streams, and lakes provide an abundance of water. Ground water is abundant in deep outwash in valleys but is scarce in the till and bedrock on the uplands. Soils: Most of the soils are Orthods. They are stony and medium textured to coarse textured. These soils have a frigid temperature regime, an udic moisture 102 regime, and mixed mineralogy. Shallow, excessively drained to somewhat excessively drained Haplorthods (Woodstock, Canaan, Lyman, and Thorndike series) and moderately deep, well drained Haplorthods (Tunbridge series) are on steep and very steep bed¬ rock ridges. Deep, somewhat excessively drained to well drained, gently sloping to steep Haplorthods (Hermon series) and deep, well drained to somewhat poorly drained, gently sloping to steep Fragiorthods (Becket, Marlow, Plaisted, Stowe, Peru, and Howland series) are on glacial till ridges. Deep, excessively drained to well drained, gently sloping to steep, nonstony Haplorthods (Colton, Adams, Stetson, and Allagash series) are on outwash deposits in valleys. Deep, somewhat poorly drained, nearly level to gently sloping Fragiaquods (Westbury series), somewhat poorly drained to very poorly drained, nearly level to gently sloping Fragiaquepts (Cabot, Ridgebury, Mo- narda, and Peacham series), and very poorly drained, nearly level to gently sloping Histosols (Cathro, Togus, and Vassalboro series) are on lower glacial till slopes and in depressions. Potential natural vegetation: This area supports northern hardwood and spruce-fir forest vegetation. Sugar maple, yellow birch, American beech, red spruce, and eastern hemlock are dominant on the better drained soils of the hills and ridges. Red spruce and baslam fir are dominant on the wetter soils of long, gentle slopes and in depressions. Stunted balsam fir and red spruce are common in some of the high mountaintop areas. 144A—New England and Eastern New York Upland, Southern Part Connecticut, Maine, Massachusetts, New Hampshire, New Jersey, New York, Rhode Island, and Vermont 52,040 km 2 (20,090 mi 2 ) Land use: About three-fifths of this area is in hardwood and pine forests, most of which are in small holdings. Some are in state forests or in other large holdings. The woodland is used for growing wood products and for hunting and other recreation. Use of woodland for residential development is increasing. About one- sixth of the area is in crops and pasture; the acreage in crops is somewhat greater than that in pasture. Forage crops for dairy cattle are grown on most of the cropland. Truck crops, small fruits, and apples are grown on some farms, mainly near the larger towns and cities. Many farmsteads are used as rural residences, and the residents earn their living from nonfarm occupations. About one-eighth of the area is urbanized, and the acreage used for this purpose is increasing rapidly. Controlling sedimentation and erosion are concerns of management in areas where urban development is expanding. Elevation and topography: Elevation ranges from sea level to 300 m in much of the area, but it is 600 m on some hills. The till-mantled rolling to hilly uplands are broken by many level to gently sloping valleys that terminate in coastal lowlands. These valleys and coastal plains are covered by glaciolascustrine and marine sediments and outwash. Relief is mostly about 2 to 20 m in the valleys and about 25 to 100 m on the uplands. Climate: Average annual precipitation —825 to 1,275 mm. Precipitation generally is evenly distributed throughout the year, but near the coast it is slightly lower in spring and in summer; inland it is slightly higher in spring and in summer. Average annual temperature— 7 to 10°C, increasing from north to south. Average freeze-free period —120 to 200 days, increasing from north to south. Water: Abundant precipitation, many perennial streams, and many natural lakes and ponds are important sources of water. Many large and small reservoirs provide municipal and industrial water. Ground water is scarce on the till-mantled uplands but is abundant in the deep outwash deposits in the valleys. Soils: The dominant soils are Ochrepts. These soils are medium textured and moderately coarse textured and have a mesic temperature regime, an udic mois¬ ture regime, and mixed mineralogy. Deep Dystro- chrepts (Charlton and Gloucester series), Fragiochrepts (Paxton series), and shallow Dystrochrepts (Hollis series) are dominant on the till-mantled hills of New England. Occurring in the sandy glacial outwash are Udorthents (Hinckley series) and Udipsamments (Windsor series). On the uplands bordering the Hudson Valley of New York and the Vermont Valley and the Taconic Mountains of Vermont, Dystrochrepts (Dut¬ chess and Nassau series) and Fragiochrepts (Ber- nardston and Pittstown series) are dominant, along with smaller amounts of Eutrochrepts (Stockbridge, Nellis, and Farmington series). Fragiudults (Rocka- way series) and Fragiochrepts (Swartswood series) are dominant on the till-mantled uplands of north¬ western New Jersey. Hapludalfs (Washington series) and Dystrochrepts (Riverhead series) are dominant in the valleys. Potential natural vegetation: This area supports a mixture of northern and central hardwoods. Sugar maple, birch, and beech, as well as oaks and hickory, are major species. White pine and hemlock are the dominant conifers; pitch pine and red pine grow on sandy outwash soils. Red maple grows on the wetter sites. Northern white-cedar reaches its northern limit in bogs. 144B—New England and Eastern New York Upland, Northern Part Maine, Massachusetts, New Hampshire, New York, and Vermont 48,570 km 2 (18,750 mi 2 ) Land use: About four-fifths of this area is in hardwood and conifer forests, most of which are in small 103 holdings. Some are in state forests or in other large holdings. Saw logs are the principal product, but maple syrup and Christmas trees are produced on some sites. The woodlands are widely used for hunting and other recreation. In some places, significant areas of forestland are used for residential and lei¬ sure home developments. About one-eighth of the area is in crops and pasture; the acreage of cropland is somewhat greater than that of pasture. Forage crops for dairy cattle are grown on most of the cropland. Truck crops, small fruits, and apples are grown on some farms, mainly near the larger towns and cities. Many farmsteads are used as rural resi¬ dences, and the residents earn their living from nonfarm occupations. About 5 percent of the area is urbanized. Controlling sedimentation and erosion are concerns of management in areas where urban devel¬ opment is expanding. Elevation and topography: Elevation ranges from sea level to 300 m in much of the area; however, it is 600 m on some hills and 900 m on a few isolated peaks. Till-mantled rolling to hilly uplands character¬ ize most of the area. Level to gently sloping valleys terminating in coastal lowlands occur in Maine. These valleys and coastal plains are covered by glaciolacustrine and marine sediments and outwash. Relief is mostly about 2 to 20 m in the valleys and about 25 to 100 m on the uplands. Climate: Average annual precipitation —900 to 1,225 mm. Precipitation generally is evenly distributed throughout the year, but near the coast it is slightly lower in spring and in summer; inland it is slightly higher in spring and in summer. Heavy snowfalls commonly occur late in winter. Average annual temperature —4 to 7°C. Average freeze-free period —110 to 160 days. Water: Abundant precipitation, many perennial streams, and many natural lakes and ponds are important sources of water. Many large and small reservoirs provide municipal and industrial water. Ground water is scarce on the till-mantled uplands but is abundant in the deep outwash deposits in the valleys. Soils: The dominant soils are Orthods. These soils are medium textured to coarse textured and have a frigid temperature regime, an udic moisture regime, and mixed mineralogy. Haplorthods are dominant on the higher hills that have a thin till mantle and on lower areas of sandy glacial outwash and till. Gently sloping to steep Fragiorthods are dominant on drumloidal landforms. The characteristic hardpan of the Frag¬ iorthods is at a depth of 60 to 90 cm. Udifluvents on narrow flood plains and Eutrochrepts on marine and lacustrine sediments are inextensive but are impor¬ tant to agriculture. Potential natural vegetation: This area supports northern hardwood forest vegetation. Beech, white and yellow birch, sugar maple, and hemlock are dominant on the better drained soils. Spruce and balsam fir are dominant on the wetter soils and on mountain tops. The northern aspects of mountain slopes favor spruce and fir, and the southern aspects support northern hardwoods. White pine is common on abandoned farmland, in river valleys, and on outwash plains. Spruce-fir, mountain cranberry, and similar acid-tolerant plants grow on alpine to subal- pine mountaintops. 145—Connecticut Valley Connecticut, Massachusetts, New Hampshire, and Vermont 6,560 km 2 (2,530 mi 2 ) Land use: About 40 percent of this area, including small private woodlands, state forests, and reservoir watersheds, consists of hardwood and pine forests. The forested land is used for residential, recreational, wildlife, and esthetic purposes or it is held for investment. Lumbering is of minor importance. Lo¬ cally, maple syrup and Christmas trees are important forest products. About 35 percent of the area is used for urban and other community developments. Ex¬ pansion of industrial and commercial facilities is rapidly using up prime farmland. Many small tracts are used as rural residences by occupants who are employed in cities and towns. About 20 percent of the area is in farms, on which about 60 percent of the area is cleared and used for crops and pasture. Forage, tobacco, vegetables, fruits, potatoes, and nursery stock are major crops. Hay and silage corn for dairy cattle make up a substantial acreage on many farms. Poultry and greenhouse products are important locally. Elevation and topography: Elevation ranges from sea level to 100 m in lowlands and from 200 to 300 m on ridges. Nearly level to sloping lowlands mantled by glaciolacustrine and marine sediments, glacial till, and outwash are broken by isolated north-south traprock ridges that have hilly and steep slopes. Local relief is 1 to 20 m on lowlands. The ridges are about 50 to 100 m above the lowlands. Climate: Average annual precipitation —1,025 to 1,275 mm. Precipitation is evenly distributed throughout the year. Snowfall in winter averages 102 cm. Aver¬ age annual temperature —7 to 11°C. Average freeze- free period —150 to 195 days. Water: Precipitation, perennial streams, lakes, and ground water provide an abundance of water. Water for municipal and industrial needs is stored in reser¬ voirs in this area and in adjoining areas. In some soils that have a fragipan, the water table is perched from late in fall to early in spring. Soils of wetlands are saturated during a large part of the year. Soils: Most of the soils are Ochrepts. The soils are deep and loamy and have a mesic temperature regime, an udic moisture regime,and mixed mineralogy. Gently sloping to moderately steep, well drained Fragiochrepts 104 (Wethersfield and Paxton series) and well drained Dystrochrepts (Cheshire and Charlton series) are on till-mantled lowlands. Shallow Dystrochrepts (Holyoke series) are on steeper slopes associated with traprock ridges. Deep, well drained Dystrochrepts (Hartford and Merrimac series), excessively drained Udipsam- ments (Windsor series), and excessively drained Udorthents (Manchester and Hinckley series) are on glacial outwash in the valleys. Deep, moderately well drained, nearly level Dystrochrepts (Berlin series) and Eutrochrepts (Buxton series) are on lacustrine sediments. Dystrochrepts (Hadley and Winooski se¬ ries) and Fluvaquents (Limerick series) are on flood plains. Potential natural vegetation: This area supports hardwood and pine forest vegetation. Oak, hickory, maple, beech, and birch species are dominant. Conif¬ erous species, white pine, and eastern hemlock are more prevalent in the north than in the south. Red maple, black ash, American elm, and Atlantic white- cedar are common on the wetter soils. 146—Aroostook Area Maine 2,700 km 2 (1,040 mi 2 ) Land use: About 60 percent of this area is cropland. Potatoes are the major crop, ttut oats, hay, peas, and buckwheat are grown in some places. Most of the remaining land is forested or is cropland reverting to forest. Forest products are used mainly in the paper industry and for lumber. Intensive cropping has resulted in extensive erosion and sediment problems in some parts of the area. Elevation and topography: Elevation is about 200 m. Long, rolling ridges in the central and southern parts have broad, gently sloping crests. The land is more sloping in the north, and some hills rise above 300 m. Gently sloping or nearly level river terraces and flood plains are along waterways. Climate: Average annual precipitation —925 to 1,025 mm. Precipitation is fairly evenly distributed through¬ out the year. Snowfall is heavy in winter. Average annual temperature —3 to 6°C. Average freeze-free period —100 to 120 days. Water: Precipitation and the many perennial streams provide an abundance of water. Ground water is plentiful in the outwash and alluvium in the valleys but is scarce in the till and bedrock on the uplands. Soils: Most of the soils are Orthods and Ochrepts. They are medium textured to coarse textured and have a frigid temperature regime, an udic moisture regime, and mixed mineralogy. Deep, well drained, Fragi- orthods (Plaisted series), Fragiochrepts (Perham se¬ ries), and deep, moderately well drained to some¬ what poorly drained Fragiorthods (Howland series) are on glacial till ridges. All these soils are gently sloping to sloping. Shallow,somewhat excessively drained, gently sloping to moderately steep Haplorthods (Thorndike series) are on glacial till ridges. Exces¬ sively drained to well drained Haplorthods (Colton, Stetson, and Allagash series) are on glacial outwash deposits, mostly in the valleys. Deep, well drained, gently sloping to sloping Dystrochrepts (Caribou series) are on glacial till ridges. Deep, poorly drained, nearly level to gently sloping Fragiaquepts (Monarda series) are on glacial till ridges. Udifluvents on flood plains are important to agriculture, but their extent is small. Potential natural vegetation: This area supports northern hardwood forest vegetation. Sugar maple, yellow birch, beech, and hemlock are on the better drained soils of the hills and ridges. Spruce species and balsam fir are on the wetter, long, gentle slopes and in depressions. 105 S—NORTHERN ATLANTIC SLOPE DIVERSIFIED FARMING REGION 105,780 km 2 (40,840 mi 2 ) This temperate, humid region consists of coastal lowlands, coastal plains, the piedmont, and ridges and valleys. The average annual precipitation is 900 to 1,275 mm in most of the region but is only 825 to 925 mm in the ridges and valleys in western Maryland and in West Virginia. Precipitation is slightly higher during spring and summer than during the remainder of the year. The average annual temperature is 8 to 14°C. In most of the region the freeze-free period ranges from 180 to 200 days, but it ranges from 120 days in the mountains to 220 days along the Atlantic Ocean and the Chesapeake Bay. Udalfs, Udults, and Ochrepts are the dominant soils. These soils commonly have a fragipan. Aquults and Aquepts occupy lowlands and depressions, particularly on the coastal plains. Soils on the flood plains, mainly Ochrepts and Fluvents, are of minor extent. Hydraquents, Sulfaquents, and Sulfihemists are in tidal marshes along the Chesapeake Bay and the Atlantic Ocean. Psamments are of major extent on the Long Island-Cape Cod coastal lowland and of minor extent on the coastal plains. Farming is highly diversified. Truck crops, fruits, and poultry are important sources of income, particularly on the coastal plains. Forage crops, soybeans, and grain for dairy and beef cattle are also important. Many large-scale corporate farms on the coastal plains are associated with the canning and frozen food industries. Many farms are operated part time by people who earn most of their living in the cities. Rural residences occupy many sites that are less favorable for farming. Throughout the region, urban areas are encroaching on farmland. Steep slopes are largely in forests used for timber production and for recreation. 147—Northern Appalachian Ridges and Valleys Maryland, Pennsylvania, Virginia, and West Virginia 48,210 km 2 (18,610 mi 2 ) Land use: Most of this area is in farms. About 12 percent is used for urban development or consists of land altered by urbanization or other activities. Ap¬ proximately 30 percent is cropland. A wide variety of crops are grown, mainly corn, small grains, and forage for dairy and beef cattle. Other important crops include potatoes, soybeans, apples, peaches, and some tobacco and vegetables. Dairy, beef and poultry farms are major enterprises. About 5 percent of the area is permanent pasture. Less than 60 percent is in hardwood forests that are mainly in small to medium-size holdings and some larger tracts of state forests, game lands, and parks. Much of the prime farmland in the valleys is urbanized. Elevation and topography: Elevation ranges from 100 to 300 m in the valleys and from 400 to 800 m on ridges and mountains, but on some mountain crests it is 900 m. Parallel sandstone and shale ridges are separated by narrow to moderately broad limestone and shale valleys. Ridges have hilly to steep slopes and narrow rolling crests; valleys are mainly undulat¬ ing to rolling but are hilly locally. Local relief in the valleys is about 5 to 50 m; ridges rise about 100 m above adjoining valleys. Climate: Average annual precipitation —900 to 1,275 mm. Maximum precipitation is in spring and in summer, and the mimimum is in fall. About 525 to 650 mm falls during the growing season. The average annual snowfall is 60 to more than 130 cm. Average annual temperature —8 to 13°C. Average freeze-free period —120 to 170 days; the shorter growing seasons are at the higher elevations and in the north. Water: Water is plentiful in this area. Springs, wells, farm ponds, reservoirs, and streams are the principal sources of water. The major streams are the Sus¬ quehanna and Potomac Rivers. Raystown Lake on the Raystown Branch of the Juniata River is one of the largest reservoirs in the area. Ground water is plentiful; the better producing wells are in the lime¬ stone valleys. Mineralized water and pollution of ground water are common land use problems. Soils: Most of the soils are Udalfs, Udults, and Ochrepts. They have a mesic temperature regime, udic and aquic moisture regimes, and mixed mineralogy. Nearly level to sloping, deep, well drained, medium textured to fine textured Hapludalfs (Hagerstown, Duffield, Edom, and Washington series) are in the limestone valleys. Gently sloping to sloping, deep, well drained or moderately well drained, medium textured to fine textured Hapludults (Allenwood, Bedington, Franks- town, Mertz, and Murrill series), Fragiudults (Buchanan and Laidig seies), and Paleudults (Frederick series) are on the lower foot slopes of the ridges and in the valleys. Most of these soils formed in residuum, colluvium, or glacial till derived from limestone, cherty limestone, sandstone, and shale. Sloping to steep, well drained, shallow to deep, medium textured Dystrochrepts (Berks, Calvin, Dekalb, Hazleton, and Weikert series) are on ridges and on the more sloping sites in the valleys. Potential natural vegetation: This area supports hardwood forest vegetation. White oak, red oak, 106 black oak, hickories, and associated upland hard¬ woods are the major species. Scarlet oak, chestnut oak, hickories, and scattered Virginia pine, shortleaf pine, and white pine are common on dry ridges and shallower soils. Yellow-poplar, red oak, red maple, and other species that require more moisture grow in sheltered coves, on foot slopes, and on north-facing sites. 148—Northern Piedmont Delaware, Maryland, New Jersey, Pennsylvania, and Virginia 29,870 km 2 (11,530 mi 2 ) Land use: Approximately 65 percent of this area is in farms, and 35 percent is either used for urban devel¬ opment or is urbanizing rapidly. Farms are intensively cropped in Maryland, in Pennsylvania, and in most of New Jersey. They are mostly in pasture or woodland in the northern parts of New’ Jersey and in Virginia. Forage crops, soybeans, and grain for dairy cattle occupy the largest acreage of cropland. Wooded areas, consisting mostly of farm w’oodlots, are exten¬ sive on the steepest parts of the area. Large centers of population and industry stimulate urbanization throughout the area. Elevation and topography: Elevation ranges from 25 to 300 m but dominantly is 100 to 300 m. On some ridges and isolated peaks, however, elevation is as much as 500 m or more. The dissected part of the Piedmont Plateau is underlain mainly by granite, gneiss, and schist. Basins are underlain by Triassic traprock, sandstone, shale, and conglomerate. The sedimentary rocks contain numerous dikes and sills of diabase and basalt. Other local areas are underlain by limestone. Topography is mostly gently sloping or sloping. Steeper slopes are mostly on the ridges at higher elevations or on side slopes adjacent to drain- agew'ays. Climate: Average annual precipitation —900 to 1,150 mm. Maximum precipitation is in spring and early in summer. Droughts of 10 to 14 days are common in summer. Average annual temperature —10 to 14°C. Average freeze-free period —160 to 200 days. Water: Precipitation and perennial streams are the important sources of water. Springs are common in rural areas and provide water for many farmsteads. Water for irrigation comes from streams, ponds, and wells. Shallow wells are important in rural areas, but most of the wells supply a limited quantity of water. Water for urban areas is supplied largely by munici¬ pal reservoirs. Soils: The dominant soils are Udults, Udalfs, and Ochrepts. They have a mesic temperature regime, an udic moisture regime, and mostly mixed mineralogy. They are dominantly well cjrained, moderately deep or deep soils. Hapludults (Chester, Edneyville, Elioak, Eubanks, and Glenelg series) are dominant on the uplands. Hapludalfs (Duffield, Hagerstowm, Montalto, Neshaminy, and Washington series) are less exten¬ sive on the uplands. Shaly Hapludalfs (Penn series) and Dystrochrepts (Klinesville series) are common in the Triassic basins on the uplands. Dystrochrepts (Cardiff, Manor, and Mt. Airy series) are common on the steeper slopes. Associated w’ith the dominant soils on the uplands are Hapludalfs (Lehigh, Mount Lucas, and Reaville series) and Fragiudalfs (Lawrence and Readington series). Soils on the flood plains are mainly Dystrochrepts (Bermudian, Codorus, Comus, and Rowland series) and Fluvaquents (Bowmansville and Hatboro series). Potential natural vegetation: This area supports deciduous hardwood forest vegetation. Chestnut oak, white oak, red oak, hickories, ash, American elm, and yellow-poplar are major species. Yellow-poplar is abundant on the northeast slopes. Tree growth and wood production is considerably less in the Triassic basins than elsewhere in the area. Black w 7 alnut and black cherry grow 7 on the well drained sites on flood plains. Eastern redcedar is common on many abandoned cropland areas. 149A—Northern Coastal Plain Delaware, Maryland, and New Jersey 20,870 km 2 (8,060 mi 2 ) Land use: About 60 percent of this area is woodland, 20 percent cropland, less than 5 percent pasture, and 15 percent urban. About 50 percent is in farms. Major crops are vegetables, corn, soybeans, small grains, and fruits. Tobacco is a special crop in Mary¬ land. Special crops in New Jersey are highbush blueberries and cranberries. Forage crops and grains for dairy cattle are important locally. Poultry, nursery stock, and sod farms also are important enterprises locally. Most woodland is in farm woodlots, but some is in large holdings. Pine pulpw’ood and hardwood lumber are the principal forest products. State for¬ ests and parks are extensive in places. A narrow band along the coast is intensively developed for resorts and for recreation. The urban developments are expanding rapidly. Improved drainage is needed on almost 25 percent of the farmland. Elevation and topography: Elevation ranges from sea level to 100 m, but it is less than 50 m in most of the area. This nearly level to rolling dissected coastal plain is underlain by unconsolidated sand, silt, and clay. Local relief is mostly 2 to 10 m, but it is 30 m or more in a few places. Climate: Average annual precipitation —900 to 1,275 mm. Most of the precipitation falls near the coast in midsummer. Snow r ranges from little or none in the south to 75 cm in the north. Average annual temperature —10 to 13°C, decreasing from south to north and from the coast inland. Average freeze-free 107 period —170 to 210 days, decreasing from south to north and from the coast inland. Water: Precipitation, perennial streams, and ground water provide an abundance of water. Domestic supplies are obtained mainly from shallow wells, but large supplies must be obtained from deep wells. In most years moisture is deficient in the coarse textured, well drained soils, and supplemental irrigation water from streams, ponds, and wells is used for high-value crops. Soils: Most of the soils are Udults and Aquults. They are deep and medium textured to fine textured. These soils have a mesic temperature regime, an udic or aquic moisture regime, and mixed or siliceous mineralogy. Well drained Hapludults (Sassafras, Downer, Matapeake, Aura, Chillum, Sunnyside, Kempsville, Freehold and Collington series) and Paleudults (Caroline series) are mostly in high posi¬ tions. Moderately well drained and somewhat poorly drained Hapludults (Hammonton, Woodstown, Matt- apex, Keyport, Holmdel, and Adelphia series) are in intermediate positions on the landscape. Ochraquults (Fallsington, Elkton, Othello, and Shrewsbury se¬ ries) are in associated low positions. There are also extensive areas of sandy soils, including Quartzi- psamments (Lakewood, Lakehurst, Evesboro, and Klej series), Hapludults (Galestown series), and Dystrochrepts (Riverhead series). Sandy Haplaquods (Atison and Berryland series) are in associated low positions. Sulfaquents, Sulfihemists, and Hydraquents are in mineral and organic tidal marshes. Potential natural vegetation: This area supports pine and hardwood forest vegetation. Loblolly pine, Virginia pine, shortleaf pine, southern red oak, black oak, scarlet oak, pin oak, willow oak, northern red oak, black walnut, yellow-poplar, sweetgum, and red maple are dominant species. 149B—Long Island-Cape Cod Coastal Lowland Massachusetts and New York 6,830 km 2 (2,640 mi 2 ) Land use: About one-half of this area is used for urban development, and urban expansion is continuing. Recreation uses are extensive along shorelines. Crop¬ land accounts for less than 10 percent of the area. Cash crops and vegetables such as potatoes, cauli¬ flower, and cabbage are particularly important. In a few places duck and poultry farms are important enterprises. About 25 percent of the land is forested. Elevation and topography: Elevation ranges from sea level to 25 m, but a few places rise as much as 100 m. Nearly level to rolling plains of deep unconsolidated outwash deposits of sand and gravel are dominant. Steeper morainic hills and ridges border the lower plains. Local relief is mainly 1 to 10 m but is as much as 20 m in the more hilly areas. Climate: Average annual precipitation —1,025 to 1,150 mm. Precipitation is fairly evenly distributed throughout the year. Snowfall is moderate to low in winter. Extended periods of no snow cover can be expected in winter because of the relatively moder¬ ate temperatures. Average annual temperature —10 to 13°C. Average freeze-free period —180 to 220 days, but in most places it is 200 to 210 days. Water: In most years precipitation is adequate for crops. High-value vegetable crops grown on the drier sandy soils usually require irrigation for optimum yields. The deep sand and gravel deposits underlying most of the area are excellent aquifers and are good sources of irrigation water. Encroachment of saltwa¬ ter from the surrounding ocean is a continuing hazard to these freshwater aquifers. There are only a few perennial streams, rivers, and lakes. Coastal inlets and bays provide many recreation and transportation opportunities. Soils: Most of the soils are Ochrepts or Psamments. They are deep, moderately coarse textured and coarse textured. These soils have a mesic temperature re¬ gime, an udic moisture regime, and mixed mineralo¬ gy. Nearly level to sloping, well drained Dystrochrepts (Riverhead and Haven series) are on outwash plains, terraces, and remnant beach ridges underlain by sand and gravel deposits. Excessively drained Udipsamments (Carver and Plymouth series) are also extensive on sandy outwash plains and in steeper hilly areas. Well drained to moderately well drained Fragiochrepts (Montauk series) are in some morainic areas dominated by glacial till. Somewhat poorly drained and poorly drained Psammaquents (Wareham series) and Haplaquepts (Walpole and Raynham se¬ ries) in low areas and in drainageways are of small extent but are important locally. Sand dunes and tidal marsh are extensive along the coastline. Potential natural vegetation: This area supports forest vegetation of hardwoods and softwoods. Ex¬ tensive areas of the oak-pitch pine forest grow on the droughty, sandy soils. Oak and beech-birch-sugar maple are other potential forest types. White and red pine can be expected in many areas. Barberry and lowbush blueberry are common early succession types in burned-over areas. Sand dunes have potential for American beachgrass on foredunes and a mixture of bayberry, sassafras, and American holly on the more protected dunes. 108 T—ATLANTIC AND GULF COAST LOWLAND FOREST AND CROP REGION 247,140 km 2 (95,420 mi 2 ) This region consists of the nearly level low parts of the Atlantic and Gulf Coastal Plains. Elevation ranges from sea level to about 100 m. The average annual precipitation is 1,025 to 1,525 mm in most of the region but decreases sharply to about 625 mm in the extreme western part. The Mississippi River Delta, however, receives as much as 1,650 mm. The average annual temperature is 18 to 21°C in much of the region but decreases to 13°C in the north. The freeze-free period ranges from 200 days in the north to 350 days in the south. Aquults, Aqualfs, Udults, and Aquepts are the dominant soils in the eastern part of the region. Aquents, Psamments, Aquods, and Histosols are important locally. Uderts, Aqualfs, Aquolls, Aquepts, and a few Histosols (locally) are dominant in the west. Most soils require drainage if they are used for crops. Most of the land in the east is forested. Forest, pasture, recreation, and range are important land uses in the west. Rice is an important crop in the west. Other important crops are soybeans and corn. Grain sorghum, vegetables, tobacco, and peanuts are important crops locally. 150A—Gulf Coast Prairies Louisiana and Texas 41,710 km 2 (16,100 mi 2 ) Land use: Most of this area is in farms, and nearly 40 percent is used for crops or hay. Rice, soybeans, grain sorghum, cotton, corn, and hay are the chief crops. About one-third of the area is range or pas¬ ture. About one-sixth is in forests, chiefly hardwood, bordering the rivers and streams that cross the area. In some places, urban development is rapidly expanding onto cropland and agricultural land. Elevation and topography: Elevation ranges from sea level to about 50 m along the interior margin. The Gulf Coast Prairie is a nearly level area with low local relief. Climate: Average annual precipitation —625 to 1,400 mm, increasing from west to east. Precipitation is fairly evenly distributed, but it is slightly higher in midsummer and late in summer in the west and slightly higher in winter in the east. Average annual temperature —20 to 21°C. Average freeze-free period —280 to 320 days. Water: Rainfall and perennial streams provide abun¬ dant water. Water for irrigating rice is obtained from streams and in some places from wells. Ground water is abundant. Most of the soils must be drained for optimum growth of general farm crops. Soils: Uderts are dominant in the western and central parts. They are deep, clayey soils that have a very slowly permeable subsoil and montmorillonitic min¬ eralogy. Aqualfs are dominant in the eastern part. They are deep and loamy and have a clayey, very slowly permeable subsoil, an aquic moisture regime, and montmorillonitic mineralogy. Most of the soils have a thermic temperature regime, but those south and west of Lavaca Bay have a hyperthermic tem¬ perature regime. Poorly drained and somewhat poorly drained, nearly level Pelluderts (Beaumont and Lake Charles series) and Pellusterts (Victoria series) are on lowlands. Poorly drained and somewhat poorly drained Albaqualfs (Crowley and Edna series), Ochraqualfs (Midland and Orelia series), and Glossa- qualfs (Mowata series) are on slightly concave low¬ lands. Argiaquolls (Bernard and Morey series) and Haplaquolls (Kaman series), Fluvaquents (Mantachie series), and Haplaquepts (Urbo series) are on the flood plains of the Brazos and Trinity Rivers. The entire area is underlain by unconsolidated sediments. Potential natural vegetation: This area supports a true prairie plant community. Little bluestem, indiangrass, switchgrass, and big bluestem are the dominant species. A few groves of live oak dot the landscape. 150B—Gulf Coast Saline Prairies Texas 13,100 km 2 (5,060 mi 2 ) Land use: Most of this area is in ranches or is used for recreation. More than 75 percent is in native range consisting mainly of salt-tolerant plant species. A small acreage is used for bermudagrass pasture for beef cattle, rice,and grain sorghum. The remainder is mostly used for wildlife and for recreation. Deer, ducks, geese, and wild hogs are common in much of the area. Urban and recreation developments are expanding, especially along the barrier islands in the central and southern parts of the area. Elevation and topography: Elevation ranges from sea level to about 3 m, but it is as much as 8 m on some of the dunes. The area is mostly nearly level to gently sloping coastal lowlands and island flats along the Gulf of Mexico. Parts of the area have been worked by wind, and the sandy parts have a gently undulating to irregular topography because of low mounds or dunes. Relief is mainly less than 1 m. Streams flowing into the bays have broad shallow flood plains. Climate: Average annual precipitation —750 to about 1,400 mm. In the southwest precipitation is abundant in spring and in fall. In the northeast precipitation is 109 evenly distributed throughout the year. Average annual temperature— 21 to 23°C. Average freeze-free period —250 to 330 days. Water: The lowest parts of the area are covered by high tides, and the remainder is periodically covered by storm tides. Rainfall is the source of water for pasture and range. A few freshwater streams and rivers flow into the area from the north, and there are many bays and small entrapments of salty waters throughout the area. There is little underground freshwater. Livestock water comes mainly from dug- out ponds or shallow wells that tap thin shallow strata of freshwater. Freshwater for urban uses is piped in from outside the area. Soils: The dominant soils are Aquents, Aqualfs, Aquolls, and Aquepts. They are mostly saline, somewhat poorly drained to poorly drained, deep, and fine textured to coarse textured. These soils have a hyperthermic and thermic temperature regime, an aquic moisture regime, and montmorillonitic, mixed, or siliceous mineralogy. Psammaquents (Mustang, Tatton, and Dianola series), Udipsamments (Galveston series), Fluvaquents (Bayucos series), and Salorthids (Segita series) are on offshore barrier islands and near shore along the bays. Nearly level to very gently sloping Haplaquolls (Hams series), Natraqualfs (Livia, Narta, and Matagorda series), Pelluderts (Francitas series), and Pellusterts (Lomalta series) are on low coastal terraces. Undulating sandy Ochraqualfs (Roemer series), Albaqualfs (Rahal se¬ ries), and Paleudalfs (Portalto series) are on wind- worked plains. Haplaquolls (Aransas series), Hapla- quents (Austwell series), and Fluvaquents (Placedo and Veston series) are on coastal flats and flood plains of major streams in the area. Potential natural vegetation: This area supports grassland vegetation. The more saline soils support a plant community dominantly of gulf cordgrass and smaller amounts of little bluestem, switchgrass, sea¬ shore saltgrass, inland saltgrass, bushy sea-oxeye, marshhay cordgrass, rushes, sedges, and pickleweed. The less saline sandy soils support a plant community dominantly of little bluestem and lesser amounts of switchgrass, gulfdune paspalum, and marshhay cordgrass. 151—Gulf Coast Marsh Louisiana 21,030 km 2 (8,120 mi 2 ) Land use: Most of this area is in marsh vegetation and is used mainly for wildlife habitat. The area is almost treeless and uninhabited. It is part of the fertile and productive estuarine complex that supports marine life of the Gulf of Mexico. The area provides wintering ground for millions of ducks and geese and habitat for many fur-bearing animals and alligators. A signifi¬ cant acreage west of Vermillion Bay is firm enough to support livestock and is used for winter grazing of cattle. A small acreage of freshwater marsh is drained by pumping systems and is used for pasture and for the production of rice. Elevation and topography: Elevation ranges from sea level to about 2 m. On beach ridges, canal spoil banks, and natural levees, elevation is as much as 3 m, and on the salt dome islands, it is as much as 50 m. The land east of Vermillion Bay, part of the Missis¬ sippi River deltaic plain, has a ragged shoreline and is made up of recent alluvial and marine sediments. The land west of Vermillion Bay is made up of older alluvial and marine sediments and has a smoother shoreline. Low, narrow, elongated sandy ridges char¬ acterize much of the area. There are many rivers, lakes, bayous, tidal channels, and manmade canals. Climate: Average annual precipitation —1,225 to 1,650 mm, increasing from west to east. During the grow¬ ing season, precipitation ranges from 900 to 1,150 mm. Average annual temperature —About 21°C. Av¬ erage freeze-free period— 280 to 350 days, increasing from north to south. Water: This area contains many rivers, lakes, bayous, tidal channels, and manmade canals. About one-half of the marsh is fresh, and one-half is salty. Tidal channels provide free movement of salty water from the Gulf of Mexico into parts of the Gulf Coast Marsh adjacent to the Gulf. Most of the area is susceptible to flooding either by freshwater drained from lands adjacent to the marsh or by saltwater from the Gulf of Mexico. Daily tides flood some parts. Tides resulting from hurricanes or tropical storms are as much as 3 m above sea level and flood most of the area. Notable ground water is scarce east of Vermillion Bay. Hard ground water is available in moderate to large quan¬ tities west of Vermillion Bay. Soils: The dominant soils are Aquolls, Saprists, Aquents, and Hemists. They have a thermic temperature regime and an aquic moisture regime. Most of the soils of the Gulf Coast Marsh are very poorly drained, and their water table is at or above the surface most of the time. These soils are susceptible to frequent flooding. They formed in alluvial and marine sedi¬ ments and organic accumulations. The Aquolls are firm, but the other soils are soft and can sustain little weight. West of Vermillion Bay, Haplaquolls (Harris series) are dominant. Soils with a thin surface layer of peat or muck and Medisaprists (Kenner, Lafitte, and Allemands series), Hydraquents (Gentilly and Scatlake series), and floating Medihemists (Carlin series) are dominant. Potential natural vegetation: This area supports freshwater and saltwater marsh vegetation of grasses, sedges, rushes, and other plants. Alligatorweed, spikerush, maidencane, cutgrass, and bulltongue char- 110 acterize the freshwater vegetation. Roseau, common reed, bulltongue, and marshhay cordgrass character¬ ize the intermediate water vegetation. Marshhay cordgrass, saltgrass, and Olney bulrush are typical of the brackish water vegetation. Saltgrass, marshhay cordgrass, smooth cordgrass, and black needlerush are included in the saline water vegetation. 152A—Eastern Gulf Coast Flatwoods Alabama, Florida, and Mississippi 34,120 km 2 (13,170 mi 2 ) Land use: Very little of this area is in farms. Much of it is in large holdings owned by pulp and paper compa¬ nies. Part of it is in state and national forests or is used as game refuges and for military training areas. Nearly nine-tenths of the area is forested; pulpwood and lumber are the principal forest products. Some of the woodland is grazed. Only about 4 percent is cropped and a like amount is in pasture. Corn, peanuts, tobacco, and soybeans are the major crops. Some fruits and vegetables are produced, mainly for home consumption. Elevation and topography: Elevation ranges from sea level to 25 m. This nearly level low coastal plain is crossed by many large streams. The areas in Florida have many lakes and ponds. Local relief is a few meters. Climate: Average annual precipitation —1,325 to 1,625 mm. Minimum precipitation is early in autumn and in midautumn, increasing moderately in winter and early in spring, with lesser amounts in May. Maxi¬ mum precipitation is in summer. Average annual temperature —19 to 21°C. Average freeze-free period —270 to 290 days. Water: The abundant rainfall and the many perennial streams are important sources of water. Ground water is plentiful but is affected by salt in many places near the coast. Soils: The dominant soils are Aquults, Aquepts, and Aquods. They have a thermic temperature regime and an aquic moisture regime. They are sandy and poorly drained or very poorly drained. Paleaquults (Plummer and Pelham series) have a loamy subsoil. Humaquepts have a dark surface layer. Haplaquods (Leon and Mascotte series) have a weakly cemented layer at a depth of about 2 ft. Other important soils are sandy, moderately well drained and excessively drained Quartzipsamments (Chipley, Kureb, and Lakeland series), very poorly drained Sulfaquents, Sulfihemists, and possibly Hydraquents near the coast. Potential natural vegetation: This area supports pine forest vegetation. Chalky bluestem, indiangrass, and several panicum species make up the understory. Palmetto, gallberry, and waxmyrtle are the domi¬ nant woody shrubs. Longleaf and slash pine are the major trees. 152B—Western Gulf Coast Flatwoods Louisiana and Texas 16,890 km 2 (6,520 mi 2 ) Land use: Most of this area is in farms, and about three-fourths is forest, principally pine and pine- hardwood. Much of the forest acreage is owned by large corporations, and lumber and pulpwood are the chief products. Cleared areas are used mostly for pasture, but some are used for crops. Rice, grain sorghum, corn,and soybeans are commonly grown. Many small subdivisions are being developed through¬ out the area. Elevation and topography: Elevation ranges from 25 to 100 m. This area is nearly level to gently sloping and has a low local relief. Climate: Average annual precipitation —1,175 to 1,400 mm, increasing from west to east. Precipitation is evenly distributed throughout the year but is slightly greater in the east during winter. Average annual temperature— 19 to 21°C. Average freeze-free period —260 to 280 days. Water: Rainfall, perennial streams, and ground water provide an abundance of water. Most of the soils must be drained for optimum growth of general farm crops. Soils: Most of the soils have a water table near the surface during at least part of the year. The dominant soils are Udalfs. They are deep and medium textured or moderately coarse textured. These soils have a thermic temperature regime, an udic moisture re¬ gime, siliceous mineralogy, and a weak fragipan or plinthite. Somewhat poorly drained Fragiudalfs (Splendora series), moderately well drained Paleudalfs (Segno and Hockley series), and poorly drained Ochraqualfs (Sorter and Acadia series) are dominant in Texas. Poorly drained Glossaqualfs (Caddo series) and Paleudults (Beauregard series) are dominant in Louisiana. Poorly drained Glossaqualfs (Waller, Wrightsville, Guyton, Aldine, and Ozan series) are in depressions. Moderately well drained Paleudults (Malbis series) and well drained Paleudults (Ruston series) are on some of the higher ridges. Fluvaquents (Mantachie series), Eutrochrepts (Marietta series), Haplaquepts (Urbo series), and Glossaqualfs (Guyton series) are on the bottom land of the streams. The entire area is underlain by unconsolidated sediments. Potential natural vegetation: This area supports pine-hardwood forest vegetation characterized by longleaf pine. Sweetgum, blackgum, post oak, black¬ jack oak, and southern red oak are the principal hardwood species. Hawthorns, myrtle, and shining sumac make up the woody understory. Mid and tall grasses are dominant in open areas. Little bluestem, pinhole bluestem, big bluestem, switchgrass, and indiangrass are the principal grasses. Longleaf uniola, Virginia wildrye, Florida paspalum, beaked panicum, 111 and several low-growing panieums and paspalums are the principal grasses in shady areas. Lespedezas, tickclovers, wildbeans, and several composites con¬ stitute the principal forbs of the area. 153A—Atlantic Coast Flatwoods Florida, Georgia, North Carolina, South Carolina, and Virginia 73,760 km 2 (28,480 mi 2 ) Land use: Most of this area is in farms, but some is in national forests or is used as game refuges and for related purposes. About 70 percent is in forests. Some are farm woodlots, but most are large holdings. Pulpwood is the main wood product; lumber and naval stores are other sources of income from forests. About 20 percent of the area is cropland, and about 1 to 4 percent is pasture. The proportion of cropland is somewhat higher in the north and is considerably lower in Florida. Vegetable crops, fruits, melons, sweetpotatoes, and Irish potatoes are important crops. There are large acreages of corn, soybeans, wheat, and tobacco. Some peanuts are grown on the sandy soils in Virginia and in Georgia. Poultry farming is an important enterprise in the north and in some parts of Florida. Elevation and topography: Elevation ranges from 25 to 50 m. Some short steep slopes border the stream valleys. The area is crossed by many broad shallow valleys that have widely meandering stream channels. Local relief is mainly less than 10 m. Climate: Average annual precipitation —1,025 to 1,400 mm. Maximum precipitation is in summer. Average annual temperature— 13 to 21°C. Average freeze-free period— 200 to 280 days. Water: Rainfall, perennial streams, and ground water provide an abundance of water. Water for domestic, municipal, and industrial uses is obtained mainly from wells. Many of the soils require artificial drain¬ age before they can be used for crops, and some of the sandy soils need irrigation during droughts. Soils: Soils having restricted drainage are dominant throughout the area. Most extensive are Aquults. They have a thermic temperature regime and an aquic moisture regime. They are deep and medium textured to fine textured. Paleaquults (Rains, Coxville, and Lynchburg series) and Ochraquults (Rembert series) are most common. The Paleaquults (Byars, Bayboro, and Pantego series) and Umbraquults (Paxville series) are on associated wetter sites. Hapludults and Paleudults (Goldsboro, Persanti, Bertie, Johns, Kempsville, Suffolk, and Foreston series) are on higher sites where drainage is somewhat better. Other locally important soils are Haplaquods (Leon, Mascotte, and Lynn Haven series), Quartzipsamments (Lakeland series), and Paleudults (Blanton and Troup series). Histosols occupy fairly large areas, especially in the Okefenokee Swamp of Georgia and Florida. Potential natural vegetation: This area supports pine-oak forest vegetation. Loblolly pine and upland oaks are dominant on the uplands, and water tupelo, swamp blackgum, sweetgum, and oaks are dominant on the bottom lands. Longleaf uniola, cutover muhly, toothachegrass, panieums, little bluestem, and asso¬ ciated grasses and forbs characterize the understory vegetation. 153B—Tidewater Area Maryland, North Carolina, and Virginia 31,020 km 2 (11,980 mi 2 ) Land use: Most of this area is in farms, but some is in national forests or is used as game refuges, for urban developments, and for related purposes. About 70 percent of the area is in forests. Some are farm woodlots, but most are in large holdings. Pulpwood is the main wood product; lumber and naval products are other sources of income from forests. About 15 percent is cropland, and a very small acreage is pasture. There are large acreages of corn, soybeans, tobacco, and vegetables. Recreation enterprises are important, and coastal marshes make up 5 to 10 percent of the area. Elevation and topography: Elevation ranges from sea level to less than 25 m. The Suffolk Scarp is the upper limit of this area. The nearly level coastal plain is crossed by many broad shallow valleys that have meandering stream channels. Most of these valleys terminate in estuaries along the coast. Local relief is mainly about 1 m or less. Climate: Average annual precipitation —1,150 to 1,275 mm. Maximum precipitation is in summer, and the minimum is in autumn. Average annual tem¬ perature —13 to 24°C. Average freeze-free period — 200 to 300 days. Water: Rainfall, perennial streams, and ground water provide an abundance of water. Water for domestic, municipal, and industrial uses is obtained mainly from wells. Many soils require artificial drainage before they can be used for crops, but during droughts irrigation is needed on some of the sandy soils. Soils: The dominant soils are Aquults and Aqualfs. They have restricted drainage, a thermic tempera¬ ture regime, an aquic moisture regime, and dominantly mixed mineralogy. Deep, medium textured to fine textured Ochraquults (Tomotley, Yemassee, and Wahee series), Umbraquults (Cape Fear and Portsmouth series), Ochraqualfs (Argent and Yonges series), and Albaqualfs (Meggett series) are extensive. Hapludults (Bertie and Tetotum series) are on higher sites where drainage is better but somewhat restricted. Other important soils are Haplaquods (Baratari and Rosedhu series) and Udipsamments (Wando, Newhan, Corol¬ la, and Fripp series). Histosols occupy large areas in North Carolina and in the Dismal Swamp of Virginia. Potential natural vegetation: Loblolly pine and some oaks are dominant on the uplands, and blackgum, 112 sweetgum, oaks, water tupelo, and baldcypress are dominant on the bottom lands. Longleaf uniola, switchcane, panicums, little bluestem, inkberry, large gallberry, greenbrier, waxmyrtle, cabbage palm, and associated grasses and forbs characterize the under¬ story vegetation. 153C—Mid-Atlantic Coastal Plain Delaware, Maryland, and Virginia 15,510 km 2 (5,990 mi 2 ) Land use: About 65 percent of this area is in farms. The area is about 45 percent woodland, 45 percent cropland, less than 5 percent pasture, and less than 5 percent urban. Corn, soybeans, small grains, vege¬ tables, and fruit are major crops. Farming is highly diversified; poultry, truck crops, or fruit crops ex¬ ceed general farming in importance in some counties. Many large-scale corporate farms produce these spe¬ cialized crops. Sod farms are important locally. Many large tracts of loblolly pine on wet soils are managed for timber production. State forests and parks are extensive in places. A narrow bank along the Atlantic coast is intensively developed for resorts and recrea¬ tion. The seafood industry is significant to the econ¬ omy of counties bordering the Chesapeake Bay. Elevation and topography: Elevation ranges from sea level to about 25 m. This nearly level to gently sloping coastal plain is underlain by unconsolidated sand, silt, and clay. Local relief is only a few meters, even where flood plains or coves from the bay are incised. Climate: Average annual precipitation —1,175 mm; snowfall is about 37 cm. Average annual tem¬ perature —13 to 14°C. Average freeze-free period — 185 days inland to 220 days along the Atlantic Ocean and the Chesapeake Bay. Water: Rainfall, perennial streams, and ground water provide an abundance of water. Water for domestic, municipal, and industrial uses is obtained mainly from wells. Many of the soils require artificial drain¬ age before they can be used for crops, but during droughts irrigation is needed on some of the sandy soils. Soils: The dominant soils are Udults. They have a mesic temperature regime, an udic moisture regime, and mixed or siliceous mineralogy. These soils are mostly deep and well drained and moderately well drained. In the north, Hapludults (Matapeake and Mattapex series) formed in 1 to 3 ft of loess over sandy and clayey stratified coastal plain deposits. In the south, Hapludults (Sassafras and Woodstown series) formed in coastal plain materials lacking the silty loess mantle. Interspersed are Ochraquults (Fallsington, Elkton, and Othello series), which are dominant in the extreme south. Quartzipsamments (Evesboro series) occupy high ridges in the south. Extensive areas of tidal marsh are along the Ches¬ apeake Bay and the Atlantic Ocean consisting of both Histosols and Hydraquents. Along the Atlantic Ocean there is a strip of coastal beach dune sand. Potential natural vegetation: This area supports oak-pine forest vegetation. Shortleaf pine, baldcypress, and Virginia pine are major softwood species. Hard¬ woods make up most of the commercial timber vol¬ ume in the area. Oaks, mainly southern red, northern red, scarlet, willow, black, and white oak, are domi¬ nant. Other trees are yellow-poplar, blackgum, sweetgum, red maple, and hickories. 113 U—FLORIDA SUBTROPICAL FRUIT, TRUCK CROP, AND RANGE REGION 94,550 km 2 (36,510 mi 2 ) This region consists of the southern two-thirds of the Florida peninsula. The average annual precipitation is 1,275 to 1,625 mm. The average annual temperature is 21 to 25°C. The freeze-free period ranges from 290 days in the north to 365 days in the south. A large part of the region is south of the southern limit of annual frost. Psamments and Udults are the dominant soils at high elevations. Aquults, Aqualfs, Aquods, and Aquents are dominant at low elevations. Locally, Saprists and Fibrists are dominant. Many of the low-lying soils require drainage if they are used for crops. Citrus fruits, other subtropical fruits, and winter vegetables are the major crops throughout the region. The acreage in pasture and range, however, is somewhat greater than that in crops. More than two-thirds of the region is in forest or other native vegetation, much of which is grazed. Beef cattle are the principal livestock, and dairying is an important enterprise near the larger cities. In the south, sugarcane is a major crop locally. 154—South-Central Florida Ridge Florida 24,290 km 2 (9,380 mi 2 ) Land use: About 40 percent of this area is in forest, including the Ocala National Forest. Pulpwood is the chief forest product, but some lumber is produced. Some of the forests are grazed. Although only about 5 percent of the area is in crops, this is the major citrus-producing area in Florida. Many kinds of win¬ ter vegetables also are grown. About 25 percent of the area is pasture, about one-half of which is im¬ proved and intensively managed. Beef cattle are the principal livestock, and dairying is an important enterprise near some of the large cities. Phosphate mines are a prominent feature in the central part of the area. Elevation and topography: Elevation ranges from 25 to 50 m, but some hills are as much as 100 m, and a narrow strip along the western edge is at sea level. The nearly level to gently rolling coastal plain has a sandy mantle of varying thickness over limestone. The land surface is very irregular because of the many sinkholes that dot the area. Local relief is mainly a few meters, but in places it is 25 m or more. Climate: Average annual precipitation —1,275 to 1,400 mm. Maximum precipitation is in summer, and the minimum is late in autumn and in winter. Aver¬ age annual temperature —21 to 23°C. A verage freeze- free period —290 to 350 days. Water: Rainfall and ground water supply an abundance of water. Wells in the cavernous limestone underly¬ ing much of the area yield large quantities of water that is highly mineralized but otherwise of good quality. There are many lakes in the sinkholes through¬ out the area but few perennial streams. Soils: The dominant soils are Psamments and Udults. They have a hyperthermic temperature regime and an udic moisture regime. Excessively drained to moderately well drained Quartzipsamments (Astatula, Candler, Tavares, and Gainesville series) are sandy throughout. Well drained and somewhat poorly drained Paleudults (Arrendondo, Apopka, Kendrick, Sparr, and Lochloosa series) have very thick and thick sandy layers over a loamy subsoil. Poorly drained, sandy Aquults and Aqualfs (Blichton, Boardman, Flemington, Fellowship, and Wacahootaseries), which have a loamy and clayey subsoil, formed in sloping areas in phosphatic materials. Potential natural vegetation: This area supports “sand hill" vegetation. Turkey oak, bluejack oak, and longleaf pine are major species. Running oak, gopher apple, and such grasses as bluestems and panicums characterize the understory. 155—Southern Florida Flatwoods Florida 54,570 km 2 (21,070 mi 2 ) Land use: About 65 percent of this area is in forest, consisting mainly of spaced pine of low quality. The forests are grazed extensively. About 15 percent of the area is improved pasture, and the same propor¬ tion is native range grazed by cattle. Only about 3 percent is cropped, principally to many kinds of winter vegetables. Some citrus fruits are grown, and other subtropical fruits are grown in the south. Elevation and topography: Elevation ranges from sea level to 25 m, increasing gradually from the coast inland. The nearly level coastal plain is mantled by sand of varying thickness over limestone. The many swamps, marshes, lakes, and streams are prominent landscape features. Most of the area is flat, but some hummocks rise a meter above the general level. Climate: Average annual precipitation —1,300 to 1,525 mm. Maximum precipitation is in summer, and the minimum is late in autumn and in winter. Aver¬ age annual temperature —21 to 23°C. Average freeze- free period —290 to 365 days. Water: Rainfall, surface water, and ground water provide an abundance of water. On much of the cropland, ground-water levels are controlled by ca¬ nals and ditches. Excess water is pumped out during the rainy season, and irrigation water is applied 114 during the growing season. Domestic and municipal water supplies are obtained mainly from wells in the underlying limestone. Water from this source is highly mineralized. Soils: The dominant soils are Aquods, Aquents, and Aquepts. They have a hyperthermic temperature re¬ gime and an aquic moisture regime. Poorly drained, sandy Haplaquods (Myakka and Immokalee, and Wabasso, Wauchula, Pomona, EauGallie, and Oldsmar series) have a weakly cemented layer at a depth of about 2 to 4 ft. Poorly drained Psammaquents (Basinger and Pompano series) and very poorly drained Hum- aquepts (Placid series) are sandy throughout. Local¬ ly, narrow to broad bands of Sulfaquents, Sulfihemists, and Hydraquents occur along and near the coast. Moderately well drained, sandy Haplohumods (Pomello series), which have weakly cemented layers, and excessively drained, sandy Quartzipsamments (St. Lucie and Paola series) are on low old beach ridges and dunes. They are of small extent but are impor¬ tant for urban expansion. Potential natural vegetation: This area supports “flatwood” forest vegetation. Slash pine, longleaf pine, cabbage palm, and live oak are the principal species. Sawpalmetto and gallberry and such grasses as bluestems and wiregrasses characterize the un¬ derstory. 156A—Florida Everglades and Associated Areas Florida 11,210 km 2 (4,330 mi 2 ) Land use: About 50 percent of this area is used as Indian reservations, national parks, and game refuges and for other large holdings. About 35 percent is forested. Cypress forests are extensive, but man¬ grove forests are widespread along the eastern and southern coasts. A large part of the area is open marsh. Much of the area is used for hunting, fishing, and other recreation activities. About 13 percent is cropland. Winter vegetables are the main crop, but some citrus fruits, avocado, and papaya are grown on better drained sites. Sugarcane is an important crop on the organic soil south of Lake Okeechobee. The acreage of improved pasture, about 6 percent, is increasing. Beef cattle are the principal livestock, and dairying is an important enterprise locally. Urbaniza¬ tion is extensive along the eastern coast. Elevation and topography: Elevation ranges from sea level to less than 25 m. The level, low coastal plain contains large areas of swamps and marshes. Poorly defined broad streams, canals, and ditches drain the area to the ocean. Most of the area is flat, but in the interior, hummocks rise a meter or two above the general level. Low beach ridges and dunes, mainly in the east, rise a few meters above the adjoining swamps and marshes. Climate: Average annual 'precipitation —1,275 to 1,625 mm. Maximum precipitation is from late in spring through early autumn, and the minimum is during the remainder of autumn and in winter. Average annual temperature —22 to 25°C. Average freeze-free period —330 to 365 days. Water: Rainfall, surface water, and ground water provide an abundance of water. Near the coast, some surface and ground water is salty. A large part of the area is flooded during the rainy season. Canals and ditches control the ground-water level for crops and pasture. Excess water is pumped out during the rainy season, and irrigation water is applied during the dry season. Domestic and municipal water sup¬ plies are obtained from wells in the underlying lime¬ stone. This water is highly mineralized. Soils: The dominant soils are Saprists and Fibrists. They are very poorly drained, organic soils that have a hyperthermic temperature regime and an aquic moisture regime. Medisaprists (Terra Ceia, Pahokee, Lauderhill, and Dania series) are over limestone bedrock in the Everglades marsh. The more shallow soils are dominant in the southern part, and the deeper soils are dominant near Lake Okeechobee. Medifibrists (Montverde and Micco series) and Medisaprists (Tomoka series) are over mineral mate¬ rial in the St. Johns marsh. Also important are poorly drained, sandy Psammaquents (Hallandale and Mar¬ gate series) and Ochraqualfs (Boca series) that are moderately deep to limestone. Especially important in Dade, Monroe, and Collier Counties are soils that are shallow and very shallow to limestone and marl. Sulfihemists and Sulfaquents are shallow to rock; they are along the coast. Potential natural vegetation: This area supports freshwater marsh and swamp vegetation. Sawgrass, pickleweed, willow, buttonbush, and maidencane are the dominant marsh species. Baldcypress is the dom¬ inant swamp species. Mangroves grow in saltwater swamps along the eastern and southern coasts. 156B—Southern Florida Lowlands Florida 4,480 km 2 (1,730 mi 2 ) Land use: Most of this area is in farms and ranches. About 20 percent is forest of mixed pine and cab¬ bage palm or of cabbage palm and hardwoods. About an equal proportion of the remaining acreage is cropland, improved pasture, and rangeland. Citrus fruits, the chief crop grown, are planted in beds between shallow ditches that are part of the water- control system. Vegetation on the rangeland consists of native grasses, forbs, sedges, and a few scattered pines. Elevation and topography: Elevation is about 25 m; the lower areas are near the St. Johns marsh and the Everglades. The very broad and nearly level low- 115 lands are mantled by sand over loamy materials and in a few places over limestone. Most of the area is almost flat, but some hummocks rise a meter or two above the general level. Climate: Average annual precipitation —1,325 to 1,525 mm. Maximum precipitation is in summer, and the minimum is late in autumn and in winter. Aver¬ age annual temperature —22 to 23°C. Average freeze- free period —330 to 360 days. Water: Rainfall, surface water, and ground water provide an abundance of water. Unless practices are used to control the water level in naturally wet areas, shallow water covers the surface during much of the rainy season. Canals and ditches control the ground- water level for crops and pasture. Excess water is pumped out during the rainy season, and irrigation water is applied during the growing season. Domes¬ tic and irrigation water supplies are obtained mainly from wells in the underlying limestone. Water from this source is highly mineralized. Soils: The dominant soils are Aqualfs, Aquolls, and Aquods. They have a hyperthermic temperature regime and an aquic moisture regime. Poorly drained, sandy Glossaqualfs (Riviera, Winder, and Pineda series), poorly drained, sandy Ochraqualfs (Parkwood and Boca series) and very poorly drained Argiaquolls (Chobee, Floridana, and Manatee series) have a loamy subsoil. Poorly drained, sandy Haplaquods (Wabasso and Oldsmar series) have cemented layers at a depth of about 2 to 3P2 feet underlain by loamy subsoil. Poorly drained, shallow Psammaquents (Hallandale series) are scattered throughout the area. Potential natural vegetation: This area supports “hummock and slough” swamp vegetation. Slash pine and cabbage palm are the dominant species. Saw- palmetto, cordgrasses, and bluestems make up the understory. 116 V—HAWAII REGION 16,850 km 2 (6,510 mi 2 ) This region consists of eight major islands in Hawaii. These islands are of volcanic origin and consist of coastal plains, upland slopes, and mountain ranges and summits. The average annual precipitation ranges from 125 to 11,425 mm. The average annual temperature is 9 to 25°C. The growing season is throughout the year except on the mountain summits. Ustox, Torrox, and Ustolls occur on broad coastal and upland slopes. Andepts are extensive on semiarid to very humic uplands. Humults and Humox are on old landscapes on the uplands. Aquods, Saprists, and Aquepts are on wet mountain slopes. There are large areas of lava flows and stony, rocky, and very steep land. Sugarcane and pineapple are the major export crops. Coffee, macadamia, papaya, and floral products are other important export crops. Truck crops, mainly tomatoes, cucumbers, head cabbage, lettuce, green peppers, snap beans, bananas, and such specialty crops as ginger and taro also are important. Cattle ranching is important to the economy. The forests are used mainly for watershed, wildlife, and recreation. The pleasant climate and the tropical island scenery help make tourism an important industry. 157—Arid and Semiarid Low Mountain Slopes 1,290 km 2 (500 mi 2 ) Land use: Most of this MLR A is pasture. Small acreages of soils suited to intensive cultivation are used for irrigated truck crops. Areas that generally are unsuited to cultivation are used for urban and tourist devel¬ opments. Elevation and topography: Elevation ranges from sea level to 1,800 m. Slopes range from nearly level to moderately steep. Climate: Average annual precipitation —125 to 1,025 mm. Most of the precipitation falls from October to May. Average annual temperature —17 to 25°C. Av¬ erage freeze-free period —365 days. Water: Low rainfall limits pasture production. No perennial streams are in this area. Water for live¬ stock and irrigation is transported from other areas. Soils: Most of the soils are Andepts and Ustolls. They are well drained, moderately deep to deep, stony to extremely stony, and medium textured. They formed in deposits of volcanic ash and have an isohyperthermic or isothermic temperature regime and an ustic or aridic moisture regime. Eutrandepts (Kikoni, Kula, Oanapuka, Pakini, Puu Pa, and Waimea series) and Dystrandepts (Pane series) are at upper elevations; Camborthids (Kawaihae series) and Haplustolls (Kamaole, Keawakapu, and Makena series) are at lower elevations. Potential natural vegetation: This area supports grass-shrub vegetation. Kiawe, ilima, piligrass, uhaloa, buffelgrass, bermudagrass, lantana, fingergrass, cac¬ tus, Natal redtop, and Japanese tea grow on the drier sites. Kikuyugrass, white clover, rattailgrass, and guava grow on the wetter sites. 158—Semiarid and Subhumid Low Mountain Slopes 1,270 km 2 (490 mi 2 ) Land use: About 75 percent of this MLRA is cropland. The remaining acreage is used for urban develop¬ ment, military installations, and other purposes. Sug¬ arcane and pineapple are the chief crops. Small acreages are used for truck and forage crops. The soils are suited to intensive cultivation. About 75 percent of the prime farmland in the state is in this MLRA. Some soils that were formerly cultivated are now used for urban development. Elevation and topography: Elevation ranges from sea level to 500 m. Most slopes are broad and nearly level to moderately sloping. The slopes are dissected by rocky gulches. Climate: Average annual precipitation —300 to 1,525 mm in most places but as much as 2,025 mm on the Island of Kauai. Most of the precipitation falls from October to May. Summers are hot and dry. Average annual temperature —22 to 24°C. Average freeze-free period —365 days. Water: Most of the water for irrigation comes from the abundant rainfall in the mountains, but in some places it comes from wells. Few perennial streams are in this area. Soils: Torrox, Ustox, and Ustolls are the dominant soils. They are deep, well drained, fine textured and moderately fine textured. These soils have an isohyperthermic temperature regime, an ustic or aridic moisture regime, and kaolinitic mineralogy. The nearly level to steep Torrox (Molokai series), Haplustox (Lahaina series), Eutrustox (Lihue and Wahiawa series), and Haplustolls (Keahua, Makaweli, and Paia series) are on upland slopes. 117 Potential natural vegetation: This area supports grass-shrub vegetation. Lantana, bermudagrass, Natal redtop, uhaloa, ilima, kiawe, klu bush, piligrass, cactus, fingergrass, buffelgrass, guineagrass, and koa-haole grow on the drier sites. Java-plum, pangolagrass, kikuyugrass, joee, yellow foxtail, and molassesgrass grow on the wetter sites. 159— Humid and Very Humid Low and Intermediate Mountain Slopes 2,320 km 2 (900 mi 2 ) Land use: Most of this MLRA is used for growing nonirrigated sugarcane. A small acreage is used for coffee and macadamia orchards and truck crops. The remainder is in native and introduced forests, pasture, and urban developments. Elevation and topography: Elevation ranges from sea level to 1,800 m. Slopes are moderately sloping to steep. The area is dissected by steep-walled gulches. Climate: Average annual precipitation —1,775 to 5,075 mm, but in places it is as low as 1,025 mm. Precipitation is evenly distributed in areas of high rainfall. In areas of low rainfall, 60 to 75 percent falls from October to May. Average annual temperature —12 to 24°C. Average freeze-free period —365 days. Water: Rainfall supports most of the agriculture. Domestic water is used for supplemental irrigation of truck crops. Few perennial streams and no storage reservoirs or lakes are in this area. Soils: Most of the soils are Andepts and Humults. They are deep, well drained, moderately fine textured and fine textured. These soils have isohyperthermic and isothermic temperature regimes and an udic moisture regime. Hydrandepts (Akaka, Hana, Hilo, Honokaa, Kailua, and Kaiwiki series) are thixotropic soils in the wetter areas, mainly along the Hamakua Coast of the Island of Hawaii. Dystrandepts (Kukaiau and Paauhau series) occur in the same area but on sites where the rainfall is less. Tropohumults having kaolinitic mineralogy (Kaneohe, Lolekaa, and Waikane series) and oxidic mineralogy (Leilehua, Paaloa, and Paumalu series) occur along the Koolau Range of Oahu on terraces, old alluvial fans, and upland slopes. Potential natural vegetation: This area supports forest vegetation. Ohia, lehua, treefem, false-staghom, koa, kikuyugrass, hilograss, and guava grow on the wetter sites. Java-plum, christmasberry, california- grass, and koa-haole grow on the drier sites. 160— Subhumid and Humid Intermediate and High Mountain Slopes 910 km 2 (350 mi 2 ) Land use: This MLRA is predominantly pasture and woodland. A small acreage is used for truck crops. Most of the area is too steep and erodible for inten¬ sive farming. Elevation and topography: Elevation is mostly 900 to 2,100 m but ranges from sea level to 2,400 m. Most of the area consists of rolling to steep mountain slopes. Climate: Average annual precipitation —750 to 2,275 mm in most of the area but is as much as 3,050 mm. The rainy season is from October to May. Average annual temperature —12 to 23°C. Average freeze-free period —365 days. Water: Domestic water comes from wells and rain catchments with storage tanks or lined reservoirs. No perennial streams are in this area. Soils: Most of the soils are Andepts. They are deep, well drained, medium textured and moderately fine textured and have an isomesic temperature regime and an udic or ustic moisture regime. They formed in deposits of volcanic ash and are nonstony to extremely stony. The rolling to steep Dystrandepts (Hanipoe, Kaipoioi, Laumaia, Maile, Olinda, and Puu Oo series) occur on mountain slopes. Potential natural vegetation: This area supports forest and grass-shrub vegetation. Bermudagrass, black wattle, guineagrass, and lantana grow on the drier sites. Ohia, lehua, koa, treefern, rattailgrass, kikuyugrass, orchardgrass, bromegrass, naio, and mamani grow on the high, wetter sites. 161—Lava Flows and Rock Outcrops 7,060 km 2 (2,730 mi 2 ) Land use: A large part of this MLRA consists of bare lava flows and rock outcrops. The area extends from the lower slopes to the tops of Mauna Kea, Mauna Loa, Haleakala, Kilauea, and Hualalai volcanoes. The Hawaii Volcanoes National Park and the Haleakala National Park are in this area. Low-producing pas¬ tures and native forests are dominant in the medium rainfall belt. Some sites are cleared and used for macadamia and papaya orchards. Elevation and topography: Elevation ranges from sea level to more than 4,000 m on mountain summits. Slopes are undulating to very steep. Climate: Average annual precipitation —250 to 6,350 mm. Average annual temperature —9 to 24°C. Av¬ erage freeze-free period —365 days at lower eleva¬ tions. Frost occurs at higher elevations. Water: Water sources are rain catchments and storage tanks. No perennial streams or natural lakes are in this area. Soils: Nearly barren lava flows and rock outcrops occur in most of the area. Cinderland occurs near the mountain summits. Medium textured to coarse textured Vitrandepts (Apakuie, Huikau, and Kilohana series), which have an isomesic temperature regime, formed in deposits of volcanic ash and cinders at higher elevations. Potential natural vegetation: This area supports forest and shrub vegetation. Kiawe, klu bush, piligrass, and ilima grow on the drier sites. Ohia, lehua, 118 pukiawe, naio, mamani, Kentucky bluegrass, sweet vernalgrass, guava, and molassesgrass grow on the wetter sites. 162—Very Humid Areas on East and West Maui Mountains, Kohala Mountains, and Mount Waialeale 590 km 2 (230 mi 2 ) Land use: This MLRA consists of heavily vegetated native rain forests used mainly for watershed and wildlife. Most sites are not easily accessible. Elevation and topography: Elevation ranges from sea level to 1,800 m. The moderately sloping to steep landscape is dissected by many steep-sided gulches. Climate: Average annual precipitation —2,025 to 11,425 mm. Fog and cloud cover occur almost daily; there is no dry season. Average annual temperature —13 to 24°C. Average freeze-free period —365 days. Water: Water is supplied to other MLRA’s for irrigation and domestic uses. Many perennial streams are in this area. Soils: The dominant soils are Aquods, Saprists, Aquepts, and Andepts. They are shallow to deep and have a high content of organic matter. These soils have an isomesic temperature regime and an udic and aquic moisture regime. Somewhat poorly drained Tropaquods (Waialeale series) and very poorly drained Tropo- saprists (Alakai series) are near the mountain sum¬ mit of Kauai. Poorly drained and somewhat poorly drained Placaquepts (Amalu and Kahua series) and somewhat poorly drained Andaquepts (Kehena se¬ ries) are in the Hohala Mountains on the Island of Hawaii. Moderately well drained to well drained Hydrandepts and somewhat poorly drained Tropa¬ quods occur on Maui. Potential natural vegetation: This area supports rain forest vegetation. Kikuyugrass, hilograss, sedges, guava, ohia, lehua, pukiawe, ohelo, koa, treefern, false-staghorn, uki uki, pamakani, and ricegrass com¬ monly grow. 163—Alluvial Fans and Coastal Plains 320 km 2 (120 mi 2 ) Land use: About 70 percent of this MLRA is used for urban developments and military installations. A small acreage is used for truck crops and the remain¬ der for irrigated sugarcane. Elevation and topography: Elevation is from sea level to 100 m but ranges to 200 m. The area consists of nearly level to moderately sloping alluvial fans and coastal plains. Climate: Average annual precipitation —250 to 750 mm. Most of the precipitation falls from October to May. Average annual temperature —23 to 24°C. Average freeze-free period —365 days. Water: There are few perennial streams. In many places, wells provide suitable water for domestic use and for irrigation. Some wells provide brackish water suitable only for irrigation. Additional water is obtained from the abundant rainfall in the mountains. Soils: Most of the soils are Ustolls. They are deep, well drained, nonstony to stony, and fine textured to coarse textured. These soils have an isohyperthermic temperature regime and an ustic moisture regime. Haplustolls (Ewa, Kekaha, Mamala, Nohili series), which have kaolinitic, montmorillonitic, or mixed mineralogy, occur on alluvial fans and on coastal plains. Excessively drained Ustipsamments (Jaucas series) formed in coral sand along the coastal fringe. Chromusterts (Lualualei series) are on talus slopes and alluvial fans. Potential natural vegetation: This area supports grass and shrub vegetation. Bermudagrass, fingergrass, bristly foxtail, sandbur, lantana, kiawe, koa-haole, and klu bush are dominant. 164—Rough Mountainous Lands 1,100 km 2 (430 mi 2 ) Land use: Most of this MLRA consists of steep to precipitous mountain slopes and gulches. The upper elevations are heavily vegetated native rain forests. Watershed and wildlife habitat are the principal land uses. A small acreage of the low and intermediate slopes is used for pasture. Elevation and topography: Elevation ranges from sea level to 1,500 m. Topography is steep to precipi¬ tous; many steep-sided gulches dissect the area. Local relief ranges from about 100 m to more than 300 m. Climate: Average annual precipitation —Mostly 1,900 to 6,350 mm, but ranges from 750 to 11,425 mm. Average annual temperature —13 to 23°C. Average freeze-free period —365 days. Water: Much of the water for irrigation and for domes¬ tic use in the region is supplied from this MLRA. Many perennial and intermittent streams are in this area. Soils: Rough broken land, rough mountainous land, and rock outcrop are among the land types occurring in most of this area. Inextensive, poorly drained, gently sloping to hilly Placaquepts (Amalu and Olokui series) are in areas at higher elevations on Molokai. Potential natural vegetation: This area supports forest and shrub vegetation. Ohia, lehua, false- staghorn, koa, treefern, hilograss, lapalapa, Java- plum, and sedges grow on sites having abundant rainfall. Kiawe, koa-haole, and fingergrass grow on the drier sites. 165—Subhumid Intermediate Mountain Slopes 300 km 2 (110 mi 2 ) Land use: This MLRA is used mainly for pasture, woodland, and wildlife habitat. In recent years wood¬ land plantings of eucalyptus and pines have been 119 made on Kauai and on Molokai. Most of the area on Oahu is very steep and inaccessible. Elevation and topography: Elevation ranges from 200 to 1,300 m. Most of the area is steep to very steep and is broken by numerous drainageways. Locally, sites are gently sloping to moderately sloping. Climate: Average annual precipitation —750 to 1,900 mm. The rainy period generally is from October to May. Average annual temperature —13 to 22°C. Average freeze-free period —365 days. Water: There are no perennial streams. Water for livestock and other uses is supplied from other MLRA’s. Soils: This area consists of rough broken land and deep to moderately deep, well drained, medium tex¬ tured to fine textured Humults, Humox, and Andepts. They have an isothermic temperature regime. Tropo- humults (Kalae and Kokee series) formed in deposits of basic igneous rock and have oxidic mineralogy. Acrohumox (Kahanui and Mahana series) formed in deposits of basic igneous rock or volcanic ash and have ferritic or kaolinitic mineralogy. Dystrandepts (Oli series) formed in deposits of volcanic ash. Potential natural vegetation: This area supports forest vegetation. Lantana, Natal redtop, ber- mudagrass, fingergrass, kiawe, and koa-haole grow on the drier sites. Guava, mossassesgrass, aalii, joee, yellow foxtail, ohia, lehua, koa, silver oak, pukiawe, ricegrass, and Bostonfern grow on the wetter sites. 166—Very Stony Land and Rock Land 1,250 km 2 (480 mi 2 ) Land use: Most of this MLR A is used for pasture or for wildlife. The pastures have a low carrying capacity. Small acreages on the wet sites are in native or planted forest vegetation. Elevation and topography: Elevation generally ranges from sea level to 900 m, but it is as high as 2,400 m on Maui. The landscape is sloping to steep and is dis¬ sected by many drainageways. Some sites are precip¬ itous. Climate: Average annual precipitation —250 to 1,525 mm. Most of the precipitation falls from October to May. Average annual temperature —19 to 24°C. Average freeze-free period —365 days except at the highest elevations. Water: In this area, there are no perennial streams or natural storage. Soils: Most of the area is very shallow and stony or rocky. Very stony land, rock land, rough mountain¬ ous land, and rock outcrop are the dominant land types. Potential natural vegetation: Sites having a soil mantle support forest or grass-shrub vegetation. Buffelgrass, lantana, piligrass, klu bush, Natal red- top, and kiawe grow on the drier sites. Guava, aalii, ohia, lehua, and pukiawe grow on the wetter sites. 167—Humid Low and Intermediate Mountain Slopes 440 km 2 (170 mi 2 ) Land use: This MLRA is used for growing pineapple on Maui and sugarcane on Kauai. It is also used for pasture, woodland, and wildlife habitat. Elevation and topography: Elevation ranges from sea level to 500 m. The nearly level to very steep landscape is dissected by many steep-sided drain¬ ageways. Climate: Average annual precipitation —1,275 to 5,075 mm. Average annual temperature —21 to 24°C. Av¬ erage freeze-free period —365 days. Water: In this MLRA, there are a few perennial streams but no natural storage. Soils: Most of the soils are Humults and Orthox. They are deep, well drained, and fine textured. These soils have an isohyperthermic temperature regime and oxidic or ferritic mineralogy'. The gently sloping to moderately steep Tropohumults (Haiku and Pauwela series) occupy slopes on the windward side of east Maui. Gibbsiorthox (Kapaa and Pooku series) and Umbriorthox (Makapili series) are on the top of broad ridges on uplands of Kauai. Poorly drained Fluvaquents (Hanalei series) occur along drainageways. Potential natural vegetation: This area supports californiagrass, christmasberry, hilograss, ricegrass, Malabar melastome, rhodomyrtus, yellow foxtail, false- staghorn, pangolagrass, kikuyugrass, kaimi clover, sensitive plant, Java-plum, and joee. 120 W—SOUTHERN ALASKA REGION 321,090 km 2 (123,970 mi 2 ) This region consists of mountains, forests, a large intermontane lowland, and islands bordering the Pacific Ocean. The higher parts of the mountains have a permanent ice cover. The eastern and central parts of the region are forested at lower elevations. In the west, grassland and tundra are dominant. The average annual precipitation is 1,275 to 2,550 mm. It ranges from 375 to 625 mm in the Cook Inlet-Susitna Lowland to more than 5,075 mm in the southeastern part of the region. The average annual temperature is 0 to 7°C at lower elevations. Soils in inland basins are the only soils that freeze deeply. Stony Cryorthods are the dominant soils in the eastern and central parts of the region. Associated with them are Histosols on lower slopes, in depressions, and in areas above timberline. Cryaquents and Cryaquepts are on outwash plains and on flood plains. Cryofluvents occupy the higher parts of the flood plains. Cryandepts are dominant in the western part of the region, where most soils formed in deposits of volcanic ash. The highest mountains have no soil cover. Farmland is largely on level to sloping soils in the Cook Inlet-Susitna Lowland. Grasses, small grains, potatoes, and other vegetables are the principal crops. Timber production is important in the eastern and central parts of the region. Some natural grasslands on islands in the west are grazed by cattle and sheep. Hunting and other forms of recreation are important in most of the region. 168—Southeastern Alaska 86,490 km 2 (33,390 mi 2 ) Land use: Most of this MLRA is forested. Logging is an important industry. Land at elevations of 500 m or more, including the ice-covered Coast Mountains, is valuable mainly for recreation. There is virtually no farming. The population is almost entirely in small coastal cities and in villages, where commercial fish¬ ing is the important industry. Because of the general steepness of the terrain, landslides and gullying are severe hazards on soils that have been cleared and logged. Elevation and topography: Elevation ranges from sea level to more than 2,400 m in the Coast Moun¬ tains. On the islands, which make up most of the area, only a few peaks are higher than 1,500 m. Long narrow bays carved into the mountains by glaciers create extremely irregular coastlines on both the mainland and the islands. Most of the bays have narrow borders of hilly moraines, and at the head, short flat-bottomed valleys. Most slopes throughout the area are very steep. Climate: Average annual precipitation —1,275 to 2,550 mm. Precipitation is mostly snow at the higher elevations, with accumulations of 600 cm or more at elevations above 500 m. Average annual tempera¬ ture —4 to 8°C. Average freeze-free period —200 to 210 days, but the long seasons are offset by low temperatures in summer and persistent cloud cover. Water: The area has abundant precipitation and many small lakes and streams. Well drained soils generally are close to the saturation point, and many soils are always wet. Soils: The dominant soils are Orthods. They have a cryic temperature regime and an udic moisture re¬ gime. Cryorthods (Kupreanof and Tolstoi series), on steep slopes, generally are very stony or shallow over bedrock and are strongly thixotropic. Cryohumods (Sitka series) are in areas with thick deposits of volcanic ash. Fragiorthods (Karta series) and Fra- giaquods (Wadleigh series) formed over compact glacial till. Poorly drained Histosols, including Cryosaprists (Maybeso series), Cryohemists (Kina series), Cryofibrists (Staney series), and Sphag- nofibrists (Kogish series) are abundant on foot slopes and on higher slopes affected by seepage, in parts of valley bottoms, and in most areas immediately above tree line. Cryofolists (McGilvery series) occur over bedrock outcrop in association with Cryorthods. Sandy Cryaquents (Stave series) are common in glacial outwash plains, usually in association with Sphagno- fibrists, and in valley bottoms. Steep mountains having no soil cover make up more than 40 percent of the area. Potential natural vegetation: At elevations below 500 m, coniferous forest vegetation is dominant. Western hemlock, Sitka spruce, and (in the south¬ ernmost part of the area) Alaska-cedar are dominant species. Sedges, mosses, and other plants adapted to wet soil conditions cover most of the area immedi¬ ately above tree line and occupy many drainageways and slopes subject to seepage. 169—South-Central Alaska Mountains 98,080 km 2 (37,870 mi 2 ) Land use: Recreation is the most important land use in this MLRA. A few sites are used for commercial forest¬ ry. The area is sparsely inhabited except in several small coastal cities that serve as ports and as centers for commercial fishing, the principal industry. Farm¬ ing is of no commercial importance. 121 Elevation and topography: Elevation ranges from sea level to more than 4,900 m. Included in this area are the St. Elias, Chugach, and Kenai Mountains bordering the Gulf of Alaska and the Wrangell and Talkeetna Mountains further inland. Icefields and glaciers cover the higher parts of the mountains. Several large coastal lowlands, consisting of glacial outwash and tidal deposits, are between the coastal mountains and the sea. High dunes are common along the coast and in areas bordering large rivers. Climate: Average annual precipitation —2,025 to more than 4,325 mm along the coast, but on the north slopes of the Talkeetna and Wrangell Mountains it is as little as 325 mm. Annual snowfall at sea level ranges from 250 to 630 cm bordering Prince William Sound, 130 cm at low elevations inland, and much deeper in the coastal mountains. Average annual temperature —About -7 to -1°C in the mountains. Average freeze-free period —170 to 205 days along the coasts and about 100 days inland. Water: Small lakes and streams are abundant in this area. In general, ground water is at a shallow depth in the coastal areas but is less available inland. Much water exists in the form of glacial ice in the higher parts of the mountains. Soils: Icefields and bare rock or rubble make up about 70 percent of the area. The dominant soils are Umbrepts and Ochrepts. They have a pergelic temperature regime above the tree line and a cryic temperature regime below. Gravelly Cryumbrepts and Cryochrepts are associated with Cryaquepts in vegetated parts of the inland mountains. On vegetated uplands in coastal regions, under both forest and tundra vegetation, Cryorthods (Kupreanoff and Kniklik series) and Cryohemists (Kina and Unakwik series) are exten¬ sive. On the coastal lowland, Cryaquents and associated Histosols are dominant. Cryorthents and Cryopsam- ments are the principal soils of dunes. Potential natural vegetation: Forest vegetation dom¬ inated by western hemlock and Sitka spruce fringe most of the Gulf coast. Sedges, mosses, and other water-tolerant plants grow on most sites immedi¬ ately above tree line in the coastal mountains and on many sites with poor drainage in the forested zone. In places, especially in pails of the Kenai and Talkeetna Mountains bordering the Cook Inlet-Susitna Low¬ land, the vegetation in a zone immediately above tree line consists principally of grasses, forbs, and wil¬ lows. Low-growing alpine tundra vegetation grows in still higher areas. In mountains bordering the Copper River Plateau, forests of black spruce, dwarf birch, and willows grow at elevations ranging to about 900 m, where they give way to the low-growing alpine vegetation. The broad coastal lowlands in¬ cluded in the area are mostly marshy, but forests of hemlock and Sitka spruce are on terraces, stabilized dunes, and beach ridges. 170—Cook Inlet-Susitna Lowland 43,080 km 2 (16,630 mi 2 ) Land use: Included in this MLRA are more than two- thirds of the operating farms in Alaska and the largest urban complex in the state. More than 80 percent of the area, however, is still in forest or natural grassland used principally for recreation. Grasses, small grains, potatoes, and many vegetables are the principal crops. Logging is important locally. Rapid growth of the Anchorage urban area is imping¬ ing on nearby farmland. Elevation and topography: Elevation is mostly below 200 m, but it is 900 m in the south and in the foothills of surrounding mountains. The long, comparatively narrow basin is surrounded by mountains except at the mouth of Cook Inlet, which opens into the Gulf of Alaska. The land surface consists principally of gla¬ cial deposits: low moraines, interspersed with many lakes and bogs, and broad outwash plains and ter¬ races. The underlying sediments are at the surface only in parts of the south. Climate: Average annual precipitation —500 to 625 mm in the south, decreasing to 375 to 500 mm in the central part. Most precipitation falls late in summer and early in autumn. The average annual snowfall is 130 to 170 cm. Average annual temperature —0 to 3°C. Average freeze-free period —110 to 150 days. Water: Perennial streams and lakes provide abundant water in most of the area, but soils on drier sites, such as in the Matanuska Valley, are often deficient in moisture in midsummer. In some places, ground water is obtainable only at great depth. Soils: The principal upland soils are Orthods. They have a cryic temperature regime. Cryorthods (Rabideux and Naptowne series) formed in a shallow to moder¬ ately deep mantle of loess and volcanic ash over glacial deposits. Cryandepts (Kachemak and Island series) are in some of the southern parts of the area. Cryorthents (Bodenburg and Knik series) are on sites having recent deposits of loess. Borofibrists (Salamatof series) and Borohemists (Doroshin and Starichkof series) occupy many depressions. Cryoflu- vents (Susitna series) are on flood plains. Sandy Cryaquents are in large outwash plains and on flood plains immediately below mountain glaciers. Potential natural vegetation: This area supports forest vegetation. White spruce, paper birch, and, in some places, quaking aspen are dominant species. Balsam poplar is common on soils bordering the principal streams and Cook Inlet. Sitka spruce and hemlock are major species in the southernmost part of the lowland. Black spruce is the principal species on wetter soils and on some well drained sites that have been burned repeatedly. Most muskegs (bogs) are treeless or support stands of stunted black spruce. 122 171—Alaska Peninsula and Southwestern Islands 93,440 km 2 (36,080 mi 2 ) Land use: Most of this MLRA is largely undisturbed. A few small sites are mined, and some parts of the Kodiak Island group and the eastern Aleutian Islands are grazed by cattle and sheep. Commercial fishing is the principal industry in all towns and villages in this area. Many large military bases on Kodiak Island and the Aleutian Islands are abandoned. Elevation and topography: Elevation ranges from sea level to more than 3,400 m; the highest peaks are in the north. The area is mostly mountainous or hilly. Most of the mountains, except those in the Kodiak Island group, are of volcanic origin. Peaks higher than about 1,800 m have a perennial ice cover and glaciers commonly flow down their sides. Climate: Average annual precipitation —375 to 625 mm on western slopes of mountains in the north and more than 1,775 mm on the Aleutian Islands. The annual snowfall is 75 to 215 cm, but snow does not persist throughout the winter except in the north and on high mountains. Average annual temperature —0°C in the north to 4°C in the Aleutian Islands. Average freeze-free period —130 days in the north (at lower elevations) to 250 days in the Aleutian Islands. Water: Water is abundant throughout the year. Lakes and streams make up more than 3 percent of the area. They freeze in winter in the north but do not freeze in the south or in the west. Soils: About 30 percent of the area consists of high mountains with no soil cover. The dominant soils are Andepts. They have a cryic temperature regime. Cryandepts (Kodiak and Umnak series) are on the better drained sites. Cryofibrists (Saltery series) occupy depressions and some seep areas. Fresh cin¬ der flows are on slopes of r.ctive volcanoes. Potential natural vegetation: Forests of Sitka spruce occupy coastal areas in the northern part of the Kodiak Island group and in the northeastern part of the Alaska Peninsula. Foothills and moraines else¬ where in the Kodiak Island group and on the Pacific Ocean side of the Alaska Peninsula have a dense stand of grasses (dominantly bluejoint reedgrass), alder, and other forbs and shrubs. Low shrubby vegetation grows on the lowlands on the Alaska Peninsula bordering the Bering Sea, as well as on other lowlands and ridges exposed to strong winds. Grasses and forbs with no large shrubs grow on many of the low rolling hills on the Aleutian Islands. High mountains in the irea have only glaciers or bare rock and cinders. 123 X—INTERIOR ALASKA REGION 659,970 km 2 (254,820 mi 2 ) This subarctic region consists of mountains, hills, and lowlands. Although the highest mountains in North America are in this region, most of the land consists of maturely dissected hills and broad basins and valleys. Forests cover the area below an elevation of about 1,000 m, and alpine tundra mantles higher ridges. The average annual precipitation is 200 to 500 mm in most of the region, but it is much higher in the Alaska Range and in mountains north of Bristol Bay. The average annual temperature ranges from about -12°C in the north to about -10°C in the south, but it is generally higher than -7°C. The freeze-free period ranges from 75 to 110 days at elevations less than 500 m. The most extensive soils in this region are Cryaquepts, which are underlain by permafrost. They are in depressions, on most lower slopes, on north-facing slopes, and in most areas of high elevation. The well drained Cryochrepts are dominant on forested sites where annual precipitation is less than 375 mm. Cryorthods are dominant on forested sites where precipitation is more than 375 mm. Forested Cryofluvents are on flood plains. Shallow Cryumbrepts, Cryorthods, and Cryorthents commonly occur in the zone of alpine tundra. Subsistence hunting and fishing are the principal economic uses of the soils in this region. Farming is confined largely to the Tanana Valley, but several other parts of the region have good potential for agriculture. Grasses, small grains, potatoes, and other vegetables are the principal crops. Timber is harvested in the Tanana Valley and in a few other places for local use. 172—Copper River Plateau 37,910 km 2 (14,640 mi 2 ) Land use: This MLRA is used principally for recreation, including hunting. A few farms are along the Copper River. Grasses, small grains, and vegetables, includ¬ ing potatoes, are the principal crops. A few small acreages have been logged. The permanent popula¬ tion is small. Most income is derived from services associated with major highways that traverse the area. Elevation and topography: Elevation is mainly 500 to 900 m, but it is as much as 1,200 m in foothills of the surrounding mountains and as low as 300 m on flood plains of the Copper and Chitina Rivers. The area is a broad basin of rolling to hilly moraines, glacial lacustrine sediments, and alluvial plains. It is completely surrounded by mountains but is drained by the Yukon drainage system and by major rivers flowing to the Gulf of Alaska. Climate: Average annual precipitation —225 to 400 mm. Most of the precipitation falls in summer. Snow accumulation is 62 to 90 cm in winter. Average annual temperature —About -4 to 0°C. Water: The soils in this area except for those at lower elevations are underlain by permafrost. The soils above perennially frozen ground are wet or moist throughout the summer. Soils on cleared sites are commonly deficient in moisture. Many small lakes and ponds are in this area. Most of the usable ground water is deep and difficult to obtain. Soils: The dominant soils are Aquepts, which have a pergelic temperature regime and an aquic moisture regime. Cryaquepts (Klawasi and Deborah series), which are underlain by permafrost, are dominant at an elevation of about 600 m to the tree line at about 900 m. Gravelly and stony Cryochrepts (Cheshina and Gulkana series) commonly occur at lower eleva¬ tions. Thin Cryorthods and Cryumbrepts, over deep permafrost, and Cryaquepts, which are shallow to permafrost, are dominant above the tree line. Potential natural vegetation: Most of the area below an elevation of 900 m supports forest vegetation. Black spruce, willows, and dwarf birch are dominant species. Burned-over forests of white spruce, paper birch, and quaking aspen are at lower elevations along the Copper and Chitina Rivers and on a few steep south-facing slopes at higher elevations. Low- growing alpine shrubs, grasses, and sedges are dom¬ inant at elevations above 900 m. 173—Alaska Range 70,500 km 2 (27,220 mi 2 ) Land use: This MLRA is largely undisturbed. Two main roads and a railroad traverse low passes in the Alaska Range. These transportation lines and the tourist sections in Mt. McKinley National Park are the only parts of the area that are intensively used. There are also a few small mines and hunting lodges, and horses maintained by guides graze on some natural grassland. There is no farming or commercial forestry. Elevation and topography: Elevation is mainly 900 to 3,000 m. The area consists of rugged mountains with many peaks higher than 3,100 m and includes Mt. McKinley, the highest peak (6,200 m) in North America. Nearly all the area is above tree line; higher parts of the mountains are perennially ice covered. The transition from the rugged mountains to adjoining lowlands is generally sharp. Climate: Average annual precipitation —About 250 mm on northern and western slopes on the mountains and about 625 to 1,275 mm on the southern and 124 southeastern slopes. The average annual snowfall is less than 190 cm on the northern and western slopes and more than 250 cm on the southern and southeast¬ ern slopes. Average annual temperature —less than —7°C at high elevations and -6 to -2°C in low passes. Water: Many streams and rivers originate in the mountains, and many carry heavy loads of glacial silt. Soils: The dominant soils are Aquepts, Orthods, Umbrepts, and Ochrepts. These soils have a pergelic or cryic temperature regime. About two-thirds of the area has no soil. Cryaquepts, shallow to permafrost, and shallow stony Cryorthods, Cryumbrepts, and Cryochrepts, underlain by deeper permafrost, are on the lower slopes and in the passes. Potential natural vegetation: This area supports shrubby alpine vegetation on most lower slopes. Black spruce forests and natural grasslands also occur. Most of the high steep slopes have no vegeta¬ tion. 174—Interior Alaska Lowlands 161,490 km 2 (62,350 mi 2 ) Land use: Many towns and villages, including Fairbanks the commercial center of northern Alaska, are along major rivers. The remainder of the area is little used other than for subsistence hunting and fishing. Much of the potential farmland of the state is in this MLRA, but farming is largely confined to the Tanana Valley in the vicinity of Fairbanks and Delta Junction. Grasses, small grains, potatoes, and other vegetables are the principal crops. Some dairy and beef cattle and hogs are raised. Logging is important locally. Marshy lowlands in the area are important breeding grounds for waterfowl. Urban growth, particularly in the Fairbanks area, is taking place at the expense of agricultural land. Flooding is a severe hazard in most settlements. Elevation and topography: Elevation ranges from about 25 m along the lower Yukon River to about 600 m in the upper Tanana Valley. The broad valleys and basins are nearly level, but there are also some low rolling hills and piedmont slopes. Climate: Average annual precipitation —Generally 250 to 500 mm, but it is 150 to 250 mm in the Yukon Flats. Maximum precipitation is late in summer. The average annual snowfall is about 120 cm. Average annual temperature —About — 7°C in the north to -4°C in the south. Average freeze-free period —70 to 120 days. Water: Surface water in streams, lakes, and bogs is abundant in most of the area. In most years, howev¬ er, well drained soils are deficient in moisture in midsummer. Ground water under such soils is usually abundant but in some places may be difficult to obtain because of permafrost. All poorly drained soils are underlain by perennially frozen ground. Soils: The dominant soils are Aquepts, which have a pergelic temperature regime and an aquic moisture regime. Cryaquepts (Goldstream and Kuskokwim series), which are underlain by permafrost, are associated with less extensive Cryofibrists (Lemeta series). Cryofluvents (Salchaket and Takotna series) occur in well drained areas of broad flood plains. Well drained, silty Cryochrepts and Cryorthents are on terraces, mostly in the Yukon Flats. Potential natural vegetation: Mosses, sedges, shrubs, and stunted black spruce grow on soils having im¬ peded drainage. Forests of white spruce, paper birch, quaking aspen, and cottonwood (balsam poplar) grow on well drained soils. The higher parts of piedmont slopes adjacent to mountains support an alpine tun¬ dra vegetation. 175—Kuskokwim Highlands 175,510 km 2 (67,770 mi 2 ) Land use: The sparse population of this MLRA is con¬ centrated in small villages on the coast and along major rivers, where commercial fishing is the major indus¬ try. The remainder of the area is little used except for subsistence and sport hunting and fishing. Many towns in which mining was formerly a major industry are deserted or are occupied only during the summer. A few mines, however, are still active. Little use is made of the forests, and there is virtually no farming. Elevation and topography: Elevation ranges from 500 to 600 m on ridges in the north to 1,500 m in the south. The area includes hills and low mountains between the central Yukon River and Bristol Bay. Deep narrow valleys separate the ridges in the north. Rugged mountains, long narrow lakes, and rolling to steep hills are in the south. Much of the south exhibits glacial features, but in the north only the higher peaks were covered by glaciers. Climate: Average annual precipitation —300 mm in the north to 625 to 1,025 mm on the coast. Precipita¬ tion is heaviest late in summer. The average annual snowfall ranges from about 150 cm in the north to 200 cm in the south. Average annual temperature — About -7°C in the north to about — 1°C in the south. Average freeze-free period —90 to 110 days. Water: Water is adequate for vegetation in the central and southern parts. Soils in the north are often deficient in moisture in midsummer. Surface water is abundant in the south. The glacially carved Tikchik and Wood River Lakes are a conspicuous feature in the southern mountains. Permafrost exists in most low-lying soils and in high mountains, but it is generally absent in soils covered by forests or by grasses and alder. Soils: The dominant soils are Aquepts, which have a pergelic temperature regime and an aquic moisture regime. Cryaquepts (Kuskokwim and Kuslina series), which are underlain by permafrost, are on the most extensive black spruce sites. The dominant soils 125 under white spruce-paper birch forest and grass- alder vegetation are Cryohumods (Nondalton series) and Cryorthods (McGrath and Aleknagik series). Cryochrepts (Hughes and Koyukuk series) support forest vegetation in the north, and Cryandepts (Kvichak series) support shrubby vegetation in the south. Potential natural vegetation: Black spruce forest vegetation is dominant in this area. Many hills and ridges, however, support only tundra vegetation consisting of sedges and shrubs. Forests of white spruce and paper birch are on hills bordering the Yukon and Kuskokwim Rivers, other major rivers, and Bristol Bay. A dense stand of grasses and alder covers the hills bordering the Wood River-Tikchik Lakes and Togiak Bay. 176—Interior Alaska Highlands 214,560 km 2 (82,840 mi 2 ) Land use: Most of this MLRA is used only for subsis¬ tence and sport hunting and, to a limited extent, for other recreation. Farms were formerly in several places along the Yukon River, but farming is now largely confined to the area near Fairbanks. Grasses, small grains, potatoes, and other vegetables are principal crops. Mining was once a major industry, with placer claims on many streams, but relatively few active mines remain. Elevation and topography: Elevation is less than 330 to 1,800 m. The area consists mostly of low mountains and hills interrupted by many flat-bottomed valleys. Slopes are generally steep. Only the highest mountains were covered by glaciers. Climate: Average annual precipitation —250 to 375 mm. Maximum rainfall is late in summer. The aver¬ age annual snowfall ranges from 120 to 250 cm. Average annual temperature —About -12 to -9°C in the north and -7 to -4°C at lower elevations in the south. Water: Many streams traverse the area, and a few lakes are in the broader valleys, but many extensive hilly sections have little surface water. Well drained soils usually are deficient in moisture in midsummer. Most valley bottoms, north-facing slopes, and hills at an elevation above 800 m are underlain by perma¬ frost. Soils above the perennially frozen ground are usually wet or moist. Soils: The dominant soils are Ochrepts and Aquepts. These soils have a cryic or pergelic temperature regime. The principal soils under white spruce-birch- aspen forests on uplands are Cryochrepts (Fairbanks and Hughes series). Soils under black spruce forest and tundra vegetation characterized by sedges are Cryaquepts, underlain by shallow permafrost (Saulich and Kuskokwim series) or by deep or sporadic per¬ mafrost (Minto and Fairplay series). Shallow stony Cryochrepts, Cryumbrepts, Cryorthents, and Cryor¬ thods are in alpine areas with tundra vegetation characterized by sparse shrubby plants. Potential natural vegetation: The vegetation pattern in the area is complex. Forests of white spruce, paper birch, and quaking aspen cover most lower slopes in the south and south-facing slopes in the north. Black spruce forest vegetation grows at higher elevations, on all north-facing slopes in the south, on all but steep south-facing slopes in the north, and on lower slopes with impeded soil drainage throughout the area. Above the black spruce forests, the vegetation is alpine tundra characterized by sedges on poorly drained sites and by low-growing shrubs on drier sites. 126 Y—ARCTIC AND WESTERN ALASKA REGION 505,510 km 2 (195,180 mi 2 ) This region consists of mountains, foothills, and extensive coastal plains and deltas. Most of this region is covered by tundra vegetation, but there are a few forested areas, mostly at the southern and eastern margins. The average annual precipitation is 125 to 300 mm in the Arctic and 250 to 500 mm in the western part of the region. The average annual temperature ranges from - 12°C in the north to 0°C in the southwest. Cryaquepts, which are underlain by permafrost, are the dominant soils in this region. In places, Cryaquolls and Cryofibrists are associated with Cryaquepts. Cryumbrepts, Cryoborolls, and Cryorthents are on high ridges and on other sites where surface drainage is good. Cryopsamments occur on dunes in the Arctic and on the coasts. All have perennially frozen substrata. Permafrost is deep or absent in Cryofluvents on flood plains in western Alaska, Cryandepts in the extreme southwest, and Cryochrepts and Cryorthods of the forested inland margins. Most of the land in this region is used only for subsistence hunting and fishing. Commercial fishing is the principal industry in settlements along the coasts and the major rivers in western Alaska. Several reindeer herds graze on the tundra range in western Alaska. There is no commercial farming or forestry. 177—Norton Sound Highlands 114,960 km 2 (44,390 mi 2 ) Land use: Except in the vicinity of villages and small cities on the coasts and along the Yukon River, this MLRA is little used. Commercial fishing and subsis¬ tence hunting and fishing are the principal occupa¬ tions. Mining, formerly a major source of income, is now much less important. Several small reindeer herds graze the tundra vegetation that covers most of the area. Forests along the western boundary and bordering Norton Bay are not used commercially. There is no farming. Elevation and topography: Elevation generally ranges from sea level to 900 m, but a few peaks are at an elevation of 1,200 m. The area consists principally of steeply sloping hills and low mountains. Some moun¬ tainous locations on the Seward Peninsula were gla¬ ciated, but most of the area has never had a perma¬ nent ice cover. Several lava flows and low ancient volcanic cones are in this area. Climate: Average annual precipitation —Less than 250 mm to about 450 mm. The annual snowfall is 75 to 190 cm. Average annual temperature —About -7°C in the north and between -4 and -1°C in the south. Water: Streams are in nearly all the larger valleys. There are many inland lakes on the Seward Peninsula and many small lakes and ponds on included coastal plains, especially in the extreme northwest. Most of the area, except for forests bordering the Yukon River, is underlain by permafrost. Soils: The dominant soils are Aquepts, which have a pergelic temperature regime. Cryaquepts (Kuskokwim and Nome series), which are underlain by perma¬ frost, are on the extensive sites having impeded drainage. The principal soils on high ridges and in other areas where surface drainage is good are the gravelly or stony Cryumbrepts (Aniak series). Cryoborolls and Cryorthents also occupy these posi¬ tions. Silty Cryorthods (Whitsol series) and Cryochrepts (Koyukuk series) border the Yukon River. Potential natural vegetation: Most of this area supports tundra shrubs and sedges. Forests of white spruce and paper birch grow in a narrow strip on the eastern edge of the highlands, bordering the Yukon River. Black spruce forests cover the lower slopes of many inland valleys. Acreages of mixed forests are northeast of Norton Sound. High ridges are very sparsely vegetated. 178—Western Alaska Coastal Plains and Deltas 80,510 km 2 (31,080 mi 2 ) Land use: Parts of this MLRA provide important breed¬ ing ground for waterfowl. The remainder is little used. A few reindeer herds graze in the area, and there is much subsistence hunting. Commercial and subsistence fishing is the principal occupation in towns and villages along the major rivers. There is no commercial farming, and the few forests in the area are not used commercially. Elevation and topography: This is an area of low elevation, with very little relief. The ground surface, however, has an irregular microrelief, and many lakes and ponds are connected by a maze of water¬ ways. A few isolated rocky hills are in the area, and low sand dunes are common. Climate: Average annual precipitation —Less than 250 mm in the Selawik-Kobuk Delta to about 500 mm in the Bristol Bay coastal plain. The average annual snowfall is 120 to 190 cm throughout the area. Average annual temperature —About -7°C in the north to more than 0°C in the south. Water: Lakes and ponds make up 15 to 20 percent of the area. Permafrost underlies nearly all areas ex¬ cept the southern part of the Bristol Bay coastal plain. Soils underlain by permafrost are nearly al- 127 ways saturated in summer. In natural levees and in sand dunes, permafrost is deep or absent, and the soils are well drained. Spring flooding along rivers and tidal inundation along the coasts are common. Soils: The dominant soils are Aquepts, which have a pergelic temperature regime. Cryaquepts (Kuskokwim and Tupuknuk series), which are underlain by shal¬ low permafrost, occupy nearly all of the area. Cryofluvents (Takotna series) are on natural levees along major streams. Sandy Cryandepts (Pustoi se¬ ries) are on low dunes in the Bristol Bay coastal plain. Potential natural vegetation: This area supports tundra vegetation. Mosses, sedges, and low-growing shrubs cover most of the area. Alder and willows and, in a few places, stunted spruce and paper birch grow along the major streams. Grasses grow on dunes along the coasts. 179—Bering Sea Islands 12,350 km 2 (4,770 mi 2 ) Land use: Fishing and hunting of sea mammals are the major sources of income in this MLRA. On Nunivak Island, reindeer are harvested commercially and a herd of musk ox is maintained. The annual harvest of fur seals on the Pribilof Islands is the major industry. Reindeer live on most of the other islands, but most of them are wild. There are no forests on the islands, and there is no farming. Elevation and topography: Elevation ranges from sea level to 600 m. The islands, except for parts of St. Lawrence and Nelson Islands, consist mostly of volcanic rock. Relief ranges from nearly level to hilly. Many dormant volcanic cones exist, but only the one on St. Lawrence Island attains an elevation greater than 600 m. Climate: Average annual precipitation —Less than 250 mm to more than 750 mm. Precipitation is greater on the windward sides of hills. The annual snowfall ranges from 120 to 200 cm. Average annual temperature —About -4°C on St. Lawrence Island to 2°C on the Pribilof Islands. All but the Pribilof Islands are icebound in winter. Water: Streams and ponds are abundant on the islands. Most soils, except for those shallow to bedrock, are underlain by permafrost and are wet throughout the summer. There is no permafrost, however, on the Pribilof Islands. Soils: The dominant soils are Aquepts and Aquolls, which have a pergelic temperature regime. Shallow, gravelly Cryaquepts and Cryaquolls, which are un¬ derlain by permafrost, occupy extensive areas where drainage is restricted. Cryofibrists (Inmachuk series) are in depressions. Gravelly Cryumbrepts and Cryoborolls are dominant on ridges and on other sites where surface drainage is good. Cryandepts are on better drained sites on the Pribilof Islands. Potential natural vegetation: Tundra vegetation, consisting principally of mosses, sedges, and low- growing shrubs, covers the entire area. 180—Brooks Range 107,470 km 2 (41,490 mi 2 ) Land use: This MLRA is largely undisturbed except for a few placer and hard rock mines in the south. There are very few settlements. In Anaktuvuk Pass, the largest settlement, subsistence hunting is the princi¬ pal occupation. Elevation and topography: Elevation ranges from 1,800 to 2,400 m in the west to 2,600 m on peaks in the east. The topography is rugged, and several peaks have a permanent ice cover. Climate: Average annual precipitation —250 to 375 mm. The number of days on which some precipitation falls is high. The total annual snowfall is 120 to 200 cm on southern slopes and 60 to 120 cm at the crest and on northern slopes. Average annual temperature — About -13 to -9°C. Freezing temperatures may occur in any month. Water: Several glacially carved lakes are at the north and south boundaries of the Brooks Range. All soils in the area, except a few on steep, forested south¬ facing slopes, are underlain by permafrost. Soils: The dominant soils are Orthents and Borolls that have a pergelic temperature regime. Soils are extremely thin or absent in more than 70 percent of the area. Thin Cryorthents and Cryoborolls are on the lower parts of steep slopes. Cryaquepts and Cryaquolls with shallow permafrost occupy most valley bottoms. Potential natural vegetation: Most of this area is barren. Forests of white spruce, paper birch, and quaking aspen or of black spruce cover some south¬ ern slopes and interior valleys. Alpine tundra covers intermediate slopes. 181—Arctic Foothills 127,310 km 2 (49,160 mi 2 ) Land use: This MLRA is used primarily for subsistence hunting and fishing. A few reindeer herds are in the southwest. Tundra vegetation covers the entire area except for a relatively small forested site along the lower Noatak River in the southwest. No commercial use is made of the forest, and there is no farming. Some sites in the central part of the area have been explored for oil and gas. Elevation and topography: Elevation is mainly less than 600 m, but on some hills bordering the Brooks Range it is 1,100 m. The area consists of maturely dissected low hills and ridges. Glaciers have never covered the area. Climate: Average annual precipitation —Generally 125 to 200 mm but 200 to 300 mm in the southwest. The total annual snowfall is generally 60 to 120 cm, but it is about 100 to 200 cm in the southwest. Average 128 annual temperature —About -12°C but about -9 to -7°C in the extreme west. Frosts may occur in any month. Water: Many streams and rivers are in swales and valleys between the hills, but there are only a few lakes. The entire area, except possibly parts of the lower Noatak River flood plain, is underlain by permafrost. Soils underlain by permafrost are usu¬ ally wet. Soils: The dominant soils are Aquepts, which have a pergelic temperature regime. Silty Cryaquepts (Umiat series) underlain by shallow permafrost cover most of the area. Gravelly Cryaquepts with deeper permafrost occupy parts of the flood plains. Cryaquolls under¬ lain by permafrost are common in hills bordering the Brooks Range. Gravelly Cryoborolls and Cryumbrepts are on high ridges and in other areas where surface drainage is good. Gravelly Cryorthents are common on terraces bordering the flood plains of major streams. Potential natural vegetation: Tundra vegetation, consisting principally of sedges, mosses, and low- growing shrubs, covers most of the area. Forests of white spruce, black spruce, and paper birch are in the lower parts of the Noatak Valley. 182—Arctic Coastal Plain (62,910 km 2 (24,290 mi 2 ) Land use: Most of this MLRA is used only for subsistence hunting and fishing. The sparse popula¬ tion is concentrated on the Arctic coast. The area is an important breeding ground for migratory birds. In¬ dustrial developments associated with oil production are important near the mouth of the Sagavanirktok River, and such developments probably will take place in other parts of the coastal plain. Elevation and topography: Elevation is less than 200 m. The area is a gently rolling to level treeless plain with many lakes and rivers. Climate: Average annual precipitation —125 to 200 mm. The total annual snowfall is 50 to 122 cm. Average annual temperature —About -12°C. Frosts may occur in any month. Water: Lakes, ponds, and streams make up more than 20 percent of the area. All soils are underlain by permafrost. Most soils usually are saturated above the permafrost table throughout the summer. Soils: The dominant soils are Aquepts that have a pergelic temperature regime. Loamy Cryaquepts are dominant, but sandy Cryaquepts are associated with Cryopsamments on dunes south of Barrow, and grav¬ elly Cryaquepts occur in broad flood plains and deltas. Loamy Cryaquolls are extensive in the east. Gravelly Cryochrepts, Cryumbrepts, and Cryoborolls are on sites having exceptionally good surface drain¬ age, but they make up only a very small proportion of the area. Potential natural vegetation: Tundra vegetation, consisting principally of sedges, mosses, and low- growing shrubs, covers the entire area. 129 REFERENCES Baldwin, M., Charles E. Kellogg, and J. Thorp. 1938. Soil classification. In Soils and men, p. 979-1001. U.S. Dep. Agric. Yearb. U.S. Gov. Print. Off., Wash., D.C. Cline, M. G., et al. 1955. Soil survey of the Territory of Hawaii. Soil Conserv. Serv., U.S. Dep. Agric. 644 p. Fenneman, Nevin M. 1931. Physiography of Western United States. McGraw-Hill, New York and London. 534 p. - 1938. Physiography of Eastern United States. McGraw-Hill, New York and London. 714 p. Hint, Richard F., et al. 1945. Glacial map of North America. Spec. Pap. 60. Part 1, Glacial map (in color); Part 2, bibliog. and explana. notes. Geol. Soc. Amer. 37 p. Harper, W. G. 1957. Morphology and genesis of Calcisols. Soil Sci. Soc. Amer. Proc. 21:420-424. Kellogg, Charles E. 1941. Climate and soil. In Climate and men, p. 276-277. U.S. Dep. Agric. Yearb. U.S. Gov. Print. Off., Wash., D.C. - 1950. Tropical soils. 4th Int. Congr. Soil Sci. Trans. (Amsterdam) 1:266-276. _, and I. J. Nygard. 1951. The principal soil groups of Alaska. Agric. Monogr. No. 7, U.S. Dep. Agric. 138p. Kiichler, A. W. 1964. Potential natural vegetation of the conterminous United States (map and manual). Amer. Geog. Soc. Spec. Pub. 36. 116 p. McClelland, J. E., C. A. Mogen, W. M. Johnson, et al. 1959. Chernozems and associated soils of eastern North Dakota, some properties and topographic rela¬ tionships. Soil Sci. Soc. Amer. Proc. 23:51-56. Marbut, C. F. 1935. Soils of the United States. Part III. In Atlas of American agriculture, p. 1-98. U.S. Dep. Agric. Marschner, F. J. 1959. Land use and its patterns in the United States. U.S. Dep. Agric. Handb. 153. 277 p. Meinzer, Oscar E. 1948. Ground water in the United States, a summary. U.S. Geol. Surv. Water-Supply Pap. 836-D. 232 p. National Weather Service, U.S. Dep. Commer. 1959. Climates of the states (climatography of the United States). No. 60-1 through No. 60-51. Oakes, H., and J. Thorp. 1951. Dark clay soils of warm regions variously called Redzina, black cotton soils, regur, and tirs. Soil Sci. Soc. Amer. Proc. 15:347-354. Simonson, Roy W., F. F. Riecken, and Guy D. Smith. 1952. Great soil groups in Iowa. In Understanding Iowa soils, p. 23-25. Wm. C. Brown Co., Dubuque, Iowa. Soil Conservation Service, U.S. Dep. Agric. 1968. Published soil surveys. In National atlas of the United States of America. Geol. Surv., U.S. Dep. Inter., Wash., D.C. - 1975. Soil taxonomy: a basic system of soil classification for making and interpreting soil sur¬ veys. U.S. Dep. Agric. Handb. 436, 754 p. Stose, George W., and O. A. Ljungstedt. 1932. Geo¬ logic map of the United States, 1:2,500,000. U.S. Geol. Surv. Tavernier, R., and Guy D. Smith. 1957. The concept of Braunerde (Brown Forest soils) in Europe and the United States. Advan. Agron. 9:217-289. Thorp, James, and Guy D. Smith. 1949. Higher catego¬ ries of soil classification. Soil Sci. 67:117-126. U.S. Department of Agriculture. 1957. Soil. U.S. Dep. Agric. Yearb. U.S. Gov. Print. Off., Wash., D.C. 784 P- 130 APPENDIX I. AREA OF LRR’S AND MLRA’S Table 1 summarizes the approximate area and proportionate extent of the revised land resource regions and major land resource areas in the United States. Major land resource areas 38, 45, 50, 68, 89, and 132, which were discussed in Handbook 296 issued in 1965, are not listed separately because they have been incorporated in other areas. Table 1—Approximate area and proportionate extent of land resource regions and major land resource areas in the United States Extent in— Land resource region and major land resource area A—Northwestern Forest, Forage, and Specialty Crop Region . . 1. Northern Pacific Coast Range, Foothills, and Valleys 2. Willamette and Puget Sound Valleys. 3. Olympic and Cascade Mountains . 4. California Coastal Redwood Belt . 5. Siskiyou-Trinity Area . B—Northwestern Wheat and Range Region . 6. Cascade Mountains, Eastern Slope. 7. Columbia Basin . 8. Columbia Plateau . 9. Palouse and Nez Perce Prairies. 10. Upper Snake River Lava Plains and Hills . 11. Snake River Plains . 12. Lost River Valleys and Mountains. 13. Eastern Idaho Plateaus. C—California Subtropical Fruit, Truck, and Specialty Crop Region 14. Central California Coastal Valleys. 15. Central California Coast Range . 16. California Delta. 17. Sacramento and San Joaquin Valleys . 18. Sierra Nevada Foothills. 19. Southern California Coastal Plain . 20. Southern California Mountains. D—Western Range and Irrigated Region. 21. Klamath and Shasta Valleys and Basins. 22. Sierra Nevada Range. 23. Malheur High Plateau. 24. Humboldt Area. 25. Owyhee High Plateau. 26. Carson Basin and Mountains . 27. Fallon-Lovelock Area . 28A. Great Salt Lake Area . 28B. Central Nevada Basin and Range. 29. Southern Nevada Basin and Range . 30. Sonoran Basin and Range. 31. Imperial Valley. 32. Northern Intermountain Desertic Basins . 33. Semiarid Rocky Mountains. 34. Central Desertic Basins, Mountains, and Plateaus . . 35. Colorado and Green River Plateaus . 36. New Mexico and Arizona Plateaus and Mesas .... 37. San Juan River Valley Mesas and Plateaus. 39. Arizona and New Mexico Mountains . 40. Central Arizona Basin and Range. 41. Southeastern Arizona Basin and Range . 42. Southern Desertic Basins, Plains, and Mountains . . 48A. Southern Rocky Mountains. United Area Region States CNJ E mi 2 pet pet 204,080 78,790 — 2.18 41,020 15,840 20.1 .44 48,160 18,590 23.6 .52 65,310 25,210 32.0 .70 13,880 5,360 6.8 .15 35,710 13,790 17.5 .37 239,650 92,530 — 2.56 37,750 14,570 15.8 .40 18,520 7,150 7.7 .19 42,730 16,500 17.8 .46 23,140 8,940 9.7 .25 44,870 17,330 18.7 .49 35,250 13,610 14.7 .38 16,380 6,320 6.8 .17 21,010 8,110 8.8 .22 167,570 64,700 — 1.79 10,380 4,000 6.2 .11 21,900 8,460 13.1 .24 2,310 890 1.3 .02 49,580 19,140 29.6 .53 7,300 2,820 4.4 .08 51,500 19,890 30.7 .55 24,600 9,500 14.7 .26 1,461,300 564,210 — 15.61 35,350 13,650 2.4 .38 65,190 25,170 4.5 .70 73,050 28,210 5.0 .78 37,310 14,400 2.6 .40 73,050 28,210 5.0 .78 23,960 9,250 1.6 .26 32,990 12,740 2.3 .35 94,260 36,390 6.5 1.00 78,150 30,170 5.3 .83 66,380 25,630 4.6 .71 194,030 74,910 13.3 2.07 9,420 3,640 .6 .10 21,210 8,190 1.5 .23 11,000 4,250 .8 .12 120,190 46,400 8.2 1.28 123,350 47,630 8.4 1.32 69,130 26,690 4.7 .74 13,350 5,160 .9 .14 111,140 42,910 7.6 1.19 47,130 18,200 3.2 .50 45,560 17,590 3.1 .49 115,470 44,580 7.9 1.23 630 240 — .01 131 Table 1—Approximate area and proportionate extent of land resource regions and major land resource areas in the United States—Continued Land resource region and major land resource area E—Rocky Mountain Range and Forest Region . 34. Central Desertic Basins, Mountains, and Plateaus . 43. Northern Rocky Mountains. 44. Northern Rocky Mountain Valleys. 46. Northern Rocky Mountain Foothills . 47. Wasatch and Uinta Mountains. 48A. Southern Rocky Mountains. 48B. Southern Rocky Mountain Parks . 49. Southern Rocky Mountain Foothills. 51. High Intermountain Valleys. F—Northern Great Plains Spring Wheat Region. 52. Brown Glaciated Plain . 53A. Northern Dark Brown Glaciated Plains. 53B. Central Dark Brown Glaciated Plains. 53C. Southern Dark Brown Glaciated Plains. 54. Rolling Soft Shale Plain. 55A. Northern Black Glaciated Plains. 55B. Central Black Glaciated Plains. 55C. Southern Black Glaciated Plains . 56. Red River Valley of the North . 58A. Northern Rolling High Plains, Northern Part. G—Western Great Plains Range and Irrigated Region.. 58A. Northern Rolling High Plains, Northern Part. 58B. Northern Rolling High Plains, Southern Part. 58C. Northern Rolling High Plains, Northeastern Part . . . 58D. Northern Rolling High Plains, Eastern Part . 60A. Pierre Shale Plains and Badlands. 60B. Pierre Shale Plains, Northern Part . 61. Black Hills Foot Slopes . . . . 62. Black Hills .. ' ’ [ 63A. Northern Rolling Pierre Shale Plains . 63B. Southern Rolling Pierre Shale Plains. 64. Mixed Sandy and Silty Tableland . 65. Nebraska Sand Hills . 66. Dakota-Nebraska Eroded Tableland . 67. Central High Plains . 69. Upper Arkansas Valley Rolling Plains . 70. Pecos-Canadian Plains and Valleys . H—Central Great Plains Winter Wheat and Range Region . . . 71. Central Nebraska Loess Hills . 72. Central High Tableland . 73. Rolling Plains and Breaks . 74. Central Kansas Sandstone Hills. 75. Central Loess Plains . 76. Bluestem Hills . 77. Southern High Plains . 78. Central Rolling Red Plains . 79. Great Bend Sand Plains . 80A. Central Rolling Red Prairies . 80B Texas North-Central Prairies. 81. Edwards Plateau. 84A. Cross Timbers . Extent in— Area Region United States km 2 mi 2 pet pet 597,250 230,600 — 6.38 2,160 830 .3 .02 282,650 109,130 47.3 3.02 32,320 12,480 5.4 .35 52,070 20,110 8.7 .56 53,150 20,520 8.9 .57 112,050 43,260 18.8 1.20 20,110 7,770 3.4 .21 32,680 12,620 5.5 .35 10,060 3,880 1.7 .10 351,990 135,900 _ 3.76 52,110 20,120 14.8 .56 30,740 11,870 8.7 .53 44,980 17,370 12.8 .48 13,870 5,350 3.9 .15 58,100 22,430 16.5 .62 32,240 12,450 9.2 .34 52,480 20,260 14.9 .56 20,240 7,810 5.8 .22 41,230 15,920 11.7 .44 6,000 2,320 1.7 .06 564,490 217,950 — 6.03 99,620 38,460 17.7 1.06 50,810 19,620 9.0 .54 8,400 3,240 1.5 .09 10,000 3,860 1.8 .11 23,600 9,110 4.2 .25 5,600 2,160 1.0 .06 8,400 3,240 1.5 .09 9,200 3,550 1.6 .10 29,610 11,430 5.2 .32 28,400 10,970 5.0 .30 28,400 10,970 5.0 .30 56,810 21,930 10.1 .61 12,400 4,800 2.2 .13 74,410 28,730 13.2 .80 34,000 13,130 6.0 .36 84,830 32,750 15.0 .91 575,720 222,280 _ 6.15 26,220 10,120 4.6 .28 77,220 29,810 13.4 .83 59,260 22,880 10.3 .63 12,210 4,710 2.1 .13 34,840 13,450 6.1 .37 19,400 7,490 3.3 .21 126,780 48,950 22.0 1.36 130,370 50,340 22.7 1.39 10,770 4,160 1.9 .12 48,840 18,860 8.5 .52 25,500 9,850 4.5 .27 720 280 — — 3,590 1,380 .6 .04 132 Table 1.—Approximate area and proportionate extent of land resource regions and major land resource areas in the United States—Continued Extent in— Land resource region and major land resource area I—Southwest Plateaus and Plains Range and Cotton Region . . . . 81. Edwards Plateau. 82. Texas Central Basin. 83A. Northern Rio Grande Plain. 83B. Western Rio Grande Plain . 83C. Central Rio Grande Plain. 83D. Lower Rio Grande Valley. J—Southwestern Prairies Cotton and Forage Region. 80A. Central Rolling Red Prairies . 84A. Cross Timbers . 84B. West Cross Timbers . 84C. East Cross Timbers. 85. Grand Prairie. 86. Texas Blackland Prairie. 87. Texas Claypan Area . K—Northern Lake States Forest and Forage Region. 57. Northern Minnesota Gray Drift. 88. Northern Minnesota Glacial Lake Basins. 90. Central Wisconsin and Minnesota Thin Loess and Till . 91. Wisconsin and Minnesota Sandy Outwash . 92. Superior Lake Plain . 93. Superior Stony and Rocky Loamy Plains and Hills . . . 94A. Northern Michigan and Wisconsin Sandy Drift . 94B. Michigan Eastern Upper Peninsula Sandy Drift. L—Lake States Fruit, Truck, and Dairy Region . 95A. Northeastern Wisconsin Drift Plain . 95B. Southern Wisconsin and Northern Illinois Drift Plain . . 96. Western Michigan and Northeastern Wisconsin Fruit Belt 97. Southwestern Michigan Fruit and Truck Belt . 98. Southern Michigan and Northern Indiana Drift Plain . . 99. Erie-Huron Lake Plain. 100. Erie Fruit and Truck Area. 101. Ontario Plain and Finger Lakes Region . M—Central Feed Grains and Livestock Region . 102A. Rolling Till Prairie . 102B. Loess Uplands and Till Plains . 103. Central Iowa and Minnesota Till Prairies. 104. Eastern Iowa and Minnesota Till Prairies . 105. Northern Mississippi Valley Loess Hills. 106. Nebraska and Kansas Loess-Drift Hills. 107. Iowa and Missouri Deep Loess Hills . 108. Illinois and Iowa Deep Loess and Drift. 109. Iowa and Missouri Heavy Till Plain . 110. Northern Illinois and Indiana Heavy Till Plain . 111. Indiana and Ohio Till Plain . 112. Cherokee Prairies . 113. Central Claypan Areas . 114. Southern Illinois and Indiana Thin Loess and Till Plain 115. Central Mississippi Valley Wooded Slopes. United Area Region States km 2 mi 2 pet pet 175,990 67,950 — 1.88 96,050 37,090 54.6 1.03 5,500 2,120 3.1 .06 20,900 8,070 11.9 .22 23,470 9,060 13.3 .25 23,470 9,060 13.3 .25 6,600 2,550 3.8 .07 145,120 56,030 — 1.55 3,860 1,490 2.7 .04 27,400 10,580 18.9 .29 15,050 5,810 10.4 .16 5,790 2,240 3.8 .06 31,650 12,220 21.9 .34 47,860 18,480 33.0 .51 13,510 5,210 9.3 .15 277,100 106,990 — 2.96 21,440 8,280 7.7 .23 31,010 11,970 11.2 .33 55,750 21,530 20.1 .60 52,780 20,380 19.1 .56 4,950 1,910 1.8 .05 56,080 21,650 20.2 .60 39,920 15,410 14.4 .43 15,170 5,860 5.5 .16 193,780 74,820 — 2.07 15,760 6,090 8.1 .17 28,530 11,020 14.7 .31 10,650 4,110 5.5 .11 5,960 2,300 3.1 .06 60,050 23,190 31.0 .64 35,780 13,810 18.5 .38 4,260 1,640 2.2 .05 32,790 12,660 16.9 .35 725,500 280,110 — 7.75 38,600 14,900 5.3 .41 43,790 16,910 6.0 .48 71,990 27,800 9.9 .77 22,640 8,740 3.1 .24 57,520 22,210 8.0 .61 27,090 10,460 3.7 .29 53,810 20,770 7.4 .57 79,790 30,800 11.0 .85 37,110 14,330 5.1 .40 26,350 10,170 3.6 .28 84,980 32,810 11.7 .91 57,520 22,210 8.0 .61 28,570 11,030 4.0 .31 34,880 13,470 4.8 .37 60,860 23,500 8.4 .65 133 Table 1—Approximate area and proportionate extent of land resource regions and major land resource areas in the United States—Continued Land resource region and major land resource area N—East and Central Farming and Forest Region. 116A. Ozark Highland . 116B. Ozark Border. 117. Boston Mountains . 118. Arkansas Valley and Ridges. 119. Ouachita Mountains. 120. Kentucky and Indiana Sandstone and Shale Hills and Valleys . . 121. Kentucky Bluegrass. 122. Highland Rim and Pennyroyal. 123. Nashville Basin. 124. Western Allegheny Plateau . 125. Cumberland Plateau and Mountains . 126. Central Allegheny Plateau . 127. Eastern Allegheny Plateau and Mountains. 128. Southern Appalachian Ridges and Valleys. 129. Sand Mountain. 130. Blue Ridge . 0—Mississippi Delta Cotton and Feed Grains Region . 131. Southern Mississippi Valley Alluvium . 134. Southern Mississippi Valley Silty Uplands . P—South Atlantic and Gulf Slope Cash Crops, Forest, and Livestock Region 112. Cherokee Prairies . 133A. Southern Coastal Plain . 133B. Western Coastal Plain . 134. Southern Mississippi Valley Silty Uplands . 135. Alabama, Mississippi, and Arkansas Blackland Prairie. 136. Southern Piedmont . 137. Carolina and Georgia Sand Hills . 138. North-Central Florida Ridge . R—Northeastern Forage and Forest Region. 139. Eastern Ohio Till Plain . 140. Glaciated Allegheny Plateau and Catskill Mountains. 141. Tughill Plateau. 142. St. Lawrence-Champlain Plain. 143. Northeastern Mountains . 144A. New England and Eastern New York Upland, Southern Part 144B New England and Eastern New York Upland, Northern Part 145. Connecticut Valley. 146. Aroostook Area . S—Northern Atlantic Slope Diversified Farming Region . 147. Northern Appalachian Ridges and Valleys. 148. Northern Piedmont . 149A. Northern Coastal Plain . 149B. Long Island-Cape Cod Coastal Lowland. T—Atlantic and Gulf Coast Lowland Forest and Crop Region 150A. Gulf Coast Prairies . 150B. Gulf Coast Saline Prairies . 151. Gulf Coast Marsh . 152A. Eastern Gulf Coast Flatwoods. 152B. Western Gulf Coast Flatwoods . 153A. Atlantic Coast Flatwoods. 153B. Tidewater Area. 153C. Mid-Atlantic Coastal Plain . Extent in— Area Region United States km 2 mi 2 pet pet 612,230 236,380 — 6.54 69,810 26,950 11.4 .75 35,470 13,690 5.8 .38 14,930 5,770 2.4 .16 27,250 10,520 4.5 .29 24,640 9,510 4.0 .26 30,990 11,970 5.1 .33 29,490 11,390 4.8 .32 52,640 20,320 8.6 .56 15,680 6,060 2.6 .17 19,040 7,350 3.1 .20 63,840 24,640 10.4 .68 50,770 19,600 8.3 .54 43,680 16,870 7.1 .47 69,430 26,810 11.3 .74 17,540 6,770 2.9 .19 47,030 18,160 7.7 .50 116,080 44,820 _ 1.24 93,600 36,140 80.6 1.00 22,480 8,680 19.4 .24 688,050 265,660 _ 7.35 1,890 730 .3 .02 285,050 110,060 41.4 3.05 140,640 54,300 20.4 1.50 51,410 19,850 7.5 .55 21,550 8,320 3.1 .23 161,430 62,330 23.5 1.72 22,680 8,760 3.3 .24 3,400 1,310 .5 .04 314,540 121,440 _ 3.36 15,030 5,800 4.8 .16 70,540 27,240 22.4 .75 3,080 1,190 1.0 .03 14,260 5,510 4.5 .15 101,760 39,290 32.4 1.09 52,040 20,090 16.5 .56 48,570 18,750 15.4 .52 6,560 2.530 2.1 .07 2,700 1,040 .9 .03 105,780 40,840 _ 1.13 48,210 18,610 45.6 .52 29,870 11,530 28.2 .32 20,870 8,060 19.7 .22 6,830 2,640 6.5 .07 247,140 95,420 _ 2.64 41,710 16,100 16.9 .45 13,100 5,060 5.3 .14 21,030 8,120 8.5 .22 34,120 13,170 13.8 .36 16,890 6,520 6.8 .18 73,760 28.480 29.9 .79 31,020 11,980 12.6 .33 15,510 5,990 6.2 .17 134 Table 1.—Approximate area and proportionate extent of land resource regions and major land resource areas in the United States—Continued Land resource region and major land resource area U—Florida Subtropical Fruit, Truck Crop, and Range Region. 154. South-Central Florida Ridge . 155. Southern Florida Flatwoods . 156A. Florida Everglades and Associated Areas . 156B. Southern Florida Lowlands. V—Hawaii Region . 157. Arid and Semiarid Low Mountain Slopes. 158. Semiarid and Subhumid Low Mountain Slopes . 159. Humid and Very Humid Low and Intermediate Mountain Slopes 160. Subhumid and Humid Intermediate and High Mountain Slopes 161. Lava Flows and Rock Outcrops. 162. Very Humid Areas on East and West Maui Mountains, Kohala Mountains, and Mount Waialeale . 163. Alluvial Fans and Coastal Plains . 164. Rough Mountainous Lands. 165. Subhumid Intermediate Mountain Slopes . 166. Very Stony Land and Rock Land . 167. Humid Low and Intermediate Mountain Slopes . W—Southern Alaska Region . 168. Southeastern Alaska . 169. South-Central Alaska Mountains . 170. Cook Inlet-Susitna Lowland . 171. Alaska Peninsula and Southwestern Islands . X—Interior Alaska Region. 172. Cooper River Plateau. 173. Alaska Range . 174. Interior Alaska Lowlands . 175. Kuskokwim Highlands. 176. Interior Alaska Highlands. Y—Arctic and Western Alaska Region . 177. Norton Sound Highlands . 178. Western Alaska Coastal Plains and Deltas . 179. Boring Sea Islands . 180. Brooks Range . 181. Arctic Foothills . 182. Arctic Coastal Plain . Total . Extent in— United Area Region States km 2 mi 2 pet pet 94,550 36,510 — 1.01 24,290 9,380 25.6 .26 54,570 21,070 57.8 .58 11,210 4,330 11.9 .12 4,480 1,730 4.7 .05 16,850 6,510 — .18 1,290 500 7.7 .01 1,270 490 7.5 .01 2,320 900 13.7 .02 910 350 5.4 .01 7,060 2,730 41.9 .08 590 230 3.5 .01 320 120 1.9 — 1,100 430 6.6 .01 300 110 1.8 — 1,250 480 7.4 .01 440 170 2.6 — 321,090 123,970 — 3.43 86,490 33,390 26.9 .93 98,080 37,870 30.6 1.05 43,080 16,630 13.4 .46 93,440 36,080 29.1 .99 659,970 254,820 — 7.05 37,910 14,640 5.7 .41 70,500 27,220 10.7 .75 161,490 62,350 24.5 1.73 175,510 67,770 26.6 1.87 214,560 82,840 32.5 2.29 505,510 195,180 — 5.40 114,960 44,390 22.8 1.23 80,510 31,080 15.9 .86 12,350 4,770 2.4 .13 107,470 41,490 21.3 1.15 127,310 49,160 25.2 1.36 62,910 24,290 12.4 .67 9,361,330 3,614,410 135 APPENDIX II. SOIL CLASSIFICATION Appendix II provides abridged definitions and brief general descriptions of the orders, suborders, and great groups in the system of soil classification used in the National Cooperative Soil Survey. Information is included for 10 orders, 47 suborders, and 230 great groups. The orders, the suborders within each order, and the great groups within each suborder are arranged alphabetically. Table 2 presents the great soil groups according to the 1938 classification, as revised in 1959, and gives their approximate equivalents in the present system of classification. Detailed descriptions and definitions of individual classes in the four upper categories are in USD A Agriculture Handbook 436, Soil Taxonomy: A Basic System of Soil Classification for Making and Interpreting Soil Surveys. Alfisols Alfisols are extensive in humid, temperate regions. They occur largely in plains having low or moderate relief. The distinguishing characteristics of Alfisols are: (1) An A horizon that has lost silicate clay, sesquioxides, and bases, (2) a B horizon that has accumulations of silicate clay (argillic or natric horizons), and (3) a moderate to high content of exchangeable calcium and magnesium. With few exceptions, an uneroded Alfisol has a dark surface horizon a few centimeters thick (an inch or two) over an ochric epipedon or an albic horizon (a pale horizon as much as 30 cm, 12 in., thick) grading below into an argillic horizon. The order of Alfisols consists of the suborders Aqualfs, Boralfs, Udalfs, Ustalfs, and Xeralfs. Aqualfs Aqualfs are the periodically wet Alfisols that occur either in depressions or on wide flats. These soils are wet much of the year but dry out to some depth from time to time. The great groups of this suborder and the features characteristic of each are: Albaqualfs—An albic horizon (nearly white A2 ho¬ rizon) or an argillic horizon with an abrupt upper boundary. Duraqualfs—A duripan (silica-cemented layer) below an argillic horizon. Fragiaqualfs—A fragipan (subsurface horizon that is compact and brittle but not indurated). Glossaqualfs—An albic horizon above an argillic horizon with tongues of pale or even white material extending into the argillic horizon. Natraqualfs—A natric horizon (a form of argillic horizon having appreciable sodium and a distinct blocky structure). Ochraqualfs—Type specimens for the suborder. These soils have the minimum required horizons and other features of the suborder. They have an ochric epipedon above an argillic horizon. Plinthaqualfs—Plinthite forming half or more of some subhorizon of the argillic horizon within 1.25 m (50 in.) of the soil surface. Tropaqualfs—An ochric epipedon or an albic hori¬ zon above an argillic horizon. Tropaqualfs occur in tropical and subtropical regions. The difference be¬ tween the mean soil temperature of the warm season and that of the cool season is less than 5°C or 9°F. Umbraqualfs—An umbric epipedon rather than an ochric epipedon like the Ochraqualfs, but the character¬ istics of the two otherwise are similar. Boralfs Boralfs are the cold and relatively well drained Alfisols of high latitudes and high mountains. The mean annual soil temperature is less than 8°C (47°F). The moisture level is moderate to high most of the time, but the soils may be dry for 90 days throughout the year. The great groups of this suborder and the features characteristic of each are: Cryoboralfs—The coldest of all the soils in the suborder. The mean annual soil temperature ranges from 0 to 8°C (32 to 47°F). The mean soil temperature during the warmest three months of the year is less than 15°C (59°F). Eutroboralfs—A high content of bases such as calcium and magnesium but not of sodium. Many have accumulations of calcium carbonate immediately below or in the lower part of the argillic horizon. Fragiboralfs—A fragipan (subsurface horizon that is compact and brittle but not indurated). Glossoboralfs—An albic horizon above an argillic horizon, usually with tongues of the albic material extending into the argillic horizon. Natriboralfs—A natric horizon (a form of argillic horizon having appreciable sodium and a distinct blocky structure). Paleboralfs—A thick albic horizon over an argillic horizon. The upper boundary of the argillic horizon is more than 60 cm (24 in.) below the soil surface. Udalfs Udalfs are relatively well drained Alfisols of temper¬ ate, subtropical, and tropical humid climates. The mean annual soil temperature is more than 8°C (47°F). The moisture level is moderate to high; some part of the 137 profile may be dry for 90 days or less in any one year. The great groups of this suborder and the features characteristic of each are: Agrudalfs— Cultivated for centuries; consequently, these soils have an accumulation of humus, clay, and silt (an agric horizon) immediately below the plow layer. Ferrudalfs —A discontinuous argillic horizon, frag¬ ments of which are coated and weakly cemented with iron oxides. Fragiudalfs —A fragipan (subsurface horizon that is compact and brittle but not indurated). Fraglossudalfs— Tongues of albic material (virtu¬ ally white soil material low in content of clay) extending through the argillic horizon, below which is a fragipan. Glossudalfs —Tongues of albic material extending down and commonly through the argillic horizon. These soils have no fragipan. Hapludalfs —Type specimens for the suborder. These soils have an ochric epipedon over a brown or yellowish brown argillic horizon. Natrudalfs —A natric horizon (a form of argillic horizon having appreciable sodium and a distinct blocky structure). Paleudalfs—A thick, reddish argillic horizon. These soils are believed to be the oldest of all the soils in the suborder. The argillic horizon extends to a depth of 1.5 m (60 in.) or more. Rhodudalfs —A dark red argillic horizon that is not so thick as that of Paleudalfs. Tropudalfs —Similar to Hapludalfs in morphology and composition, but these soils occur in tropical re¬ gions. The argillic horizon commonly is red or reddish brown. The mean annual soil temperature generally is more than 15°C (59°F). The difference between the mean soil temperature of the warm season and that of the cool season is less than 5°C or 9°F. Ustalfs Ustalfs are the well-drained Alfisols of warm-temper¬ ate, subtropical, and tropical regions where most of the rain falls during the warm season. The mean annual soil temperature is more than 8°C (47°F). Some part of the profile is dry for as much as half of the year, but the profile is moist for 90 consecutive days during the growing season. The great groups of this suborder and the features characteristic of each are: Durustalfs —A duripan (silica-cemented horizon) be¬ neath an argillic horizon. Haplustalfs —Type specimens for the suborder. The profile has no horizon in addition to the required sequence nor any special features. Natrustalfs —A natric horizon (a form of argillic horizon having appreciable sodium and either a blocky or prismatic structure, or both). Paleustalfs —A thick, reddish argillic horizon. These soils are believed to be relatively old. They have an argillic horizon that has a high proportion of clay to a depth of 1.5 m (60 in.) or more. Plinthustalfs —Plinthite forms one-half or more of some subhorizon of the argillic horizon within 1.25 m (50 in.) of the soil surface. Rhodustalfs —A dark red argillic horizon that is thinner than that of Paleustalfs. Xeralfs Xeralfs are the well-drained Alfisols of temperate regions in which most of the rain falls during the cool season. The mean annual soil temperature ranges from 8 to 22°C (47 to 72°F). The profile is dry throughout for at least 45 consecutive days during the growing season. Except for the great group Rhodoxeralfs in this suborder, these soils have an A horizon that is very hard when dry. The great groups of this suborder and the features characteristic of each are: Durixeralfs —A duripan (silica-cemented layer) be¬ neath an argillic horizon. Haploxeralfs —Type specimens for the suborder. The profile has only the number and kinds of horizons required for the suborder. Natrixeralfs —A natric horizon (a form of argillic horizon) having appreciable sodium and either a blocky or prismatic structure, or both. Palexeralfs —A thick, reddish but not dark red, argillic horizon having a high content of clay. The proportion of clay decreases slightly but slowly with increasing depth. Plinthoxeralfs —Plinthite forms more than half of some subhorizon of the argillic horizon within 1.25 m (50 in.) of the soil surface. Rhodoxeralfs —Fairly uniform dark red through¬ out the profile. Aridisols Aridisols are major components of soil patterns in dry regions (the deserts), which make up about one-fourth of the land surface of the earth. Landforms range from fairly level plains to distinct mountains. Characteristics common to Aridisols are: (1) Extended periods in which little or no moisture is available to plants, (2) one or more evident horizons, (3) a thin and rather pale surface horizon that has slight accumulations of humus (ochric epipedon), and (4) a soil surface without wide cracks at any time. All Aridisols have a low content of organic matter and relatively pale colors. Most have an accumulation of calcium carbonate at some depth in the profile. The order of Aridisols consists of the suborders Argids and Orthids. 138 Argids Among the Aridisols, Argids occupy the oldest land surfaces. All members of the suborder have a B horizon marked by an accumulation of silicate clays. Some have a B horizon that has appreciable sodium (natric horizon) but others do not (argillic horizon). The great groups of this suborder and the features characteristic of each are: Duragids— A duripan (silica-cemented layer) below an argillic horizon. Haplargids —The simplest profile of all the soils in the suborder; they have an ochric epipedon (light- colored A horizon) over an argillic horizon but no extra features beyond the required minimum. Nadurargids— A natric horizon overlying a duripan. The natric horizon is sticky and plastic when wet and hard when dry. Structure commonly is prismatic or blocky, or both. Natrargids —A natric horizon in which the struc¬ ture is prismatic or blocky, or both. Paleargids —A thick argillic horizon having a high content of clay or a petrocalcic horizon (carbonate- cemented subsurface layer), or both. Orthids Orthids have a pale surface horizon (ochric epipedon) and one or more of some type of distinct subsurface horizons, other than the B horizon, marked by an ac¬ cumulation of silicate clay. Such subsurface horizons extend to a depth of 25 cm (10 in.) or more. The great groups of this suborder and the feature characteristic of each are: Calciorthids —A calcic horizon (subsurface layer greatly enriched in carbonates) and a profile that gen¬ erally has a moderate to high calcium carbonate content. Camborthids—A cambic horizon that is brownish or reddish and brighter than the overlying and underly¬ ing horizons. Camborthids have an ochric epipedon (light-colored A horizon) and usually have an accumula¬ tion of carbonates below the cambic horizon. Durorthids —A duripan within 1 m (40 in.) of the soil surface usually, but not always, below a cambic horizon. Gypsiorthids —A gypsic horizon (subsurface layer enriched in gypsum) within 1 m (40 in.) of the soil surface. Gypsiorthids are pale in color throughout the profile. Paleorthids —A petrocalcic horizon (carbonate- cemented subsurface layer) within 1 m (40 in.) of the soil surface. Salorthids—A salic horizon (layer enriched in salts more soluble than gypsum) within the uppermost 75 cm (30 in.). The soils generally occur in depressions. Entisols Entisols are on land surfaces that range from level alluvial plains to steep mountain slopes, most of which are young. The lack of horizons except for a thin one at the surface is the identifying characteristic of Entisols. Many have an ochric epipedon (pale but not white surface layer), and some have an albic horizon (a white layer near the surface). These layers are so thin that they would be destroyed if the soils were plowed. The order of Entisols consists of the suborders Aquents, Arents, Fluvents, Orthents, and Psamments. Aquents Aquents are the wet Entisols that occur in low places such as marshes and parts of flood plains and deltas. The great groups of this suborder and the features characteristic of each are: Cryaquents —Coldest of all the soils in the subor¬ der. The mean annual soil temperature ranges from 0 to 8°C (32 to 47°F). The mean soil temperature during the three warmest months of the year is less than 15°C (59°F). Fluvaquents —Wet soils on flood plains and in del¬ tas in regions of middle and low latitudes. The vertical distribution of organic matter in the profile is irregular. Haplaquents —Occur in upland depressions where small amounts of sediments infrequently accumulate. These soils lack stratification. Their content of organic matter gradually decreases with increasing depth, and they are firm underfoot. Texture is sandy loam or finer throughout most of the profile. The mean annual soil temperature is above 8°C (47°F). Hydraquents —Always saturated with water. These soils have a high content of clay and a low bearing capacity. They are too soft to support grazing animals. Psammaquents —The sandy soils of the suborder. Sulfaquents —Contains moderate to large amounts of sulfides and few or no carbonates in the uppermost 50 cm (20 in.). These soils are saturated with water all or most of the time. Tropaquents —Occur in upland depressions in the tropics and subtropics. The mean annual soil tempera¬ ture is above 8°C (47°F). The difference between the mean soil temperature of the warm season and that of the cool season is less than 5°C (9°F). Arents Arents are Entisols in which the original horizons have been destroyed by mechanical disturbances. Frag¬ ments of former horizons, such as argillic horizons and fragipans, occur in some Arents. These soils have been identified chiefly in western Europe but probably occur 139 widely in eastern Asia and will become more common elsewhere as progressively larger equipment becomes available for earthmoving and landshaping. No great groups have been defined for this suborder. Fluvents h luvents are well drained and moderately well drained Entisols that formed in recent alluvium, much of which accumulated during the last few centuries. They are on flood plains that are subject to active deposition but not to ponding. Texture in the upper 1 m (40 in.) of the profile is sandy loam or finer. Organic carbon is irregularly distributed in the profile. The great groups of this suborder and the features characteristic of each are: Cryofluvents— The coldest of all the soils in this suborder. The mean annual soil temperature ranges from 0 to 8°C (32 to 47°F). The mean soil temperature dui'ing the warmest months is below 15°C (59°F). When these soils thaw, they are not dry for long periods. Torrifluvents— Dry throughout the profile or in most parts more than half of the year. The profile is never moist throughout for 90 consecutive days. Tropofluvents —The mean annual soil temperature is above 8°C (47°F). The difference between the mean soil temperature of the warm season and that of the cool season is less than 5°C or 9°F. The profile is not dry throughout for as many as 90 days during the year. Udifluvents —Dry throughout the profile less than 90 days per year. Ustifluvents —Moist in some part of the profile for half of the year or continuously moist for 90 days during the growing season. Xerofluvents— Profile is dry throughout for 45 or more consecutive days during the growing season. Most Xerofluvents have a mean annual soil tempera¬ ture higher than 0°C (32°F). Orthents Orthents occur chiefly on recently eroded slopes, but some are in recent loamy or finer loess, mudflows, and gravelly or cobbly alluvium. Some Orthents have a faint or thin A horizon, but most have a C horizon at the surface. The great groups of this suborder and the features characteristic of each are: Cryorthents— The coldest of all the soils in the suborder. The mean annual soil temperature is below 8°C (47°F). The mean soil temperature during the three warmest months of the year is below 15°C (59°F). Torriorthents— The driest of all the soils in the suborder. The profile is dry throughout most of the year and is never moist throughout for 90 consecutive days during the year. Troporthents— Occur in tropical and subtropical re¬ gions where rainfall is plentiful. The profile is not dry throughout for as many as 90 days a year. The mean annual soil temperature is above 8°C (47°F). The difference between the mean soil temperature of the warm season and that of the cool season is less than 5°C or 9°F. Ldorthents —Occur in regions where moisture is adequate. These soils are not dry throughout the profile for a total of 90 days per year. Ustorthents —Occur in subhumid and semiarid re¬ gions. The profile is moist in some part for half of the year or is continuously moist for 90 days during the warm season. Xerorthents— Occur in regions where most of the rain falls in winter. These soils are dry for 45 or more consecutive days during the warm season. Psamments Psamments are the sandy Entisols. The soil is sand to a depth of at least 1 m (40 in.) and is neither gravelly nor cobbly. Quartz is the most common mineral in these soils. The great groups of this suborder and the features characteristic of each are: Cryopsamments— The coldest of all the soils in the suborder. The mean annual soil temperature is below 8°C (47°F). The mean soil temperature during the three warmest months of the year is below 15°C (59°F). Quartzipsamments —Contain a high percentage of quartz, the grains of which are largely free of any coatings. Torripsamments— The driest of all the soils in the suborder. These soils are dry for half of the year and are never moist for 90 consecutive days a year. They are dry most of the time because of their limited capacity to hold water. Tropopsamments— The warmest of all the soils in the suborder. The mean annual soil temperature is above 8 C (47°F). The difference between the mean soil temperature of the warm season and that of the cool season is less than 5°C or 9°F. Udipsamments —Occur in regions that have ade¬ quate rainfall. The mean annual soil temperature is above 8°C (47“F), but the difference between the mean soil temperature of the warm season and that of the cool season is 5°C or 9°F or more. Ustipsamments —Occur in subhumid and semiarid regions that have adequate rainfall. Rainfall comes during the warm season but is generally ineffective because of the limited capacity of the sands to hold moisture. Xeropsammerits—Occur in regions where most of the rain falls during usually mild winters. The precip¬ itation is ineffective because the moisture storage ca¬ pacity of the sands is low. 140 Histosols Histosols are dominantly organic. Most Histosols have restricted drainage and are saturated with water most ol the year. The distinguishing characteristics are: (1) A high percentage of organic matter. (2) wetness, and (3) some mineral matter in the profile. The content or proportion of organic matter may be a little more than one-1 > weight Ts a minimum, but is always more than one-half by volume. The profile may have sequences of layers, but they refect stages in accumulation of materials rather than the formation of soil horizons. The order of Histosols consists of the suborders Fibrists, Folists, Hemists, and Saprists. Fibrists Fibrists consist mainly of slightly decomposed or¬ ganic matter. Plant structures are evident, and the plant species can be determined. Fibrists generally are light in weight and low in ash. The great groups of this suborder and the features characteristic ol each aie. Borofibrists —The mean annual soil temperature is below 8°C (47°F). The profile does not remain frozen in some part nor does it remain very cold during the summer. Cryofibrists —The coldest of all the soils in the suborder. The mean annual soil temperature is below 8°c (47°F). The profile is likely to be frozen at some depth or to remain cold throughout the summer. Luvifibrists— A subsurface layer at least 2 cm (0.8 in.) thick in which downward moving humus has accu¬ mulated. Medifibrists —The mean annual soil temperature is above 8°C (47°F). The difference between the soil temperature of the warm season and that of the cold season is 5°C or 9°F or more. Sphagnofibrists— Consist largely of the remains of sphagnum mosses. The mean annual soil tempeiatuie is generally below 8°C (47°F). Tropofibrists —Occur in tropical and subtropical regions, chiefly in coastal swamps. The mean annual soil temperature is above 8°C (47°F). The difference between the mean soil temperature of warm seasons and that of cool seasons is less than 5°C or 9°F. Folists Folists consist of forest litter resting on gravel, rubble, or rock, commonly on strong or steep slopes. Drainage is free, but some combination of one oi moi e of frequent rain, fog, and low temperatures keeps the litter wet much of the time. The great groups of the suborder and the features characteristic of each are: Borofolists —The mean annual soil temperature is below 8°C (47°F). The mean soil temperature during the three warmest months is above 15 C (59 f ). Cryofolists —The mean annual soil temperature is below 8°C (47°F). The mean soil temperature during the three warmest months is below 15 C (59 f ). Tropofolists: —The mean annual soil temperature is above 8°C (47°F). The difference between the mean soil temperature of the warm season and that of the cool season is less than 5°C or 9°F. Hemists Hemists consist of moderately decomposed organic residues. Few plant structures are evident, but vigor¬ ous rubbing of soil materials between the fingers does not destroy all fibers. The great groups of this suborder and the features characteristic of each are: Borohemists —The mean annual soil temperature is below 8°C (47°F). The profile does not remain frozen in some parts nor does it remain very cold during the summer. Cryohemists —The mean annual soil temperature is below 8°C (47°F). The profile remains frozen in some parts or is very cold throughout the summei. Luvihemists —A subsurface layer at least 2 cm (0.8 in.) thick in which downward moving humus has accu¬ mulated. Medihemists— The mean annual soil temperature is above 8°C (47°F). The difference between the mean soil temperature during warm and cool seasons is 5°C or 9°F or more. Sulfihemists —Appreciable amounts of sulfides in some part of the profile within a depth of 1 m (40 in.). Sulfohemists —Appreciable amounts of sulfuric acid in some part of the profile. Tropohemists —The mean annual soil temperature is above 8°C (47°F). The difference between the mean soil temperature of the warm season and that ot the cool season is less than 5°C or 9 F. Saprists Saprists consist of strongly decayed organic matter. Very few plant structures can be identified. Vigorous rubbing of soil materials between the fingers destroys virtually all fibers. Saprists are dry for part of the year. The great groups of this suborder and the features characteristic of each are: Borosaprists —The mean annual soil tempeiatuie is below 8°C (47°F). The profile does not remain frozen in some parts, nor does it remain very cold in all parts throughout the summer. Cryosaprists —The mean annual soil tempeiatuie is below 8°C (47°F). The profile remains frozen at some depth or is very cold throughout in summer. Medisaprists —The mean annual soil temperature is above 8°C (47°F). The difference between the mean soil temperature of the warm season and that ot the cool season is 5°C or 9°F or more. Troposaprists —The mean annual tempeiatuie is above 8°C (47°F). The difference between the mean soil temperature of the warm season and that of the cool season is less than 5°C or 9 f . 141 Inceptisols Inceptisols are most extensive in humid regions. They also occur in subhumid and semiarid zones but not in deserts. These soils are moist for appreciable periods, and available water is present either for more than half of each year or for more than 90 consecutive days each year. Identifying characteristics are: (1) Few or faint horizons, (2) a good to fair moisture regime, (3) some weatherable minerals, (4) a texture finer than loamy fine sand, and (5) clay fractions with moderate to high activity. Many Inceptisols have a subsurface horizon of alteration and loss known as a cambic horizon. The order of Inceptisols consists of the suborders Andepts, Aquepts, Ochrepts Plaggepts Tropepts, and Umbrepts. ’ ’ Andepts Andepts formed in regoliths consisting of volcanic ash or pumice or having large components of pyroclastic materials. Most Andepts have a dark A horizon, below which the moist soil materials smear badly when rubbed vigorously between the fingers. The soils have a low bulk density and therefore are light and fluffy. Most are acid, and some are strongly acid. Although not all these soils are well drained, none of them is wet. The great groups of this suborder and the features characteristic of each are: Cryandepts— The coldest of all the soils in the suborder. They occur in high latitudes and in high mountains. The mean annual soil temperature is below 8°C (47°F). The mean soil temperature during the three warmest months is below 15°C (59°F). The coldest soils have permafrost. Durandepts —A duripan (silica-cemented horizon) below a cambic horizon within 1 m (40 in.) of the soil surface. Dystrandepts— Moderately to strongly acid. These soils have a low level of bases such as calcium and a high content of organic matter. Eutrandepts— Slightly acid to neutral. They have a high content of bases such as calcium and a high content of organic matter. Hydrandepts —Dark soils through which water moves downward almost continuously because of the uniform rainfall in regions where they occur. These soils never dry out under natural conditions, but if artificially dried, the soil material hardens into small lumps. Placandepts —A placic horizon (thin and hard sub¬ surface layer cemented by oxides of iron or oxides of iron and manganese or by iron-organic complexes). \ itrandepts —A high proportion of slightly weath¬ ered volcanic glass or pumice. These soils feel like sandy loam or loamy sand rather than silt loam. Aquepts Aquepts are the wet Inceptisols that occur mostly on flats and in low places. Water is present in the soils most of the time. Many Aquepts have a dark A horizon a few centimeters thick, but in some this horizon is as much as 30 cm (12 in.) thick. The great groups of this suborder and the feature characteristic of each are: Andaquepts —Formed in parent materials containing large amounts of volcanic glass or other pyroclastic sediments. Most Andaquepts have a thick, dark A horizon. Cryaquepts —Coldest of all the soils in the subor¬ der. The mean annual soil temperature is below 8°C (47°F). The mean soil temperature during the warm season is below 15°C (59°F). The coldest Cryaquepts have permafrost. Fragiaquepts —A fragipan (subsurface horizon that is compact and brittle but not indurated). Halaquepts —Contain appreciable quantities of ex¬ changeable sodium and could be considered sodic soils. Some of these soils are saline. Haplaquepts —Type-specimens for the suborder. These soils have the gray cambic horizon required for the suborder but no extra horizons or other features. Humaquepts— A thick, dark A horizon or thin coverings of peat or peaty materials above a gray cambic horizon. Placaquepts—A placic horizon (layer a few centi¬ meters thick cemented by one or more of the oxides of iron and manganese or by iron-organic complexes). This layer is within 1 m (40 in.) of the soil surface. Plinthaquepts— Plinthite forms half or more of some subhorizon within 1.25 m (50 in.) of the soil surface but at a depth of more than 30 cm (12 in.). Plinthite consists of local concentrations of iron oxide that appears as dark red mottles on an exposed face and that hardens upon repeated wetting and drying. Sullaquepts —Moderate or larger amounts of sul¬ fides in the profile have been converted to sulfuric acid through drainage and oxidation. Tropaquepts— Occur in tropical and subtropical regions. The mean annual soil temperature is above 8°C (47°F). The difference between the mean soil temperature of the warm season and that of the cool season is less than 5°C or 9°F. Ochrepts Ochrepts are the freely drained Inceptisols charac¬ teristically having an ochric epipedon (pale but not white A horizon) over a brownish cambic horizon. The great groups of this suborder and the features charac¬ teristic of each are: Cryochrepts—Coldest of all the soils in the subor¬ der. The mean annual soil temperature is below 8°C (47°F). The mean soil temperature during the warm season is below 15°C (59°F). 142 Durochrepts— A duripan (silica-cemented horizon) below a cambic horizon but within 1 m (40 in.) of the soil surface. Dystrochrepts— Moderately to strongly acid. These soils have a low level of bases such as calcium. Eutrochrepts— Slightly acid to neutral. These soils have a high level of bases such as calcium and a moderately high organic matter content. The profile is moist throughout at least 90 days a year. Fragiochrepts —A fragipan (subsurface horizon that is compact and brittle but not indurated). Ustochrepts— Occur in subhumid to semiarid re¬ gions where most of the rain falls during the warm season. The profile of these soils is moist in some part for 180 days a year or is continuously moist for 90 days during the growing season. Xerochrepts —Occur in regions where most of the rain falls during the cool season. All parts of the profile are dry for 45 or more consecutive days during the growing season. Plaggepts Plaggepts are the Inceptisols that have a very thick dark surface horizon formed by additions of mixed organic and mineral materials such as manure or human wastes. The dark surface layer is called a plaggen epipedon. No great groups have been defined for this suborder. Tropepts These soils are the well drained and moderately well drained Inceptisols of tropical and subtropical regions. Most have an ochric epipedon or a light-colored A horizon, but some have a dark A horizon. All have a brownish or reddish cambic horizon. The mean annual soil temperature is above 8°C (47°F). The difference between the mean soil temperature of the warm season and that of the cool season is less than 5°C or 9°F. The great groups of this suborder and the features charac¬ teristic of each are: Dystropepts— Moderately to strongly acid. These soils have a low level of bases such as calcium. Eutropepts— Slightly acid to neutral. These soils have a high level of bases such as calcium. Humitropepts —A high or relatively high percent¬ age of organic matter and a low level of bases such as calcium. Some of these soils have an ochric epipedon, but many have an umbric epipedon (dark and strongly acid A horizon). All have a brownish or reddish cambic horizon. Sombritropepts —High organic matter content. These soils have a sombric horizon (dark or very dark subsur¬ face horizon) either in the cambric horizon or below it. Ustropepts— Moderate to low organic matter con¬ tent, high level of bases such as calcium, and relatively shallow depth to rock. The soils are moist in some parts for a total of 180 days per year or are continuously moist for 90 days during the growing season. Umbrepts Umbrepts are the freely drained Inceptisols that have either an umbric epipedon (thick, dark, acid A horizon) or an ochric epipedon (light-colored A horizon that does not have a high content of organic matter) over a brownish cambic horizon. The soils are moder¬ ately to strongly acid and have a low level of bases such as calcium and a moderate to high content of organic matter. The great groups of this suborder and the features characteristic of each are: Cryumbrepts —Coldest of all the soils in the subor¬ der. The mean annual soil temperature is below 8°C (47°F). The mean soil temperature during the warm season is less than 15°C (59°F). Fragiumbrepts —A fragipan (subsurface horizon that is compact and brittle but not indurated). Haplumbrepts —Type specimens for the suborder. These soils have an umbric epipedon over the cambic horizon but no extra features. The profile is not dry throughout for 90 days of the year. Xerumbrepts— Generally an ochric epipedon over a cambic horizon. The soils occur in regions where most of the rain falls during the cool season. The profile is dry throughout for 45 or more consecutive days during the growing season. Mollisols Mollisols are extensive in subhumid and semiarid, temperate regions; do not occur in deserts; and are of small extent in humid climates. Land surfaces are chiefly undulating to rolling but some areas are flat, some hilly, and some depressional. The soils are mainly in broad, sweeping plains such as the prairies of North America. Identifying characteristics of Mollisols are: (1) A thick dark A horizon having a high content of humus (mollic epipedon) and U) a high or moderate level of bases such as calcium throughout the profile. The profiles of many sods are calcareous in some parts, and distinct horizons are at some depth of carbonate accumulations. The order of Mollisols consists of the suborders Albolls, Aquolls, Borolls, Rendolls, Udolls, Ustolls, and Xeiolls. Aibolls have a mollic epipedon, an albic horizon (white oi very pale gray subsurface horizon that has lost silicate clays Albolls are seasonally wet Mollisols that occur on and sesquioxides), and a prominent argillic horizon (B wide upland flats and in shallow depressions. The soils horizon of clay accumulation) that is sometimes called a 143 claypan. The great groups of this suborder and the features characteristic of each are: Argialbolls —Type specimens of the suborder. Natralbolls —A natric horizon (a form of argillic horizon having an appreciable amount of sodium and a distinct prismatic structure). Aquolls Aquolls are the wet Mollisols that occur largely in depressions where water stands on the surface for part of the year. They also occur on some upland flats. Most of the soils have a very thick mollic epipedon, but some have a surface layer of peaty materials over a thinner mollic epipedon. The great groups of this suborder and the features characteristic of each are: Argiaquolls —An argillic horizon (B horizon of silicate clay accumulation). Calciaquolls —A calcic horizon (horizon of marked accumulation of calcium carbonate) within 40 cm (16 in.) of the soil surface. Many of the soils are calcareous throughout. Cryaquolls —Coldest of all the soils in the suborder. The mean annual soil temperature is below 8°C (47°F). The mean soil temperature during the warm season is below 15°C (59°F). Duraquolls —A duripan (silica-cemented horizon) within 1 m (40 in.) of the soil surface. Haplaquolls —Type specimens for the suborder. These soils have the features required for the suborder and no others. Natraquolls —A natric horizon (a form of argillic horizon having an appreciable amount of sodium and a distinct prismatic and blocky structure). Borolls Borolls are the cold Mollisols of high latitudes and of mountains. They occur in semiarid and subhumid cli¬ mates. The mean annual soil temperature is below 8°C (47°F). Borolls generally have a black or nearly black mollic epipedon, a brownish B horizon, and a paler C horizon. The great groups of this suborder and the features characteristic of each are: Argiborolls —An argillic horizon. The upper bound¬ aries are no more, usually less, than 60 cm (24 in.) below the soil surface. The mean annual soil tempera¬ ture ranges from 0 to 8°C (32 to 47°F). The mean soil temperature during the warm season is 15°C (59°F) or more. Calciborolls —A calcic horizon (horizon with marked accumulations of carbonates) within 1 m (40 in.) of the soil surface. The mean annual soil temperature ranges from 0 to 8°C (32 to 47°F). The mean soil temperature during the warm season is 15°C (59°F) or more. t ryoborolls —Coldest of all the soils in the subor¬ der. The mean annual soil temperature is below 8°C (47°F). The mean soil temperature during the warm season is below 15°C (59°F). Haploborolls —Type specimens for the suborder. These soils have the required features for the suborder and no more. The mean annual soil temperature ranges from 0 to 8 C (32 to 47°F). The mean soil temperature during the warm season is 15°C (59°F) or more. Natriborolls —A natric horizon (a form of argillic horizon having an appreciable amount of sodium and a prominent prismatic structure). f aleborolls —An argillic horizon beginning more than 60 cm (24 in.) below the soil surface. \ ermiborolls —Soils that have been mixed by ani¬ mals. One-half or more of the mollic epipedon consists of worm and insect casts and filled animal burrows. Rendolls Rendolls are Mollisols that formed in highly calcare¬ ous regoliths in humid regions. These soils have a mollic epipedon that grades into materials that are almost half calcium carbonate. The moisture regime is udic (profile is not dry in any part for 90 consecutive days a year). No great groups have been defined for this suborder. Udolls Udolls are well drained and moderately well drained Mollisols having an udic moisture regime (profile is not dry in any part for 90 consecutive days during a year). Udolls have a very dark brown or brownish-black mollic epipedon, a brown B horizon with or without clay accumulation, and a paler C horizon. The A and B horizons are characteristically acid, but the C horizon may be neutral or slightly alkaline. The great groups of this suborder and the features characteristic of each are: Argiudolls —An argillic horizon of moderate thick¬ ness. Hapludolls —A brownish cambic horizon (B horizon of alteration and loss). The Hapludolls have the sim¬ plest profile of all the soils in the suborder. Paleudolls —A thick argillic horizon. The percent¬ age of clay in the argillic horizon drops by less than 20 percent of the maximum within 1.5 m (60 in.) of the soil surface. \ ermudolls —Udolls that have been mixed by ani¬ mals. One-half or more of the mollic epipedon consists oi worm casts, worm holes, and filled animal burrows. Ustolls Ustolls are the well drained and moderately well drained Mollisols of subhumid and semiarid regions. The moisture regime is predominantly ustic (profile is moist in some parts for 180 days of a year or is continuously moist for 90 days during the growing season). The great groups of this suborder and the features characteristic of each are: Argiustolls—An argillic horizon (B horizon of silicate clay accumulation) of moderate thickness. C alciustolls—A calcic or petrocalcic horizon. Over- lying horizons are also calcareous but have a lower 144 content of carbonates. The calcic horizon is within 1 m (40 in.) of the soil surface, and a petrocalcic horizon is within 1.5 m (60 in.). Durustolls—A duripan (subsurface silica-cemented layer) within 1 m (40 in.) of the soil surface. Haplustolls—A cambic horizon (subsurface horizon of alteration) or a C horizon immediately beneath a mollic epipedon. These soils have the simplest profile of all the soils in the suborder. Natrustolls—A natric horizon (a form of argillic horizon having an appreciable amount of sodium and a prominent prismatic structure). Paleustolls—A thick reddish argillic horizon. The percentage of clay in the argillic horizon drops by less than 20 percent of the maximum within 1.5 m (60 in.) of the soil surface. These soils usually have a petrocalcic horizon within 1.5 m (60 in.) of the soil surface. Vermustolls—Ustolls that have been mixed by an¬ imals. One-half or more of the mollic epipedon consists of worm casts, worm holes, and filled animal burrows. Xerolls Xerolls are the Mollisols in regions where most of the rain falls during the cool season. The moisture regime of the soils is xeric (profile is dry in all parts for at least 45 consecutive days during the growing season). The great groups of this suborder and the features charac¬ teristic of each are: Argixerolls—An argillic horizon (B horizon of silicate clay accumulation) of no more than moderate thickness. Calcixerolls—A calcic horizon (subsurface horizon of marked accumulation of carbonate) within 1.5 m (60 in.) of the soil surface. Durixerolls—A duripan (subsurface silica-cemented layer) within 1 m (40 in.) of the soil surface. Haploxerolls—A cambic horizon (subsurface hori¬ zon of alteration) or a C horizon immediately beneath a mollic epipedon. Haploxerolls have the simplest profile of all the soils in the suborder. Natrixerolls—A natric horizon (a form of argillic horizon having an appreciable amount of sodium and a distinct prismatic structure). Horizons having an accu¬ mulation of carbonates are commonly below the natric horizon. Palexerolls—A thick, dark brown or reddish brown argillic horizon that has an abrupt upper boundary. The percentage of clay in the argillic horizon drops by less than 20 percent from the maximum within 1.5 m (60 in.) of the soil surface. These soils have a petrocalcic horizon (subsurface layer cemented by carbonates) within 1.5 m (60 in.) of the soil surface. Oxisols Oxisols occur in low latitudes, mostly in the humid Tropics and subtropics. A few occur in arid and semiarid parts of the Tropics. The mean annual soil temperature is largely, but not entirely, above 15°C (59°F). For the most part, land surfaces are level to moderately sloping, but some are strongly sloping. Identifying characteristics of Oxisols are: (1) Faint horizonation (poorly expressed horizons) and an oxic horizon (subsurface horizon consisting of minerals highly resistant to further weathering) with high porosity, (2) friable or very friable consistence, and (3) clay fractions with low capacity to hold bases such as calcium. Freely drained Oxisols have an A horizon about 30 cm (12 in.) thick that is darkened by organic matter. Below this horizon, the profile is uniform to a depth of 2 m (80 in.) or more. Colors are red, yellowish red, brown, or yellowish brown. The order of Oxisols consists of the suborders Aquox, Humox, Orthox, Torrox, and Ustox. Aquox Aquox are the wet Oxisols in shallow depressions and on sites receiving seepage water. Plinthite marks the profile of some Aquox, whereas others have gibbsite as aggregates or as cemented sheets. The great groups of this suborder and the features characteristic of each are: Gibbsiaquox—Cemented sheets or a high percent¬ age of gibbsite gravel within 1 m (40 in.) of the soil surface. Ochraquox—An ochric epipedon (pale but not white A horizon) over a gray oxic horizon. Plinthaquox—Plinthite forms a continuous layer within 1.25 m (50 in.) of the soil surface. Umbraquox—An umbric epipedon (thick, dark, acid A horizon having a relatively high content of organic matter) or a peaty layer at the surface. Humox Humox are freely drained Oxisols that are dominantly reddish and have a high content of organic matter and a low level of bases such as calcium. These soils have a dark A horizon. The moisture regime is udic or wetter (no part of the profile is dry for a total of 90 days during a year). The mean annual soil temperature is below 22°C (72°F) but generally is above 15°C (59°F). The great groups of this suborder and the features characteristic of each are: Acrohumox—Most weathered of all the soils in the suborder. Gibbsihumox—Cemented sheets or aggregates hav¬ ing a high percentage of gibbsite (hydrated aluminum oxides) within 1 m (40 in.) of the soil surface. Haplohumox—Least complex profile of all the soils in the suborder. These soils lack features other than those required for the suborder. 145 Sombrihumox—A sombric horizon (very dark subhorizon) within an oxic horizon. Orthox Orthox receive adequate, well-distributed rainfall. The mean annual soil temperature is above 15°C (59°F), generally above 22°C (72°F). The difference between the mean soil temperature of the warm season and that of the cool season is less than 5°C or 9°F. The great groups of this suborder and the features characteristic of each are: Acrorthox—Most weathered of all the soils of the suborder. Eutrorthox—The least weathered of all the soils in the suborder. These soils have a relatively high level of bases such as calcium and magnesium. Gibbsiorthox—Cemented sheets or aggregates hav¬ ing a high percentage of gibbsites (hydrated aluminum oxides) within 1.25 m (50 in.) of the soil surface. Haplorthox—Simplest profile of all the soils in the suborder. Sombriorthox—A sombric horizon (very dark subhorizon) within the oxic horizon. Umbriorthox—An umbric epipedon (thick, dark, acid A horizon having a relatively high proportion of organic matter) or a surface layer having a high content of humus. Torrox Torrox are the few Oxisols that occur in arid and semiarid regions. They are dominantly red and have a low content of organic matter and a relatively high level of bases such as calcium. All known Torrox have a torric moisture regime (all parts of the profile are dry for more than half of a year and are never moist for a total of 90 days). The mean annual soil temperature is above 22°C (72°F). The difference between the mean soil temperature of the warm season and that of the cool season is less than 5°C or 9°F. No great groups have been defined for this suborder. Ustox Ustox are freely drained Oxisols occurring in regions having long dry seasons but having enough rain to keep the soil profiles moist for 90 days a year. The mean annual soil temperature is above 15°C (59°F). For most of the Ustox, the difference between the mean soil tem¬ perature of the warm season and that of the cool season is less than 5°C or 9°F. The great groups of this suborder and the features characteristic of each are: Acrustox—Most weathered of all the soils in the suborder. Eutrustox—Least weathered of all the soils in the suborder. These soils have a moderate to high level of bases such as calcium and magnesium. Haplustox—Simplest profile of all the soils in the suborder. Sombriustox—A sombric horizon (very dark sub¬ horizon) within the oxic horizon. Spodosols Spodosols are scattered from the tundra through the Tropics in humid climates. These soils are of greater extent in cold and cool-temperature regions. Land surfaces are mostly undulating to rolling but some are flat, others depressed, and still others hilly. Spodosols have a spodic horizon (B horizon with accumulations of one or more of organic matter, aluminum, or iron). The order of Spodosols consists of the suborders Aquods, Ferrods, Humods, and Orthods. Aquods Aquods are the wet Spodosols occuring on wide flats and in low places. These soils are wet much of the time, but the upper part of the soil dries out periodically. The great groups of this suborder and the features characteristic of each are: C'ryaquods—Coldest of all the soils in the suborder. For the most part, the mean annual soil temperature is below 8°C (47°F). Some of the soils have a mean annual soil temperature below 0°C (32°F). The mean soil tem¬ perature during the warm season is below 15°C (59°F). Duraquods—A duripan (silica-cemented layer) in the albic horizon. The mean annual soil temperature is above 0°C (32°F). The mean soil temperature during the warm season is 15°C (59°F) or more. Fragiaquods—A fragipan (subsurface horizon that is compact and brittle but not indurated) below the spodic horizon. The tnean annual soil temperature ranges mainly from 0 to 8°C (32 to 47°F). The mean soil temperature during the warm season is 15°C (59°F) or more. Haplaquods—Type specimens for the suborder. These soils have a spodic horizon that is chiefly organic matter and aluminum. Placaquods—A placic horizon resting on a spodic horizon, a fragipan, or an albic horizon above the spodic horizon. Sideraquods—Contain much more iron in the spodic horizon than the other soils in the suborder. The mean annual soil temperature is above 0°C (32°F). The mean soil temperature during the warm season is 15°C (59°F) or more. Tropaquods—Occur in tropical and subtropical re¬ gions. These soils formed in sands that are almost pure quartz. In most profiles, a spodic horizon is at a great depth. It is usually black in the upper part and reddish brown below. The mean annual soil temperature is above 8°C (47°F). The diffei'ence between the mean soil 146 temperature of the warm season and that of the cool season is less than 5°C or 9°F. Ferrods Ferrods are freely drained Spodosols in which the spodic horizon is dominantly iron and contains little organic matter and aluminum. No great groups have been defined for this suborder. Humods Humods are the well drained and moderately well drained Spodosols that have a B horizon that has a high content of organic matter, a low content of iron or no iron, and an intermediate level of aluminum. The spodic horizon generally is black throughout or black in the upper part and brown below. The great groups of this suborder and the features characteristic of each are: Cryohumods—Coldest of all the soils in the subor¬ der. The mean annual soil temperature is below 8°C (47°F). The mean soil temperature during the warm season is below 15°C (59°F). Fragihumods—A fragipan (compact and brittle ho¬ rizon that is not indurated) beneath the spodic horizon. Haplohumods—Type specimens for the suborder. These soils have a spodic horizon that has a high content of organic matter. They have only the horizons and other features required for the suborder. The moisture regime for most Haplohumods is udic (no part of the profile is dry for 90 consecutive days during a year), but a few are xeric (profile is dry throughout at least 45 consecutive days during the growing season). The mean annual soil temperature is above 0°C (32°F). The difference between the mean soil temperature of the warm season and that of the cool season is 5°C or 9°F or more. Placohumods—A placic horizon (indurated and involuted layer cemented by one or more oxides of iron, mixed oxides of iron and manganese, or iron organic complexes). Tropohumods—Similar to Haplohumods in mor¬ phology and composition, but the mean annual soil temperature is above 8°C (47°F). The difference between the mean soil temperature of the warm season and that of the cool season is less than 5°C or 9°F. Orthods Orthods are the well drained and moderately well drained Spodosols that have about equal accumulations of organic matter, iron, and aluminum in their spodic horizon. The great groups of this suborder and the features characteristic of each are: Cryorthods—Coldest of all the soils in the subor¬ der. The mean annual soil temperature is less than 8°C (47°F). The mean soil temperature during the warm season is below 15°C (59°F). The coldest Cryorthods have permafrost. Fragiorthods—A fragipan (compact and brittle ho¬ rizon that is not indurated) below the spodic horizon. Haplorthods—Type specimens for the suborder. These soils have the characteristics required for the suborder and lack extra features. Placorthods—A placic horizon (indurated and involuted layer cemented by one or more oxides of iron, mixed oxides of iron and manganese, or iron organic complexes). Troporthods—The mean annual temperature is above 8°C (47°F). The difference between the mean soil tem¬ perature of the warm season and that of the cool season is less than 5°C or 9°F. The morphology generally is like that of Haplorthods. Ultisols Ultisols are major components of soil patterns in humid, warm-temperature regions. They also occur throughout the humid Tropics. The mean annual soil temperature is above 8°C (47°F). Land surfaces are mostly level to hilly, but some Ultisols occur in depressions or on wide flats, and others occur on steep slopes. Identifying characteristics of Ultisols are: (1) An argillic horizon (B horizon of silicate clay accumulation), (2) a low level of bases such as calcium, and (3) a warm temperature regime. This order consists of the suborders Aquults, Humults, Udults, Ustults, and Xerults. Aquults Aquults are the wet Ultisols that occur either in low places or on wide flats. These soils are wet much of the time but dry out for brief periods, at least down into the argillic horizon. Many of these soils also have iron- maganese concretions in their A and B horizons. The great groups of this suborder and the features charac¬ teristic of each are: Albaquults—An argillic horizon having an abrupt up¬ per boundary. Many of these soils also have an albic horizon (white A2 horizon). Fragiaquults—A fragipan (subsurface horizon that is compact and brittle but not indurated). Ochraquults—An ochric epipedon (light-colored but not white A2 horizon) set apart from the underlying argillic horizon by a gradual boundary. Paleaquults—Oldest of all the soils in the suborder. These soils have a thick argillic horizon in which the proportion of clay remains high to a depth of 1.5 m (60 in.) or more. Plinthaquults—Plinthite forms half or more of some subhorizon in the argillic horizon within 1.25 m (50 in.) of the soil surface. 147 Tropaquults—Similar to Ochraquults and Umbra- quults in morphology and composition, but these soils occur in tropical and subtropical regions. The difference between the mean soil temperature of the warm season and that of the cool season is less than 5°C or 9°F. Umbraquults—An umbric epipedon (thick, dark, acid A horizon having a high organic matter content) but characteristics otherwise are like those of Ochraquults. Humults Humults are the freely drained Ultisols that have a high content of organic matter. Some Humults have an ochric epipedon (light-colored A horizon), and others have an umbric epipedon (thick, dark, acid A horizon having a high content of organic matter). The great groups of this suborder and the features characteristic of each are: Haplohumults—An argillic horizon of moderate thickness that contains some weatherable minerals. Palehumults—An argillic horizon of great thick¬ ness having few or no weatherable minerals. The percentage of clay in the argillic horizon remains high to a depth of 1.5 m (60 in.). Plinthohumults—Plinthite forms half or more of some subhorizon in the argillic horizon within 1.25 (50 in.) of the soil surface. Sombrihumults—A sombric horizon (dark subsur¬ face layer) in the argillic horizon within 1 m (40 in.) of the soil surface. Tropohumults—Occur in tropical and subtropical regions. The difference between the mean soil tempera¬ ture of the warm season and that of the cool season is less than 5°C or 9°F. These soils have a thin argillic horizon, usually red, and a relatively high content of organic matter. Udults Udults are well drained and moderately well drained Ultisols having a low content of organic matter and an udic moisture regime (no part of the profile is dry for 90 days a year). The great groups of this suborder and the features characteristic of each are: Fragiudults—A fragipan (subsurface horizon that is compact and brittle but not indurated). Hapludults—An argillic horizon of moderate thick¬ ness. Paleudults—An argillic horizon of great thickness that has few or no weatherable minerals. The percent¬ age of clay in the argillic horizon remains high to a depth of 1.5 m (60 in.) below the soil surface. Plinthudults—Plinthite forms half or more of some subhorizon of the argillic horizon within 1.25 (50 in.) of the soil surface. Rhodudults—Dark colors throughout the soil pro¬ file; the colors may be dark shades of red, reddish brown, or brown. Tropudults—Occur in regions where the difference between the mean soil temperature of the warm season and that of the cool season is less than 5°C or 9°F. Ustults Ustults are freely drained Ultisols that have a low content of organic matter and an ustic moisture regime (some part of the profile is moist for 180 days a year or is continuously moist for 90 days during the growing season). The great groups of this suborder and the features characteristic of each are: Haplustults—An argillic horizon of moderate thick¬ ness. The percentage of clay in the argillic horizon decreases appreciably with depth. Paleustults—An argillic horizon of great thickness having few or no weatherable minerals. The percentage of clay in the argillic horizon remains high to a depth of 1.5 m (60 in.) below the soil surface. Plinthustults—Plinthite forms half or more of some subhorizon of the argillic horizon within 1.25 m (50 in.) of the soil surface. Rhodustults—Dark colors, mostly dark red or dusky red, throughout the profile. The argillic horizon is of moderate thickness. Xerults Xerults are freely drained Ultisols that have a low to moderate content of organic matter and a xeric mois¬ ture regime (all parts of the profile are dry for 45 consecutive days during the growing season). The mean annual soil temperature ranges from 8 to 22°C (47 to 72°F). The difference between the mean soil tempera¬ ture of the warm season and that of the cool season is 5°C or 9°F or more. Xerults have an ochric epipedon (light-colored A horizon) and a brownish or reddish argillic horizon. Their total extent is limited. The great groups of this suborder and the features characteristic of each are: Haploxerults—An argillic horizon of moderate thick¬ ness. The percentage of clay in the argillic horizon decreases appreciably with depth. Palexerults—An argillic horizon of great thickness having few or no weatherable minerals. The percentage of clay in the argillic horizon remains high to a depth of 1.5 m (60 in.) below the soil surface. Vertisols Vertisols occur in warm-temperate, subtropical, and tropical regions having one or more long, dry periods each year. The mean annual soil temperature is more than 8°C (47°F). Land surfaces are mostly level to gently sloping but range to strongly sloping and are generally old. Vertisols have a high content of active clay, a low content of organic matter, dull colors, extended periods when little moisture is available, and marked swelling and shrinking with 148 alternate wetting and drying. During some time each year, cracks several centimeters (1 in. or more) across are either at the soil surface or at the bottom of the plow layer. The order of Vertisols consists of the suborders Torrerts, Uderts, Usterts, and Xererts. Torrerts Torrerts occur in arid regions. These soils have cracks that remain open most of the time. The cracks are never closed for more than 60 consecutive days during the warm season. No great groups have been defined for this suborder. Uderts Uderts occur in humid regions. Some part of the profile of these soils usually is moist but dries out enough that cracks form at least once in most years but not every year. The great groups of this suborder and the features characteristic of each are: Chromuderts—A gray or grayish brown A horizon that is only slightly darker, if any, than the material deeper in the profile. Pelluderts—A black, very dark grayish brown, or very dark gray A horizon that is appreciably darker than the material deeper in the profile. Usterts Usterts occur in subhumid regions, chiefly in regions that have two rainy seasons and two dry seasons each year. Cracks form in these soils and remain open for 90 days during the year, but they are closed for at least 60 consecutive days. The great groups of this suborder and the features characteristic of each are: Chromusterts—A gray or grayish brown A horizon that is only slightly darker, if any, than the material deeper in the profile. Pellusterts—A black, very dark gray, or very dark grayish brown A horizon that is appreciably darker than the material deeper in the profile. Xererts Xererts occur in regions that have warm, dry sum¬ mers and cool, wet winters. Cracks form in these soils every year and remain open for more than 2 months during the latter part of the warm, dry season. The great groups of this suborder and the features charac¬ teristic of each are: Chromoxererts—A gray or grayish brown A hori¬ zon that is only slightly darker, if any, than the material deeper in the profile. Pelloxererts—A black, very dark gray, or very dark grayish brown A horizon that is appreciably darker than the material deeper in the profile. 149 Table 2.—Great soil groups in the 1938 classification, as revised in 1959, and their approximate equivalents in the present system of classification Revised 1938 classification Present classification Great soil groups Great groups or other taxa mostly included Great groups or other taxa partly included Alluvial soils Alpine Meadow soils Ando soils . Bog soils . Brown soils . Brown Forest soils . Brown Podzolic soils . Brunizems (Prairie soils) . Calcisols . Calcium Carbonate Solonchaks Chernozems . Chestnut soils Degraded Chernozems . Desert soils . Gray-Brown Podzolic soils - Gray Wooded soils . Ground-Water Laterite soils Ground-Water Podzols . Grumusols . Half-Bog soils . Humic Ferruginous Latosols Humic Gley soils . Humic Latosols . Hydrol Humic Latosols . Laterite soils . Latosolic Brown Forest soils Latosols (great groups of) -- Fluvaquentic and fluventic subgroups of Incepti- sols and Mollisols; great groups of Fluvents. Cryaquods . Dystrandepts . Great groups of Fibrists, Hemists, and Saprists. Mesic families of aridic subgroups of Argiustolls, Ar- gixerolls, Haploxerolls, and Haplustolls; mesic families of ustollic and xerollic subgroups of Ar- gids and Orthids. Eutrochrepts . Cryandepts; mesic families of entic Fragiorthods and Haplorthods. Mesic families of Argiudolls and Hapludolls; mesic and thermic families of Argixerolls and Haploxerolls. Calciborolls, Calciorthids, Calciustolls, Calcixerolls, and Paleorthids. Calciaquolls . Cryoborolls; mesic families of typic and udic sub¬ groups of Argiustolls and Haplustolls; udic sub¬ groups of Argiborolls and Haploborolls. Frigid families of Argixerolls, Durixerolls, Haploxerolls, and Palexerolls; mesic families of aridic subgroups of Argiustolls, Argixerolls, Haploxerolls, and Haplustolls; typic subgroups of Argiborolls and Haploborolls. Mollic Eutroboralfs; Haploborolls . Mesic families of Durargids, Haplargids, and Pa- leargids. Hapludalfs . Eutroboralfs . Plinthaquults, Plinthudults, Plinthustalfs, and Plinthustults. Great groups of Aquods . Great groups of Vertisols . Histic subgroups of Aquepts . Tropohumults . Argiaquolls, Cryaquolls, Haplaquolls, Humaquepts, and Umbraquults. Tropohumults . Hydrandepts. Acrorthox. Dystrandepts . Humoxic Tropohumults; Tropepts . Cryorthents; Cumulic Haploxerolls; entic subgroups of Haploxerolls and Haplustolls; Fluvaquents; great groups of Psamments; Haplaquents; Hapla- quepts; Hapludolls. Cryaquolls and Cryumbrepts. Other great groups of Andepts. Frigid families of xerollic subgroups of Argids, Or¬ thids, and Durixerolls; Aridic Haploborolls. Haploxerolls and Hapludolls. Dystric Eutrochrepts; Dystrochrepts; Fragiochrepts. Cryoborolls; mesic families of Durixerolls, Pale¬ xerolls, and udic Argiustolls. Camborthids, Durorthids, Ustochrepts, and Xero- chrepts. Aquic Calciustolls. Mesic and frigid families of Haploxerolls. Aridic subgroups of Argiborolls and Haploborolls; mesic and frigid families of calcic subgroups of Argixerolls and Haploxerolls. Boralfic Argiborolls. Mesic families of Camborthids and Durorthids. AericOchraqualfs;Fragiudalfs;Glossoboralfs; mesic families of Hapludults. Other great groups of Boralfs. Haplohumods. Vertic subgroups of Haplaquepts and Haplaquolls. Histic subgroups of Aquolls; Umbraqualfs. Dystrandepts; great groups of Orthox. Andaquepts, Calciaquolls, Fluvaquents, Mollic Haplaquepts, and Mollic Orchraqualfs. Dystrandepts, Gibbsihumox, and Hydrandepts. Vitrandepts. Great groups of Oxisols; Hydrandepts; Rhodustults. 150 Table 2.—Great soil groups in the 1938 classification, as revised in 1959, and their approximate equivalents in the present system of classification—Continued Revised 1938 classification Present classification Great soil groups Treat groups or other taxa mostly included Great groups or other taxa partly included Lithosols Low-Humic Gley soils . Low Humic Latosols . Noncalcic Brown soils . Planosols . Podzol soils . Prairie soils . Red Desert soils . Reddish-Brown Lateritic soils Reddish Brown soils . Reddish Chestnut soils Reddish Prairie soils . Red-Yellow Podzolic soils Regosols Rendzina soils Sierozems Lithic subgroups; shallow families of Orthents. Great groups of Aquults; Haplaquents; Haplaquepts; and Ochraqualfs. Ustropepts . Durixeralfs, Haploxeralfs, and Palexeralfs. Albaqualfs, Argialbolls, Fragiaqualfs, and Glossa- qualfs. Cryorthods, Fragiorthods, and Haplorthods. (See Brunizems) . Thermic and hyperthermic families of Camborthids, Durargids, Haplargids, and Paleargids. Great groups of Humults; rhodic subgroups of Pa- leudalfs and Paleudults; Rhodudults. Haplustalfs; Paleustalfs; thermic and hyperthermic families of typic and ustollic subgroups of Calcior- thids, Camborthids, and Haplargids. Haplustalfs; Paleustalfs; thermic and hyperthermic families of aridic and typic subgroups of Argiustolls and Paleustolls. Thermic families of udic subgroups of Argiustolls and Paleustolls. Thermic families of Fragiudults, Hapludults, and Pa¬ leudults. Great groups of Psamments; subgroups of Orthents other than lithic; Vitrandepts. Rendolls . Mesic and frigid families of ustollic and xerollic sub¬ groups of Camborthids; Durargids, Haplargids, Lithic subgroups and shallow families of Alfisols, Aridisols, Inceptisols, Mollisols, Ultisols, and other Entisols. Cryaquents; Fluvaquents; other great groups of Aquepts and Aqualfs; Psammaquents. Haplustox. Xerochrepts. Fragiaquults; Albaquults. Haplohumods. (See Brunizems). Thermic and hyperthermic families of Calciorthids. Isothermic and isohyperthermic families of Eutran- depts; thermic and hyperthermic families of aridic Argiustolls, Calciustolls, and Haplustolls. Thermic and hyperthermic families of Haplustolls. Isothermic and isohyperthermic families of Eutran- depts; thermic families of Paleudolls. Mesic families of Fragiudults, Hapludults, and Pa¬ leudults; thermic families of Paleudalfs; thermic families of ultic subgroups of Haplustalfs and Paleustalfs. Entic subgroups of Haploxerolls, Hapludolls, and Haplustolls; Grossarenic Paleudults; Psamma¬ quents; Xerochrepts. Calciustolls, Hapludolls, and Haplustolls. and Paleargids. Solonchak soils . Salorthids . Solonetz soils . Natric great groups of Alfisols, Aridisols, and Mollisols. Soloth soils . Sols Bruns Acides . Dystrochrepts, Fragiochrepts, and Haplumbrepts. Subarctic Brown Forest soils . Cryochrepts . Tundra soils . Pergelic Cryaquepts . Yellowish-Brown Lateritic soils 1 Halaquepts. Natraqualfs; natric subgroups of Cryoborolls, Dura- quolls, Durixeralfs, and Haploxeralfs. Udorthents and Xerumbrepts. Cryoborolls. Cryandepts, Cryochrepts, and Cryumbrepts. 'Combined with Reddish-Brown Lateritic soils in 1949 Source: USDA Agriculture Handbook 436. 151 APPENDIX III. CARIBBEAN REGION Appendix III describes the major physical characteristics of the Caribbean land resource region (designated by the capital letter Z ) and major land resource areas (see p. 154). Z—CARIBBEAN REGION The Caribbean Region includes Puerto Rico, the adjacent islands (Vieques, Culebra, and Mona), and the U. S. Virgin Islands (St. Croix, St. Thomas, and St. John). Puerto Rico is surrounded by the Atlantic Ocean in the north and by the Caribbean Sea in the south. Approximately three-fourths of the island consists of mountain ranges. Cerro de Punta, the highest peak, is 1,338 m high, and the elevation of El Yunque is 1,065 m. Other prominent physical features are limestone karst in the northwest and coastal plains of varying width along the northern and southern coasts. In about 15 percent of the Caribbean Region, slopes are 15 percent or less; in 25 percent, slopes range from 16 to 45 percent; and in the rest of the region, they are more than 45 percent. Average annual precipitation ranges from 2,100 mm in the humid uplands, 1,600 mm in the humid coastal plains, 1,150 mm in the semiarid mountains and valleys, to 900 mm in the semiarid coastal plains. The average annual temperature is 24°C in the humid uplands, 25°C in the humid coastal plains, 26°C in the semiarid mountains and valleys, and 26°C in the semiarid coastal plains. The soils in the Caribbean Region are extremely variable and complex. Tropepts and Humults are the principal soils in the mountainous areas, and Udults and Orthox are dominant on coastal plains. The poorly drained Aquepts, Aquolls, and Aquents are common on flood plains, and Ustolls and Udolls are on the better drained sites. Rendolls and Udalfs occur in areas of limestone karst. Principal limiting characteristics of the soils in this region are shallowness to bedrock and steepness of slope. Forest is the climax vegetation. The importance of sugarcane, once the main cash crop, has declined because many sugar mills have been closed because of inefficiency and high labor costs. Coffee grown under shade was once a prosperous enterprise, but hurricanes and labor problems have contributed to its decline. Pasture of native and improved grasses grown for dairy and beef enterprises is the main land use. Woodland, mostly unimproved, is widespread, especially on the humid uplands. Such food crops as plantains, bananas, yams, taniers, vegetables, and some citrus fruit and coconuts are grown. Some unique farmland is used for growing pineapples and rice. Urban developments, highways, and recreation sites are encroaching upon the better farmland, especially near the metropolitan areas. 270—Humid Mountains and Valleys Puerto Rico 4,910 km 2 (1,895 mi 2 ) Land use: Most of this area is in farms. About 70 percent is pasture of improved forage and native grasses. Approximately 10 percent of the area is planted to coffee. Most of the coffee is grown in the shade, but some is grown in the sun. About 7 percent of the area is ungrazed forests. The remainder is used for growing such food crops as plantains, bananas, taniers, yams, and pigeon peas and for orchards and other purposes. Urban expansion is not a significant land use problem. Forest is the climax vegetation. Elevation and topography: Elevation ranges from 50 to 1,340 m. Three distinct mountain ranges are in the area. The Central Ridge, Cordillera Central as it is known locally, is the highest and largest of the three. It is oriented in a general east-west direction. Cerro de Punta, its highest peak, is 1,338 m above sea level. Los Tres Picachos and Monte Guilarte are about 1,205 m high. Second in extent and elevation is the Sierra de Luquillo in the northeastern part of Puerto Rico. The three highest peaks are El Toro, 1,074 m above sea level; El Yunque, 1,065 m; and Pico del Este, 1,051 m. The third range is the Sierra de Cayey in the east-central part of Puerto Rico. The Cerro La Santa, 903 m high, and Cerro La Tabla, 890 m high, are the highest peaks of this range. Climate: Average ajmual precipitation —2,075 to 2,150 mm. Maximum precipitation is in May and in Sep¬ tember. Average annual temperature —24°C. There is little difference between the temperature in sum¬ mer and that in winter. Water: Surface water from precipitation, perennial streams, and lakes is abundant. Ground water is limited to water that seeps into the soil and is stored in the dense and massive underlying volcanic rock. Soils: Most of the soils are Tropepts and Humults. Shallow and moderately deep, medium textured Eutropepts (Caguabo, Mucara, Quebrada, and Morado series) have an isohyperthermic temperature regime 153 U. S. DEPARTMENT OF AGRICULTURE SOIL CONSERVATION SERVICE MAJOR LAND RESOURCE AREAS OF PUERTO RICO AND THE VIRGIN ISLANDS BASE SOURCE uses 1 240.000 TopoQuad. 195 2 Apnl 1979 Z-CARIBBEAN 1 270 1 Humid Mountains and Valleys 1 271 | Semiarid Mountains and Valleys [ 272 1 Humid Coastal Plains 1 273 | Semiarid Coastal Plains REVISED APRIL 12. 1978 APRIL 1979 c«A,..cr,^ ic.iui»«. AT t ANTIC OCEajv Sul* C»y Outer 8 - o Lolim liltni St Jeme^T^ Oou ltlsnd "HP* _' Frencheep Cey Cepe'S* telendt - l^J —18* 1 1*’ VIRGIN ISLANDS of the UNITED STATES ST THOMAS AND ST. JOHN ISLANDS CARIBBEAN SEA CARIBBEAN s S b ,bbean SEA VIRGIN ISLANDS of the UNITED STATES ST. CROIX ISLAND 1 0 l J } i Him LEGEND ===== Good motor road —*—■ Stream -— — National torest boundary BASl SOURCl USD A SCS Crn+tjl Soil Mjp Mjy 1969 AGRICULTURE HANDBOOK 296 154 and mixed mineralogy. They are on steep side slopes, mainly in the east-central part of Puerto Rico. Deep, fine textured Tropohumults (Humatas and Los Guineos series) have isohyperthermic and isothermic temper¬ ature regimes and kaolinitic and oxidic mineralogy. They are on steep side slopes in the west-central part of Puerto Rico. Soils of minor extent are the deep, extremely weathered Acrorthox (Nipe series) in the western part of Puerto Rico. 271—Semiarid Mountains and Valleys Puerto Rico, Outlying Islands, and U.S. Virgin Islands Puerto Rico—960 km 2 (369 mi 2 ) U.S. Virgin Islands—220 km 2 (85 mi 2 ) Land use: Most of this area in Puerto Rico is in farms. About 60 percent is pasture, mainly of native adapted grasses. About 35 percent is natural forest, about 10 percent of which is in improved species of such hardwoods as mahogany, teak, cadam, and eucalyp¬ tus. Urban expansion is not a land use problem. The mountainous region in northwestern St. Croix, the largest of the U.S. Virgin Islands, supports a fairly dense tropical forest. In other parts there is a dense growth of thorny bushes and cacti, which generally grow in semiarid regions having low rainfall and high evaporation. Although the soils in the Virgin Islands have severe limitations that preclude their use for dwellings, urban development is significant. Elevation and topography: Elevation in Puerto Rico ranges from 50 to 400 m. Slopes range from moderately steep to very steep; near-vertical slopes occur in the northernmost part of the area. These semiarid mountains are in the southern slopes of the central mountain chain that runs east and west the length of the island. All streams in the Puerto Rican part of this area flow to the south. The U.S. Virgin Islands are mountainous. St. Croix is characterized by a ridge of mountains in the north flanked by a rolling plain to the south. Mount Eagle, the highest peak in St. Croix, is 355 m high. St. Thomas and St. John are characterized by irregular coastlines, many bays, steep slopes, and small drainage areas. Crown Mountain, the highest peak in St. Thomas, is 457 m above sea level. Bordeaux Mountain, the highest peak in St. John, is 390 m above sea level. Climate: Average annual precipitation —1,150 mm. Maximum precipitation is in May and in September. Average annual temperature —26°C. The difference between the temperature in summer and that in winter is less than 5°C. Water: The source of surface water is about 1,143 mm of rainfall a year. Because of high evaporation rates in this area, much of this precipitation is lost in the atmosphere before reaching the small streams and rivers. The few manmade lakes are used for storing water for human consumption and for irrigation. Ground water is scarce because the steep topography and the high evaporation rates prevent sufficient quantities of water from entering the soil and establishing underground deposits. Soils: Most of the soils are Tropepts. They are shallow and moderately deep and medium textured. They have an isohyperthermic temperature regime and mixed mineralogy on volcanic rocks. The well-drained, shallow Ustropepts (Descalabrado series) are domi¬ nant throughout the area and are on the steep southern side slopes of the east-west central ridge of mountains. The well-drained, moderately deep Us¬ tropepts (Callabo and Jacana series) are on side slopes and foot slopes. Of minor extent are shallow, well-drained Haplustalfs (Guayama series) on steep side slopes. 272—Humid Coastal Plains Puerto Rico 2,420 km 2 (933 mi 2 ) Land use: Most of this area is in farms averaging 35 acres. Pasture of native and improved grasses make up nearly 50 percent of the area. Many large dairy farms are in the Humid Coastal Plains. About 17 percent of the acreage is cropland, and sugarcane is the chief cash crop. About 7,000 acres of unique farmland is planted to pineapples on Oxisols. Rice production is a new agricultural enterprise. Orchards, mainly orange trees; grapefruit; and coconut are important in some locations. Urban development is significant, especially around the large metropolitan section, and contributes to a serious land use prob¬ lem. Elevation and topography: Elevation ranges from sea level to 700 m, rising gradually from the beaches on the Atlantic Ocean to the hilly karst area to the south. This area is divided into two distinct zones—the flat alluvial plains and terraces along the coast and the irregular features of the karst limestone inland. Streams generally flow to the north, but most of the drainage in the karst zone is underground. Climate: Average annual precipitation —1,600 mm. Maximum precipitation is in May and August. Aver¬ age annual temperature —25°C. There is little differ¬ ence between the temperature in summer and that in winter. Water: Surface and ground water are plentiful. Surface water consists of runoff from rainfall in the humid uplands. Some large manmade lakes are used for hydroelectric power and as a source of water for human consumption. Ground-water supplies are de¬ rived from water in the joints and fractures of the underlying volcanic rock and the contiguous lime¬ stone aquifers of this humid coastal area. Soils: There are four distinct geomorphic areas— coastal plains, river flood plains, small lagoonlike depres¬ sions, and limestone karst areas. All the soils have an isohyperthermic temperature regime. In the coastal plains, the dominant soils are deep, well-drained, acid Paleudults (Almirante, Aceitunas, and Vega Alta series) and Haplorthox (Coto and Bayamon series). On the flood plains, the poorly drained Tropaquepts (Bajura series), the somewhat poorly drained Fluvaquents (Coloso series), and the well- drained Hapludolls (Toa series) are the main soils. Poorly drained Troposaprists (Tiburones, Palmas Altas, and Saladar series), Fluvaquents (Martin Pena se¬ ries), and swamps and marshes are dominant in small depressions. In the extensive limestone karst, Rendolls (Colinas and Soller series) and Tropudalfs (Tanama and San Sebastian series) are major soils. 273—Semiarid Coastal Plains Puerto Rico, Outlying Islands, and U.S. Virgin Islands Puerto Rico—580 km 2 (223 mi 2 ) U.S. Virgin Islands—120 km 2 (48 mi 2 ) Land use: Most of the Puerto Rican part of this MLRA is in farms. More than 50 percent is pasture of native and improved grasses used mainly for beef produc¬ tion. The production of hay for race horses is an important enterprise in some locations. More than 80,000 acres are under different systems of irriga¬ tion, mainly for sugarcane production. Several hundred acres are drip irrigated for the production of avoca¬ dos, mangoes, and oranges. Growing vegetables under irrigation is becoming of local economic importance. Urban expansion is a land use problem near the larger cities of Puerto Rico. For many years the sugarcane grown in St. Croix was an important part of the economy, but the sugar mills have been closed, and it has been difficult to find a suitable cash crop because of the scai’city of water for irrigation. Rapid urban expansion has increased the need for new roads, schools, and recreation developments. Elevation and topography: Elevation in the Puerto Rican part of this area ranges from sea level to 400 m. Most of the area is nearly level to gently slopii g. Elevation increases gradually from the beaches on the Caribbean Sea to the foothills of the semiarid mountains to the north. Limestone hills and ridges are similar to those in the Humid Coastal Plains, but they lack the striking karst features. All drainage is surficial and flows in a southerly direction. On the Island of St. Croix, of the U.S. Virgin Islands, mountains are broken by nearly level to gently sloping alluvial fans, flood plains, foot slopes, and low rolling limestone hills. Climate: Average annual precipitation —900 mm. Maximum precipitation is in May and in September. Average annual temperature —26°C. The difference between the temperature in summer and that in winter is small. Water: Surface water is scarce because of limited rainfall and high evaporation rates. Low rainfall and the steep topography of the adjacent semiarid moun¬ tains to the north provide little additional surface water. Streams and rivers generally are intermit¬ tent. Aquifers are affected by saltwater intrusion because of overuse. In places artesian pressure brings saline and sodic ground water to the surface. Three organized irrigation districts are in southern Puerto Rico, but there are none in the U.S. Virgin Islands. Soils: Aquolls, Ustolls, and Usterts are the dominant soils on flood plains and on high terraces. These soils have an isohyperthermic temperature regime and mixed or montmorillonitic mineralogy. On the flood plains, deep, somewhat poorly drained, fine textured Calciaquolls (Constancia series) and well-drained Haplustolls (Jacaguas and San Anton series) are dominant. On the high terraces, deep expansive clayey Chromusterts (Fraternidad and Paso Seco series) and Pellusterts (Aguirre and Guanica series) are dominant. 156 * U. S GOVERNMENT PRINTING OFFICE 1982 328-477 (1570-Bid) URCE REGIONS AND MAJOR LAND RESOI u s department of agriculture, soil conservation service X'.KU U H KM 11 \N1)|U H)K RESOURCE AREAS jIONS AND MAJOR LAI' OF THE UNITED STATES LAND c Wf» CUSTtH Prinop.il Islands o( HAWAII SEE REVERSE SIDE FOR DETAILS OF ALASKA AND HAWAII REGIONS Albers Equal Area Proieciion SCALE 1:7,500,000 ALASKA SCAIC 117XOO.I RIVISID APRIL 12. 1978 SOURCl USCS National Altai hate, 1 .7. 500.000 lot 48 conterminous states and Alatka. J 2.000.000 RESOURCE REGIONS AND LAND 1 Northern Pacific Coast Range, foothill., and Valievs i Willamette and Puget Sound Valievs 1 Olympic and Cascade Mountains. Western Slope 4 California Coastal Redsvood Belt 5 Siskivou-Trinity Area HB NORTHWESTERN WHEAT AND RANCE RECION 0 Cascade Mountains, Eastern Slope 7 Columbia Basin 8 Columbia Plateau 9 Palouse and Nez Perce Prairies 10 Upper Snake River Lava Plains and Hills 11 Snake River Plains 12 Lost River Valleys and Mountains 1J Eastern Idaho Plateaus 24 Humboldt Area 25 Osvyhee High Plateau 26 Carson Basin and Mountains 27 Fallon-Lovelock Area 28A Great Salt lake Area 28B Central Nevada Basin and Range 29 Southern Nevada Basin and Range 10 Sonoran Basin and Range )1 Imperial Valley 52 Northern Intermountain Desertic Basins 33 Semiand Rocky Mountains 14 Central Desertic Basins. Mountains, and Plateaus )S Colorado and Green River Plateaus 5b New Mexico and Arizona Plateaus and Mesas 37 San |uan River Valley Mesas and Plateaus 39 Arizona and New Mexico Mountains 40 Central Arizona Basin and Range 41 Southeastern Arizona Basin and Range 42 Southern Desertic Basins. Plains, and Mountains 48A ISeeE) r~ p—| C At If ORNIA SUBTROPICAL FRUIT, TRUCK. AND Ut—I SPECIALTY CROP REGION 14 Central California Coastal Valleys 15 Central California Coast Range 16 California Delta 17 Sacramento and San loaquin Valleys 18 Sierra Nevada Foothills 19 Southern California Coastal Plain 20 Southern California Mountains m ROCKY MOUNTAIN RANCE AND FOREST RECION 43 Northern Rocky Mountains 44 Northern Rocky Mountain Valleys 46 Northern Rocky Mountain Foothills 47 Wasatch and Uinta Mountains 48A Southern Rocky Mountains 48B Southern Rocky Mountain Parks 49 Southern Rocky Mountain Foothills SI High Intermountain Valleys EE WESTERN RANGE AND IRRIGATED RECION cn NORTHERN CREAT PLAINS SPRING WHEAT RECION 21 Klamath and Shasta Valleys and Basins 22 Sierra Nevada Range 23 Malheur High Plateau 52 Brown Claciated Plain 53A Northern Dark Brown Claciated Plains S3B Central Dark Brown Claciated Plains 53C Southern Dark Brown Claciated Plains 54 Rolling Soft Shale Plain cc* Black Claciated Plains 55B Central Black Claciated Plains 5SC Southern Black Claciated Plains 56 Red River Valley of the North 57 (See K) 58A (SeeC) 79 Creat Bend Sand Plains BOA Central Rolling Red Prairies BOB Texas North Central Prairies 81 (See I) CD SOUTHWEST PLATEAUS AND PLAINS RANCE AND COTTON RECION WESTERN CREAT PLAINS RANCE AND IRRICATED RECION 58A Northern Rolling High Plains. Northern Part 58B Northern Rolling High Plains, Southern Part 58C Northern Rolling High Plains. Northeastern Part 58D Northern Rolling High Plains, Eastern Part 60A Pierre Shale Plains and Badlands 60B Pierre Shale Plains, Northern Part 61 Black Hills Footslopes 62 Black Hills 63A Northern Rolling Pierre Shale Plains 63B Southern Rolling Pierre Shale Plains 64 Mixed Sandy and Silty Tableland 6$ Nebraska Sand Hills t* Dakota-Nebraska Eroded Tableland 67 Central High Plains 69 Upper Arkansas Valley Rolling PLains 70 Pecos-Canadian Plains and Valleys | |j 1 NTRAl CREAT PLAINS WINTER WHEAT AND R \NCE RECION 71 Central Nebraska Loess Hills 72 Central High Tableland 73 Rolling Plains and Breaks 74 Central Kansas Sandstone Hills 75 Central loess Plains 76 Bluestem Hills 77 Southern High Plains 78 Central Rolling Red Plains 81 Edwards Plateau 82 Texas Central Basin 83A Northern Rio Crande Plain 83B Western Rio Crande Plain 83C Central Rio Crande Plain 83D Lower Rio Crande Valley CD SOUTHWESTERN PRAIRIES COTTON AND FORACE RECION 80A (See Hi 84A Cross Timbers 84B West Cross Timbers B4C East Cross Timbers 85 Grand Prairie 86 Texas Blackland Prairie 87 Texas Claypan Area I' „ I NORTHERN LAKE STATES FOREST AND —!S_J FORACE RECION 57 Northern Minnesota Cray Drift 88 Northern Minnesota Clacial Lake Basins 90 Central Wisconsin and Minnesota Thin Loess and Till 91 Wisconsin and Minnesota Sandy Oulwash 92 Superior Lake Plain 93 Superior Stony and Rocky Loamy Plains and Hills 94A Northern Michigan and Wisconsin Sandy Drift 94B Michigan Eastern Upper Peninsula Sandy Drift CD LAKE STATES FRUIT TRUCK AND DAIRY RECION 95A Northeastern WisconsIrxQnfi.P***"—.-' * 95B Southern Wisconsin and Northern Illinois Drill Plain % Western Michigan and Northeastern Wisconsin Fruit Belt 97 Southwestern Michigan Fruit and Truck Belt 98 Southern Michigan and Northern Indiana Drift Plain 99 Erie-Huron Lake Plain 100 Erie Fruit and Truck Area 101 Ontario Plain and Finger lakes Region 119 Ouachita Mountains 120 Kentucky and Indiana Sandstone and Shale Hills and Valleys 121 Kentucky Bluegrats 122 Highland Rim and Pennyroyal 123 Nashville Basin 124 Western Allegheny Plateau 125 Cumberland Plateau and Mountains 126 Central Allegheny Plateau 127 Eastern Allegheny Plateau and Mountains 128 Southern Appalachian Ridges and Valleys 129 Sand Mountain 130 Blue Ridge CD CENTRAL FEED CRAINS AND LIVESTOCK RECION 102A Rolling Till Prairie 102B Loess Uplands and Till Plains 103 Central Iowa and Minnesota Till Prairies 104 Eastern Iowa and Minnesota Till Prairies 105 Northern Mississippi Valley Loess Hills 106 Nebraska and Kansas Loess-Drift Hills 107 Iowa and Missouri Deep Loess Hills 108 Illinois and Iowa Deep loess and Drift 109 Iowa and Missouri Heavy Till Plain 110 Northern Illinois and Indiana Heavy Till Plain 111 Indiana and Ohio Till Plain 112 Cherokee Prairies 113 Central Claypan Areas 114 Southern Illinois and Indiana Thin loess and Till Plain 115 Central Mississippi Valley Wooded Slopes \m MISSISSIPPI DELTA COTTON AND FEED CRAINS RECION 131 Southern Mississippi Valley Alluvium 134 | See P) m SOUTH ATLANTIC AND CULF SLOPE CASH CROPS FOREST AND LIVESTOCK RECION 112 (SeeM) 133A Southern Coastal Plain 133B Western Coastal Plain 134 Southern Mississippi Valley Silty Uplands 135 Alabama, Mississippi, and Arkansas Blackland Prairie 136 Southern Piedmont 137 Carolina and Ceorgia Sand Hills 138 North Central Florida R idge [~N~| EAST AND CENTRAL FARMINC AND FOREST RECION 116A Ozark Highland 116B Ozark Border 117 Boston Mountains 118 Arkansas Valley and Ridges □□ NORTHEASTERN FORACE AND FOREST RECION 139 Eastern Ohio Till Plain 140 Claciated Allegheny Plateau and CaUk.ll Mountains 141 Tughill Plateau 142 St LawrencoChamplam Plain 143 Northeastern Mountains 144A New England and Fastern New York Upland. Southern Part 144B New England and Eastern New York Upland. Northern Part 145 Connecticut Valley 146 Aroostook Area CD NORTHERN ATLANTIC SLOPE DIVERSIFIED FARMINC REGION 147 Northern Appalachian Ridges and Valleys 148 Northern Piedmont 149A Northern Coastal Plain 1490 Long IslandCape Cod Coastal Lowland m ATLANTIC AND CUlf COAST LOWLAND FOREST AND CROP RECION 150A Culf Coast Prairies 1S0B Culf Coast Saline Prairies 151 Culf Coast Marsh 1S2A Eastern Culf Coast Flatwoods 152B Western Culf Coast Flatwoods 1S3A Atlantic Coast flatwoods 153B Tidewater Area 1S3C Mid Atlantic Coastal Plain ORIDA SUBTROPICAL FRUIT. TRUCK CROP AND RANCE RECION 154 SouthCerU/al f londa R idge 155 Southern Florida flatwoods 156A Florida Everglades and Associated Areas 156B Southern Florida lowlands Areas 38 45. 50. 68 89. and 132. shown on the 1965 edition, are no longer separate maior land resource areas 1-13 227 was*. SIPTtMIll AGRICULTURE HANDBOOK 2% U S DEPARTMENT OF AGRICULTURE. SOIL CONSERVATION SERVICE &X 3 * t/n no << 12 - / A J I cy-l LAND RESOURCE REGIONS AND MAJOR LAND RESOURCE AREAS OF THE UNITED STATES I w I SOUTHERN ALASKA REGION 160 Southeastern Alaska 169 Southcentral Alaska Mountains 170 Cook Inlet Susitna Lowland 171 Alaska Peninsula and Southwestern Islands m INTERIOR ALASKA REGION 172 Copper River Plateau 173 Alaska Range 174 Interior Alaska Lowlands 175 Kuskokwim Highlands 176 Interior Alaska Highlands m ARCTIC AND WESTERN ALASKA RECION 177 Norton Sound Highlands 170 Western Alaska Coastal Plains and Deltas 179 Bering Sea Islands 100 Brooks Range 101 Arctic Foothills 102 Arctic Coastal Plain m HAWAII RECION 157 And and Semlarid low Mountain Slopes 158 Semiand and Subhumid low Mountain Slopes 1V» Humid and Vcrv Humid low and Intermediate 160 Subhumtd and Humid Intermediate and High Mountain Slopes 161 lava Flows and Rock Outcrops 162 Vcrv Humid Areas on East and West Maui Mountains, Kohala Mountains, and Mount Waialeale 163 Alluvial Fans and Coastal Plains 164 Rough Mountainous Lands 16$ Subhumid Intermediate Mountain Slopes 166 Very Stonv land and Rock land 167 Humid low and Intermediate Mountain Slopes \v\ ttco& S,rr 0F ILLinois -ur *"”* 19B1 HANOb °OK C Z 4 HinoT( 21 9 2531rI