= paTmeses AT i Pew Pork State College of Agriculture At Cornell Gniversity Bthaca, N. VD. Librarp ornell University Libra Forest distribution in the northern Rock PRESS OF MISSOULIAN PUBLISHING COMPANY MISSOULA MONTANA FOREST DISTRIBUTION IN THE NorTHERN Rocky MOUNTAINS Vig. 31. Larch (Larix occidentalis) and pine (P. ponderosa) forest along east shore of Flathead Lake. Undergrowth //olodiscus ariacfolius, Ceanothus sanguineus, Lepargyraca Canadensis, ete. June, UNIVERSITY OF MONTANA. STUDIES Forest Distribution in the Northern Rocky Mountains By J. E. KIRK WOOD Professor of Botany in the State University of Montana STATE UNIVERSITY MISSOULA, MONTANA JUNE, 1922 Bulletin No. 247—-State University Studies Series No. 2 Published bi-monthly at Missoula, Montana. Entered as second-class matter at the postoffice at Missoula, Montana, under act of Congress, August 24, 1912. THE UNIVERSITY OF MONTANA Epwarp C, ELLio1r. Chancellor of the University The University of Montana is constituted under the provisions of Chapter 92 of the Laws of the Thirteenth Legislative Assembly, approved March 14, 1913 (effective July 1, 1913). 7 The general control and supervision of the University are vested in the State Board of Education. The Chancellor of the University is the chief executive officer. For each of the component institutions there is a local executive board. Montana State Board of Education J. M. Drxoy, Governor .-Ex-officio, President W. D. Raykry. Attorner General. Ex-officio May TRUMPER, Supt. of Public Instruction... .-Ex-officio. Secretary Ay Je VIOLETTEygs.. ences. (1922) WHITFIELD SPADN..W..220....- (1924) ... (1922) J. W. FREEMAN... (1923) JOHN DIETRICH.. FRANK ELIEL The University comprises the following institutions, schools and depart- ments: The State University, Missoula Established February 17, 1893, and consisting of The College of Arts and Sciences The School of Business The School of Law Administration The School of Pharmacy The Summer Quarter The School of Forestry The -Biological Station (Flathead Lake) The Public Service Division The Graduate Division The School of Journalism The School of Music Charles H. Clapp President The State College of Agriculture and Mechanic Arts, Bozeman Established February 16, 18938, and consisting of The College cf Agriculture The School of Music The College of Engineering The Summer Quarter The College of Applied Science The Secondary School of Agricultu-e The College of Household and The Agricultural Experiment Station {Industrial Arts The Agricultural Extension Service Courses for Vocational Teachers Alfred Atkin Bo OS Av|dog ., mobsnig © Aquaby mora u hanes SUILUBID AG “yoourys 74490. sapmnogg “NO “BOUSMOUSO iladsipy O or ~« 24ADHO hoa of se ¢c NG 40 CLIMATE 41 May and June are the months of heaviest rainfall, comprising possibly as much as one-fourth the total of the year, and that the months of July, August and September are comparatively dry. At these stations the precipitation during the growing sea- son, from April to September inclusive, represents about 54% to 63% of the total of the year. At some places, however, as at Troy, in the extreme western part of the State, the climate more nearly approaches that of the Pacific Northwest, and of the total annual rainfall (about 23 inches) about 35% only occurs during the same period. On the eastern side of the Divide the rainfall from April to September varies from 62% to 82% of the year’s total. The reason for the heavier precipitation during the months of May and June on the western slopes of the Rockies is doubt- less due to the altitude of the land and the coolness owing to accumulated snows. During these months the snows are rapidly melting, the rivers are at flood, and the air is more heavily loaded with moisture. By the first of July the snows have mostly disappeared, except from the highest peaks, and the tem- perature of the whole region becomes noticeably higher. Through- out the whole summer showers occur among the higher moun- tains, but the valleys and foothills are usually almost rainless during July and August. Most of the observation stations are at moderate altitudes (2,000 to 6,000 feet) so that almost no data are available from the higher ranges, either in winter or summer, Precipitation during the winter is usually in the form of snow. Table 1 presents precipitation data, both rain end snow, and the stations selected from various parts of the State afford representative figures. Strange as it may seem, the snow fall on the main range ef the Rocky Mountains is comparatively light, notwithstanding their greater altitudes. This no doubt is largely due to the Bitter Root and Cabinet Ranges to the west where the snows fall to great depth. The figures from Saltese and Snowshoe are far above anvthing that occurs on the main Divide, being in the neighborhood of 12 feet for Saltese and 23 feet for Snowshoe. Butte, at an altitude of 5,716 feet, and within a few miles of the Divide, has an average snowfall of less than 5 feet. Philipsburg, at 5,275 feet, has 31‘, feet, while 3S 42 FOREST DISTRIBUTION Table 1. Distribution of precipitation in Montana. From data fur- nished by the Weather Bureau. Lotal Precipi- | Length Length tation, of Altitude,| Average of Place Inches, Record, Feet Snowfall,| Record, Annual Years Inches Years Mean Western Montana : | (Pacifie Slope) | | Missoula 15.84 | 33 3212 «| 34 23 Ovando 1836 | 16 } 4101 | 698 | 9 PERO cscs deiedeceess, [ 24.23° | 15 | 18s0 6.3 | 11 Hamilton 10.71 d1 BATS | 38 T Philipsburg 15.55 7 | APTA 42.2 6 Snowshoe 69.70 | 4 | 4500 | 2709 | 38 Kalispell 15.73 | 13 | 2965 42.1 10 Saltese _ 37.63 | 5 3600 142.3 | 5 Plains. | 13.00 r) 2475 | 25.6 11 Butte _.. w! ~TR0S 14 | 5716 | a5 14 Southwestern Montana | | (Atlantic Slope) i | | Bozeman 18.60 | no AS7S TL 6 Boulder 10.00 | iy | 4920 | 304 | 9 Dillon 17.20 | 10 IAT 5S.2 9 Fort Logan 13.01 | 30 | 6000 | aoe Harlowton 15.50 | 417 4165 | i 66 Helena .... .| 121 ! 29 | 4110 » 99 Red Lodge.. | 20.85 6 | 5548 ! 6 Virginia City. I 15.03 23 | 5880 aa Yellowstone Park.......) 18.97 19 | 6200 2], North Central Montana! (Atlantic Slope) Y I | Adel... | 2014. || phe | Sey 10 Babb _.... 2249 a] | 493.7 3 Fort Benton. Las 50 34.2 7 Great Falls. 1048 | 24 411) dt Havre ooeeceeeeees. .! 13.63 30 37.0 | 10 Lewistown _............ 19.77 14 | | 662 10 Northeastern Montana | Chinook 20.02.2022... , 1256 14 2502 DTD s Glasgow | 15 2002 2a | 7 Glendive 1 20 » 2060 2 sea tf ae Jordan | Bl i aetna ae Poplar 147 | 2020 41S 13 Valentine [ [recesses Someta re BOTS MOUS i ca OG é 3 Gc 0a LN rs | STIR 5 LT &6 Go OG Of Le ST GS i 98 Wd ee el 06 Ge 96 NG Ge 6T 98 0 OL OPT) OZ 86 Go «GOL Re 0G ws OOS t re LILONSTTY. to «688 Ge G6 uc 9G EE. Aes) Wieser rer css Tadst ey 82 «68 9g tb SE St 06 GT) Age. Persea ore” HOUTAR TT (ado[Q OTe } BURYUOTY TLLOJso Ay deg ee sine ounr ACTA ady suol}ei1g “UTA 'XBIAL | UNN OXB yy ‘UTA, «'XBIN “UTI “XB ‘UL XB IA “UL XUIA, ‘UOSBIS BSUIMOIS eu at} JO SIJUOUT NIS OY} SULMp vANZWOTY UF SIOZVIS GE AOJ plOI TO sorNzvodetoy Jso.woy PCL JSOUSUL OLE "GY OTIBAL CLIMATE St 90T S& 6OE és GOT 0S y nearly all of the species above ascribed to western origin (30) possibly excepting Lyall’s larch and others ordinarily found only on the highest elevations. It is evident that this range is the main highway for the Pacific species into western Montana. The con- figuration of the land, its low altitude. its proximity to the lake region of northern Idaho. all serve to make this range at once a convenient harbor and highway for the more tender mesophytie species of the Humid Transition. These species as-cnd the west- SOURCES OF THE VEGETATION 71 ern slopes of the Bitter Roots but usually fail to get over, and again to the north the region is inhospitable on account of its altitude in some places and in others on account of greater aridity. Some of the species apparently have come into Montana from the northwest along the Rocky Mountains. Some have a distribution from Alaska to Oregon and in the Rockies to Mon- tana or Wyoming. Others seem to have made their way across from the coast by way of the Okanogan country and the Selkirks. Shaw (57) found in the Selkirk Range most of the species listed above. It is not improbable, as already stated, that formerly conditions were much more favorable for a direct eastward mi- gration across the inland basin which now would be impossible. Certain species in this eastward migration have moved on- ward across the main range of the Rockies. The Continental Divide in its general course and altitude has been discussed under topography. It constitutes the main barrier between the eastern and western floras. Many species, however, have crossed it both from the east and the west. In many places, up to 7000 feet or more the crest is wooded, sometimes with dense forests, more often with scattered pines and junipers, and here and there a bleak, wind-swept, rocky ridge, tenanted only by low, caespitose perennials of xerophytic habit and structure. While the ridge is not uniformly high, the greater part of its length in Montana is 7000 feet or more in elevation, dropping in some of the passes to less than 6000 feet. These gaps, how- ever, are not wide and climatically are quite different from the Coeur d’Alenes farther west. They share in large measure the rigors of the winters which are long and severe in the neighboring heights. At these elevations the summers are short and the growing season two to three months, with great diurnal range of temperature and with nights frequently marked by heavy frosts. The snow usually disappears during the summer except in patches on sheltered north slopes, or in the glaciers which occupy some of the high depressions in the northern ranges. Plants are abundant and over most of the high slopes vig- orous, during the short season allotted to them, but on the whole the region of the high divide is inimical to many species and in general an effective barrier to eastward and westward move- ments. It is interesting, however to note how many of those 72 FOREST DISTRIBUTION plants among the herbaceous perennials which flourish in such numbers in the high mountain parks are conspicuous elements in the spring floras of lower altitudes, and in some species almost to sea-level. Still other factors besides those of altitude and length of the growing season figure in determining the range of these plants and such are found in their moisture requirements and the trying conditions which at all times beset the crest of the main Divide and all exposed places in its immediate vicinity. The continental crest in itself is hardly a barrier of suf- ficient height to prevent transmigrations. Flanked, however, as it is by massive ridges and high parallel ranges. its effect is re- inforved by repetition. The topography offers a succession of parallel ridges rising on both sides to the main Divide. These eut by valleys would have even less effect individually as bar- riers, but they serve to increase the mass elevation and contrib- ute to the general effect upon the climate over a region 250 to 300 miles from east to west. and north and south for some dis- tance beyond the jimits of the region here under discussion. The proximity of surrounding peaks has of course a marked influ- ence on temperature, humidity and precipitation and conse- quently upon the flora of localities, themselves not of great ele- vation. The following species of eastern origin have reached the west- ern slope: Populus tremuloides Salix cordata Nalir candida Ribes americanum “ amygdaloidvs Symphoricarpos orbiculatus It is probable that some of the species have traversed the Rocky Mountain barrier in many places. In the case of trans- continental species in the north their southward extension has doubtless followed along both slopes of the Divide and wherever else suitable conditions offered. These of western or southwestern origin which have reached the eastern slope or the plains are listed below. Some of these have extended their ranges much further than others. Pinus contorta Ceanothus velutinus FPseudotsuga tarifolia Ledum glandulosum Picea Engelmannii Phyllodoce empetriformis SOURCES OF THE VEGETATION 73 Salix Mackenziana Phyllodoce glandulifera * erigua Menziesia ferruginea ** Scouleriana Kalmia polifolia “* glaucops Cassiope Mertensiana Betula fontinalis Gauitheria humifusa Odostemon Aquifolium Vaccinium membranaceunr be Rubus parviflorus oreophilum Amelanchier aliafolia " scopartum Crataegus Douglasis Artemisia camporum Prunus demissa a frigida Pachystima Myrsinites ne cana Rhus Rydbergti The following species seem to have entered from the south- ern Rockies or the Great Basin: Yucca glauca Opuntia polyacantha Atriplex truncata Mammillaria missouriensis Sarcobatus vermiculatus af vivipara Eurotia lanata Gilia pungens Grayia spinosa Sambucus glauca Ribes aureum Aplopappus suffruticosus Rosa Fendleri -LTetradymia canescens “ ultramontana ye spinosa Cercocarpus ledifolius Chrysothamnuus nauscosus a montanus 7 viscidiflorus Purshia tridentata Artemisia tridentata Amelanchier oreophila o spinescens a utahensis Yueca is a common plant in many localities on the plains of eastern Montana. It is usually found on the slopes of the foothills or benches. On the other hand Opuntia polyacantha, also plentiful in the same region, is more abundant on the low flat benches. The most interesting species in the above list is the mountain mahogany, Cercocarpus ledifolius, which is found as far north in the Rocky Mountains as Helena. It is plentiful about the head of the Bitter Root Valley where it has apparently arrived from the hills of southern Idaho across the Bitter Root Range. Purshia probably came from the same source but is somewhat more widely distributed through the Bitter Root Val- ley and sparsely farther north in the Flathead Valleys and T4 FOREST DISTRIBUTION elsewhere. Both of these occupy the highlands. the former the higher rock outcrops. the latter the more gentle southern and western slopes of the foothills. In addition to the species discussed above there remain a number of woody forms as to the origin of which there seems to be no evidence. Some of these dcubtl-ss are indigenous to the region under discussion. others. as Harshberger suggests. may be descendants of species which at some past time had a much wider distribution in the same region. CHAPTER IV. GENERAL Forest ASPECTS, the State, or nearly 50,000 square miles. Over much of this area the landscape is diversified by alternate forest and prairie, and the forests, thus divided, extend further east and west and reach to farther limits than the statement in square miles would implv. The forests are continuous for considerable distances only, as a rule, above certain altitudes (4000-5000 feet) ; below this forests and prairies alternate. The western end of the state, owing mainly to climatic conditions, is far more heavily timbered than the part east of the Continental Divide. From the western boundary eastward the forests in the southern part of the state become gradually more open; in the northern part their volume is better sustained. The rainfall is much heavier in the northwestern part than in the southwestern and the forest development proportionately greater. It presents on the whole a more rugged topography and a greater variety of exposure and shelter. The heavier precipitation is reflected in the drairiage and the frequent lakes, springs and streams pro- vide the mesophytic conditions requisite for heavier forests and a greater variety of species. Prairies are smaller and less nu- merous and continuous forests occur at lower levels, at 4000 feet and above. In the southwestern part of Montana the lower margin of the continuous forest is at least 1000 feet higher than in the north. About the head of the Bitter Root, the Jefferson and the Big Hole the grasslands may extend in some places to 6000 feet or even more. The topography is less rugged, the country much drier, and the forests accordingly more open. The forest here is sufficiently open to admit grasses and other herbaceous plants. The number of shrubs, however, is much less than in the north, both as to species and individuals. Vy | NHE forests of Montana cover about one-third the area of Throughout the region coniferous vegetation is dominant. Yellow pine and Douglas spruce are the prevailing species over the greater part of the region, as seen from the highways. Broad 7 5 76 FOREST DISTRIBUTION leaved, deciduous vegetation, is dominant. as 2 rule, only along the bottom lands and stream banks. It is hardly too much to say that in these places nine-tenths of the forest consists of the spe- cies of Populus, Salir, Alnus and Betula. On the western slope Populus trichocarpa is the only large cottonwood of the river bottoms. It is usually accompanied by Alnus tenuifolia and Betula fontinalis. These three species are found along every stream on the western slope. Along with these. usual or fre- quent, are Populus tremuloides. Salix cordata, 8. fluviatilis, Cornus stolonifera, ete. On the eastern slope and the plains the bottomlands are commonly covered with Popuius Sargentii, accompanied more or less frequently by P. tremuloides, Salix fluviatilis, Betula fon- tinalis, Amelanchier alnifotia, Acer Negundo, Lepargyraea ar- gentea, ete. As to the upper limit of tree growth there seems to be no clearly defined timber line except such as may be due to the desiccating influence of wind. Onlw the crests are usually bare or occupied by stunted pines. spruces or firs and this way oc- cur at relatively low altitudes of 6000-7000 feet, while on neigh- boring mountains of greater elevation forests may be found ex- tending much higher up the slopes. Other factors, like the steep- ness and ruggedness of the land have much to do with the matter of forest occupation both as to moisture and as to foothold. Consequently high and pinnacled crests like the southern peaks of the Mission Range. the Bitter Roots from St. Mary's Peak to the Nez Perce Pass. the precipitous declivities of the main range of the Rockies from Glacier Park to Lewis and Clark Pass, the high summits south of Georgetown, all are barren, due in part to their elevated exposure and to the inhospitable charac- ter of their surface. Elsewhere the high elevations of rounded contour are forested sometimes by pines, firs or spruces. some- times by an open stand of Rocky Mountain juniper (J. scopu- lorum) as shown near the Mullan Pass and the Continental Di- vide southeast of Butte. The principal trees in the forests west of the Divide are Pinus ponderosa, P. contorta and P. albicaulis, Larix occidentalis, Pseudotsuga tarifolia, Picea Engelmannii, Abies lasiocarpa, and Juniperus scopulorum, Locally Pinus monticola, Tsuga hitero- GENERAL FOREST ASPECTS 17 phylla, Abies grandis and Thuja plicata are important, but these are confined to relatively narrow areas. Among the rarer or less important gymnosperms may be included Larix Lyallii, Tsuga Mertensiana, Juniperus scopulorum, J. communis, and Taxus brevifolia. East of the main Divide the forest is more open and assumes a more xerophytic aspect. In the more sheltered canyons good forests are developed, but along ridges and slopes, more or less exposed, the trees straggle out in open stands, with lessening frequency as they descend to the foothills and plains. The num- ber of species diminishes also and only the more hardy are rep- resented. The following are the more common trees on the east- ward slope of the Rockies and the outlying ranges. Pinus flexilis, P. contorta, P. ponderosa, Pseudotsuga taxifolia, Juniperus scop- ulorum, Picea Engelmannii and Abies lasiocarpa. J. communis and J. Sabina also occur, the latter more or less common on prairie slopes. The spruce and fir are confined to the higher elevations; the most common trees at low elevations and about the foothills are the vellow pine, the Douglas spruce and the Rocky Mountain juniper. These are usually present on the bluffs and along the rim-rock at the margins of the valleys of the Yellowstone and the Missouri and their countless tributaries over most of Montana down to the eastern boundary. The higher elevations of land known as the Crazy Mountains, the Snowy Range, the Bear Paws and the Prvor Mountains, and others all support forests of some or all of the above species in greater or less numbers and sizes. However, the forests as such are found only on the mountains and become less and less frequent eastward until the Black Hills are reached. The following sum- mary presents the usual distribution of the species and their approximate altitudes in different parts of the state. In considering the problem of forest distribution it is essen- tial to determine as far as possible the relative abundance of the constituent species and the place which each occupies in the composite formations of which it is a part: Jt is likewise impor- tant to determine the areas occupied by the several species and to relate the species wherever possible to their controlling factors. In connection with the facts of horizontal extension the altitudinal distribution also claims attention, especially in a region where UY SUOLo0g “LELLOSST ND ns ‘§ *ol OUT PSor ' g I ‘KPOATPodsoa TP JO Poa pcou TT PP AMOUR Ppt VOOM HOTEL Y lo AY PUB Y JO JSvorP LOU Ont Spoxprurein MUSQY EL ‘8 fo lop U Ae DOS PSOLOgT GENERAL FOREST ASPECTS 79 differences in altitude are so prcnounced and where soil and climatic conditions present wide variations. The facts of horizontal and vertical distribution are pre- sented from various sources,* with data on the relative impor- tance of the various species. By this means it is hoped to present a conception of the forest as it appears in different parts of this region. It is admitted that the data here assembled can be interpreted only in the most general way. The figures on percentages are to be taken merely as indicators of the approxi- mate proportions of the species in the forest covering of the area in question, and not as an accurate final result. The extent of the area and the extent of the work involved must entail a large probability of error. The figures presented below, how- ever, point to safe conclusions as to the facts of general distribu- tion, which is the purpose of this paper, and from this stand- point it is doubtful whether any further refinement of the per- centage data would be either necessary or profitable. A study of the forests of the northern Rockies brings into view certain aspects of their composition and distribution related to particular topographic and climatic conditions of the different geographic units or sections which they occupy. For convenience, therefore, as well as for conformity with the points of ecological significance the area will be considered by sections determined in accordance with certain physiographic features which either individually or in groups seem to stand in some important rela- tion to the flora. Fifteen such sections are recognized. The first three lie in adjacent parts of Idaho, the forests of which, in their composition, should be considered in connection with those of Montana, as in fact being in large degree the immediate source from which many of the species have found their way eastward into the higher mountains and valleys. The sections are numbered from the west and will be discussed in the same order. They are named for some significant physiographic fea- ture. See Figure 12. The first or Priest Lake Section occupies the panhandle of Idaho and includes the drainage of the Priest River and the Kootenai in Idaho. It extends from the international boundary *The writer wishes here to acknowledge with thanks the generous co- operation of the officers of the Forest Service in District 1, who supplied much of the information essential to this discussion. 80 FOREST DISTRIBUTION southward to include the southern arm of Lake Pend d’Oreille. It includes some of the most mesophytic conditions of the region. A survey of the forest of this section gives the following data: Table 9. Forests of the Priest Lake Section. Species re ee | Range of Altitude Pinus monticola -..........00-.----eeee eee 21-30 9000-5000 OF SMOUMAEFOSO:. <20:22.2.2ss-dinseeche cents 7-10 2000-4000 £6 CONE OTE, weccnc cect cessecessceceeccsseee 2000-6000 66 AbD CATS oe .eeeee ee ieeee ener 6000-7000 Larix occidentalis ......22...2.-..:0------- 18-20 2000-5500 Picea EHngelmannti «20-2... se. 20-25 2000-7000 Tsuga heterophylla ....-..--.------.e-- De 2000-4500 Pseudotsuga taxifolia -........-.----------- 8-15 2000-6000 Abies QrANIS --...-.-..-.2.000 ne cen 5- 2000-5500 6 MAStOCEP DG: sexcsenect-oscccteeccsnceasess 5000-7000 Thiutqe pUcata .ec22- cee ceca uses 9-10 2500-5500 Juniperus scopulorum ........2-------- 3000-5000 oS COMMURIS ..2.2ceeeeeeeeee 4000-6000 Taxis brevifolia 22... ee 2500-5000 The forests of this section vary from open stands of yellow pine and Douglas spruce in some localities. or in others of typ- ical forests of lodgepole, to the heavy forests of white pine, hemlock and grand fir, such as may be found along the bot- toms of Priest River. In this stand is a copious undergrowth of young hemlock and arborvitae, but in many places the forest is too dense to support more than a light undergrowth of broad- leaved shrubs. The second section, here designated as the Coeur d’Alene, lies southeast of the first. It extends for about 130 miles in length and from 50 to 75 in breadth. It lies about equally in Montana and Idaho, across the Coeur d’Alene Range. It includes on the western side the drainage of the Coeur d’Alene and St. Joe rivers in Idaho, and on the Montana side the lower valley of the Clark’s Fork and reaching to the summits of the Cabinet Mountains and Evaro Pass. Its southeastern corner lies near Missoula at the junction of the Bitter Root and the Clark’s Fork rivers, This area, as discussed above, is notable for the richness of its flora. It includes the only stations thus far reported for Tsuga Mertensiana in this region, and in shrubby and herbaceous GENERAL FOREST ASPECTS 81 forms alike is of marked interest. In this section the species ap- pear distributed as follows: Table 10. Forests of the Coeur d’Alene Section, Species | ee | Range in Altitude Pinus MONEMCOlE -2...2..20ce cee eneeeee nee | 2-36 2100-5000 68 MONMEL OSA ...rccecceececcececesereeeeee | 2-25 2100-5000 E COMBOTEG cote ms eae | Qa 7 2100-7500 6 ALDI CAUNMS eects tee tence | 4500-7000 Larix occidentalis 2000.20 6-24 2100-6000 OS VOUT dasie ese ee 7000-8000 Picea Engelmanntt -...--------:0------+- 2-11 2500-5500 Tsuga heterophylla 0.0.0.0. 7 2100-5500 6 Mertensiang .......20.c0ceee ee 4000-7000 Pseudotsuga taxtfolia -......2.. -..----- 13-25 2100-7000 Abtes grandis .... 2-0-0000 sees -12 2100-5000 66 ASIOCOP PA oo. ceceeereeeeeeeeeeeeee 1- 4000-7000 Juniperus scopulorum -....2..2..-2---+ 5-15 2100-5500 Thuja Piicata oo... cece cee ee eee 3000-5000 ee COMMUNIS Loe eee 4000-6000 Tarus brevifolia .....00.2--cec eee 2100-5000 With referenec to the differences of percentage composi- tion and altitude some of the facts are worthy of comment. No- where is the influence of a mountain range more evident. The Coeur d’Alene section as above described is traversed by a water- shed of some 5000 to 7000 feet elevation, extending from north- west to southeast. To the north east flow numerous lesser affluents of the Clark’s Fork on the Montana side, to the south- west on the Idaho side the St. Joe and the Coeur d’Alene rivers flow to Lake Coeur d’Alene. This ridge lies squarely across the path of the rain-bearing winds with the result that the pre- cipitation is greater on its western slope. This, together with the greater relative humidity of the lake region supplies the requisite couditious for the growth of the white pine and the species usually associated with it. On the western slope the white pine may reach as much as 36% of the stand, while on the east it is estimated at about 2%. Abzes grandis forms 12% on the western slope and a neghgible amount on the eastern. Thuja plicata forms 15 % on the western slope, 5% on the eastern. Tsuga heterophylla forms 7% of the stand west of the ridge and a negligible amount on the eastern side. Similarly Engelmann 82 FOREST DISTRIBUTION spruce favors the western slope. On the other hand Pinus pon- derosa, Laris occidentalis and Pseudotsuga tacifolia are far more heavily represented on the eastern side than on the west- ern, forming respectively 2, 6, and 13% per cent on the western side, as against 25, 24 and 25% on the drier eastern slope. Another feature of the difference is in the vertical distri- bution of the species. On the western side the lower limit of distribution is from 700 to 1000 feet below that of the eastern and the upper limits from 500 to 2000 feet lower. It is noticeable also that certain species like the grand fir and western hemlock are confined to a much narrower vertical range on the eastern than the western slopes, falling within a zone of 1000 to 1500 feet in the former and of about 3000 feet in the latter case. These facts can only.be interpreted in terms of the moisture conditions and the lower limits of temperature encountered at the higher altitudes. Several species listed in the table were not of sufficient importance to merit calculation as to their quantitative relations in the forest. The third or Clearwater section lies on the western slope of the Bitter Root Range and embraces the drainage of the upper branches of the Clearwater, its North, Middle and South Forks. The area reaches the summit of the Bitter Root divide on the east and covers about 100 miles from north to south and from 40 to 60 east and west. The course of its principal streams is mainly westward to a junction with the Snake River. In its northern part the forest vegetation is more nearly related to that of the western slope of the Coeur d’Alenes. The white pine, arbor vitae grand fir and Douglas spruce are the dominant species. In its southern part these species appear very sparingly, and the dominant species are yellow and lodge- pole pines and Douglas spruce. In this part the climatic con- ditions are merging into those of the arid plains of the Snake Valley. The marked variations in the percentage of different species will thus be interpreted accordingly. GENERAL FOREST ASPECTS 83 Table 11. Forests of the Clearwater Section. Species | eae ciate | Range in Altitude Pinus monticOla -..2..22.. eee ene 30 1800- 6000 £6 PONAEV OSA 2. ..---e2cceevceeceeeeenne 2-25 1700- 7500 £6 CONFOT ED eae eeneee en erece ects neces 7-40 2500- 9500 66 AUDI CO UTES ence eeee ease eeeneneee 1 5000- 6500 Larix occidentalis 2.0... 7 3000- 5000 STG OMI ooo Rei ae A 7000-10000 Tsuga heterophylla 22.22.0000. 3 5000- 6500 Picea Engelmannta 2... 5- 6 2000-10000 Pseudotsuga taxifolia 2. 14-20 1800- 7000 Abies grandis 222... 2.5-18 2000- 5500 66 UOSVOCOP DA 2. ccceeeteeeceeee 2 4000-10000 Thuja PUicata ........200-00 seen 14 1800- 5000 TUNIPCLUS SCOPULOTWM -.222.20-0-2---2-+ 2000- 5000 ee COMMUNIS oo eeeee eens Tarts brevtfolta .2.2--.ceccececeeeeeee 2000- 4000 Here also in the southern and drier part of the section the various species are found at correspondingly greater elevations. In the first three sections which cover an area 60 miles or more in width from the Canadian boundary to the Salmon River, a distance of about 250 miles are represented the forests of northern and northeastern Idaho lying adjacent to Montana. This constitutes the White Pine Belt of the Rocky Mountains. With the white pine are the species usually associated as men- tioned above and the strip is favored with more ample precipi- tation and higher relative humidity than the areas lyine farther to the east. Although the species typical of this belt do oecur in the sections subsequently to be treated they are not except in localities, a dominant feature anywhere over large areas. These conditions are almost entirely limited to the valleys of the Flathead and the Kootenai. The Kootenai Section, No. 4, covers the area drained by the Kootenai River in Montana, about 3200 square miles. This river crosses the international boundary and enters Montana near the 115th Meridian, flows south about 50 miles and turning sharply to the northwest, recrosses the boundary about 60 miles west of its first crossing. The southern boundary of this sec- tion is the summit of the Cabinet Range, the eastern the divide between the Kootenai and the Flathead, sometimes known as the 84 FOREST DISTRIBUTION Flathead Mountains. The Cabinet Range rises, especially at its eastern end to heights of 8000 to 9000 feet, rugged and pic- turesque. The Flathead Mountains are lower. In the bend of the Kootenai lies the Purcell range, only its southern end reach- ing into Montana. The range is fairly even in height except a group of sharp summits which rise to 7500 feet near the south- ern end of the chain. Table 12. The Forests of the Kootenai Section. Species | Sanne eeadion | Range in Altitude Pints PONACr OSA -2...22-eeeeeneeeeee ene 9 1900-5000 BO" POTTNCOLG: excexscies cette 3 2200-4000 WE CORLOTE G22 sanes seta vaa ees 17 1900-6000 £e GUDICQUIIS © eectcetent ecu nteenn co 5000-7000 Larter occidentalis ..2..2--.2---02------- 21 2000-4000 OS SEY QUGN ao eS al 7000-7500 Picea Engelmannti 220.00 | 21 2000-7000 Tsuga heterophylla ..........222..--------- 14 3000-4000 ADCS SG TORCIS: 2. coopera cetera 14 3000-4000 * lasiocarpa 2200-7000 Pseudotsuga taxifolia -......-.-----2------ 18 1900-5000 LG DUCA O Bic caps ceceeeag ee 2200-3000 Juniperus scopulortm 2.2. ee COMMUNIS eee eeeeeeeeennee Tarus brevifolta 2222 Most of the Kootenai section is heavily forested. In the narrower valleys, on low flats and about lakes are suitable con- ditions for the white pine, arbor vitae, grand fir and hemlock, on some of the upper benches are extensive pure stands of lodge- pole pine, sometimes of young larch. The hills are often cov- ered with open growths of vellow pine. The fifth, or Flathead Section, covers the drainage of the Flathead River, including the North, Middle and South Forks and the Swan river. It extends its northern line 60 miles along the Canadian boundary and reaches south 180 miles to the extreme sources of the South Fork. Its western margin joins the Kootenai Section. its eastern follows the crest of the Conti- nental Divide. It includes a part of Glacier National Park. The Flathead Section is one of the most significant of Montana, both in its topography and its vegetation. It includes several high and rugged mountain ranges. some of them bearing gla- GENERAL FOREST ASPECTS 85 ciers. The marks of previous glaciation are extensive and con- spicuous. Numerous lakes, large and small, are fed by cold mountain streams, many of which flow from glaciers or perpetual snows. There are many cirque basins occupied by deep, cold and dark waters and fringed by forests of fir and spruce. Table 13. Forests of the Flathead Section. Species | compagition| Range in Altitude Panis MOnteCola 0. ee eee enn 3.5-11 3000-5000 €6 PONrOsa eee eee 2.0 3000-4000 OES «SCONE OIE Go Resco oes ounces 1.0-14 3000-6500 6 LD CAUSE olen eee 5-1 4000-7000 Larix occidentalis ........2.....20000-----) 35.0-50 3000-5000 EY QUAG aia oe ered 5000 Picea Engelmanntt 2.000.000.2000 90.0-23 3000-6000 Tsuga heterophylla 2.2... 1 3100- Pseudotsuga taxifolia 0... 11.0-17 3000-6000 Abies grandis -.2..2--. seen 1 3000 TCC) 1) 1.0 3000-7000 Thuja Plicata, 2...2..ecccccccereneeeeeeeeee 17 3000-5500 Juniperus scopuUlorunr 22-2 3000 oh COMMUNAS ..2..202ececeeeeeeeeeee 3000-6500 Taxus brevifolid ........21ceccecceeene ee 3000-6000 In this section it will be observed that the white pine, grand- fir, hemlock and arbor vitae are still present but in greatly reduced amounts. Larch and spruce are the main species with lodgepole pine locally dominant. The white pine formation appears usually in the narrower valleys and canyons, protected from excessive influence of wind and sun. The essentially moist condition of the soil is maintained, and atmospheric moisture is relatively high. While the white pine is a less common tree than in some other sections, vet some of the largest trees are found, one on McDonald Creek in Glacier Park measuring seven feet in diameter. Hemlocks also reach a large development in Glacicr Park, as in the case of a grove near Avalanche Basin, where some of the trees are three feet or more in diameter. The ranges in altitude will be noted. In nearly all of the species the lower limit is near the lowest possible altitude in the section. The upper limit in some of these cases extends to the uppermost altitude habitable by trees. This range differs but little in different parts of the section. 86 FOREST DISTRIBUTION The sixth section includes the Bitter Root Valley, an area of about 3000 square miles. It is bounded on the west by the summit of the Bitter Root Mountains and on the southeast it reaches to the crest of the Continental Divide. On the east its margin rests upon the top of the divide between the Bitter Root River and Rock Creek. Table 14. The Forests of the Bitter Root Section. T Species Gennes iBion | Range in Altitude Pinus PONdCTOSG ...1.22.220220--2-222 eee | 32.0 | 3500-7000 ONTO Er science Pc oc ad » 40.0 | 3500-8000 * albicaulis 2 7500-8500 “* monticola sat Larix occidentalis 2..22...22..10-------- 3 3500-5000 Be PAPA CU EE cascete Dante 7300-9000 Picea Engelmannii ........ 1.6 3500-7500 | Pseudotsuga tacifolia ..... 242 3300-7000 ‘ Abies lasiocarpa ..........-- 3000-8000 grandis 2.2... 4000-5000 Thuja plicata -.....-.2---------- 4090-5000 Juniperus scopulorum -.--....------ It will be observed that the prevailing species in this sec- tion are those adapted to drier conditions. viz., the yellow and lodgepole pines and the Douglas spruce. All others are in a small minority. The species of the humid forests. the white pine and its associates. are now mostly confined to the upper canyons of the Bitter Root Range. This conforms exactly to the climatic conditions of the section. The Bitter Root Valley has an annual precipitation record of 10.71 inches. representing the average of a good many years of observation. This is a lower figure than is shown at most of the plains stations in eastern Montana. They are, however, the observations at only one sta- tion that of Hamilton near the center of the valley. It is easy to understand this condition since the whole valley is sheltered on the west by the lofty Bitter Roots, which effectually intercept the rain bearing western winds. The temperature of the Bitter Root Valley is, moreover, usually a little higher than that of the neighboring localities, which must further influence its water supply. The lower limits of vertical distribution are considerably GENERAL FOREST ASPECTS 87 higher here than in the preceding sections, a fact correlated with the dryness of the region. The floor of the valley is almost de- void of the species cited and the foothills are mostly bare, rising to the scattering pines at about 3500 feet. The whole section is distinctly in contrast to the northern portion of Number 3 on the opposite side of the Bitter Root Range. The Hellgate Section is the seventh of the series. It em- braces the drainage basins of the upper Clark’s Fork (formerly called the Hellgate) and the Blackfoot. On the east and south it reaches to the Continental Divide, which forms a huge are about the heads of these streams and their principal tributaries. The western limit of this section is the Bitter Root Valley. The whole area is nearly 8000 square miles. It rises graduallv to the eastward for about 80 miles, from an altitude of 3200 feet near Missoula to 6000 to 8000 on the crest of the Divide. It is a region of comparatively light rainfall and moderate tempera- tures. Prairie and forest alternate according to slope and ex- posure and the forest is often open and the trees of medium size. The upper valley of the Blackfoot widens out at 4000 feet into a broad basin twenty miles or more across, treeless and rela- tively arid. The upper Hellgate valley presents much the same appearance. Much of both basins is covered with glacial gravels, and drumlins are common especially in the valley of the Blackfoot. The grass range is extensive, and the rolling foothills gradually merge into the wooded slopes which extend from 4000 or 5000 feet to many of the high sum- mits. Table 15. Forests of the Hellgate Section. Species Garmotticion | Range in Altitude Pinus PONAECL OSG --..2---2.22-2--2002eeeen 3.5- 3500-7000 6 CONFOTEG een ee eeeeeeeeeneeeeeeeeenes -72 3500-9000 66 @bbicaults 2. ieee 1.0- 6000-9000 Larix occidentalis 22.20.2200. -1------ 5 3300-6000 OO TSUQUING ecko ietnscst nstied ea 7000-8500 Picea Engelmannti 22.22.2220 2.0- 3 3300-9000 Pseudotsuga taxtfolta .......2.2..-..2---- 15.0-2% 3300-7000 Abies lastocar pod -...22..2-20c1ceereeee 1.0- 3500-9000 Juniperus scopulorum 3300-5500 bi COMMUNIS oe eeeeeereeeeeees 3400-5500 838 FOREST DISTRIBUTION In the previous cases the percentage composition was in terms of volume estimates; in this it is in terms of the forested areas. In neither case does it give more than a general impres- sion of the relative importance of each species. The figures on this area are with reference to the ‘‘type’’ as it is called 5x the Forest Service, which means practically the same as the terms society and association in the ecological sense, as where species in pure or mixed stands assume certain characteristic aspects under the control of climatic and physiographic influences. In this case it will be seen that the leading species are lodgepole pine, Douglas spruce, larch and yellow pine. The larch is confined chiefly to the western side of the section, and to northern slopes and creek bottoms. The yellow pine. often mingled with Douglas spruce, occupies the southern slopes but with its lower limit at 4000 to 5000 feet elevation. The lodge- pole is found in dense and extensive stand at high elevations along the main range of the Rockies. Pinus monticola and Abies grandis are rare in this section and are found only in isolated localities; however. limited stands of white pine are to be found, as in the upper end of the Blackfoot valley close to the Divide, on the Clearwater and elsewhere. Where the moisture is suffi- cient in the soil, that of the atmosphere seems deficient or the temperatures too low. For the most part this section seems to be beyond the easternmost limits of the white pine, grand fir, western hemlock, arbor vitae and western yew. The eighth division of the Rocky Mountain forest will here be called the Sun River Section. Its western margin lies along the continental crest from the Canadian boundary to the 47th parallel in a strip 20 miles or less in width. It lics on the east- ern slope of the Divide in the narrow timbered zone between the mountain ridge and the prairie foothills. Its northern portion includes a part of Glacier National Park. The Sun River Valley is heavily timbered. but the Teton and Marias Rivers traverse elevated plains and prairies. GENERAL FOREST ASPECTS 89 Table 16. Forests of the Sun River Section. Species Leemmtciaen | Range in Altitude LUNUS CORTOTEA eee ceeeeeeeeeeeee eee 50 4000-8000 OY PORLBUBN LDS ae eters es acna ds kn 10 5000-8500 Picea Engelmanntt 2... 20 6500 Pseudotsuga taxifolia —........02002.---. 15 7500 Abtes lasiocarpa ......... -...- jaescese 4 8500 The above are the principal species found in this strip and their approximate proportions. The larch and whitebark pine are together reduced to about 1% of the entire stand. They are present only near the top of the Divide where they have dropped over from the western slope. It is probable that Pinus ponderosa is also represented, though sparingly, as well as small quantities of Juniperus scopulorum, J. communis and J. Sabina. The sit- uation on the whole is one of low rainfall and of general difficulty for forest species. The Belt Section (No. 9) extends from the top of the Con- tinental Divide near the head of Clark’s Fork eastward over 100 miles including the Big Belt and the Little Belt ranges. From north to south the area extends roughly from Great Falls to the Three Forks of the Missouri, about 120 miles. This sec- tion is very largely prairie. Only the higher elevations are wooded, so that the forest for the most part lies above 5000 feet. Besides the Belt Ranges are several othcr more or less elevated masses, the Highwood Mountains and the Little Rockies, which also are forested. Table 17. Forests of the Belt Section. Species lena e opera | Range in Altitude Pints CORtOTtA -..2..2---2-22020eeeeereee 56-84 5500-8200 66 PONEEL OSG ~-.12-222--2-20ereeeeeee en 7-15 7500-8300 BE PLOY Sf tt 8 at is sc aaa 7500-8300 | wh ibnemr ie ea 7000-8300 Picea Engelmannti .....2-220000------- 2- 6 7000-8000 Pseudotsuga tacifold ....-..2---------- 5-44 6000-7500 | Abies lasiocar pa, 1.222222... 7000-8300 The percentages here are in the area covered by the several species. The variations in the percentages indicate their relative 90 FOREST DISTRIBUTION importance on the different mountain ranges in this section. Leiberg (32) gives the volume per cent for the different species in the Little Belts as follows: Pitts, FleD AS: se. 2 serveces eet eS 8.2 CO GUDICONITS, 20 oe) css eter en sere 909 SO ° SCOWEGREG. Seacsces santas och cb ian eget au eee 34.2 FE AD ONGEROSG woascosss 25S te iO ones OT Picea. Fngelmaqnnit ..cc:sccncexexisseesce ee 114 Pseudotsuga tarifolia -....2.22..2-.:0-.0-0---- 44.7 Abies lASiOCANPA «...---------2---0- ene 14 In addition to the above species it is probable that Juniperus scopulorum and J. communis are likewise present. Isolated as most of the outstanding ranges are, the influence of the climatic conditions are readily felt, so that the lower timber line is fixed at elevations unusually high. In sheltered canyons and valleys. however. many of the species may descend to where they open out upon the plains. The Three Forks Section (No. 10) is an area 140 miles from east to west and 100 miles in round figures from north to south. The westward direction of the Continental Divide from the vicin- itv of Butte, and its wide curve to the south and thence to the east to Yellowstone Park forms a huge embayment, drained by the three main sources of the Missouri, the Gallatin, the Madi- son and Jefferson rivers, which push their ultimate branches to the high walls of this huge amphitheater. The western por- tion of the basin is known as the Bighole. particularly that part drained by the Bighole River which is the main western branch of the Jefferson. The basin is traversed by several low moun- tain ranges, and in altitude most of its floor lies above 5000 feet. The country is largely prairie and only the highest elevations are forested and these with few species and comparatively meager growth. It is largely glaeiated and climatically dry and cold. GENERAL FOREST ASPECTS 91 Table 18. The Forests of the Three Forks Section. Species eee cei | Range in Altitude LUNus PONAECLOSA .....-2-.20.2eeeeeeereeeeneen 5600- 6500 WP SCOMEOV UD pict oce Corio a cog 60-75 5600- 8500 66 albicaulis eee 14 7000-10000 BO PCTS os tk AS NN Ne a ae SS cel 7000-10500 Picea Engelmannit -..2..-222:.0-c--- 4-5 5500- 8500 Pseudotsuga taxtfolia ....22-2.2.0---- 20 5000- 8000 Abies lastocarpa, «....2..2-.--2:20--0---- 7000-10000 Juniperus scopUulorwm, .......2--2------ 6000 ee COMMUNIS......- 200 --senes The forests are confined to higher elevations mostly above 6000 feet and consist mainly of lodgepole pine as the main zone, merging below into yellow pine and Douglas’spruce and above into limber and whitebark pine, Engelmann spruce and alpine fir. In some places the lodgepole forest covers the Divide at 7000 feet. Only as the summits rise to greater heights does the character oftheir forest covering assume the aspect imparted by the spruces and firs, though in the sheltered canyons these genera may descend much lower. The Yellowstone Section (No. 11) occupies the upper Yel- lowstone drainage in Montana. From the uorthwest corner of the Yellowstone Park it extends 120 miles along the southern boundary of Montana, and 100 miles to the north including the Crazy Mountains. In this section, covering some 10,000 square miles, are the highest peaks and some of the most rugged topug- raphy in Montana. From the Absaroka and the Beartooth ranges flow numerous streams northward to the Yellowstone River, which from the north gains a few affluents from the Crazy Mountains. To the west the Gallatin and Bridger ranges form the watershed between the upper Yellowstone and the Mis- souri, in altitude varying from 5000 feet in Bozeman Pass to 10,000 on some of the higher peaks. In the Absarokas the high- est peak reaches nearly 13,000 feet. The Yellowstone Valley ‘is broad and treeless, except along the immediate stream bottoms. The coniferous vegetation occurs above 5500 or 6000 feet where a fringe of limber and yellow pine, Douglas spruce and juniper marks the lower edge of the forest. Between 6000 and 8000 feet the lodgepole pine forms 92 FOREST DISTRIBUTION almost the whole of the forest, but above 8000 feet gives place to white bark pine, alpine fir and Engelmann spruce. The upper timber line occurs at elevations of 9300 to 9800 depend- ing on direction or exposure. though on the Beartooth Mountains toward the east it ascends in places to 11,000 feet. At the timber line Engelmann spruce is the dominant and most conspicuous species. Table 19. The Forests of the Yellowstone Section. Species ee ee Range in Altitude | Pinus PONM OOS eee eee | av0O | | ** contorta | 30-60 ; 6000- 8500 flerilis 0... wen i = §000- 8000 * albicaulis ois 7500- 9000 Picea Engelmannii..... 00000. 1... : 15 6000- 9000 Pseudotsuga tarifolia ...000000000..-... 21-30 . 5000- S000 Abies lasiocarpa es 7000-10000 Juniperus sCOpulorum —.....20.c00-200--- | TAN, The above species are all represented in this section. though some of them very sparingly, and the yellow pine probably the least of all. The above figures were tabulated from Forest Service data and have the advantage of being the most recent obtainable. Leiberg, (31). however, gives a somewhat different and more detailed account as follows: TERTIUS LR LUG ct semerocote aera oes 23S RES COME OTE ea wih aah a theca Rare 45.6 BES DONO CROSOE ine ae Beer eae ve araas 003 ES GUD UC GINS: siese sets ka oan ature saan Ss 5.3 PAGER FENGOLMNANIOE cocci wo ciecs mesg eccceeeaneeys 21.8 Pseudotsuga tartfolia 222.2. 122 ADEs LOSUOCOY PO eesti coos eae 1 In this estimate trees are considered of three inches basal diameter and upwards. Leiberg states that the lodgepole pine forms fully 75“ of the forests below the subalpine zone, and even as much as 90° in its own proper belt akove the lower fringe occupied by Douglas spruce and limber pine. Leiberg cites also the occurrence of Pinus monticola in one locality in the Absarokas but this is very doubtful, as it there would appear to be in a locality far removed from its known range and in the only position reported for it cast of the Divide. As it is not GENERAL FOREST ASPECTS 93 now known to the Forest Service in that locality and as the con- ditions would seem to be so unlike those of its usual habitat, it would seem that Leiberg’s report is in error on this point. Engel- mann spruce and Douglas spruce are common trees throughout the section in their particular zones. Though the latter is lim- ited to a lower belt, the former is found as low as 6000 feet and from there up to timber line. The next is the Bearpaw Section (No. 12) including for the most part the Bearpaw Mountains and the Sweetgrass Hills, with altitudes of 6000, 7000 and 8000 feet respectively. These have scant forests of lodgepole and yellow pines, and Douglas spruce. Two junipers (J. Sabina and J. communis) oceur in this region. This section covers about 20,000 square miles, ex- tending along the northern boundary about 200 miles and south- ward about 100. It embraces a good deal of the Missouri Valley and the upper sources of the Milk River, besides portions of the drainage of the Marias and the Teton. It is mostly prairie with elevation ranging from 3000-4000 feet. The forests where pres- ent are found mainly above 5000 feet. The Snowy Section (No. 13) is occupied mainly by the Snowy Mountains and the sources of the Musselshell River. Some of the peaks of the Snowy Range rise to an altitude of 8000 feet. Thev are in fact the farthest outpost of the high mountains in Montana east of the main Rockies. They, like the Crazy Mountains and the Belts, are forested only above 5000-6000 feet. Only four species are here conspicuously represented. These are: Pinus CONCOTEG -.2-2.2.222202e-eeceeeereeeee teens 76. % 66 PONACTOSA «--------sseeeenseeeeceeseceeceeeeeeeeeee 13.5 Picea Engelmanntt «...2..2.-22:2.2ceeereeee eee 6.5 Pseudotsuga taxvifolta 1.2.2.2... 4, These figures, however, are for area covered and not for volume. It is probable also that Abies lasiocarpa, Pinus albi- caulis, Juniperus scopulorum, J. communis and J. Sabina are sparingly represented. The 14th, or Bighorn Section, covers a few forested areas in southeastern Montana. Various southern affluents of the Yellowstone, including the Bighorn and Powder rivers drain these hills which reach altitudes from 3000-3800 feet. Here also 94 FOREST DISTRIBUTION most of the country is prairie, but in the hills especially in the ravines and canyons the few forest species are distributed at all altitudes. On portions of this area the yellow pine (P. pon- derosa) is reported as forming 95% of the stand and Juniperus scopulorum about 2%. J. communis is also reported. In the 15th, or Missouri Section, no forests of any conse- quence occur. The margins of the benches a ove the river valley are occupied by a sparse growth of Pinus ponderosa and Juniperus scopulorum and the isolated elevations here and there are similarly wooded. Reviewing the facts on general distribution as above stated. several conclusions are evident. In the first place the species decrease in numbers from the west toward the east. until of the fifteen or more gymnosperms of the Idaho forest only four or five appear near the eastern border of Montana. With the decrease in the number of species comes also a decrease in the volume of the forest. The same cause which limits the forest flora to the more resistant species likewise limits the volume production. viz., the lack of sufficient moisture. Again it will be noted that the altitudinal range of the species in most parts of the region is very wide. The influence which tends to nar- row the vertical range of distribution is again the influence of scant rainfall and the other conditions which tend toward a xerophytic environment. Such influences not only narrow the vertical range, but push the lower limits of forest distribution further up the mountain slopes. CHAPTER V Forest ZONES AND ForMATIONS, in the Hudsonian, Canadian and Transition zones of Merriam (43). Sometimes the Hudsonian and Canadian are called the supalpine and montane zones respectively (55). The Transition is confined mainly to the foothills, valleys and plains. The Upper Sonoran, if it extends into Montana at all, is confined to the lowlands and benches along the rivers in the plains and bears little relation to the forests. The zones as such, however, are more easily defined by given sets of condi- tions than by the species which are supposed to represent them, since few species are so clearly limited by temperature, either in latitude or altitude, as to be plainly identified with either zone. This is especially true with reference to the middle zones in this region, viz., the Transition, the Canadian and the Hud- sonian. The upper Sonoran and the Arctic-Alpine, as repre- senting the extremes of conditions, are the more clearly recog- nized by some of their species which, being at the extremes of their ranges, are mainly excluded from the other zones. Such are the Yucca and the cacti of the former and the dwarf willows of the latter, although even some of these may transgress their allotted limits. Many plants which Cary (11) cites as marking the upper Sonoran of Wyoming occur in neighboring parts of Montana. Among these may be mentioned the following: Lf | NHE forests of the northern Rocky Mountains are included *Populus occidentalis (P. Sargenti) Yucca glauca Hg acuminata Opuntia polyacantha *Saliz amygdaloides *Plantago Purshit ‘fluviatilis *Artemisia tridentata Five of these, however, (*) are so widely distributed in Montana, and in such varied conditions, as far to exceed the pos- sible limits of the Upper Sonoran Zone. The Transition Zone is a belt of wide vertical range and 95 96 FOREST DISTRIBUTION diversity. It extends from the benches and plains at 2000 to, 3000 feet to the level of continuous forest at 4000 to 6000. It may thus from cne part cf the region to another cover a vertical distance of 4000 feet. It is largely the foothill country. varying with exposure and location from arid to humid conditions, inter- rupted and divided here and there by descending extensions of the montane forests. Im some places it is the bunchgrass (Agropyron spp.) or the bunehgrass and sagebrush (Artemisia tridentata, A. cana, A. frigida, etc.) or these merging into open stands of Rocky Mountain juniper, or yellow pine or Douglas spruce, or all of them intermingled. Again it appears in areas in composition similar to the Pacific Coast Humid Transition with hemlock, grand fir, arbor vitae, western yew and many other forms commonly found in the forests of the low lands of western Oregon and Washington. The humid forest is the more rare and is developed where neighboring areas are elevated to the degree necessary to induce condensations and abundant rain, where the valleys are not too wide and where the proximity of considerable bodies of water and the structure of the soil combine to afford the requisite conditions. These are forests of moderate or low elevations, 2000-4000-feet. The forests of the Transition alternate frequently with prairies and the vege- tation of this zone extends in the southern part of Montana about 1000 feet higher on the mountain sides than it does in the north, reaching even to 6000 feet. The forest of the foothills (Transition) merge gradually into those of the montane (Canadian) belt. Especially in the humid forest is the line of demarcation uncertain. Reference to the tables under the discussion of general aspects of distri- bution will show that in most sections the vertical range of many species may be 2000 to 4000 feet and in different parts of the state some species may be found at altitudes varying from 2000 to 9000 feet. The following figures indicate the approximate extent of vertical distribution of the species cf gymnosperms within this region. as far as at present known. FOREST ZONES AND FORMATIONS 97 Table 20. Ranges in Altitude. Species [Aide | “aineeae Pinus PONderOsa oe eee 1,300 7,000 COMPUTE GE, les ea 1,900 9,500 £6 MONE COLA cece eee 1,800 6,000 £6 abbicaulis 0c 4,000 11,000 OS OPVORUAS sscteectcitet as ote od 3,000 10,500 Lurie occidentalis 2... 2,800 7,000 BDA QU aos aces ptawacsontinees 7,000 10,000 Picea Engelmanntt 0c cece 2,000 11,000 Tsuga heterophylla ..0.0..0.0020000002.- 2,900 5,500 66 Mertenstana o.ccecccceccccc eee 4,000 7,000 Pseudotsuga taxifolta 2.0 0... . 1,900 8,000 Abtes grandis 2... ..cceceeccee cece een 2,000 7,000 66 VASIOCOP PA oo eeeeceeeeeeee eee 2,000 11,000 Thuja Plyredtae cece eee eeeen ene 2,000 5,500 Juniperus scopulorwm 2.0.2.0... 1,900 6,000 ie COMMUNIS —W... sonar 3,000 6,500 ee SQDind o.oo oeeeeoecee eee 2,900 4,000 Taxus brevifolia 0000000 1.900 5,000 The wide range in altitude of the species here indicated and the fact that at all elevations between 4000 and 6000 feet, within their range and habitat thev are likely to be intermingled makes difficult the distinction between the Canadian and Hudsonian zones, or the montane and sub-alpine, if indeed there is any in this region. The term sub-alpine, when used herein, is intended to designate the forests immediately below the higher crests. The trees of this belt, however, have few species which do not descend to the foothills. The alpine fir, Abies lasiocarpa, is the most conspicuous tree at high elevations, but is commonly found in the canyons about Missoula at about 4000 feet and descends at least to 2000 feet along the Kootenai in Montana. The same may be said for the Engelmann spruce. The white bark pine, (P albicaulis) also a common timber line tree, is abundant down to 5000 feet in Glacier Park, and scattering individuals may be found occasionally in the valley of the Clark’s Fork and its trib- utaries at 3500 feet or less. The only tree of this region which is confined to the highest elevations is Lyall’s larch (LZ. Lyallit) but this species is found only in a part of the Bitter Root Range and along the highest summits of the main divide. The black J (MIN!) ‘Symon snjouargy MUunadad saqry ‘Duns “Pr Mormon nisrmapepe “ds wap yp ‘vsomds viva ‘snpppnotitoa sngpqooiwy copys pun ALQ “quo ‘oAtpuopH avou spuvipegr “EL “Fhy FOREST ZONES AND FORMATIONS 99 hemlock (7. Mertensiana) is of still narrower horizontal range, being found in this region only in a small part of the Bitter Root and some of the mountains of Northern Idaho. Ordinarily a tree of the high mountains it was found by the writer in the vicinity of Wallace at: 5000 feet in association with Pinus monticola. Juniperus communis, which forms extensive low thickets at 6500 feet in Glacier Park, is common about Flathead Lake at 3000 and elsewhere at various altitudes. Of the undergrowth much the same may be said.