tT beSedcheO T4cT E UTM siee it sbetiey isseat it ie + esirtas ; babe tess if Ht i si Frhstn rites i +f 3 fittt ste tritee Bi t aati Be pittesttt ¢3 is i aes attr ita ait HK Hs Hat hei! 33 sagt si Ag be Feseteie! ie 1a, aii eeu eeet ae Cea st bar y Aare a! | r ee sa Te ee GO Fab http://www.archive.org/details/forestdistributi0Okirkuoft t > 2 “fi FOREST DISTRIBUTION IN THE NORTHERN Rocky MOUNTAINS maw ia ds 4 a , ‘ ponderosa) pine (P. nde ind ‘ t occidentalis ) Flathead sanguineus, Lepargyraea Canadensis, etc. ( La ria Larch +1, Holodiscus owth ‘rer U wake. I of shore t along « ariae folinug. fore June. Ceanothus UNIVERSITY OF MONTANA STUDIES Forest Distribution in the Northern Rocky Mountains By J. E. KIRKWOOD Professor of Botany in the State University of Montana etl id Se sy LS 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. «# LLU THE UNIVERSITY OF MONTANA _ - EpwaArp C, Ev.idrr, Chancellor of the University Ries bl [< The University of Montana is constituted under the provisions of Chapter _ ver $2 of the Laws oo as ange Legislative Assembly, approved March 14, i 3 fective July 1, ji eT. Perea enarel comtro? and supervision of the University are vested in the | State Board of Education. he Chancellor of the University is the chief executive officer. For each of the component institutions there is a local executive board. Ss . Montana State Board of Education “J. M. Drxon, Governor Ex-officio, President W. D. RANKIN, Attorney General Ex-officio May TruMper, Supt. of Public Instruction Ex-officio, Secretary A. J. VIoLerre (1922) WHITFIELD SPAIN...............-.. (1924) SYDNEY SANNER (1922) J: W. WREEMAN.........ca5ee (1924) Cc, H. Foor (1923) JOHN DIETRICH (1925) R. C..LINE.... (1923) FRANK ELIEL (1925) ae 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 Publie 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, 1893, and consisting of The College of 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 Atkinson, President The State School of Mines, Butte Established February 17, 1893 Course in Mining Engineering Course in Metallurgical Engineering Bureau of Mines and Metallurgy George W. Craven, President The State Normal College, Dillon Established February 23, 1893, and consisting of The Teachers’ Certificate Course The Two-years Course The Three-years Course The Rural Teachers’ Course The Course for Supervisors The Teachers’ Service Division Sheldon E. Davis, President For publications and detailed information concerning the different schools and colleges address the president of the particular institution concerned. Communications intended for the Chancellor of the University should be ad- dresssed to the State Capitol, Helena, Montana. PREFACE It is the purpose of the following pages to present a general account of the forests of a region comprising about 175,000 square miles lying across the Rocky Mountains south of the 49th parallel and marked by great diversity of topography, soil and climate. The many factors involved in the development and maintenance of the present physiognomy of the vegetation merit careful study, both as to the sources whence its component parts have been derived and as to the agencies and conditions at present effective in their local movements and inter-relations. It is designed to open the way to a critical study of this area and to emphasize the point of view from which this and all other such studies should be approached. The usual approach to the study of problems in ecology, both in matters of association and succession and of local and general distribution has up to the present time been mainly from the side of the physical factors involved, and hardly, if at all, from the standpoint of individualities of the species con- cerned. It is the intention herein to lay particular emphasis upon the latter and, while taking account of the climatic and topographic influences, to stress those characteristics of the most important species as far as known, as furnishing the clue to the solution of problems of competition and dispersal. It is but a truism to say that the fuller the knowledge of the specific pe- culiarities of a plant the more may its place in the flora be understood. Acknowledgment of valuable suggestions and criticisms of the manuscript by Prof. John W. Harshberger of the University of Pennsylvania and Dr. Forrest Shreve of the Desert Laboratory of the Carnegie Institution of Washington is due and is hereby gladly rendered. J. E. KirKwoop. Missoula, Mont., May 1, 1922. 1s i eae —— CONTENTS Page DEEN ONS ERECSSE 1 Se PO is SE cae eh 9 OR, a ee 15 UNOS ES SIT A et ce io UR eA Se ET 15 NW GRETA LSE GS cola Oey 2 Sic ene ee Ce OO 16 Later collectors........... so gp ht aR I ee, re ae EA 19 MMe I IeMEL UO LPAV ON oo oe ee 20 acy TRE RR? aa eke 24 mountain ratiwes and altitudes...........<.-.-...00c.2.2 elas. 24 Ree eM RIBS 2 a i ee Be EO EUS aE ae ee A a 35 a SSS 2 SNE ena ON a oc ONL ae 39 (TA INES 1 ou UNG yA Re EO Ege SAU RR PE 39 eA RMI ENE 2 oe on Fen cosh Ueber keane oa 45 TNO EERE Ol RON Se PLO OE 49 ST SSE HIG AE oo 62 PERC MEIRMRM Ye 0s res kare a sy es 62 MAIER RE re fe oe es ear ng Ma TY 64 eeMpeeN POUL AISENI EAI RDOCIOS ., 2052. cas ces ovale oo nec nc cglietewdekoccas dees 66 URC UDG TURES 122 7c: | SERN i ee bee a Re a a 66 PMO WOSUOTH CLOMIOD Ee eo repent ast ctg baxaiceluacaccceedlect 68 OEE TSF gl a4 Cag 0 ei ee a cee 73 Deemer intom en ner i: o I ein a ee 79 I We, aes Ree a tas 76 BPE ROTPAL COPOCAG 501.5. MM Ac. Sccsat Sued sen ee sak evel ence eon dup eSects 78 RPmenE ZONES ANG LOTMELIONS. <2 coe.ccs0d=ccuSascseeaccedelgscosemececsdedeese 95 The foothill transition forests..........0....0--cc0e-ccceeeceeeeeeeee: 101 The ‘‘slide-rock’’ successiOM..---.---:----:-0---ccc-lcscececeecceesseeeees 114 The humid transition—western valleys....................2..---.--- 118 eee unenaniin TOPGSIA. oo es 137 oles ASO ASS ID nS lle ne RRR DE ein SWE 159 ETE Gage SS a lO a 169 ARC CARON en Ee et ne ea 175 ‘ eA ; | Le. wi oe ¢ | le ‘s , 5 sd P —. (oh < wath Ya ¥ mh Wik | ia ware |.ene . « i % v . oa y= s PY = . > " : a * a i i , < : end <=" : Reka’ P ; de cfy oe a , a | <6 a A, } : G- ; # ; * ‘ ean ¥ 7 a NP) ao “e, = a ‘” a ‘eS * ti Fe - Lif Figure nt Page 1. Routes of early exploration in Montana............-... 22 po Phymographic-map of. Montana: 2.00... cc esesece. 26 3. Profile Idaho-Montana topography on the pare Be MI Ce Ger: OU ANI LOR cise nce see eh hee te 30 4. Profile Idaho-Montana topography on the 46th parallel ©32 5. Profiles of certain mountain ranges in Montana............ 36 6. Chart of Montana showing direction of prevailing winds 40 7. Diagrams showing monthly distribution of precipita- tien-. im Montana. 1.655000.) tees Sey ey DRL et 44 8. Mean temperature diagrams for the year. Distrib- pO IAS UR led GRE Oa aD es A Ed oe eb ae SR eT 48 9. Mean temperature diagrams for the year at two stations near the same meridian, but 200 miles apart................ 54. 10. Chart showing temperature, relative humidity and precipitation at Missoula, 1910 22k: 56 11. Isotherms for mean temperatures in Montana, 1911.... 60 Pere CME SOCRIONAL | APCAS 2... a acne eendeg lee oaeee te 78 13. Badlands near Glendive, Montana.........02..0000000200..2220.22---- 98 14. Vegetation of the rimrock near Roundup, Mont............. 104 15. Alluvial bench along the Musselshell, near Melstone, CE ee dae Fee tec ete es ated he orto Site ee 108 16. Populus Sargenti ee the Musselshell.........000...2.002... 112 17. Yucca glauca near Forsyth, Montana................2.........-- 116 18. Buffalo berry along the Milk River...........0000000000000002... 120 19. Vegetation on south slope near Havre, Montana............ 122 20. Creeping Juniper on plains near Havre........................ 124 21. Junipers near Boulder, Montana.............00.........0..0...2.-.- 126 22. A western slope near Missoula, Montana.......................- 128 23. oe dog ner yee 6 eo R% ye 2 Lsabe ced ¥ ee OR ae laa it ss et Rai | BRB wie Bae ene ae” 2 aw psees pasa y €3 Seal eee 3 engs heeeee S€eee tb Se eee 2 eRe SOGhy BS #1 Oe Oh He ee ie BaP a an im he : rs ead eases Pies Peretics nS B ae Oe SEE Races 4 ¢ = ¥ » 1 ee 255 ETSY reese ret prey sae74 29588 ered a 4 a et eee $3% * PEPHA E + CRBS ESTO HDD PREBLE RT RES Se f i Seale maps oO B, boundary line. After topographic O, mean sea level. 1000 feet. Dotted lines represent gaps filled in from other data. h eal; % les, verti 25 mi inch Section of Idaho-Montana topography on the parallel 48° 30’. ine Fig. 3. % horizontal, the U. S. Geol. Sury. TOPOGRAPHY 31 ually toward the valiey of the Clark’s Fork of the Yellowstone. The canyons in this section are often mere narrow rifts between nearly perpendicular rock walls, which sometimes rise to nearly 3000 feet above the floor of the canyon, which here and there is strewn with boulders and glacial debris. Toward the west the country decreases in elevation. The lowest canyons are 4000 feet above sea level and from that all elevations occur up to 10,000 the usual elevations of the East and West Boulder Plateaus. Here again glacial action has left its traces, but not of such a character as to indicate that they have been reduced much in height since the ice age began. Through all this region of high peaks there is not a snow cap, so completely is the not too ample snow dissipated by the sum- mer’s wind and sun. Some perennial snow fields lie in the lee of high ridges and peaks where the winds have piled the snow too deep for it to disappear entirely during the short summer. In this group the Bridger and some lesser ranges form lower plateaus or rounded ridges, forested to the summits, and in outlines far less severe than those of their more lofty neigh- bors. In the second area are several groups of mountains which constitute forest islands in the central part of the State. The most western of these, the Big Belt Range, is the only group which is extended in the form of a chain. They le parallel with the main divide at a distance of 40 to 60 miles for nearly 100 miles in ‘a direction from southeast to northwest. Through the intervening valley flows the Missouri River in places through narrow gorges which Lewis and Clark called the Gate of the Mountains. East of the Big Belts are the Little Belts with spurs radiating from a central elevation and supplying the sources of Smith and Judith Rivers and other minor affluents of the Missouri. South of the Little Belts at a distance of 50 miles more or less are the Crazy Mountains and east at about the same distance lies the Snowy Range. These several ranges are separated by valleys of greater or less agricultural possibil- ities, and with broad rolling grassy uplands, which gradually merge into sparsely timbered foothills. The higher elevations, in conformity with meteorological conditions, support ample 5 . ! i . ; “AING *[Oo4y) ‘Ss "n oy] jo sdvm o1ydeasodo} JojJy ‘[aAe] Bes UBETT ‘Gy “JooT OOOT : Gout G ‘[Roljaea fsaptut GZ : your 4% ‘[RyUOZT -10Y :ayRog ‘oul, Arepunog ‘gq ‘jvj[BVavd YIOF vy} Suope Aydvasodo}, vuvjuo_-oyVpy JO Uoljoeg “FSW —_ sy eee ” ; 3S ogee: “tt eo Reese | : Pe ei fe + LSeey * _ a > —_ ~ ——- a - teed ie aa ene ~~ / ~~ @ ¢ +H rs on - canes ee - oa ) — : Po] fl + . " = << — <1 on oS -* ; ; bees eR EE SESS S334-331 ~ 3 ' << { . eee >. ote hee ;aeess awe | TOPOGRAPHY 33 forests. The ranges here enumerated thus constitute forest islands in the plains country. Some peaks of this region rise to 9000 feet or more above sea level. In the Little Belts, the central group of the area, the average elevation is above 7000 feet. They are mainly limestone uplifts, seamed by numerous dikes of eruptive rock with extensive areas of metamorphics. The ridge crests are in some places narrow, in others flattened out into plateaus, as at the head of the Lost Fork of the Judith and even marshy in others, as where the divide descends into what was originally part of the South Fork of the Judith Basin. Some of the secondary ranges are largely of ignecus rock. Ridges radiate on the eastern slopes of the main axis into long spurs of narrow and winding form which separate the streams flowing to the Judith River. They are seldom high but are usually of low and rounded contour. On the west the spurs are short and steep and on the north they form a labyrinth of tortuous can- yons. Many of the canyons throughout the area are narrow and flanked by steep slopes or by limestone cliffs buttressed by talus accumulations. Above they widen out into amphitheater-like basins. To the north of this range a short distance stands a small detached group, the Little Rockies which have an altitude of 6500 feet or less, and support a forest growth. To the east of the Belts the neighboring elevations of the Snowy Range are separated from the former by Judith Gap, a rolling and fertile prairie country. These summits have eleva- tions of 4000 to 8000 feet and are themselves divided into two groups, the Big and the Little Snowys. The latter is the more easterly and represents the most distant outpost of the Rocky Mountains with forest vegetation between the Missouri and the Yellowstone. The most southern members of this second general group are the Crazy Mountains. They cover an area of some 360 square miles and reach an altitude of 10,000 feet. Geologically and topographically they resemble the Absarokas of the southern group, from which they are separated by the broad valley and rolling grassy benches of the Yellowstone. They rise abruptly from the plains and their rugged sides and sharp ridges ascend to clear cut peaks often cloud-crested and mantled with snow. 34 FOREST DISTRIBUTION & — The third group remains to be considered. From the Snowy Range across the Missouri to the north, about 100 miles from summit to summit, lie the Bearpaw Mountains. These are of comparatively low altitude yet of sufficient elevation to support forest growth. They practically constitute a culmination of the divide between the Milk River and the Missouri. They reach an altitude of 6000 feet and with the Sweet Grass Hills and a few other low elevations represent almost the only forested slopes within 100 miles of the main front of the Rockies in a strip 100 miles wide below the Canadian Boundary. Geologically, of course, the State presents a great variety of formations. The eastern half is mainly Upper Cretaceous (with an extensive coal bearing portion) and Early Tertiary. Later Tertiary formations appear in several isolated tracts in the western part, occupying portions of the Flathead, Bitter Root, Blackfoot, Big Hole, and other valleys, alternating in the southwest and center with larger areas of the Paleozoic. The northwestern portion from the Continental Divide te the boun- dary and from the British possessions to the head of the Bitter Root Valley is mainly Proterozoic (Algonkian). The Bitter Root Range and the high mountains of the main divide about Butte and southeastward through the Absarokas are chiefly granitic, but the northern ranges are sedimentary. Volcanic rocks and lavas form a very small portion of the State. The soils derived from these sources are necessarily varied, both locally and regionally. Over much of the eastern part of the State the soil is of that comminuted variety known as loess (18), in many places overlying glacial drift and now supporting a typical prairie vegetation, mostly grasses. It is a fertile soil and when broken up and sown to grains yields heavy crops. Extensive glaciation characterizes the greater portion of the State and morainic deposits are common (9). Many of these are thinly covered with soil and, while fertile enough when pro- vided with water, are usually dry and very difficult situations for plant life. Deltas at the mouths of canyons, river bottoms of silt, sand or heavy clay, and in varying areas and depths, form, west of the divide, a limited part of the vegetation-bearing land, composed of transported materials. The slopes which, in the western portion of the State support nearly all the coniferous TOPOGRAPHY 35 forests, are usually formed of fragmented rock, mingled with the products of its decomposition and small additions of humus. The different phases of vegetation on soils of this character are usually expressions of reactions to moisture coutent in relation to exposure. While the uplands of eastern Montana are largely of fine soil or gravels the bottom lands are often of fine heavy soil commonly known as ‘‘gumbo’’ formed by sedimentation from decomposed shales (40). These in the aggregate involve a con- siderable area. They are usually more or less heavily impreg- nated with soluble salts and are the so-called alkali lands (52). The salts most commonly present are sodium-chloride (very slight) sodium sulphate, magnesium chloride, and calcium sul- phate. Sodium earbonate is practically absent. Much of this sort of soil is found in the lower Yellowstone Valley, where strong erosive action is still going on, especially in the ‘‘Bad Lands,’’ where the bluffs are dissected into a rugged wilderness of hills and gullies. Wind action also is still evident. Fantastic forms of sandstone stand isolated here and there, caverns are carved in the faces of cliffs, boulders are gradually reduced and obliterated. Along the crumbling cliffs and on the margins of broken terraces is a fringe of forest growth, seant, scattering and depauperate. The benches above and below support only herbaceous or shrubby vegetation. The stream bottems invariably support cottonwoods and other hard-wood species. The eastern slope of the Continental. Divide in Montana is drained by the Missouri River, the western slope by the Clark Fork of the Columbia. Along the peaks of the main and outlying ranges are the innumerable sources of these streams; some take their rise in high sub-alpine bogs and meadows, others flow from cirque basins where quiet lakes lie under forested slopes. Of these there are many of varying size and depth. Again there are countless small streams that flow from melting snows all summer, flowing freely by day and ceasing by night. The slopes of all the ranges are thus watered abundantly; every canyon has its brook or torrent which soon unites with others forming swift, clear streams uniting into the main tributaries of their respective systems (17, 49). * © * 2 om 2 % * +3 sani rever cee 41 PRET bees OF a hegen sew en ai Pm Oy EROS REG TREES | eB CA RRM BH EH % hi id $4: ae ereenee OR eee we Fig. 5. Profiles of certain mountain ranges in Montana. Seale: horizontal and vertical, % inch: about 5000 feet. O, mean sea level. \ and B, along the international border (49th parallel) from Kintla Lakes to Belly River, across Glacier National Park and the Conti- nental Divide. C, section of the Bitter Root Range on the 46th parallel; from the summit to the Bitter Root River. D, Continental Divide on the 46th parallel. E, the Absaroka Range and the Yellow- stone River on the 46th parallel. F, the Crazy Mountains on the 46th parallel. 36 TOPOGRAPHY 37 % The Missouri and some of its lesser affluents drain the whole of the eastern slope of the Divide in Montana, from the Milk River in the north to the ultimate sources of the Madison, over 500 miles. The Jefferson, the largest of these mountain tributaries, is formed by the Big Hole River and the Beaverhead and carries the waters from 250 miles of the Divide, which describes a wide and deep embayment, partly known as ‘‘The Big Hole’’ and occupying the southwestern corner of the State. The Jefferson, the Madison and the Gallatin unite at Three dorks to form the Missouri and from this point on to the mouth of the Dearborn there are no streams of considerable size. From the south the Missouri receives the Musselshell which drains the Crazy and the Snowy ranges, the highlands of the central part of the State. Near the eastern boundary the Yellowstone River enters but its waters have their sources mainly outside of the State, in the Yellowstone National Park and in northern Wyo- ming, although some are supplied by the Absaroka and the Bear- tooth Ranges in the southern part of Montana. On the western slope, from the northern boundary to the head of the Bitter Root, somewhat over 300 miles, the waters are gathered by the North, the Middle and the South Forks of the Flathead, by the Blackfoot, the Bitter Root and the upper source of the Clark’s Fork, commonly known as the Hellgate, all uniting to form the Clark’s Fork which drains the whole-of western Montana beyond the Divide. This stream finds its out- let through the narrow valley between the Coeur d’Alene and the Cabinet Ranges and finally empties into Lake Pend d’Oreille. The main sourees of these rivers lie ultimately in the winter’s snows. During the long winters these accumulate, more on the western than on the eastern slopes, and as the warmth of summer dissolves them their waters run off in torrents or, percolating through the soil, feed the numberless springs and sources of the small streams. In February the waters are low, but in June the streams are at flood and their volume is increased as much as 70 fold as measured in second feet. Similarly, on the Atlantic drainage the streams are swollen by the melting snows but the mininum may come in March or in August depending on the location of the stream sources, and the maximum may occur ac- cordingly anywhere from March to June. Measurements of flow 38 FOREST DISTRIBUTION indicate that some of the streams at flood may attain more than 1000 times their low water volume, but more often the increase is about 20 to 30 fold. The tributary valleys of western Montana mostly have a north and south direction and occupy trench-like depressions between high ranges. The valleys are often or even usually narrow, but occasionally broaden out into numerous inter- mountain basins, as some parts of the Flathead and the upper Blackfoot Valley. Some are the basins of old lakes with the evidence of their ancient shore lines still intact. The positions of the ranges and their alternating valleys in most cases is squarely across the lines of eastward or westward movement. CHAPTER II. CLIMATE, precipitation and temperature. Precipitation as the source of moisture is a matter of interest to be considered in connection with its seasonal distribution, with soil structure and composition, and with temperature, relative humidity and other atmospheric conditions. Data upon most of these points are available from records of the Weather Bureau, from over 90 stations fairly evenly distributed throughout Montana and covering periods varying from three to thirty or more years (70). y VHE climatic influences affecting vegetation are chiefly The prevailing winds of Montana are from the west. Fig. 6 indicates the direction in different sections of the State. Tables published by the Weather Bureau giving the usual wind direc- tion by months at the numerous stations show west, northwest and southwest with few exceptions throughout the year. Easterly winds at times are strong, but such are usually of short duration. On the western slope of the Divide the prevailing winds are the bearers of rain, which comes chiefly in the cooler months of the year. In this respect the climate of the western slope of the Rocky Mountains is not essentially different from that of the Pacific Coast west of the Cascades, except in the quantity of the precipitation. The seasonal features are much the same on the whole, however, with lower minimum temperatures. On the eastern slope of the Rockies, however, the rainfall features are diametrically opposite. Here the principal precipitation comes in the warmer months of the year, a fact of distinct ad- vantage to the agricultural operations as well as to-the native vegetation of the Plains region, and of importance as linking the climate of the eastern slope with that of the central states of which it is logically a part. A diagramatic representation of the distribution of rainfall 7. The distribution by localities and seasons is shown and it will be noted that at most of the stations on the western slope (Plains, Missoula, Hamilton, Kalispell and Butte) is shown in Fig. 39 ‘ NeaIng Jay VIA, 8] JO spalodea UOA ‘sdO}ORBy JVyYIO puRe uoTRdDHead ‘ganjyeazadura} 10} pod Uleley BIVpP SULYSIUAINJ UOTPRAJesSqo JO SuUOT} RIS pues uopesyidioeid [enbo JO soul, ‘SpUIM Sulpieacid JO UOTJOeIIP SULMOYS “BUR]UOT_, JOy YARYH “9 “SLT Cl tburidc Loy 44 OMDA G Aquaby Cora stuingo > = 0AD1D43O areagc epnoggo “N+ Ayip 22006 DINOS Si py XNPGIMO . OPUDAQ ae IULUBID AG uDp4or.> siyv4 +0219,.6 vy) a vopusg io 4 r?) Ni. bel 3 ~<_— AD\doy MObsSOID O ee susohc your A041 0 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 »fford representative figures. Strange as it may seem, the snow fall on the main range of the Rocky Mountains is comparatively hght, 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 anything 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 314 feet, while 42 Table 1. FOREST DISTRIBUTION nished by the Weather Bureau. Distribution of precipitation in Montana. “ From data fur- hy . ; Precipi« Length Length tation, of Altitude,| Average of Place Inches, | Record, Feet |Snowfall,| Record, Annual Years Inches Years Mean Western Montana (Pacific Slope) Minsomlay $5, 260 Asta: 15.84 33 3212 24 ae OVA) tn Sa | 18.36 | 10 4101 69.8 9 Troy |, 2422 15 1880 56.3 11 Hamilton 22s | 10.71 11 B5T5 37.8 7 Philipsburg: .25...5..2-22. 15.55 7 5275 42.2 6 MnOWShOG (2 a ht 69.70 4 4500 270.9 3 Kalispell 15.73 13 2965 42.1 10 Battide S85 Fs Sec ort 37.63 5 3600 142.3 5 OE ea Se OER In 13.00 | 10 2475 28.6 iB ig BRGIEOO: \cangeeec oats sath 13.08 | 14 5716 55.2 14 Southwestern Montana (Atlantic Slope) | Bonemian .54.5.5.20:2 [ .18:60- “Poss 4878 TA 6 Boulder | 10,00 | 17 4920 30.4 9 Dillon at TAN ig! 10 5147 58.2 9 Fort: Logan © 0.22. | 48-01 30 GOO EE oo Baszeees nt Harlowton § .........2......- | 15.50 17 4165 59.9 6 Helena igs 53 85 | 29 4110 54.7 29 Red Lodge.......:............ | 20.85 6 5548 115.8 6 Virginia City................ ' —§-15.03 23 Re. eM ee teh Yellowstone Park........ | 18.97 19 . 6200 105.2 21 North Central Montana | (Atlantic Slope) / | Ape A Ai Ae. 32014 hee 5200 82.3 10 Babb Su es | 22.49 3 4461 103.7 3 Fort Benton:.2x...<....5. | 13.38 30 2630 34.2 7 Great Falls....2............. ! 10,48) 1s ee 3350 41.1 14 Sev TO oe ES aes | “AS6S°°) SSO 2505 37.0 10 Lewistown. .......:....-..:.-. See ee 14 4010 66 2 10 Northeastern Montana! | CRiInpOK } couse 1 ES 14 2502 27.5 8 Giisgow * 322 ions. ee os A ee 2092 25.5 7 CFICTMIVG «5.82 i: 2 ee Le 20 2069 45.4 13 Jordan ....3:..... oe es 49607 1 § 9) lee eee est ONY oo | 13.59 | 17 2020 41.5 13 {ls ee oy ap ey ae 8 ‘See eee Southeastern Montana! | Senpannees (TS ee Ae | 14.96 | 16 | $115 43 16 Crow Agency................ | 14.56 | 80 3041 43.9 30 Ekalaka jorelabtacteoe hee 1 12 Meee 29.7 9 peasee. OMe x=... katewet ae, Le 32 2371 27.2 51 Wrihetie 66 27 ae 1419 | 14 | 2674 | 306 9 CLIMATE 43 Ovando, at 4,101, has nearly six. It is a matter of further interest in this connection to point to the snowfall in Yellowstone Park at 6,200 feet elevation as being normally 814 feet and at Red Lodge, 5,548 feet elevation in the Absaroka, 914 feet. Both of these stations, which represent the highest east of the Divide, are within 80 miles of the summit and in the direct path of the southwesterly winds which sweep across the range at points un- protected by any high barriers to the windward. The Bitter Roots, which shelter the main divide further north, have no influence here, having merged with the main range some 200 miles to the northwest. } If we reckon 10 inches of snow on an average as equal to one inch of water, the equivalent of the winter’s precipitation in acre feet would amount to a considerable volume in stream flow and is important in its relation to power and irrigation. It is an important factor as related to the vegetation of the region. In this respect, however, it is not equally distributed, and much of it doubtless is lost by evaporation, but it is swept by winds into gulches and into sheltered pockets in the lee of peaks where, piled to great depths, it furnishes a constant supply for innumerable streams throughout the warmer season. In this form it is less significant to the vegetation of the crests and exposed slopes, except as these are forested and so enabled to hold the snows that they receive. In such cases, which are numerous, the snows become of the utmost importance, and furnish conditions highly favorable for certain species. ‘The countless lakes and streams fed by the melting snows furnish a natural irrigation system, and by furnishing suitable habitats for trees along their banks facilitate the spread of forests over intervening and adjoining areas. Locally rainfall conditions vary within wide limits. The western slopes of the Bitter Roots are amply watered. The rain bearing winds from the west sweep up their high inclines and deposit their burden in frequent showers and heavy snows. There is probably no part of the Rocky Mountains more heavily watered than the higher Bitter Roots and their western slopes, or with snows so deep. In the lee of this range lies the Bitter Root Valley, and Hamilton, near the center of the Valley and at the foot of the mountains on the east has an annual rainfall incues HARLOWT ON HELENA HAMILTON Ea eae MISSOULA PLAINS 3- TTT st hd LLL TN | | 4 | ' GRAHAM Rian EKALAKA Wo. Tuttliattn MILES CITY a HE TL Het ef LL LLL pate! i OR | REE | FF | Pa oT FAT | AREER mM Wha; GLASGOW POPLAR RIDGELAWN TT Aa | Tine Tid | 4 LHL Lit nth : | 1 pauem | Qaeanue a Been | It UUs tat ; Fig. 7. at twenty-five ological Data of the Weather Bureau. LIVINGSTON DILLON BUTTE 8 Bas Lot ean al BS | 6 ! WU sees poReouani Mi i AD Wiese’ a fh A LLL ut ; id fia Pe PB ah Wes aly) (Bs, ba fy Be He / j Vy st aantitin: Tio V0 tia: GOLDBUTTE HAVRE +f 6 ME) LE é NE MAHOOANHHORRNOUOAN iW CU TT - ee Wo) Pot stations in Montana. United States. Diagrams showing monthly distribution of precipitation From Summary of the Climat- Reproduced by permission of the CLIMATE 45 of 10.71 inches, the average of 11 years of observation. Missoula, near the mouth of the Bitter Root Valley and on a direct line some 30 miles from the higher Bitter Root summits, has an annual record of less than 16 inches, the average of over 30 years of observation. Similar comparisons may be made in various other places. The heavy precipitation at Snowshoe in the Cab- inet Range may be due to the position of the lake country in northern Idaho, lying as it does directly to the west, and to the fact that the southwestern winds have few opposing altitudes to diminish their moisture before striking this range. To the east lies the broad basin of the Flathead Valley with about one- fifth the total annual rainfall which occurs at Snowshoe. The more amply watered western slopes of the Bitter Root, Coeur d’Alene and Cabinet Ranges are heavily forested, and support a type of vegetation more mesophytic than is to be found in other parts of the region, with some few and limited excep- tions. In this feature some portions of northern Idaho may be included and in all such areas in western Montana and northern Idaho there is a conspicuous element in the flora suggestive of Pacific Coast humid conditions and undoubtedly derived from that source. The areas of this character in western Montana are few and are mostly confined to the moister valleys of the Flathead drainage. East of the Divide the annual precipitation is on the average less. It varies from 10 to 22 inches, but for most places from 10 to 15. The lower plains have less and the amount increases with the altitude. Red Lodge, Babb and Lewistown, situated among or near mountains, have about 21, 22 and 20 inches re- spectively. The mountainous areas, due to the greater rainfall, have forests of considerable extent, but the plains are devoid of trees except along the streams or under other exceptional con- ditions. Relative humidity and the rate of evaporation in Montana have not been established by a sufficient number of observations, but some facts are available from the records of the Weather Bureau at Helena, Havre, Kalispell and Yellowstone Park and from observations by the writer at Missoula, and these are sub- mitted herewith. Table 4 summarizes the data from the Weather Bureau’s 46 FOREST DISTRIBUTION publications, which show that the mean maximum at Helena, Yellowstone Park and Kalispell were between 60 and 87 per cent and that the lowest relative humidity of which there is a record is 30 per cent at Helena in August. Table 2 gives the mean daily relative humidity, maximum and minimum for a period of three years and table 3 the mean daily variations during the same period. The record was made by a standard hygrograph under standard conditions and cor- rections made from time to time by aid of a sling psychrometer. The instrument shelter, on the University campus, was placed in an area of natural prairie vegetation as dry as usually can be found in the region. A mountain rising to the east shut off the early morning sun, but the station was fully exposed through- out the rest of the day. From the table of mean daily variations it will be seen that these may range from 50% to 64%. The curve traced by the recording pen shows, especially during the summer months, a rythmic daily rise and fall, the maximum about 6:00 a, m., the minimum about 4:00 to 6:00 p.m. The pen in rising traces a more or less zigzag and irregular line until the maximum is reached. At this point there is usually a sharp peak, for the maximum is of short duration, then a steady downward sweep during the day to the minimum late in the afternoon. The max- imum of each dav’s record usually shows strong throughout Table 2. Mean daily relative humidity at Missoula. Maximum and minimum. Jan. Feb, Mch. Apr. May June July Aug. Sept. Oct. Nov. Dec. Max SS 92 94 95 8S 87 96 89 88 1915 Min 34 41 40) 34 21 38 43 5O 60 Max 8&6 94 89 S4 83 83 83 82 82 83 79 76 1916 Min 64 66 45 o+t 32 51 24 20 18 54 45 58 Max 80 80 & Tt ~T..7%" 4a (5 IS “a 1917 Min 55 51 42 3 25 25 9 13 19 22 52 52 Max 72 1918 Min 50 Table 3. Mean daily variations in the relative humidity at Missoula. Jan. Feb. Mech. Apr. May June July Aug. Sept. Oct. Nov. Dec. BSPSD .. catia Py 1 ae 61 67 49 53 49 28 22 28 44 50 Dl 2 59 62 34 49 34 18 209) BS 46 42 48 59 4 52 5D 21 20 CLIMATE 47 Table 4. Data from the Weather Bureau on the mean relative humidity by months at three places in Montana and one in the Yellow- stone National Park. An- Stations Hours Jan. Feb. Mar. Apr.May Jun. Jly. Aug. Sep.Oct.Nov.Dec.nual Helena SAM. 72 73:71 65.66 67 60 59: 64 66 68 T1 67 . 8P.M. 66 63 56 42 42 41 31 30 39 48 56 65 48 Yellow- SA.M. GW 74 7 74 Wl 4 TT 8 T1 .74 7 % T4 stonePk. 8P.M. 71 64 65 48 51 46 36 38 40 55 58 59 58 Havre Sie de Os -GS 63 57, -56:'62 “68° 75." 79" 6O Kalispell 6A.M. 86 86 81 78 82 82 78 TT 82 86 86 87 8 6P.M. 80 73 58 42 49 47 37 36 50 62. 76 83 58 the year, even in relatively dry seasons, since the nights are always cool. In the winter the rythmic quality of the curve is much less marked, the maximum is comparatively low and the peak flat, while the sharper angle in the day’s tracing now falls at the minimum. ‘The situation is one of exceptional severity for vegetation. Two months or more of drouth during the summer, mostly cloud- less days, day temperatures of 80 to 90 degrees, low relative hu- midity and a highly porous soil, all tend to xerophytic conditions in the vegetation. This station may be considered the most severe, all points considered, in western Montana. During the seasen of 1917 10 weeks in June, July and August were without a trace of rain, and but .62 of an inch fell in three months. At the close of this time, in the vicinity of the instruments, soil at the depth of a foot was within 1.1% of actual air dry condition and when heated for three weeks at a temperature of 120 degrees C. gave off less than 2% of its original weight. The lower alti- tudes in this valley are treeless except where sheltered from sun and wind, a fact which is evidently related to the dryness of the situation. There is little but inferential evidence as to the rate of evaporation at any point in Montana. One record in the Judith Basin in 1909 showed evaporation amounting to 32.6 inches, presumably for the year. At Missoula during the season of 1917 the evaporation was 14 inches in 10 weeks (July, August and September) from an exposed water surface of 4 square feet protected by wire netting of one-third inch mesh. Sometimes the evaporation was as much as 2 inches per week. The Signal Service and the Geological Survey have con- s ‘ . ee ee ‘ Prien. Stee Ces 7) 5 tee D 7 - ; + Tris trrrh titistts sir $isoss teaasteseaeets J ae wate 22 : i i = Lh, #9 + Ha oa gesoeses: t : t . sees cee eeees tests a Titi; 9 = re : iit BH EE ee es H sSseccegs: teesetecei tseedtegh teaedas spedsteaed yercs rad +H aH Btoess coescesecs : of eos bestececes cesecses: : fiyft trie] yas tthe ro Trt Tiif ieee tT f win h / + sth essegegs! p ede of Pepog peens sesun goes titrcN! ras : : seas ie SSS ESS0i E280; Stes Seed Ses th: Hd Sota eres bs : FHEH ttt f ¢ uy ie t - ans t + tu I T t t a tT ath; t prt TA ¢ + . ; te rs ii] N } J ; = aoe on - _ eose owngs ©. = £ >» ‘i 7 WH % Sep apeel sseteeaaey segs = Hi i! + : i “| eres + $ t + 3 gaes © Ft He } f + t Ps mon non= gageen pe: SS EESe! = tt ; 3s rh a T t 4 i tr ; geass t Saueee By eb aut b> . t apd t r 4 Fetttt; : : an ‘ . E 4 ; iE “7 r tt H me eeeeie! . H AN Han os Ey pape lepton 2 rs toot TTT ah TH ers) eee EERE i . Pebetaes We t be t 1 4 beoerd rt rt - r pasa ro Bi . i r aoe: Be Bf ar rit ts a 4 4 Pees * by been if Li s PEE aeeedbeeeaed es © Hitt Ha pees 1 ebaedasaea eases beted fatesaas 384 § di: af > okt? : T Tht “aia tht WES2I STII TSaste daa : * HH i i}tt rt 1b)? G54 bade] pad i t $s sea eesaa teagan Be i santgeepscsapaesg pevcs Ceapsence facgs tesa] peal gargs eas ss ttt t » . + - bi pertebis ty Thee sees HS ai ipest stay arihise Ht {i rieabceeet cite ‘ REET EE : 2] ESBS EES Lah 1H HH iH ses Eebeiee bad bests a Tehite 717 ttt mt be ee Se . Boal Hilit tht 3 eae Poddt Posegbagay tse: t ath rs sopted teees Sete tees } oy ‘ : f; Seite itt qaeees Ha ttt. j int atid i +H 1th} ; i He earage t Herr thee Shining TP Ee Pee e epg en = 2 7: r . ~ 7 ie ui itt | rf C i we OoeTa reeenactes SEN: Ea E a83 52621 rH : THth : ‘\ That } The ; eH ES So : oy bat iH HT HES a i a3 te! : 5 aad AGy et haesd ITETT EER s 7 "7 Lt u 44 Hh reas ' Ped be! . = +4 sei +4 eee eens ttt: tH ee HEE Ta aa $segd toese bets att tet Ay rea Pei tthe 4 . 4 ts 7 * HHT i} Tey, Ceectsds oy cab opgiatetesgeed cated ts 326 rit sihaees " : ; 4 eh r rth 4 Si ae , eee o7 weerdee CE 4 +t { ttt senaai A + ry + pepe bere teed SH ! THY { Hite tbegeag sey seces oSees peste pe tt tHibsreghite : i . Ti Ly] Hf tr ae be foedeg trout 3333 Ai th SLT t std bbees tat)! esey basagpaees HE t nets Ps Ruther t 4 ait? Hath see + + r “dr br Od H : + + 4 ! Hiiditt : ; { : ‘ t oH apfecsdispss | tt + 4 ™ rite .. crt ore SP eSe t ; i } ray adele ait ty] operas tes - - 7 a" t TE at +3 ia HAN are > 4i% i. redtt n =e PS > (hal + y _ »- ‘+ + 4 ~ itt EET y HP HTH Ht 4 hikes NS 4 qeeee begs : ere ater } iN 4 t > abit } ; t age ; it r ; i i 38 ree ttre th / silanes a baa f tir is 4 Sieg 2) s38 see Sdestisaaistsdcasss ; es res ' Ms y see tt eeehes sanbhee he at eee tit 1 Liisattites m 4 bs tt + sees tecesues et SEES E27 : ees r +44 3 } > ; ’ tit : ; ; toh eee } 354 ° - : t thot : Pest et t peat ptese tate pass . : itt + r - t + + ; : .' 2 73 Ps tt 23 33 S33! 3333 8325833 u Fig. 8. Mean temperature diagrams for the year. A, Mammoth Hot Springs, Yellowstone Park, altitude 6200 feet. B, Anaconda, altitude, 5300 feet. C, Philipsburg, altitude, 5275 feet. D, Ovando, altitude, 4101 feet. KE, Missoula, altitude, 3212 feet. F, Troy, altitude, 1880 feet. The figures at the right represent the ratios of the growing to non-growing seasons. The mean temperatures for the months are on the curves midway between the vertical lines. 48 CLIMATE 49 ducted experiments showing that evaporation from a water sur- face on the western plains of the United States may amount to from 50 to 80 inches, and in some localities to even 100 inches a year, while the rainfall (diminishing in inverse ratio) over this area is from 30 to 12 inches and less. (25) In a series of experiments to determine the relation of wind to evaporation they arrived at the following conclusions: evaporation with the wind at 5 miles an hour was 2.2 times greater than in a calm; “at 10 miles, 3.8; at 15 miles, 4.9; at 20 miles, 5.7; at 25 miles, 6.1, and at 30. miles, the wind would evaporate 6.3 times as much water as a calm atmosphere of the same temperature and hu- midity.’’ During these experiments the temperature of the air was 84 degrees and the relative humidity 50 per cent. In four years in Montana from 1908 to 1911 the maximum wind velocity was 60 miles per hour. This was in March. Sum- mer winds of 46 miles per hour were reported during the same period. These figures are for the plains country. West of the Continental Divide the winds are much more moderate.’ Winds which rise to considerable velocity are of short duration. In this section of the State the only places where winds seem to be effective are on high and exposed ridges and peaks, and on the more arid southern and western exposures at low altitudes. Temperature records from many places in Montana, rep- resenting observations of from 10 to 30 years, afford a reason- able basis for judgment of the climatic conditions of the region in relation to the vegetation. The lowest temperature thus. far recorded in Montana is -65 degrees, at Miles City, ana the high- est 117 degrees at Glendive. Glendive and Miles City are about 75 miles apart, and, while the figures just cited as to tempera- tures represent the greatest extremes for these places and do- not at all indicate the-usual conditions, they do indicate that that section of the state is subject to seasonal extremes and that the annual range of temperature may be considerable. As a matter of fact it may range from 125 to 175 degrees. Other sections of the State on the plains may likewise be subject to extremes and the annual temperatures range from 120 to 150 degrees. The lowest mean annual temperature in Montana is recorded from Bowen in-the Big Hole, averaging 34.1 degrees, and the highest recorded mean annual temperature is at Billings, 50 FOREST DISTRIBUTION 47.2 degrees. For the climatological sections established by the Weather Bureau, the mean annual temperatures range as fol- lows: Northeastern Montana.............. 39.6 to 43.3 degrees Southeastern Montana.............. 42.9 to 47.2 degrees North Central Montana............ 36.8 to 45.8 degrees Southwestern Montana.............. 34.1 to 45.5 degrees Western Montana...................... 38.9 to 45.8 degrees Northeastern Montana is characterized by lower tempera- tures usually and by higher winds and more sudden changes of temperature than other parts of the state. There is a sudden transition from winter to summer in the middle of June, from snows and freezing weather to the long hot days of summer; autumn is dry, and mild weather often extends to December. The normal temperature for April is about 40 degrees, which marks the beginning of the spring growth of the prairie flora. In the southeastern part of the State there is a wider range of temperature, both daily and annual. During the summer the diurnal variations may be as much as 40 degrees or more. Snow falls from October to March. The north central portion of the State is colder and drier than the northeastern part. The winter minimum sometimes falls to 45 degrees below zero, and the summer maximum of 100 degrees is experienced in many localities. In southwestern Montana the several high ranges of mountains collect abundant snows. High altitudes, low humid- ity and the absence of high winds are features of this section. The temperature records are more uniform than might be ex- pected, owing probably to the more or less sheltered locations of the various stations.of observation. Western Montana is a region of widely differing altitudes and topographic conditions, and in some of the mountain valleys frosts and even snows may occur in all months of the year. In some parts the snowfall is exceedingly heavy. Two tables are provided giving the significant facts of at- mospheric temperatures. Table 5 gives the average mean tem- peratures during the months of the growing season and the average annual means at 29 different stations in the State. The last six are within the timbered section of Montana and in proximity to important forests. The others are mostly in the - CLIMATE 5 § prairie country. Table 6 shows the highest and lowest tem- peratures on record for 35 stations in Montana during the six Table 5. Average mean temperatures during the months of the growing season and average annual means. Yrs. An Alti- Station Obs Vape: | tay June fed SN eee) Berl feet Glendive 6... ic. | 20 | 46.0 | 56.3 | 65.1 | 72.1 | 71.0 | 59.4 | 43.3 | 2069 Poplar | 24 | 42.9 | 54.3 | 63.3 | 69.7 | 67.3 | 57.1 | 39.8 | 2020 rel | 14 | 44.3 | 56.2 | 62.7 | 69.9 | 67.8 | 56.0 | 40.2 | 2092 SSS 20 Cee | 9 | 42.7 | 50.4 | 59.2 | 66.5 | 67.0 | 55.8 | 43.1 | 4150 COO aiken: | 10 | 48.0 | 54.5 | 62.6 | 69.9 | 67.4 | 56.8 | 41.9 | 2502 Havre | 29 | 42.7 | 54.1 | 62.4 | 68.1 | 66.9 | 57.6 | 41.9 | 2505 Cut Bank | 11 | 38.3 | 48.8 54.8 | 60.6 | 60.0 | 50.4 | 38.6 | 3700 Fort Benton.............. | 30 | 44.6 | 55.1 | 62.7 | 69.6 | 67.8 | 57.2 | 44.1 | 2630 Great Falls.............. | 18 | 45.5 ! 53.6 | 60.9 | 67.8 | 66.7 | 57.1 | 45.8 | 3350 Port “Sha worse. | 21 | 40.1 | 54.1 | 62.6 | 68.3 | 64.7 | 55.6 | 44.0 | 3500 Lewistown . ...........--- | 12 | 42.1 | 50.4 | 57.5 | 64.2 | 63.0 | 53.7 | 42.6 | 4010 UGS opr s fe | 9 | 46.3 | 56.2 | 61.7 | 69.7 | 66.8 | 56.8 | 42.9 | 2674 Milas. -City sc. 2203: | 31 ! 47.0 | 56.5 | 66.3 | 72.6 | 71.5 | 59.8 | 44.6 | 2371 Healata: 2.2. 9 | 43.5 | 53.0 | 61.9 | 68.9 | 67.9 | 59.8 | 43.7 | ........ | Crow Agency... 30 | 46.6 | 55.6 | 63.6 | 70.9 | 69.5 | 58.6 | 45.2 | 3041 Biinge ko... 16 | 45.3 | 55.7 | 62.1 | 71.7 | 70.4 | 60.5 | 47.2 | 3115 Fort Logan.............. | 24 | 39.1 | 48.1 | 55.8 | 63.1 | 61.6 | 51.1 | 39.3 | 6000 Harlowton _.............. | 14 | 41.4 | 51.0 | 57.5! 65.2 | 64.0 | 48.1] 41.0 | 4165 Helena 28 | 44.0 | 51.8 | 59.1 | 66.9 | 66.2 | 56.2 | 43.6 | 4110 Boseiian= 2232.0... 29 | 40.3 | 50.0 | 58.7 | 65.8 64.3 | 53.3 | 43.5 | 4700 eaaed ~ Lodge.......2..2. 9 | 39.6 | 46.0 | 55.6 | 61.2 | 60.7 | 52.4 | 40.8 | 5548 Virginia City.......... 20 | 40.0 | 47.6 | 55.5 | 64.5 | 64.0 | 53.5 | 41.2 | 5880 Yellowstone Park....| 22 | 37.4 46.1 | 58.8 | 64.7 | 61.0 52.4 | 39.5 | 6200 Columbia Falls........ 14 | 42.9 | 51.0 | 56.8 | 63.9 | 62.4 | 53.3 | 42.6 | 3100 Btepell “\.2). 0. | 11 | 42.5 | 51.0! 58.8 | 64.3 | 62.9 | 53.9 | 42.4 | 2965 Troy 15 | 46.1 | 53.6 | 58.8 | 64.2 | 63.0 | 55.0 | 45.1 | 1880 Plains 11 | 44.6 | 51.7 | 57.5 | 65.8 | 64.1 | 56.0 | 44.7 | 2475 Missoula — .:.....-..:--.---- 30 | 44.8 | 53.7 | 59.8 | 67.1 | 62.9 | 55.8 | 43.8 | 3219 Deer Lodge .............. 14 | 406 ! 49.2 | 58.0 | 62.9 | 60.3 | 51.7 | 41.0 | 4768 months of the growing season. Again the figures for western Montana are the most significant as representing a more heavily forested region. But in other parts of the State represented by these figures there are forests locally important, or at least forest species more or less common. While it may be seen that in all sections the maximum may rise to 100 degrees or more, the minimum for each month falls more often below the freezing point than above it. The vital phenomena of plants are mostly confined to tem- peratures above freezing. While it can be shown that certain functions are performed at a diminished rate below 32 degrees I*., it is also evident that all functions increase in vigor in geo- metrical ratio from this point up to the optimum. 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Ge «L808 Lo OUT lo =6 SOT CT #01 GIl- 66 ivjdod Go = OOT cs FOL aa. SGk FE = B Se 26 e 16 “~~ UBp.Lo SF Sot fee ot 9€ LIT 6G. “£04 9T Tor 9 96 JATPUYTS) FL 6O0Or OG. ° MED Gs Sit O¢ GOL 0c 86 gles’, 5 uae REE ORRn RES aie tae MOSSBLY) 0G 96 cé = 6OL 96 90T | c& §=660T St 36 Si 88 yooury,) RBUBJUOT UdldJSBOq ION dos ‘Snv Ane aun: AVN [lady suolyeig “ULI “XBW ‘ULI XBW Ul = CXBIN ‘UlIN « XBIN UN *XEW ‘UAL XBIA (*penuTyu0oy) “9 e[qRy 54 FOREST DISTRIBUTION © of time, therefore, between the cool weather of spring and au- tumn, which marks annually the time of awakening and of re- tarding of plant life, is important as determining to a large extent the limits of the distribution of species when other things are equal, but hotter summers in certain areas may furnish the required total of heat for the support of species which would not be able to endure in another region having a growing period of equal length but of lower temperature. The length of the frostless period in the year must deter- mine, of course, the northern limit of distribution of certain species of native as well as of crop plants. The sum total of heat required for the maturing of the plant and the production of seeds must in most cases be the minimum even among those hardy species which resist frost, and furnish the northern limit of their distribution. In this region the frostless period of the year varies from 40 days to 4 months or more, depending on location and altitude. Table 7 presents frost data for a number t t + t t t H 4 H . . : . 43 tH - < es z la ig 1¢ 1s 1% ie i$ je } 1 } + i 1 i + i tt Syese seeesseety 53333 seas es s See es t . seeee ® sogeeses base 5 hee . t ® etprecsghy + } e Itt Mh * 8 58 $9300506 é . 2s oe 3 rs os 23 . '. + es . . ss 8 oe t rt Ht : tt r > + 4 i — srassass Bessoeseserteslsts lo. zt i 7) 7 Ty tt tt ttt tt . a ae . a, -* io 4de pa S3sssse3' t: rt Ht tittt > tt t : tt tt St tt ; Ht seees 33s t tT ps Fessessees: + ; tt Os E009 SO8R8 | } ‘ 7 Tritt 33s 3 he } * 4 Ht t trtttt tt > at 3th: $ 333 > +t HH > $33} 3 + siists + 2+ ttt ee +h . + H P. + ree eee 335 S233 poeee sees 34 33 +} +r seeee ° +4 +h ttt ttt + ssssees 3 tFt ttt ttt bE ts + 333 . eee r++44 peree rs re hee ° 33 _-- = s Fig. 9. Mean temperature diagrams for the year. A, at Billings, altitude, 2371 feet. B, at Havre, 200 miles north of Billings, altitude, 2505 feet. The figures at the right represent the ratios of the growing to the non-growing seasons. The mean temperatures for the months are indicated by the cross-marks on the curves, midway between the vertical lines. CLIMATE 5D Table 7. Average dates of last killing frost in spring and first in autumn. Station Years of Last fr First frost mera ag in autumn Glasgow ........ os 14 May 22 Sept. 12 Chinook 10 Bee a “alee Glendive 16 e249 oe Ee Poplar i 16 Sa cee & | St. Paul 10 Pek Me! a ee OL) Seen CORES ye aa ee 10 June 25 Aug. 24 Chouteau 11 May 30 r Sept. 6 Fort Benton: -..:............ 9 aa as i srt ee Lewistown 12 June 5 33 3 Great Falls 18 May 7 eiete Cut Bank é June 14 Aug. 29 Billings 10 May 7 Sept. 16 Crow Agency 27 Me hone 28 LOSE G9 gee es ee 18 Jy 7 = Od Red Lodge 8 June 13 e 2 Bozeman 8 May 28 jf ‘ Butte . 14 June 5 See Fort Logan ...... 12 rE Aug. 30 Helena 55 May 7 Sept. 28 Dillon 9 June 9 % 1 Anaconda 8 cape ar 4 Columbia Falls : 16 * 9 Aug. 22 Kalispell 12 May 13 Sept. 30 EEE coal Sa 10 ay meat P: valamegs * Ovando oN 10 July 4 Aug. 12 ie: (Lo: as eee Hn 13 June 1 Sept. 7 of stations within the State. In these as in most temperature records, other elements are to be considered besides latitude and altitude. Some stations much higher than others have a longer frostless season and some with a difference of 100 miles or over in latitude have a difference of 30-50 days in the frostless period in favor of the more northerly stations without compensating difference in altitude. The proximity of mountain ranges, the width and direction of valleys, the exposure of the slope, and the direction and velocity of winds, all have their influence on the temperature at any time of the vear. Owing to the charac- ter of the topography and the extent of the area involved, the figures on temperature can have only the most general sig- nificance. Figure 11 gives the mean annual isotherms of 1911, one of the colder years, and indicates the complexity of the temperature problem as far as distribution of species is con- cerned. When local areas are under consideration their tem- peratures must be a subject of local investigation. os - 3 : at ei 2 stTt = ONE z Bs peeeEs rT tlt 3 + p eae 2 i % 3 g past s Pa re - se 8s ps i re Tit —= _— sa 2 ° ~- : H+ . aaa ~ = 208 Tt | es 4 dud [eee anaes . — 2 Spee oo _ 7 4 +4 ese es < 4 ee + isi seesaess + cama BBY Se : > povebag dete ssrititt - wate} i ts pare § Peeege pres & 2 337 yr nl 1s * 3 t as z ses é 4 ge ese ss J “ = © : s+ + i : : — fra: AS =e is’ <4 > et es ah. 4 at. rt aaa en! * : > . > : t i sa a Ba + x * rs > . — peel ee z 33 es 4 = 77? z : 4 + : 7 -* =+ ; zt at 20 : w res ae. T - he ne b ae = < 4 Abe i r t Tr ; ee ‘4 cai rs rs rs 3. x z ; is Pee eo | 7 rete be la. May to Sep- humidity, maximum issou ipitation at M ive ly. week A and D, represent weekly means of relat The broken lines, B and C, represent ively. pect Chart showing temperature, relative humidity and prec The continuous lines, Inimum res Fig. 10. tember, 1915. and m CLIMATE he The ratio of the growing to the non-growing portion of the year is graphically shown in Fig. 8, which applies to sev- eral stations at altitudes varying from 1880 to 6200 feet. For each station a base line is drawn representing 40 degrees F., the approximate minimum of temperature as related to seasonal vegetative activity. Above and below parallel lines are drawn at intervals of ten degrees. Each diagram thus represents a vertical range of temperature of from 40 to nearly 60 degrees. The mean temperature for each month is fixed by points above and below the base. A line drawn through these points forms a seasonal curve for the temperature of the station. This curve falls below the base during the winter months. Descending sharply it reaches the minimum sometime in January, then it ascends, crossing the line usually in April, and reaches the maximum in July, whence it sinks again to the base line in October or November. Between the curve thus described and the base are included two areas, one above and the other below, which together represent respectively the positive and the neg- ative temperature conditions of the year. They represent also, from the standpoint of vegetation the relative values of the months indicated. The vertical lines separate the months. The mean tem- perature for each month is fixed at the middle or half way be- tween the verticals. On some of the curves these points are marked and indicated by figures expressing the mean tempera- ture of the months. (Figs. 8, 9.) The relative lengths of the growing and the non-growing seasons can readily be compared. In some cases the two periods are seen to be about equal, six months of each. In others, the ratio is 5 to 7 in favor of the erowing season. The vertical distances determine the areas which are proportional to the values of the periods. In comparison the growing seasons are seen to have relative values of 7, 8, 9, 11, 12, 14, ete., in different parts of Montana, as reckoned by the total areas of the squares. While the curve is a generalized one and the actual temperature variations would show sharp oscillations above and below, the areas included may, in the long run, be taken as fairly representative of the seasonal values. Livingston (35) has suggested a method of reckoning tem- peratures in relation to field vegetation according to exponential 58 FOREST DISTRIBUTION law. By this method it is conceived that with every increase of 18 degrees F. from 40 degrees to the optimum there is a doubling of the rate of growth and of activity of other physiological processes. MacDougal (37) has applied this principle in de- vising a method of integrating temperatures, whereby the area below the line of a thermograph record and above the line of 40 degrees may be made to represent hour-degrees in relation to plant growth, when applied to the rate of growth within fixed limits of temperature. In the diagrams (Figures 8, 9) herein presented for Montana the duration and intensity of the growing temperatures is shown. The spaces between the heaviest vertical lines represent months. The same distance between horizontal lines represents 10 degrees of temperature. The tallest of these vertical lines represents therefore 72 degrees as the mean for the month of July at Billings. The lowest here given is 61 de- grees which is the mean for the same month at Ovando. In the former case there are as a rule 32 degrees of temperature favor- able for growth, in the latter 21. The others may be seen to vary from 22 to 28 degrees. The duration, however, varies, as indi- eated by the character of the curve which in some cases ascends directly to the maximum and falls off again quickly, in others the higher temperatures are sustained longer and the curve accordingly has a flat or broadly rounded top. These features figure largely in the sum total of the productive temperatures of the locality, and stand in relation also to the variety of crop plants usually grown under irrigation in the several places. The curves of total heat required for all species must nat- urally fall within the limits of the curve thus determined for each locality, when established upon the same basis. It is also evident that the curve for the species must more nearly approxi- mate the curve for the locality the higher the latitude or altitude. If the exponential interpretation of temperatures in relation to plant life is applied, it means that in one month of higher tem- perature as much substance of the plant body may be formed as in a longer period at lower temperature. It must be borne in mind, however, that the brevity of the far northern summer seasons is accompanied by the shortening of the vegetative period and the production of seed in much less time than is required by the same species in warmer climates. Wheats which require CLIMATE 59 129 days to mature in temperate latitudes, if taken farther north gradually, after some years, reduce the period of life from sow- ing to ripening to ninety days or less (1).: The rapid develop- ment of northern vegetation during the short summers is well known. The same is true of alpine floras. Schimper’s refer- ence (56) to the effects upon the rate of growth of trees and the period required for their maturity may be cited in this connection, and many other facts of similar import. The sunshine data for this region are far from being ade- quate for our purpose but some facts can be given indicative of the conditions. They show an abundance of clear. days for the Table 8. The average sunshine record for four years (1908-1911) in different parts of Montana. Station | Clear | toady Cloudy Miles City 159 125 Si Havre He eke ln Py Ree Ce RR | 159 128 104 Helena ...... kad 120 122 123 Great Falls....... | 160 149 56 Dillon | 156 110 96 Butte 151 62 145 Lo ETE eae ag RCS al A ee Ree | 205 7 152 Saltese ab ene h At 127 TOES «ort Ri rn te wb eS | 2110 117 138 limited period to which they apply, though unfortunately the distribution of the clear days by seasons can not be indicated, nor the intensity of the light. In the state the average number of clear days in the year varies from 160 to 178, the number of those partly cloudy from 95 to 108, and those recorded as cloudy from 83 to 101. At Poplar in northeastern Montana, the number of clear days from year to year varies from 260 to 280, those partly clear from 33 to 58, while the cloudy days at the most cover less than two months, varying from 45 to 59 days. These figures as well as those in the accompanying table are to be taken only as a general indication, allowing for errors of observation and the lack of related data. On the Western Slope the clear days predominate in the summer and autumn, though many are scattered through the other seasons. In eastern and central Montana, the rains coming freely in the growing season probably indicates a good many days during the summer at least partially clouded. ‘neaing Jaq}BeA\ PY} Jo uorsstuitod Lq “TIGL ‘vuByUOW UL Soin} vivd U9} ULSI IOJ SUID JOST OV ‘IL ‘SI 60 CLIMATE 61 In connection with this reference to light it should be re- membered that on the parallels of latitude extending through this region the period of daily illumination during the summer is relatively great. On the longest days of the year, actual darkness hardly amounts to more than 6 hours of the 24. That the amount of carbon assimilated stands in direct ratio to the - duration of daylight during the growing season is, of course, obvious. While the fundamental importance of light in the economy of plant life is widely known, not so general is the knowledge of the relation of light to other climatic factors in the growth of plants, or of the peculiarities, with reference to light, of the particular forest species. In discussing the forest conditions of a region it is pertinent to point out that the amount of light required by a tree is increased with the lowering of the tem- perature. In warmer latitudes, therefore, a tree may endure a ertain amount of shade, while in more northern regions it re- quires full exposure to sunlight. A difference of this sort may be seen in the western yellow pine, which in Montana and else- where in the northern Rocky Mountains is very intolerant of shade; in Arizona, however, this tree is much less sensitive, and, like many other plants of that region, actually prospers better for a time under a moderate shade. This is, however, not wholly a matter of temperature difference, since the sunlight is more intense in latitudes toward the equator, and, as all plants are attuned to a certain range of light intensity, any excess of light is avoided wherever possible. Whether the difference of be- havior is due to a difference of light intensity or of temperature, or both, it finds expression in the appearance of the forest, which must be mcre open in the cooler latitudes, in order to provide sufficient illumination. This opening of the stand may give an opportunity for the entrance of other species less sensi- tive to shade, giving rise to a forest of mixed species, and even resulting in the end, perhaps, in the total elimination of the intolerant ones. CHAPTER ITI. SOURCES OF THE VEGETATION: MIGRATIONS. gion and plains have been glaciated and the subsequent plant covering derived from outside areas in later times (24). The sources from which these migrations have ensued were several, including chiefly Atlantic and Pacific elements as indi- cated by the existing species. A southern element likewise enters to some extent, but is important only here and there locally, so far as the woody species are concerned. P eon ana pat all of the northern Rocky Mountain re- That any relation exists between the species at present growing in this region and those antedating the glacial period is neither impossible nor improbable, but is difficult of proof. Of the many (50) genera of woody angiosperms listed below, mostly from the strata of the Tertiary of this immediate regicn, nearly all are represented by one or more species within the temperate latitudes of North America, and the majority of the existing genera of like sort in Montana are represented in the fossils of that period. Of the Tertiary gymnosperms three out of four genera are likewise now native to temperate North Amer- ica, while the earlier Cretaceous genera representative of this group are mostly extinct, though some are allied to existing fam- ilies. The rich flora of the Tertiary, abounding in broad-leaved, deciduous forests, must have developed under conditions far dif- ferent from any that have existed since, both as to temperature and moisture, and doubtless far more favorable for the origin of new forms. The following lists from the works of Newberry (44), Les- quereux (33), Knowlton (28) and Ward (69) are doubtless in- complete but will serve to indicate something of the past history of the flora of this region. The genera at present existing here are marked by an asterisk (*). GYMNOSPERMS Araucaria Glossozamites Sequowa Cycadospermum 62 Taxodium *Thuja Glyptostrobus * Pinus Ginkgo A bietites Cycadella Cycadeoidea Nilsonia Nageiopsis Zamites Sabal *Populus *Salix *Corylus * Alnus Alnites * Betula Quercus Quercophyllum *Ulmus Ulmophyllum Celtis Planera Carya Juglans Ficus Ficophyllum Protoficus Liriodendron Magnolia Laurus Sasafras Tetranthera Hamamelites Liquidambar SOURCES OF THE VEGETATION 63 Walliamsonia Araucarioxylon Araucarites Leptostrobus Arthrotaxopsis Geinitzia Sphenolepidium Baieropsis Cyekanowskia Cephalotaxus ANGIOSPERMS Platanus * Amelanchier * Prunus * Rhus Euonymus Celastrophyllum * Acer *Negundo Sapindus Sapindopsis *Rhamnus Rhamimites *Vitis Cissites Tilia * Aralia *Cornus Nyssa : * Andromeda Sapotacites Diospyros *Fraxinus Cinchonidium Viburnites *Viburnum It has long been known that in times next preceding the glacial period, in the latest Tertiary, from Spitzbergen and 64 : FOREST DISTRIBUTION < Iceland to Greenland and Kamtchatka a mild temperate climate prevailed and forests like those from New England to Virginia and California clothed the land. In the words of Gray (20): ‘*We appear to be within the limits of scientific inference when we announce that our existing temperate trees came from the north.’’ All species were probably crowded southward by the ice and doubtless found at least a narrow zone suited for their occupation during the period of glaciation. Upon the retire- ment of the ice some of these species or their descendants must have reoceupied portions of the land. During all of this period selective influences were undoubtedly sifting out the spezvies which were the distant forebears of our present flora. Climatie, topographic, and edaphie conditions determined the final types of vegetation (prairie, forest, etc.) over large areas of the land reoccupied. Since none of the existing species of this region, as far as we know, have appeared in the Tertiary deposits it seems probable that they have entered or evolved since that period. | The present alpine flora of the northern Rockies shows little evidence of its connection with the Tertiary flora above mentioned. Few species are common to the old and new world, and no closely related forms are here known in the fossil state. Rydberg (55) mentions one woody plant, a dwarf willow (Salix reticulata) as common to the arctic regions of both continents and to the higher altitudes of the Alps and the Rockies. Beyond a few other shrubby willows and heaths, with aftin- ities more or less evident with European species, immediate con- nection between the woody alpine flora of this region and that of the old world can hardly be admitted. As to some of the sub- alpine species (admitting the difference of opinion as to the identity of the old and new world forms of Juniperus Sabina and communis a few may be cited as having general circum- polar distribution in the pre-glacial period. Probably a consid- erable number of plants may be regarded as indigenous to the northern Rocky Mountain region since the glacial period. Cer- tain species considered by some to be transcontinental are by others divided into two or more species with lesser ranges con- tiguous or overlapping; without considering the merits of these SOURCES OF THE VEGETATION 65 distinctions it suggests the possible origin of new species from the invading stock. As to whether a species is immigrant or indigenous is often difficult or impossible to determine. In some cases it may be apparent from geographical evidence that a species has entered from a contiguous or distant area, but in others it may appear to have originated within the area, and if so the question of interest is the identity of the parent race or species, a fact which may be suggested by a comparison with associated or neighboring species, but which, if at all susceptible of proof, can be deter- mined only by detailed structural comparisons or by experiment- al means. In this paper such conclusions as may reasonably be drawn from geographic evidence or other external facts will be presented, but with appreciation of the uncertainties involved. With reference to the geographic evidence it would seem that at least three considerations may be recognized. (1) The edge or limits of the range of any species may fall within the region under examination and if so its source may logically be referred to the center from which it seems originally to have emerged. Southward extensions along the Rocky Mountains of boreal transcontinental species, or western margins of the ranges of conspicuous eastern or middle states species lying along the eastern base of the Rocky Mountains or eastern margins of ranges in the case of typically Pacific Coast forms would be cases in point. (2) The degree of development of a species as representing the supposed center of its distribution. The Doug- las spruce falls under this category. This species occurs in extraordinary vigor and abundance along the Pacific Coast west of the Cascades, whence it seems to have emerged eastward until it has found its effective barrier in the plains between the Rocky Mountains and the Mississippi River. While this is not usually a safe argument in view of the well known facts of the luxuri- ance of many introduced forms in various parts of the world, it seems more logical in the case of naturally developed species in their proper ranges to view them as indigenous to the regions of their greatest and most varied development. (3) The geo- graphic center in which the genus or family are conspicuous or characteristic may be regarded as the source from which the outlying species have emerged. The cacti and yuceas of the 66 FOREST DISTRIBUTION oy Southwest and the Mexican Plateau. may be regarded as ex- amples. The representatives of these groups in the Montana flora can be regarded only as having a southern origin. With such points in mind a grouping of species is attempted accord- ing to the sources from which they seem to have migrated into the northern Rocky Mountains. The following species mostly have a northern transcontinent- al range and appear to have moved southward along the Rocky Mountains into Montana and in some eases far beyond: *Juniperus communis Dasiphora fruticosa eer enne Sabina Elacagnus argentea Populus tremuloides Lepargyraea canadensis ‘© balsamifera Rhus glabra Salix cordata Rhamnus alnifolia ** chlorophylla Cornus stolonifera ‘fluviatilis ns canadensis ‘< — Bebbiana Andromeda polifolia ‘© Barclayi *Arctostaphylos Uva-ursi ‘* pseudomyrsinites Chiogenes hispidula Betula papyrifera *Vaccinium uliginosum *Alnus incana is caespitosum Ribes lacustre g ovalifolium ‘* hudsonianum Sambucus racemosa Rubus strigosus Symphoricarpos pauciflorus Rosa acicularis Lonicera involucrata There is, of course, no barrier to the southward movement of species along this highway through the region here under con- sideration. Five of the above species (marked *) occur around the world in the northern hemisphere. Most of the others are middle or northern Atlantic Coast or eastern species which apparently have extended their ranges far to the northwest, passing north of the Great Plains to the Rocky Mountains and thence southward; some are extensively distributed from the coast of New England and Labrador to Alaska. The following have entered Montana and the Rocky Moun- tains from the east: Populus angustifolia Prunus americana = Sargentii Acer Negundo Salix pedicellaris Sambucus canadensis SOURCES OF THE VEGETATION 67 Salix candida Symphoricarpos orbiculatus ‘* amygdaloides Fraxinus lanceolata Ribes americanum Bessey (3) concluded from a study of the trees of Ne- braska that most of the species had entered that state from the southeast, influenced largely by the direction of the prevailing winds in the spring and early summer. The cottonwoods, two willows (S. amygdaloides and fluviatilis) and the boxelder were included in his list. Populus Sargentti, which by some authors is considered as at best only a variety of P. deltoides, is contin- uously distributed along all the bottom-lands of the Missouri and the Yellowstone and their tributaries, and evidently has followed up these streams from the lower regions to the southeast. The favorable conditions which woody species usually find on river bottoms and the continuity of such conditions. along the many drainage channels across the plains should have provided a larger representation of such species in the Montana flora. The low relative humidity of the plains and the desiccating winds that sweep across them serve apparently as effective preventives of any departure of woody plants from the lower and more favorable levels. The tops of the cottonwoods along the upper tributaries (16) are distorted and repressed as they reach above the protection of the bordering benches. The matter of at- mospherie humidity is as important for certain trees as the mat- ter of soil moisture, and specific requirements must be met in one condition as well as another. Whether this is the determining factor or not in this case is impossible to say without further study, but for various reasons it seems probable. Prunus Ameri- cana is reported only from the eastern part of the state, and on uncertain authority as far west as the Bearpaws, south of Havre. The ash (Fraxinus lanceolata) probably occurs sparingly in the eastern end of Montana. As the western or Pacific slope of the divide is the more favorable for forest growth and is tenanted by a greater variety of species, it naturally follows that the western element is the most conspicuous in the forest flora of the Rocky Mountains. On this point several considerations should be noted. Aside from the more favorable climatic conditions enjoyed by this region, its more ample precipitation, its higher relative humidity 68 FOREST DISTRIBUTION 2 and more moderate winds, there is also an historical reason in the events subsequent to the glacial period. The more varied top- ography of the Pacific Slope from the mountains to the coast furnished conditions of greater diversity and thus more favorable for varied vegetation. Bodies of water formerly occupied areas now sparsely timbered or prairies and these must, at least during the time of their subsidence, have offered conditions more favor- able for the existence and the movements of arborescent species. The distance to be covered, no less than the character of the intervening country, has doubtless been a factor, for the dis- tance from the Cascades to the Rockies is less than half of that across the plains eastward from the summit, and the time neces- sary for movements would have been correspondingly less even if topographic conditions had been equal. Furthermore the direc- tion of the prevailing winds favor the eastward migrations. It is significant also that of the 63 species enumerated below as having entered from the west 27 have seeds winged or otherwise more or less fitted for wind dispersal, 21 bear succulent fruits with small seeds, such as may be carried readily by birds. The others have small or minute seeds. There are no heavy seed- ed species, unless the whitebark pine is excepted, and the seeds of this tree are eagerly sought by squirrels, birds and other forest animals. There are, of course, few heavy seeded species on the coast in neighboring latitudes. According to all reports no oaks have yet reached Montana either from the west or the east, al- though they oceur in Wyoming. Following is a list of the species which have entered the Rocky Mountains from the west or northwest: *Pinus contorta * Betula occidentalis *Pinus monticola * “© — fontinalis ‘« albicaulis ‘* alaskana Larix occidentalis ‘f glandulosa *Larix Lyallii : *Alnus tenwifolia *Pseudotsuga tarifolia *Odostemon Aquifolium *=Abies grandis *Ribes cereum *Tsuga heterophylla *Philadelphus Lewisti ‘* — Mertensiana *Spiraea Douglasii *Picea Engelmannii * Holodiscus ariaefolius *=Thuja plicata *Rubus parviflorus SOURCES OF THE VEGETATION 69 *Taxus brevifolia Rosa nutkana *Populus trichocarpa ‘© pyrifera *Salix fluiatilis 3 ‘* gymnocarpa ‘* — melanopsis *Amelanchier alnifolia ‘< exigua *Crataegus Douglas ** — argophylla Sorbus scopulina ** Mackenziana *Prunus demissa “¢ vestita Prunus emarginata ‘< sitchensis *Pachystima Myrsinites ‘* Geyeriana *Rhus Rydbergii ‘< Scouleriana Ceanothus velutinus <> bella ey sanguineus ‘* — glaucops Kalmia microphylla *#Rhamnus Purshiana Cassiope Mertensiana +Echinopanax horridum =Gaultheria humifusa #Cornus Nuttallii Vaccinium occidentale Ledum glandulosum Poe amet membranaceum =Rhododendron albiflorum ok oreophilum Phyllodoce empetriformis ne scoparium fs glandulifera Symphoricarpos vaccinioides *Menziesia ferruginea The species listed above vary widely both as to their abun- dance and as to the extent of their areal distribution. Some (marked *) are found generally distributed throughout the re- gion under discussion in their appropriate altitudes. Those marked (+) are either rare or uncommon, confined to the lo- ealities or altitudes suited to their peculiar demands, which in * According to Bebb (Bot. Gaz. 102-108, Ap. 1891), the group Longifoliae, to which belong Salix fluviatilis, S. melanopsis, S. exigua, and S. argophylla, “is distinctly American, clearly defined on every side, shading off into no other by variation, hybridizing with none. It is not connected with the Old World forms by any synthetic type of the present or of any preceding period, but apparently was derived from the Mexican Plateau at the close of the Tertiary. In keeping with this view it finds its fullest development and greatest variation in form and structure on the Pacific Slope. Eastward it declines in vigor and variability until on the Atlantic Coast it is of rare occurrence from New Brunswick to the Potomac.” Taking this view into account, there is some doubt as to whether the species named should be regarded as coming from the south or west. Considering, however, that the group is most fully represented today in numbers and forms in western Oregon and Washington, it seems most probable that they have come into our region from that source and are so listed. TU FOREST DISTRIBUTION — all but a few cases means mesophytie conditions, or they are found only along the western boundary of the State. The other species are more or less abundant locally but have no very wide range, or they may be sparingly and uniformly scattered over the area. The number of Pacific Northwest species increases with the distance westward from the Divide. As nearly the whole of Montana west of the Range is drained by the Clark’s Fork of the Columbia and its several main affluents, the Flathead, the Bitter Root, the Blackfoot, and the Hellgate (the upper continuation of the Clark’s Fork and now known by the same name), the re- gion falls naturally into four divisions corresponding to these main drainage basins. Of the two most westerly, the Flathead lying to the north and the Bitter Root to the south, the Flathead presents the most humid conditions and contains the largest number of western species. The Bitter Root, on the other hand, is the least humid and presents fewer mesophytic situations. It lies in the rain shadow of the Bitter Root Mountains. Only in the passes and the deeper gcrges of this range are mesophytie conditions found and in these some of the moisture loving species appear, but most of them are excluded by the high barrier to the west. In discussing the topography it was pointed out that a high mountain barrier extends along the western border of Montana, except where the Coeur d’Alene Range interrupts the higher ele- vations with a broad plateau-like formation, dissected into nu- merous canyons and relatively low summits. Just north of this lies the channel of the Glark’s Fork bearing all the waters of the Continental Divide over a distance of 300 miles of its western slope. North of this the high ranges again arise, extending far to the north. The Coeur d’Alene Range is occupied by 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 ascend the west- SOURCES OF THE VEGETATION Pa i | 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- eration 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 xerophytie 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 erowing 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- inforced 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 limits 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 Salix candida Ribes americanum ** — amygdaloides 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. Those 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 Pseudotsuga taxifolia Ledum glandulosum Picea Engelmannii Phyllodoce empetriformis SOURCES OF THE VEGETATION 73 Salix Mackenziana Phyllodoce glandulifera ‘* exigua Menziesra ferruginea ** Scouleriana Kalmia polifolia ‘* glaucops Cassiope Mertensiana Betula fontinalis Gaultheria humifusa Odostemon Aquifolium Vaccinium membranaceum Rubus parviflorus as oreophilum Amelanchier alnifolia o scoparium Crataegus Douglasii Artemisia camporum Prunus demissa 3 frigida Pachystima Myrsinites : 2 cana Rhus Rydbergu 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 ne vivipara Eurotia lanata Gilia pungens Grayla spinosa Sambucus glauca Ribes aureum Aplopappus suf fruticosus Rosa Fendleri Tetradymia canescens ‘* —ultramontana He spinosa Cercocarpus ledifolius Chrysothamnus nauseosus ‘ montanus se viscidiflorus Purshia tridentata Artemisia tridentata Amelanchier oreophila ef spinescens = utahensis Yucea 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 lst 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 74 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 doubtless 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 imply. 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 drainage 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. f VHE forests of Montana cover about one-third the area of 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. 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 ) 76 FOREST DISTRIBUTION . leaved, deciduous vegetation, is dominant, as a 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, Salix, Alnus and Betula. On the western slope Populus trichocarpa is the only large cottonwood of the river bottoms. It is usually accompanied by Alnus tenwifolia 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, S. 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 alnifolia, 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. Only 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 taxifolia, Picea Engelmannii, Abies lasiocarpa, and Juniperus scopulorum, Locally Pinus monticola, Tsuga hetero- GENERAL FOREST ASPECTS 77 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 Engelmanni 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 yellow 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. It 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 ‘AJOATIOAMSaA TT JO JSOMYIAIOU puR g JO Jsvet}A0U O1¥ ‘poyreUTUN ‘¢ puBw } SUOTIIBgG “LINOSSIT “ET “WoyNsiq “FL “AMOUg “ET “AMVdIveg “ZI “RYOIESGY “TT ‘SYO 9A “OL ‘og “G6 MOAT UNG “gS ‘a}VS[[OH “2 JOOW AIA ‘9 “‘PRoWeLA “GE “TRUEB}OOY “F “AoVAABTD “GE “OUTY.P MON *Z “UOLOoOS OYW'T] Sold *[ ‘SUPRJTNOPW! AYOoY W1oyJAOU oY} UE SBAIB [BUTS JSoLOT “TT “SLA 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 souree 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 mesophytie 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 cinasnetaon | Range of Altitude Pinus monticola ........-----.---.---2--+s---0-- 21-30 2000-5000 $F DGTEALOT ORE apse os 7-10 2000-4000 SSS Meantorta@: . ct. scccues toon 2000-6000 64> > Qiicaulis 2c. onl Go 6000-7000 Lariz occidentalis .....------..-.-.-2:0---<-- 18-20 9000-5500 Picea Engelmanniy. ......-----.---00-----2- 20-25 2000-7000 Tsuga heterophylla .......------------------- ge 2000-4500 Pseudotsuga taxifolia ........-------------- 8-15 2000-6000 Abies Granilis~...uin on ee - 2000-5500 68 LASVOCON DG: 22.520. cinevtte-n peer 5000-7000 Thija plicats -.....2.2-0-1. sie 9-10 2500-5500 Juniperus scopulorum. .....---------+----- 3000-5000 e COMMUNAB. Soke hsc ee 4000-6000 Taxus: brett alaa. ..22c.-s0:--se-saeeeaone 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 arboryitae, 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 9 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 | coeapecnia'| Range in Altitude Pinus monticola .............- Pir See 2100-5000 i MONGEROSE. ez. he , OBS 2100-5000 em CONTOFTR Sich. Pe. ae 2100-7500 PE MEL DER ULES. = osc ec eae 4500-7000 Larix occidentalis ......2.....-.....---2.---. 6-24 2100-6000 [LA ELL MET iets | 7000-8000 Picea Engelmannii ..........22..0.---20---- 2-11 2500-5500 Tsuga heterophylla .................. rap 2100-5500 PETE OH SURI sc. - k. -cbeks sc kes . 4000-7000 Pseudotsuga taxifolia ........... -....-.-- 18-25 2100-7000 Abies grandis .... ................- eee 49) 2100-5000 PIE SIOCATIOR 0 5.5isc0i acco j- 4000-7000 Juniperus scopulorum _........2222------ -b5 2100-5500 [1 EG" ge VT, cr ar 3000-5000 ‘f COMMUNIS 2.2.22 o Lecce ens 4000-6000 PETS PUTOCUTFOUG® 2.02.2. 5.002 Aces. 2100-5000 With referenee 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 conditions 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%. Abies grandis forms 12% on the western slope and a negligible 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 Y = spruce favors the western slope. On the other hand Pinus pon- derosa, Larix occidentalis and Pseudotsuga taxifolia 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 climatie 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 | earsngseceltecey Range in Altitude Pinus monticola ............. 30 1800- 6000 ONS SS 2 2 SR a 2.95 1700- 7500 BR CON LOT Eh oases cn ce coaastiny 7-40 2500- 9500 Ra YI UECOULIS 2 nes ood. ees 1 5000- 6500. Larix occidentalis. -..2.200..220.0..02022.-3.- 7 3000- 5000 SATE SERRE Se oe 7000-10000 Tsuga heterophylla ...................-..--- 3 5000- 6500 Pacca Engelmannii. .......2....2..2....-.-. a- 6 2000-10000 Pseudotsuga taxifolia -........-.....--..-- 14-20 1800- 7000 PROCS HIP ORGIS 25sec isa ncen cee sndee 2a-bo 2000- 5500 I a a ae 2 4000-10000 fC SS I Se 14 1800- 5000 Juniperus scopulorwm. .«..-.-------------- 2000- 5000 4 COMMUNIS ......2.0..-.--.---> POLUS OFCUIFOUG ..<...--.-.---2/--- 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 lying farther to the east. Although the species typical of this belt do occur 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. “J 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 Jower. 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 | Gameecition| Range in Altitude Pinus ponderosa x 9 1900-5000 “f)) QRORTIOOLE Wo ee 5 2200-4000 8 CONtOTtE a ee 17 1900-6000 ‘< albicauhs ... | 5000-7000 Lari occidentales 208 21 2000-4000 amie B15 RN 8 ee ae 7000-7500 Picea Engelmannii. .....2.....-2---0-0000 21 2000-7000 Tsuga heterophylla ........------..---++--+- 14 3000-4000 A.btes grandts in. eee 14 3000-4000 “\ < laslocarpd: so304. eae 2200-7000 Pseudotsuga taxifolia .......-..--.-------- 18 1900-5000 Thija plicdta Ans Soca eee 2200-3000 Juniperus scopulorum .......--------+-- = COMMINUAAS scdices nncceesese Tazus brevif 0G) cst coe 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 yellow 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 lCompegttian | Range in Altitude PUM E POW UICOUG 02550022 Scents 3.02.1 3000-5000 NT LOS 9 ea ee 2.0 3000-4000 Oe ASS a ae eae 1.0-14 3000-6500 ER GT OY ae b- 1 4000-7000 «Bari occidentalis. ................0..200.0-2-. 35.0-50 3000-5000 ‘ Lyallii Net 5000 Picea Engelmannii ..... | 20.0-23 3000-6000 Tsuga heterophylla ..........-.--..-------- 3 1 3100- Pseudotsuga taxifolia -..................-- 11.0-17 3000-6000 OWA 110 | Xe 1 3000 OT POSTOCUP DE. <..--.-sa-2n0cscnoe-nci os 1.0 3000-7000 HOG, Sl 17 3000-5500 JUNPErUS SCOPULOPUM -..22-22-20-00------- 3000 oN COMMUNAS ooecnncconnccccece----- 3000-6500 Taxus brevifolia. ...-.-.-.--.--..----------- 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, yet 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 Glacier 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. Species | beiheeian | Range in Altitude Pinus ponderosa ..x.tcoci5 hon 32.0 3500-7000 © CONLOVEG "cil nce 40.0 3500-8000 “>” “QOSCRULIS 2a aaa eee 2 7500-8500 Sf. MBOMTCOL IR -5 tates teats Lariz, occidentalis... ssc. o nee: 8 3900-5000 0° ERO, ee ata 7500-9000 Picea Engelmann .......-..-------000----- 1.6 3500-7500 Pseudotsuya taxifolia -.........-....------ 24,2 3500-7000 Abtes lasiocar pa .....-..-c01--5--eeeeee-ane 5000-8000 60 TUNES: Scere 4000-5000 Thitja placate, c.sac ence 4000-5000 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 gradually 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 sade idan | Range in Altitude PiNUs PONE OSG, .....-------.---2-24--2---0---- 5.5- 3500-7000 LES <1, SIE Or a ae =te 3500-9000 oes Cry CS Re a a eee a 1.0- 6000-9000 Larix occidentalis ......-....----- ---+-+--+- e 5 3300-6000 Na SY SOS Settee Ono Seen 7000-8500 Picea Engelmannw .......--.--------------- 2.0- 3 3300-9000 Pseudotsuga taxifolia ............--------- 15.0-23 3300-7000 ALOVCS TASUOCUT AG: 2251-5 a- oooh oe ene 1.0- 3500-9000 Juniperus scopulorum -...-..2..2------- 3300-5500 te COMMUNIS ...-...c00202200--2- 3400-5500 88 FOREST DISTRIBUTION or 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 by 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 les 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 omertertiae | Range in Altitude eMC ICON OTE co 2.5-< Aon evces neo cnacsee 50 4000-8000 BRE RECDNEIS earl p oe Su oe accesses vee 10 5000-8500 Picea Engelmanniy - ...-..0..2..-2.2.22.0:05. 20 6500 Pseudotsuga taxifolia -.................... 1D 7500 PE DICS MESTOCOT DG — <<..-522)-oocn-ocncosnngcnes 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 ig 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 other more or less elevated masses, the Highwood Mountains and the Little Rockies, which also are forested. Table 17. Forests of the Belt Section. Species iGaneesttion | Range in Altitude PEWUS CONTOTUY 25.2 sooo oasele nena 56-84 5500-8200 Sie MIITTP CPO) 2302 aneee te, 7-15 7500-8300 MO EGLO NS ae ie i: Cae a Ee 7500-8300 IS AOE CR a ea 7000-8300 Picea Engelmannti ....-.------------------- 2- 6 7000-8000 _ Pseudotsuga taxifolia ..-...-.------------- 5-44 6000-7500 | Abtes lasiocarpa. ....-..---..-2----2-0-2---++ 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: | Pinus flexilis ....... 8.2 ‘< albicaulis 009 ‘* contorta 34.2 ‘* ponderosa ...--- OT Picea Engelmannivi 11.4 Pseudotsuga taxifolia 44.7 Abies lastocarpa ......2----+----- zs 1.4 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- ity 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 glaciated and climatically dry and cold. GENERAL FOREST ASPECTS 91 Table 18. The Forests of the Three Forks Section. Species ore Range in Altitude Pinus ponderosa .........-.--- 5600- 6500 ‘* — contorta 60-75 5600- 8500 oS. UD UCOUST nce : 14 7000-10000 argh BE Tie, NS Rat Se a 7000-10500 Picea Engelmannii .. ia Sol, AD 5500- 8500 Pseudoisuga taxifolad, ....-..2-2.2.0....- 20 5000- 8000 Abtes lasiocarpa .-.1-<.-21.--2.-..-..----- 7000-10000 Juniperus scopulorum. .....-------.----- 6000 Ss EL a 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 of their 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 northwest 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 e 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 Baum nrciniun Range in Altitude Linus ponderosa 2.5 ee 5000 <4" SC ONFORTAN © Doxa ke ee epeec es 50-60 6000- 8500 etiam 71.1, Meine ae we a, ny Ce ee AS 5000- 8000 ‘6 So GAD CODRHG ARS Cee aaee pe 7500- 9000 Picea Engelmannity....: 2.222222. eseene-eoe 15 6000- 9000 Pseudotsuga taxifolia -..............22..-.. 21-30 5000- 8000 Abtes lasvocar pds. sb ene 7000-10000 Juniperus scopulorum ........2222-2------ 7500 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: Pinas FlCLNAE. oe eet Ak sac ay 2.3% °° COMEOPET aoe hs oe Re ee 45.6 °* PONDETOSO seis ccsat pictaases Yuae Wikeheecttase 005 6o albvealige nea wee 5.3 Picea Engelmann ..........c.0..-2-rentensecsestesoqee 21.8 Pseudotsuga taxtf old ..2.:....-c-cecccenacrencesene 12,2 Abies lastOCar pa ic2.c.cecsiodessassctenesacex oe 11.1 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 above 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 east 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) occur 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. They 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: FV COMT OTT oe act eatin ieee 16. % Oe a TIO CHM 2) cas anne sce 13.5 FUEL EA CCUM Oe. hei as ohn ute Sees . 6.5 SF SOU OUSMOE TARDE OU co. gecencdn-c2ieencshece ote geteet ” 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 above 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 eondi- 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 Arctice-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: 7 | VHE forests of the northern Rocky Mountains are included *Populus occidentalis (P. Sargentii) Yucca glauca a acuminata Opuntia polyacantha *Salix amygdaloides *Plantago Purshivi ‘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 es 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. In some places it is the bunchgrass (Agropyron spp.) or the bunchgrass 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 of gymnosperms within this region, as far as at present known. FOREST ZONES AND FORMATIONS 97 Table 20. Ranges in Altitude. ; Minimum Maximum Species | Altitude | Altitude PRUE DONC CVORG < .c0leickosacecdt ess hc8s 1,500 7,900 ST Se a 1,900 9,500 PO WEL COLE 9 ca kids x sce decency: 1,800 6,000 MP PUSOMIES, (eco oes c ogee once steaet: 4,000 11,000 emer So. Sons a elas 3,000 10,500 WPI E OCCIACNIQUS: 2526: 2,800 7,000 aN es eons 7,000 10,000 Picea Engelmann .....0...2..cscc2.00.- es. 2,000 11,000 Tsuga heterophylla .........0..2.....22....- 2,900 5,900 IRS Sg ee 0 ye 4,000 7,000 Pseudotsuga taxifolva ..........22........- 1,900 8,000 OS) SCA Ta 2) Ca nea 2,000 7,000 ae ETT, 5 a ai eee 2,000 11,000 TRAP PU Cire wee ee. 2,000 5,900 Juniperus scopulorum .........0-..... 1,900 6,000 ee COMMUNIS. ....22.-.-202-2.000 ne. 3,000 6,500 “ OS a a 2,500 4,000 Taeus brevifolia:~.......--.006..000 cs. 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 they 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 lascocarpa, 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 (L. Lyallii) 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 ‘Ae “ds ‘nizasuayny ‘synov snjouayy ‘wnasad saquy ‘vuva “Pp ‘vajnmosw msvuajzsp “ds xajd 4p “vsomds milivisy ‘snynjnoyuiaa snqoqoouwg ‘ayeys pue Av[Q “Wo ‘PAtpua—y avou spuelpeg ‘gr “Fy 9S 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. A few shrubs Cassiope Mertensiana, Phyllodoce empetriformis, Salix Barclayi, ete., are found only in the high mountains. Many other species occur freely at elevations from 4000 feet, through- out most of the upper forest belt. Among such the following may be mentioned: Pachystima Myrsinites Sorbus scopulina Valeriana sylvatica Ribes lacustre Erythronium grandiflorum Vaccinium membranaceum Calochortus apiculatus aie uliginosum Veratrum californicum Menziesia glabella Xerophyllum Douglasii Before proceeding to a discussion of the several zones it is desired to call attention to a few facts determined for the six species most important and widely distributed. These figures on the viability of seeds and the rate of growth of seedlings are to be interpreted in connection with the behavior of the species in the field. The observations which extend over a period of several years are the results of experimental work by the writer at the University of Montana. The experiments were conducted under the climatie conditions of the prairie, more difficult at Missoula than those to which most of the species are accustomed in their natural situations. Comparisons are made between seeds from different sources. The prosperity of plants in the field is largely measured by their possession of advantageous characteristics among which their seeding behavior and rate of early growth are important. The special study of seeds and seedlings pertained to six species, viz., Pinus ponderosa, P. monticola, P. contorta, Larix occidentalis, Picea Engelmannii and Pseudotsuga taxifolia. The seeds were obtained from various sources in California, Oregon, Washington, Idaho, Montana and Colorado, and their behavior 100 FOREST DISTRIBUTION 2 in the experimental operations compared under dissimilar con- ditions. The seeds within one year of their production showed from 3 to 54% defective in different lots and species as deter- mined by physical examination, while in the beds none of them showed more than 10.4% viable, although the most favorable conditions were provided. This estimate of viable seeds, how- ever, is doubtless much too low, owing to the fact that it was based upon the number surviving at the end of the first season. The percentage of response in germination showed no relation to the percentage of apparently viable seeds by dissection, Thus where Pinus ponderosa showed 91% viable by dissection 10.4% actually produced seedlings, while the same species in another lot showed 94% apparently sound there resulted only 7.7% of seedlings, and in the case of the spruce the figures were respec- tively 91% and 2.8% for one lot and 74% and 3% for another. The only constant relation revealed by the studies seemed to be that the time required for germination is inversly proportioned to the number of seeds responding, or, in other words, percentage of germination and rapidity of response were directly propor- tional, a condition to be expected. The results obtained from the few species examined and experiments conducted under the favorable, conditions of cultivation suggest that the rate of propagation in the field under natural conditions must be very much less. It is seen also that radical differences obtain be- tween seeds from different sources, as to size, soundness, and response in germination, facts which must weigh in the final determination of the place which each species must occupy in the different parts of its range. Observation of the seedlings of this planting through a peri- od of several years shows a marked acceleration of growth in height after the second vear in nearly every case, being least in the Engelmann spruce and most in the larch. The greatest growth in height at the end of the first season was 414 inches in the case of Douglas spruce, at the end of the second season the larch with 13 inches and at the end of the fourth with 59 inches. The Douglas spruce reached a height of 22 inches at the end of the fourth year, the yellow pine 23 inches, the white pine 13, the lodgepole 27 and the spruce 16, though the latter was exceptional, the heights in other lots of the spruce being FOREST ZONES AND FORMATIONS 101 10 or 11 inches. The average heights attained are more sig- nificant. Those for the yellow pine at the end of 1, 2 and 4 years were respectively 2, 4 and i8 inches; for the white pine 1, 3 and 9; for the lodgepole 1, 4 and 18; for the larch 1, 8 and 40; for the spruce 1, 2 and 6 and for the Douglas spruce 1, 4 and 12 inches. The disadvantages of delaved growth in compe- tition with other species are of course obvious and these are most pronounced in the earliest stages of growth in each species. As between these species it will be seen that the greatest growth in height occurs in those most intolerant. : In the study of these seedlings parallel experiments were conducted under a lath screen of half shade, 8 feet above the soil. Under such conditions growth was usually slower than in the open, apparently indicating the retarding effect of shade in the growth of young trees. This result, however, was reversed in the case of the larch and Douglas spruce which exceeded in height those grown in the open. Thus in the case of the seeding habits of various species peculiar conditions obtain which affect their prosperity under the varying circumstances of their environment. Probably few features in the life are so intimately concerned with their preva- lence as are those of their seeding habits. Tor Fooruint VEGETATION. Over a large area of western Montana, from the Divide westward to the Bitter Root Range and embracing the drainage of the Clark’s Fork and its tributaries the Bitter Root, the Blackfoot and the lower Flathead, the landscape is strongly diversified by alternate forest and prairie. Forest distribution is in strong relation to topography, sheltered slopes are forested, open and exposed slopes are grassy. The latter are usually, but not always southern or western, often sharply marked in contrast with a vigorous forest at the turn of a ridge which leads to a northern or eastern slope. High slopes rising 2000 feet as in the Hellgate Canyon are thickly wooded on the north with an abrupt transition at the crest to grassland on the southern face. Such alternation of forest and prairie are common and on a lesser scale may be seen in miles of land- 102 FOREST DISTRIBUTION . > scape in the Bitter Root and the Jocko Valleys. Even low undu- lations on the mountainside present the same aspect. Where the direction of the slopes fails to present a sufficient contrast of conditions the transition is more gradual and scattered forest trees are sprinkled through the grass land diminishing in size and numbers with the increase in distance from the main stand until the farthest limits of the forest are represented by a few low pines set at wide intervals. A tension between the prairie and the forest is evident. It is also evident that the forest is gradually replacing the grasses. Here the pine leads the way followed closely by the Douglas spruce, these two and rarely other species, Juniperus scopulorum. The migration is usually from above downward, but local conditions may vary this and show a migration from wooded canyons onto the neighboring prairie. An interesting reversal of the usual course is to be seen on Wild Horse Island in Flathead Lake, where the forest, governed apparently by the proximity of the lake waters, became established first at the foot of the slopes and is gradually oe- cupying the higher ground. Owing to local features of the physiography the directions of the wooded and barren slopes may be altered, or even re- versed. The western slopes of the Mission Range, rising from Flathead Lake are densely wooded and steep, while the opposite shore, a series of low foothills, is mainly grass-land. The evi-. dent explanation here lies in the influence of the lake upon the moisture content of the westerly winds. The foothills of the west shore lie in. the rain-shadow of the Cabinets, a high range to the west. Narrow valleys or canyons extending north and south and transverse to the direction of the west winds some- times show the western slope more heavily wooded than the eastern. This fact is due, apparently, to the protection from the desiccating influence of the westerly winds afforded by the mountain opposite and the normally higher temperature of a western exposure. In the vicinity of Haugan, near the western boundary of the State, the dry exposures are distinctly north- eastern. This locality was once heavily forested but many years ago was denuded by fire. A series of slopes here shows a sharp contrast between the southwestern and western exposures which were, at the time of the observation, in 1910, producing a sturdy THE FOOTHILL VEGETATION 103 young growth of Pseudotsuga tavrifolia, Larix occidentalis and Pinus monticola, and the northeastern slopes on which no re- forestation had taken place, but which were occupied by a low and scattering stand of Ceanothus velutinus. | That the slopes at Haugan were originally forested by the slow process of conquest which seems to be the rule where the pines invade the prairie is of course impossible to say, but that transitions occur from the grassland to an open pine forest, and then to the full occupation by Douglas spruce, larch and other species, has heen pointed out in the case of the forests of the Flathead Valley (73), and apparently is of common occurrence elsewhere. The severity of the conditions on an exposed western slope is not at first evident. Such slopes are usually covered with tall waving bunchgrass. Agropyron spicatum, and a host of herbaceous, plants mostly perennials, among which the following are conspicuous : Balsamorrliza sagittata Cogswellia macrocarpa Senecio canus —Cogswellia simplex Monarda menthaefolia Pentstemon Wilcoxii Delphiniwm bicolor Arabis Nuttall Zygadenus venenosus Comandra pallida Mertensia oblongifolia Woodsia scopulina Cogswellia montana Selaginella densa Achillea lanulosa Lupinus ornatus Clarkia pulchella The active vegetative period of most of these plants comes early in the season before the rains have ceased, and by the middle or the end of July they have finished fruiting. The test of the season comes during July and August, when scant pre- cipitation, high temperatures, clear skies and dry winds draw from the thin soil almost its last vestige of moisture. Such con- ditions are impossible for forest trees, except: where the seedling is sheltered in the lee of some rock or in the bottom of a gully. Now and then on such slopes a single yellow pine has rooted and grown to large size where one chance in millions has placed a seed in favorable conditions. A series of experimental operations conducted to determine the practicability of forest planting on sites of this character, pue saoqe sured oy, sursivul oy} jo peordAy, ‘ABI “SS9[991} JIB MOTIG ‘RURJUOTY Ulo}JSvo UL sUIva1]s JOYyJO pu [eYspassny_ “9UOJSMOT[A A VY Buoype sAapyea jo ‘uniojndoss sniadiunp pur vsosapuod. snug ‘juoyw ‘dnpunoy avaN “FL ‘BI 104 THE FOOTHILL VEGETATION 105 indicate something of the severity of the conditions involved. Three situations were chosen on the grassy slope of a mountain facing the west and southwest. One of these by reason of a slight depression and less direct exposure to the sun was con- sidered more favorable than the others; the other two areas, lying on a steep and rocky slope directly facing the southwest, were regarded as exceptionally severe. Upon these areas plant- ings were made in three successive seasons (1910-1912) with considerable numbers of vellow pines, both seedlings and trans- plants one or two years old. Unusual conditions in the form of drouth and fire at first beset the efforts, but in the end, owing to circumstances attending the planting and a season more than usually favorable, the plantations weathered the first summer with about 25% of the trees surviving. It was thought that the main difficulty besetting either natural or artificial afforestation was the establishment of the seedling, and that if the first season could be survived they might maintain themselves indefinitely. Such, however, seems not to be the case, for in these experiments the number surviv- ing waned rapidly from year to vear until none were left. The stems and leaves eventually turned dry and erisp, and, inasmuch as the planted seedlings could be clearly identified, any conclu- sion that they had been destroyed by other agencies was obviated. Growth, as usual under such circumstances, was slow. Even the plants that survived two years or more grew a scant inch or more of stem and a few dwarfed leaves while those of the same stock remaining in the nursery increased by several vig- orous inches and a full brush of healthy leaves. Seeding operations were even less successful, as was expect- ed. Several variations of method gave uniformly negative re- sults. The difficulties that beset natural seeding are largely present in artificial methods and that forest extension over grass- lands by natural means is exceedingly slow is generally true and a matter of common knowledge. Along the tension line of yellow pine forest and bunch-grass prairie of western Montana the direction and rate of transition is evident in the scattered pines successively younger and more sparse from the forest outward. It would hardly be safe to say that successful forestation of such areas with Pinus ponderosa is impossible, but the fail- 106 FOREST DISTRIBUTION ee ures attending the above experiments indicate something of the hazards involved. Of all native species of forest trees the yellow pine undoubtedly is the most capable of surviving in such situ- ations, from the standpoint of its water requirements, but in addition to this we may consider also the fact of considerable amounts of seed produced, their high percentage of germina- tion and the facility with which they are sown by the wind. Millions of seeds must be produced for every tree that shows its head above the herbaceous vegetation, and such are very few. These soils absorb practically al! the rain that falls, except what is lost by evaporation from the surface of plants. There is rarely any run-off. The soil is porous and stony and absorbs quickly any rain that may fall upon it. In the invasion of the grassland the constant companion of the yellow pine is the Douglas spruce (Pseudotsuga taxifolia). No more adaptable species is to be found among the forest trees in the northwest. Partial as it is to abundant moisture, never- theless it resists almost as much drouth as the pine, and grows to large size, albeit more slowly than elsewhere. It is this spe- cies which more than any other marks the transition from the open yellow pine to the mesophytie or near-mesophytice forest. On account of its greater tolerance it is capable of supplanting the pine. In these situation, however, it is slow to develope density and grows with the pine in an orchard-like stand and not crowded, as its habit is on more favorable ground. The western yellow pine and Douglas spruce are, however, characteristic of the semi-arid zones and belts of irregular form and determined by elevation, exposure, precipitation and wind in the tension zone between woodland and prairie. On the Mis- souri drainage they often occur associated with Juniperus scopu- lorum, either on the foothills or along the rim-rock bordering the benches on the Yellowstone and other streams far out into the plains. Of the two species the yellow pine has a little the best of the struggle as the pioneer in the invasion of the grass- land, but owing to its intolerance, is at a decided disadvantage in competing with the Douglas spruce in the better watered soils. One of the most striking features of the forests at middle elevations, especially on the western face of the divide is the strong influence of topography in the matter of forest distri- THE FOOTHILL VEGETATION 107 bution. South and southwest slopes are usually grassy, or covered with an open forest of yellow pine and Douglas spruce, the former the more abundant. The northern and eastern slopes usually bear heavy forests in which Douglas spruce prevails, or in which larch is locally strong sometimes over considerable areas. ! The difference between opposite slopes is a common and striking phenomenon over wide ranges of landscape and con- cerns mainly the vellow pine and Douglas spruce. That this is a reaction to soil moisture would seem to be evident. Experi- mental operations, however, do not wholly support this view. Soil samples taken from the depth of a foot at five different stations on each of two slopes for comparison, the one facing north, the other south, were placed in glass stoppered bottles and removed to the laboratory. This was at the close of a rain- less period of three months. By the removal of the stoppers they were allowed to become air dry. After a lapse of several weeks the samples from the slope facing the north had lost an average of 3.0% of their original weights; those from the oppo- site slope had lost 2.5% of their original weights. The samples were then kept for three weeks in an oven at a temperature of 120 degrees C. At the conclusion of this period the samples of the former lot had lost an additional .9% and of the latter .8%. The total loss therefore. in terms of the original weight, was 3.9% from soil of the northern and 3.3% from soil of the south- ern exposure. There was a difference therefore of only .6% in moisture between the two series. The southern exposure presented the usual open yellow pine forest with almost bare soil; the other bore a dense cover of young Douglas spruce and larch with ground cover of mosses and other small plants. Com- parisons were also made on a series of soil samples from the level gravelly plain and an open treeless slope, covered with grasses and other plants, according to the same methods and subject to the same conditions. The former showed a total water content of 1.9%, the latter 4.3%. While the evidence from soil examinations is not so con- vincing as one might expect, the data are too meager to justify conclusions. It may be expected that the longer the period of drouth the more closely will the different sites approach uni- ‘Avy ‘vsouapuod snug Ajureu Suravaq SPN %uULIsIp oY} UT “Wleatjs ay} Suole wjzuahing snyndog punosSyovq oy} uy ‘dds wisrwajupy pue vyjuvo -pijod vyundg punoasas0; ey} Ul “vURyUOIT ‘OUOYSTOP TvoU T[PYSTessny_ oy} Zuoye yey oquny ‘ey “S1yq 108 THE FOOTHILL VEGETATION 109 formity in the percentages of soil moisture. It is obvious also that the water supply in soils is depleted by absorption and transpiration, which may in large measure account for the dry- ness of the soil on the more heavily wooded slope. The yellow pine seldom favors the steeper north slopes, even where space is available, except upon outjutting promon- tories or elevations, which seems to indicate certain relations to light or temperature. Experimental operations show that the yellow pine grows more rapidly, on the whole, exposed to full light at Missoula than it does under half shade, while the reverse is true of the Douglas spruce. It has been suggested above that the study of distributional problems should be approached from the standpoint of the nature of the species, rather than from the standpoint of the external factors. Ecological literature has usually been concerned more with the effect of climatic and other factors upon the vegeta- tion as a whole on a given area and for the most part has neg- lected the critical examination of the specific qualities which identify the important species. Irom this point of view phy- sical data is none the less necessary, but each species is a complex entity which reacts to its environment in its own way. Each has its individuality and the study of that individuality, the specific reactions to light, temperature, moisture, etc., efficiency in seed bearing, periods of fruiting, immunities and the like, in short the sum total of its resistance and response, must throw lght upon the nature of the plant. and the conditions of its distribu- tion. Every species is a complex of positive and negative quali- ties, the positive qualities those that are advantageous, the nega- tive those that are disadvantageous. The balance of these qualities may show an excess for or against the species, and this balance will be found to be proportional as a _ rule to its geographic range and abundance. The negative qualities are limiting factors in its distribution, the positive make for dispersal. The more stringent the limitations the more circumscribed the distribution locally and generally, al- though in the latter aspect the limits of geographic range are not due to the lack of similar and suitable conditions elsewhere, so much as to the more effective action of intervening barriers. These conclusions, it is thought, will be supported by reference 110 FOREST DISTRIBUTION = to the particular species which occur in this region. The three species which occur most commonly in the foot- hill regions of Montana are the yellow pine, the Douglas spruce and the Rocky Mountain juniper. Taking first the case of the pine certain highly important positive qualities may be pointed out. This species produces abundant seed amply winged for distribution by the wind and with high percentage of via- bility. The moisture requirement both as to soil and air is relatively very low, within its range it is subject to a tempera- ture range of at least 180 degrees, and it will grow on soils of widely differing texture and composition. Add to these quali- ties that of immunity to most diseases and, on account of its thick bark, to ground fires of ordinary intensity, and also the general vigor and robust habit of the tree, and it appears that the yellow pine is equipped with an unusual number of impor- tant positive qualities which make for extension and survival. The only serious limiting factor which seems to militate against its success is its intolerance of shade. Owing to this weakness it is largely excluded from moister soils suited to the more vig- orous and rapid development of its bulk, and eventually sue- cumbs in the gradual march of succession to the more tolerant species which compose the climax forest. From the point of view here advanced it is this combination of positive qualities which accounts largely for the wide distribution of the species over most of the western half of North America and its common occurrence in most places within its range. The Douglas spruce offers a similar case. Its seed bearing capacity is large and the light seeds are readily carried by winds to considerable distances and show a high degree of viability. It is a tree of vigorous growth up to maturity and has the added advantage of greater tolerance than the pine, in favorable sit- uations forming dense stands to the exclusion of almost every other green plant. This species also resists as wide a range of temperature as the pine, and seems impartial as to most soils. Toward maturity the tree is largely resistant to slight fires. In its moisture demands, however, it is slightly less resistant than the yellow pine. While a close second to the pine in the tension line between prairie and forest, yet the Douglas spruce more readily shows the effect of adverse condition in diminished THE FOOTHILL VEGETATION 111 erowth. The species has a wide range of adaptability. While it grows with the greatest luxuriance in the region of heavy rainfall west of the Cascades it also occupies the outposts of forest vegetation bordering the dry prairies in the Rocky Moun- tains and adjacent plains. In the latter situations, however, its inferior size and form indicate the hardships to which it is subject. In another way also is it inferior to the pine in the Rocky Mountain region where it succumbs frequently to the attacks of Razoumofskya Douglasw. As these negative qualities are only relatively of importance, the Douglas spruce is remark- ably well fitted for successful competition and becomes locally here and there in the Rockies, and far more extensively farther west, the dominant species. Its geographic range is greater than that of the western yellow pine. The extensive distribution of Juniperus scopulorum, an- other of the Transition, or foothill species, seems largely to be the result of its rugged adaptability to adverse soil conditions, both as to moisture and other qualities, and to the effective means of the distribution of its seeds by birds. It is however, never abundant to the extent of forming forests, but appears, in the few places where it is pure, in widely open stands. This fact is perhaps associated with the relative paucity of its seeds and to its exceedingly slow growth. It is nevertheless a species resistent to a wide range of temperature and apparently suited to many different soils. It is quite evident that the grassy slopes of this region have not been forested since pre-glacial times. The condition about Missoula furnishes an interesting study in this particular. The city is built upon a gravel plain at one time the bed of a sup- posedly Pleistocene lake; on all sides to the hight of 1,000 feet above the city are clearly marked shore lines of the ancient sea. For miles these may be traced horizontally and they mount one above another in a close succession of slight undulations. The lines of these shore terraces lie chiefly in loose materials, eravels, soils or broken rock. In view of the effects of large roots upon such materials and the minor displacements con- sequent in the course of time, it seems impossible that forests eould ever have occupied these slopes without obliterating the qusosaloqie ay} jo eaidfy, “BUR UOW Ula}sva JO survaijs ay} Fuoye UOT}RJVSIA “TPATY «TTPYSTIssnyy 9y} Jo Spuvywozj0q ay} uo wzuabing snjyndog ‘OL ‘Sq THE FOOTHILL VEGETATION BD sharp definition of the shore lines or at least interrupting their continuity. Some of the foothills are morainal in character, and where unsheltered, support only the herbaceous prairie flora. The higher slopes show numerous outcroppings of the country rock, such as may be found in all stages of disintegration, from jutting bluffs to mere mounds, and usually with more of less exposed talus below. [t is significant that such outcroppings, if not too bold, and much of the older talus, is occupied by deciduous shrubs: Amelanchier alnifolia Opulaster malvaceus Philadelphus Lewisit Rosa Woodsu Ribes cereum Acer glabrum Prunus demissa The species which occupy such situations, it appears, may be for the most part those which are plentiful in the region, and not especially xerophytic forms. Some places are occupied by Populus tremuloides, which may occur here and there as small islands, sometimes on high grassy and otherwise treeless slopes. On the east and west forks of the Bitter Root the southern slopes, grassy and treeless over considerable areas, support in patches scrubby growth of Cercocarpus ledifolius. Over a whole moun- tain side the rock outcrops may be located at a distance by the gray bunches of the mountain mahogany. It clings to the faces of cliffs and seemingly in the most severe and inaccessible places. This obvious feature of the distribution of deciduous shrubs over a slope otherwise unfavorable can have but one meaning and that is the locally greater supply of available moisture. Competition of grasses and other plants over most of the area may operate toward exclusion by withdrawing too much water from the soil, but not by the density of the stand, for there is always sufficient space for many more plants than are actually to be found in the sparse and open stand of the bunch grass. The shrubs above mentioned are often seen aligned up and down the slope in drainage channels so shallow as hardly to be notice- able, but apparently supplying the roots from a source hidden under the coarse fragments which. compose the surface of the talus. 114 FOREST DISTRIBUTION a THe ‘‘Stuie Rock’’ SUCCESSION. One feature which is noticeable in the topography alike toward all points of the compass are the rock fields which com- pose extensive slopes of talus and are known as “‘rock slides’’ or ‘‘slide-rock’’. Such areas consist of rock fragments mostly under a foot in diameter. The succession of vegetation on these areas is a matter of much interest and importance. ’ . 1 na Pinus ponderosa, ( hrysothamnus nauseosus and Agropyron spicaium in the foreground. \ugust. 132 THE WESTERN VALLEYS 133 large degree their preference for distinctly mesophytic situa- tions. With respect to its particular qualities, the statement may be made as follows: The positive elements in the nature of the arbor vitae, are found largely in its seeding habits. The tree produces an abundance of seed throughout a long life. The seeds show a high germination response, and find a suitable substratum on the mossy litter of the moist forest floor. The seeds are the lightest of any produced by our coniferous species and are easily distributed. The arbor vitae is very tolerant and is not very partial as to soils. It is little subject to serious disease. The principal negative elements in the composition of this species are its strict moisture requirements, its limited tempera- ture range, its slow growth in its earliest years and its suscep- tibility to injury by fire. It is evident that the positive qualities of the species out- number those of a negative character, but the moisture limita- tions are locally important to a degree sufficient to outweigh all other considerations. It frequents river bottoms and moist flats, stream banks, the bottoms of canyons and the borders of high lakes in the Rocky Mountains, but in the Coast Mountains of Oregon, where precipitation is ample it occurs plentifully on mountain tops and stony ridges. In Montana it is found mostly in the northwestern part of the State and neighboring regions, and is most aboundant, in the cooler, moisture sections of the north, as on the flats below Lake McDonald and elsewhere in the Glacier Park, and the tributaries of the Kootenai. Fine stands of this tree are pictured by Whitford and Lindgren about the lakes and in the creek bottoms of the Mission and Clearwater Mountains. It forms a conspicuous understory in some parts of the white pine forests of the Priest River Valley where the writer observed it in 1910. It reaches its best development within the limits of moderate temperatures where the soil is perennially moist. The seasonal temperature range must be usually from about -35 to 100 degrees or more but with the usual upper limits of summer heat at 85 or 90 degrees. In the case of the arbor vitae one seldom finds many small seedlings, such as usually are to be found under hemlocks. The growth cf seedlings at first is very slow, rising to a height of aby ; : Fa) br iS par? fed J Fig. 25. On the East Fork of the Bitter Root. On the left, slope facing the southeast, Cercocarpus ledifolius; on the right, north- west exposure, Pinus ponderosa and Pseudotsuga tawxifolia. August, 154 THE WESTERN VALLEYS 135 six to ten inches in four years, but accelerating for a time during later years. In this respect the tree is at some disadvantage as compared with other species like the fir and hemlock and is saved only by its great tolerance of shade. Thus it may con- tinue for some time under deep shade without suffering sup- pression. The trees grow to great age and are very tenacious of life; often with much of the trunk and crown dead a few living branches may survive indefinitely. There are few parasites which attack the arbor vitae though owing to its thin bark it, easily succumbs to fire and the ground which it occupied may become covered with Douglas spruce or lodgepecle pine, or as appeared in one case, with a dense growth of the more rapidly erowing white pine and grand fir. Among the mesophytic companions of the white pine men- tion should be made of the western yew (Taxus brevifolia) while almost a rare tree in western Montana, it reaches a diameter of a foot and a height of twenty to thirty feet, where it occurs in some of the deep, moist canyons east of Flathead Lake, always thriving best in the vicinity of permanent water, but forming a shrubby undergrowth in the shade of old forests. It seldom is abundant, even locally, which may partly be accounted for by the paucity of its seeds and the slowness of its growth. Like some of the other species, however, it may be taken as a good indicator of the humid qualities of the soil and climate. The broad-leaved, deciduous element in the forests of this zone is seldom conspicuous, but along open river bottoms, Pop- ulus trichocarpa is everywhere the dominant tree, sixty feet or _more in height, three feet or over in diameter, and sometimes with a clear, cylindrical trunk of 40 feet in length. The sec- ondary species on the river bottoms are Populus tremuloides, Alnus tenuifolia, Betula fontinalis, B. papyrifera, Prunus demis- sa, Crataegus Douglasii, Salix fluviatilis, 8. Bebbiana, S. cordata, and 8, Scouleriana. Betula papyrifera is much more restrict- ed in its range in Montana than any of the other species and is confined to the northwestern slopes and valleys, where also the aspen shows larger and more abundant development, with Cra- taegus rwularis, Ceanothus sanguineus, Ribes lacustre, Rhamnus Purshiana, R. alnifolia, Holodiscus ariaefolius, Spirea lucida and numerous other shrubs. The trees which appear most con- A bluff on the East Fork of the Cercocarpus ledifolius. South exposure at an altitude of about Bitter Root near Medicine es THE MONTANE ZONE 137 spicuous in the mesophytic pine forest, where openings of the forest permit, are Populus trichocarpa and Betula papyrifera, often well shaped trees of unusual size. The mesophytie forest as discussed above is essentially the same as the. Pacific Coast Humid Transition. It merges by degrees into the Montane or Canadian forest in northern Montana at an altitude of near 4,000 feet. The white pine shows a tendency to ascend the slopes ahead of its usual companions on the lower levels and so in places becomes identified with the mountain forests. THe MonrTANE ZONE. The forests of the Montane or Canadian zone are not clearly differentiated from those of the sub-alpine or Hud- sonian. By reason of the occurrence of some trees more abundantly at higher altitudes and the restriction of a few species of herbs and shrubs to the same elevations the areas im- mediately below the highest peaks and ridges have a physiognomy more or less their own, but the trees that constitute the bulk of this so called sub-alpine zone also enter largely into the com- position of the lower belt, if indeed they do not in some places constitute it fully. The same species which on high and exposed sites are depressed and misshapen may form the main stand of good form and quality a thousand or two thousand feet lower on the mountain side. The species which form the bulk of the Canadian forest zone are Pinus contorta, P. albicaulis, Picea Engelmann and Abies lasiocarpa. An examination of Table 20 will show the wide range of vertical distribution of these species and reference to the tables presented under the discus- sion of the sections will show that this feature is not confined to one locality. On the eastern slope of the main Rockies the limber pine (P. flexilis) has also a large part in the forests of this zone. At about 4,000 feet one begins to meet occasional representa- tives of the higher mountain flora and with mounting altitude their numbers increase until the level of maximum development is reached. This level is not the same on different ranges nor on different peaks of the same range, since the conditions vary. Root bottom of the August In the ia. ifol 4000 feet, upper Bitter vt altitude ga ta Open forest of Pinus ponderosa. South exposure, thick stand of Pseudotsuc ~ ‘ } S ee We .. a ee — a oe = = & — ~~ So & — = & THE MONTANE ZONE 139 So far as observed, none of the plants seen first on the slope at 4,000 feet or above fail to extend to the sub-alpine zone, some in sheltered canyons and ravines and others on open and eres slopes. Among such may be mentioned : NVerophyllum Douglasi. Menziesva glabella Veratrum californicum Pachystima Myrsinites Vaccinium membranaceum Referring’ again to the trees of the Montane or middle mountain belt, the first of the species from the standpoint of its numbers, its characteristics and the breadth of its distribution is the lodgepole pine (P. contorta). The lodgepole forests have been studied by Clements (12) in Colorado and by Mason (39) in Montana and elsewhere. From various standpoints they are of great interest and importance. They represent a form which is able with remarkable rapidity to reoceupy denuded land, made possible by prolonged viability of the seed, by the large numbers of seeds produced and the facility of their dispersal. The lodgepole represents a species which by reason of its own power to reproduce is usually pre- vented from attaining great age and maximum dimensions. The density of the stands, the resinous character of its tissues, and the habitats which it often seeks on high and exposed ridges make lodgepole peculiarly susceptible to fires which often’ re- peatedly sweep the same area. During at least the earlier period of its development the lodgepole stand is often as effective a barrier to the movements of neighboring species as a lake or a snowfield, for stands of trees six to eight feet in height may be so dense as wholly to exclude even the most tolerant of the lesser green plants. In older stands which have begun to open there is, however, opportunity for the entrance of competitors and in some places the white pine may be seen making headway under the much older growth of the lodgepole. Under conditions favoring the entrance of other species the lodgepole must ulti- mately become supplanted. Whitford has found in the forests of the Flathead Valley the invasion of the lodgepole stand by white pine, lowland fir, Engelmann spruce and occasionally ar- bor vitae and western hemlock. If the seeds of western larch, Douglas spruce, or other species of rapid growth in height are Zurmoys pyofien, vinsjopnasg pue vsoiapuod snuig ‘aye’y ‘Aine ‘otarerad oy} OyUT uOIseAUT Zurpusose uv pvoyye[y Ul puR[s] es1OypTIM UO ‘ss “By 140 THE MONTANE ZONE 141 sown with the lodgepole these may become the dominant com- petitors. The character of a lodgepole stand clearly indicates a wind- sown forest. Extensive areas are seeded so evenly as to permit of no alternative explanation although authors above men- tioned are inclined to question this view. The lghtness of the seed and the amplitude of the wing make possible their trans- portation by even a moderate gale. The behavior of the lodge- pole recalls no other species so much as the Douglas spruce, which with great facility in its most favored regions reoccupies clear cut slashings and burns many acres in extent with a uni- form thicket growth propagated from the borders. And the seeds of the Douglas spruce are heavier than those of the lodge- pole pine. The reseeding of a burned area by lodgepole presents no difficulties if the area has previously been occupied by that species, even as a partial stand, unless the fire has been so intense as to consume the tops. The writer recalls that the severe fires; of 1910 swept a part of the valley of the North Fork of the Flathead River. The ground cover was entirely consumed and the crown fire had stripped the leaves from the branches over- head. Some trees had fallen and among them lodgepoles. Upon examination, within 36 hours after the passage of the fire, the cones of the lodgepole were found open and the seeds were seen lying upon the ground. The opening of the cones had followed after the passage of the fire at an interval sufficient to allow the seeds to fall uninjured, for not even the edges of the delicate wings were singed, a fact which seems difficult to reconcile with the findings of Clements that the flame of the Bunsen burner opened the cones in ten seconds.. If such were the case in a forest fire the seeds must surely perish. In the case above cited, however, the cones evidently were opening slowly, for at the time they were observed they were not entirely expanded. On the top of the standing trees the cones undoubtedly were opening likewise in response to the drying action of the fire and from this vantage were being broadcasted effectively onto the cleared and receptive soil, Of course the action of fire is not the only means of opening the cones. They may he observed in some cases fully expanded * ee ie ve ee Fa te ham*. eee * am * * . ‘lat- EF Tsuga Abies grandis and other trees, representing the most humid conditions River, tributary to the Swan the of the papyrifera, In ) Betula ta I valley monticola, Pinus with associated head. hete rophylla, forest July. 142 region. the of THE MONTANE ZONE 143 on green trees, but this is relatively rare. There is at hand a branch about a foot in length bearing 27 cones, about evenly dis- tributed over a period of 12 years, and not one of them has be- eun to open. Of 167 cones collected in August five years ago and kept continuously in the dry air of the laboratory, 70 still show no signs of opening, 14 are beginning to open, and 83 have opened enough to liberate a few over 200 seeds in all. These seeds when tested showed a high percentage viable. Lodgepole pine is not abundant in the immediate vicinity of Missoula. It is restricted mostly to north slopes at elevations of about 5,000 feet. This feature of its distribution seems to be mainly a response to temperature. Lower elevations though well watered rarely support vigorous stands in this locality, but farther north in the Glacier Park at 4,200 feet, and in the Kootenai Valley at less than 2,000, are vigorous forests of pure lodgepole. In these regions heavy frosts may occur in any month of the year. Northward the lodgepole forests become more continuous and homogeneous; southward the continuous and extensive forests of this species are found at seccessively higher altitudes. Westward, of course, the lodgepole extends to the coast; its eastward distribution in Montana reaches a merid- ian traversing the State midway. In the north it is found in the Bearpaw Mountains, a low range between the Milk River and the Missouri south of Havre. It occurs also in the Crazy Mountains almost in the exact center of the State and in the Beartooth Mountains northeast of the Yellowstone Park. In this region Leiberg, reckoning trees of all ages with a basal diameter of three inches and upward, concluded that the lodge- pole constituted 45% of the forest species, and in the Little Belt 43%. Elsewhere it may be more or less according to circum- stances, more where fires have occurred at intervals sufficient to repress competing species, less where time has sufficed for the maturing of the forest and invasion, or where conditions of re- production have established a mixed stand from the start. A summary of the biotic elements which enter into the composition of the lodgepole species leaves no doubt as to its fitness and capacity for distribution and survival. Among these several qualities may be mentioned as positive factors. First may be mentioned the abundance of the seed produced, which Somat RR | oe a i Py at x So oe is = ¢& Fig. 30. Priest River Valley in northern Idaho, Pinus monticola, Teuga heterophylla, Abies grandis, Thuja plicata. In the foreground Lysichiton Kamtschatcensis and Asplenium Filix-foemina. 144 THE MONTANE ZONE 145 probably excels that of any other native speeies. Not only is the annual crop abundant but the lodgepole begins early to bear seeds, as early as the sixth year in some places. The lightness of the seeds and their marked adaptability for wind dispersal, their usual high rate of germination and long continued viability are all points of marked importance. The ability of the lodge- pole to grow in dense stands operates to exclude other species, and its ability to recover from prolonged suppression further makes for dominance. The lodgepole is also largely resistant to disease. Against these points may be set off certain limiting traits most of which are, however, not very definite or pro- nounced. There appear to be certain limitations in soil require- ments, and light and a marked susceptibility to fire injury. It has been estimated that the average production of seed per tree in Colorado varied from 20,000 to 50,000. Considering the fact that the tree may begin as early as its 5th year to pro- duce cones and that the cones remain closed for many years and that when seeds are most needed, i. e., just after a fire there is available for sowing not merely one season’s crop but the combined fruitage of several years, considering also the extended viability of the seeds and their high germinative capacity it is evident that the lodgepole pine is beyond all competitors in the advantage derived from a reproductive capacity. The facility with which it preempts and holds newly seeded, especially fire- swept lands, is a fact related partly to its preference for bare soil as a seed bed, but more decidediy to the large amount of seed available for distribution at the opportune time. It is found under recorded temperatures of —-55 to 112 degrees F. in the United States and doubtless has much wider range. In the same locality (Anaconda) it may be subject to an annual varia- tion of temperature through 165 degrees F. In the ability to recover after years of suppression is one of the important factors in the persistence of the lodgepole. Un- hke many other species which would suffer permanent injury from early shading, the lodgepole, after years of repression is able to push forward rapidly to full vigor and reproductive capacity as soon as the dominating individuals are removed. Es- pecially may this be the ease where the cutting or destruction of 146 On the right Pinus Vegetation in the mountain valleys of the upper Bitter Root, West Fork. Fig. 32. ponderosa, in the center foreground P. contorta. glaucops, Alnus tenuifolia, ete. Salix Bebbiana, S. Picea Engelmannii in the background. THE MONTANE ZONE 147 the larger trees of the stand may throw open the land to a con- test for supremacy among the local species. There are few parasites to which the lodgepole is seriously subject, and most of these do not destroy the tree, nor apparent- ly retard its production of seed. The most serious enemies are the bark beetles of the genus Dendroctonus which kill the stands. Among the vegetable parasites Peridermium cerebrum and P. Harknessii and the small mistletoe Razoumofskya ameri- cana are the most common, but they are seldom conspicuous. Against these more or less favorable traits may be set off three which have a limiting effect upon its distribution. The soil limitations are not a serious handicap to migration. Locally ‘such limitations are effective as in over-watered soils, the lodge- pole requiring well aerated land with a medium amount of available moisture. Some authors hold that the lodgepole shuns caleareous soils, but that is a matter affecting local rather than general distribution. Otherwise the lodgepole seems indifferent as to the qualities of the soil. The effect of the intolerance of this species, as was mentioned above, is seen mainly in the re- tarding of its growth until such time as the shade may be re- moved. The specific heht requirements of this species, however, like the edaphic relations, are more important locally than as effecting the whole range of the species. In the third negative element, that of susceptibility to fire, is a factor which must in a far-reaching way affect the prosperity of the species through- out its range and operate to reduce the area over which it may hold sway. Thus it will be seen that the positive factors in the make-up of this species far outweigh those which are negative and which would tend to weaken it in its struggle for survival. Such adaptability is reflected in its wide distribution which extends from the peninsula of lower California almost to the Arctic circle and from the Black Hills to the very shores of the Pacific. The Engelmann spruce (Picea Engelmann) is one of the most widely distributed trees of the Rocky Mountain forests. Within the boundaries of Montana it has a wider altitudinal range than any other species. From the crests of the highest ranges it descends to the lowest point, within the State (Troy, 1,880 feet) and in Idaho to 1,500 feet. It is a prominent tree -l1jsiqy ‘AT[NS MoTpeYys Ul sypzuapi900 aiuw/T BunoX ‘Yoiey{ ‘S}jlip Mous Y}IM yuspourod uornq ‘yuo|W ‘epnosst avou odojs ureyunow yWION ‘Eg “SIT oe ws t Es 4 a, mi et, 148 THE MONTANE ZONE 149 of both the Hudsonian and Canadian zones. It is found plenti- fully both east and west of the divide, forming 11% to 21% in the Belts and Absaroka, 13% in forests of the Kootenai Val- ley and more or less in other parts. At lower elevations the species finds its best conditions on bottom lands and in cool canyons and frequently reaches 3 or 4 feet in diameter. Pure forests of Engelmann spruce occur and such are found in Gla- cier Park, over limited areas, in the upper Avalanche Basin and a good, uniform stand on the slopes of Brown Pass over the Continental Divide between Waterton and Bowman lakes. Certain factors are conspicuous in the nature and habits of this species. It produces abundant seed; the seeds are small, light and amply winged, and easily carried by the wind; the seeds germinate well; the tree endures much shade and the seedlings do well under heavy cover. The trees have great long- evity and bear seeds for an extended period of time. On the other hand the Engelmann spruce grows slowly even under the best of conditions; it demands much moisture in the soil; its temperature limits while they may be wide for brief periods (-60 to 108) are more especially favorable toward the cooler end of the scale. The chief determining factors in the distribution of Engel- mann spruce are water and temperature. It has been held (27) that moisture alone is the dominant influence and that low tem- peratures operate mainly in increasing relative humidity. .This seems to be true and the fact that in regions where the species abounds it grows to large size in narrow canyons but may rarely appear in the broader open stretches of river bottoms in the same locality and at the same altitude where conditions are unfavor- able for an equal degree of relative humidity. The effect of high relative humidity, however, must not be regarded merely as insuring a greater amount of soil moisture, but, as in the case of the yew and other species, seems to operate directly on some phase of the transpiratory function. Places where soil waters are near the surface and never lacking are seldom if ever occupied by Engelmann spruce under conditions where the weather is continuously warm during several weeks of sum- mer and the relative humidity low. While day temperatures may be occasionally high, in the favored habitat of this species, ‘UOTPLULIOT 94} JO WSvjs Jopjo ue Surjuasaidaa ‘sqnays 1940 pue ‘Yo1e snunig ‘leap ‘aypg pure vyofixn) vinsjopnasg ‘sypjuapios0 aiuwy Aq pordnos0 punoasyovq ay} UL snye} Aaplo sy J, ‘eynossij_ avou odo[s urejunow yyiou y “FE “By ‘adoyjs snje} ‘vaiv yood-aprjs [eord Ay B puNno.tda10} oy} UT * fe ’ . bi j ¥ f ne. 150 THE MONTANE ZONE Tot the nights usually are cool, almost to frost, and the usual daily temperatures of July and August about 75 to 85 degrees. Engel- mann spruce is sometimes planted in Missoula, but does not thrive even under careful summer irrigation, although the Col- orado blue spruce (Picea Parryana) and the Norway spruce do very well. Within the limits of its range the abundance and dominance of Engelmann spruce is conditioned upon its seeding habits and tolerance. As a competitor with other species it has the distinct advantage of being stronely shade resistant, and this quality is its sole compensation for its slow growth in height. Field seedlings gain in height less than 4 inches in 4 years under conditions apparently favorable. Other data on growth are to - be found in Tables 22 and 23. The growth of this species may easily be checked by fires, as the bark is very thin and the trees easily destroyed. Fires are less frequent, however, in this kind of forest than in some others, owing to the moister conditions under which the tree usually grows. The species is subject to few serious parasites among the fungi, though some among the insects operate to re- duce its vitality or shorten its life. The most frequent companion of the Engelmann spruce at all elevations, but especially in the higher ones, is the alpine or sub-alpine fir (Abies lasiocarpa). It has almost as wide a range of vertical distribution as the spruce, but in altitudes above 6,000 feet it becomes much more conspicuous and abundant, probably owing to the lessened frequency of other species. | The salient characteristics of this species are, in the posi- tive direction, a liberal production of seed from early youth, facility of dispersal and free germination. The species is tol- erant and resistant to cold. Negatively its seeds have transient vitality, the tree requires much moisture both in soil and air, its upper temperature limit is low, its early growth is slow and it is not resistant to fires (61). The alpine fir is the most typical tree of the high mountains in Montana, and from the highest slopes it descends to 2,000 feet in canyons in the northwestern part of the State. The most favorable situations for this species are to be found in. the sheltered basins at altitudes from 5,000 to 7,000 feet. It is found usually upon slightly elevated knolls of sloping ground ‘Voieyy = ‘dajo -WBIp Ul JOOF B NOge Sauojs ysasi1v'T “W9Yy} UVAaMjeq Surmois wnudfiyT Jo pu ‘sauojys oy} uo vaAsuUes sayJ]O pue pyaumiwg ‘vavjdojpg jo sajwedg ‘asvys ssoul-usyoIT ey} ut odoys YyAOU UO sN{e} VY} JO MIA VSOTQ ‘eg “BIY THE MONTANE ZONE 153 providing good drainage but where there is sufficient moisture during the growing season. Unlike the spruce it seems to shun the wetter soils. Groves of the alpine fir often shelter snow drifts until August or even through the entire year. This fir endures the most rigorous climate. Its temperature range must extend from —60 to over 100 degrees for short periods, with the prevailing summer temperatures between 30 and 85 at 6,000 feet elevation. It is. the temperature which appears to be the special controlling factor in the distribution of the alpine fir, both local and general. Moisture likewise is influential but is likely never to be absent during the growing season in the zone where this species reaches its best development. The alpine fir seldom grows in dense stands, but appears more or less scattered and in groups. Its tolerance, however, makes possible a dense forest which here and there is realized over small areas. The foliage of the crowns is dense, especially in older trees where it is sometimes almost impenetrable, and fre- quently descending to the ground. Young trees may endure shade for years and recover with rapid growth when the dom- inating influence is removed. Abies lasiocarna finds conditions favorable for its growth throughout the Rocky Mountain region from Alaska to Arizona and to some extent in the Cascades and coast ranges. In the southernmost parts of its range its lower limit in altitude is about 9,000 feet. Another species forming a large part of the mountain for- ests is the whitebark pine (Pinus albicaulis). It forms some- times pure forests at 7,000 to 8,000 feet in clear orchard-like stands of trees of medium size a foot, more or less, in diameter and about 40 to 50 feet in height. Sometimes the trees of this species in more favored situations between 6,000 and 7,000 feet may reach a diameter of 5 feet or more, but such are rare. Trunk diameters of two to three feet, however, are not uncommon. On exposed, wind-swept situation at all altitudes within its range it assumes a stunted and spreading habit, usually of 5 or 6 feet in height. The white bark pine is the usual companion of the alpine fir and Engelmann spruce, and its characteristically branching tops can be recognized far and near. It enjoys a natural range from British Columbia to southern California and eS a Fig. 36. A slide-rock slope, southern exposure, bearing Pinus pon- derosa and Douglas spruce. Heavier forest to right Abies lasiocarpa, spruce and lodgepole pine. Near head of Bitter Root Valley, about 6000 feet, August. THE MONTANE ZONE 155 in the northern Rockies, where it seems to reach its best develop- ment at 6,000 feet or above. The positive qualities of the whitebark pine are few; it produces seed liberally, endures a wide range of temperature and seems adapted to rocky situations and meager soil. On the other hand it is limited by the lack of facility in seed dispersal, the seeds being heavy and large, which also renders them at- tractive to squirrels and other animals. The tree is intolerant, it thrives only in moist soil and having thin bark is readily in- jured by fires, The seeding habits of this species are somewhat peculiar. Wind can have little influence on seed dispersal in a case where the seeds are devoid of wings or structures which serve a sim- ilar purpose. The cones do not open to discharge their seeds but disintegrate at the core. Cones falling to the ground if spared by animals, often give rise to trees in groups. Such trees may differ much in size, but an examination of the stem section will usually reveal the fact that they are of the same age. As one tree of the group gains the ascendancy it comes ultimately to stand alone. Ag the seeds of this species are wingless, their distribution is not dependent upon the wind, and other agencies must therefore account for their dispersal, in which squirrels and other seed-eating animals doubtless have a large share. The rare appearance of seedlings at relatively low altitudes, and where it is practically certain there is not a seed tree within miles, suggests the influence of birds. Among birds it is prob- able that the chief agency is the Clark Nut-cracker or Clark Crow (Nucifraga columbiana). Skinner (58) states that it pre- fers pine seeds, sometimes tearing cones to pieces while yet at- tached to the branch. More often the cone is detached and car- ried away to a strong limb where it is held with oné foot while the bird strikes strong downward blows at it with its pickaxe bill. In its temperature relations the whitebark pine shows a ¢a- pacity to endure a wide seasonal range said to be from 60 to 100 degrees, but for the most part it is restricted to cooler levels of elevation, seldom below 6,000 feet in Montana, though the writer has sometimes found isolated individuals at 3,500 feet in western Montana. It is found at about 6,000 feet in Glacier Park and about the same in the Swan Range, from 6,000 to % ¢ : peg *- Pte ‘ ee Me: iy thie et ee... sy « ee ee - es Wee ‘tle ime we. ¢ I ee %* cf tl Deeg about the head of August. mannv jel Eng al Park. 56 15 ation of Picea icier N ind © c Pure sté ~ /. 5 Te ig. I Avalanche Lake in G] THE MONTANE ZONE 157 8,000 in the Bitter Roots, and in the Absaroka Range above 7,000. In the Little Belt Mountains it is found only on the highest points above 8,000 feet. Its endurance of high temperatures is only for brief periods at the altitudes which it usually inhabits. In its local distribution it shuns the wet soils and is found usually on rocky ridges which have better drainage and aeration. Here it grows to its best size and so partial is it to the rock, either fixed or in the form of fragments or boulders, that no case can be recalled where trees of more than seedling size were found in the wet soil. It is a common accompaniment of the topography which is exhibited in crumbling outcrops of rock, alternating with depressed areas composed of finer materials, but seldom occupied by trees except at times the spruce. Sloping mountain sides are also favorite situations for this species. Uni- form stands have been found by the writer where the ground cover consisted mainly of a thick carpet, ankle-deep, of small heaths mainly Cassiope Mertensiana. Its relation to tempera- ture and to soil conditions are thus the important factors which control its local distribution. Owing to its very thin bark it is easily destroved by slight fires and areas are known where whole stands are reduced to dry and bleaching trunks with little evidence of reoccupaticn by the same species, in marked contrast to the progress of the lodgepole pine. At its best the whitebark pine is not vigorous in propagation, and stands once destroyed are very slowly restored. Nevertheless this tree is readily found, as a rule in all the higher altitudes of the State and ranks third among the native species as to the extent, and uniformity of its distribution in this region. Closely related to this species is Pinus flexilis, limber pine, which in this region is found east of the main divide. Cases re- ported of the finding of Pinus flexilis on the west slope in Mon- tana seem not to be clearly substantiated. The two species are similar in requirements and in altitudinal range. The twigs and leaves are practically indistinguishable but the cones differ in form, color, thickness of the scales and manner of opening. The tree occupies high and exposed situations, and responds in the manner of its growth and its form much as other trees in similar situations, severely distorted and repressed. The positive qualities of this species are found mainly in lee * ‘psosapuod snuig jo 4sooyy if \ “a ‘AYR’ peoyyryy] ‘oune "SE . > ‘satoods Jay}O pue siyypzUapIos0 Biv] “Y}2.10]U09 “J Sulyoo,aao VsueY UOISSI_ Oy} JO adoTs UsI}SA AY By THE SUMMITS 159 its liberal seed production, its capacity for resisting a vigorous climate, where the temperature falls to -60 degrees, high winds, adaptability to various soils but not strict in its demands upon soil moisture. It is thin barked and could easily be injured by fire, but in the open stands where it usually oceurs there is less danger from this menace than is usual with other species. It seems not to be especially susceptible to disease. On the other hand its disadvantages in the matter of seeding, the limitations in the facilities for dispersal, the size of the seeds and the eager- ness with which they are sought by animals, and its intolerance of shade militate against its dominance in the range which it occupies. The limber pine has an extensive total range from Alberta, southward threugh the Rocky Mountains to New Mexico and westward to California. In the Belt Mountains it comprises about 8% of the forest species and about 2% in the Absaroka Range. It mingles more or less with lodgepole pine at the upper limits of distribution of that species and in the higher sub-alpine zone is found with spruce, fir, and whitebark pine. THe SuMMITs. The sub-alpine zone of the Montana Rockies, as above defined, represents the Hudsonian zone of Merriam and is with reference to all parts of its vegetation, a zone of sur- passing interest. Its tree forms are few, it has a limited num- ber of shrubby species and a considerable number of herbaceous perennials. The trees are Pinus albicaulis, P. flexilis, Larix Lyalli, Picea Engelmannn, Tsuga Mertensiana, Abies lasiocarpa, and Juniperus scopulorum. In shrubby form Juniperus com- munis also occurs in abundance. All of these except Lyall’s larch and the black hemlock have a distribution extending across the State from north to south, and all except these two and the limber pine are found on both sides of the Continental Divide. Two of them, Picea Engelmannii and Juniperus scopulorum, have a wide range of altitude, from the crest of the divide at 6,000 feet or more down to the lowest point in Montana, Larix Lyallii belongs consistently to the high altitudes. The aspect of the sub-alpine zone is not that of a continuous ‘sung ‘vsosapuod snug Ajasaey puejys [eulsug *(n710ju09 snug) aud ajodaSpo7y Aq patdnosoas Sureq Surpuevjs satvad [es1vavs Jo ung YW ‘“ayv’y peoy,eyy Jo 4svo “osueyYy uorssip_Y Vy} Jo adojs ysaM, “EE “SI — hanes 160 THE SUMMITS» 161 forest, but of limited tracts of even though usually not dense stands, or more often of bunched trees in small groups, separated by meadows, bogs, lakes, rock fields, snow fields, chasms, ete. Snow is perennial only in small patches, and even the glaciers of the northern part are of very limited extent. The growing season is short, however, and at an altitude of 6,000 feet may be limited to about two months or less during July and August. Heavy frosts usually occur and snow may fall during this time. Small brooks fed by melting snow run low or cease to flow at night and the days are usually long and bright and warm. Veg- etation awakens quickly and advances rapidly to flowering, fruition and rest, so-that usually before the end of August fresh snows have begun to mantle the peaks and higher ridges. The Rocky Mountains of Montana have no summer snow line, and in rare eases only a distinct timber line. Most of the high mountains are clothed with trees of fair size almost to their very summits, especially on their more sheltered slopes, and where forests are lacking, the influence is not snow nor cold but chiefly wind and desiceation. Mt. Lolo of the Bitter Root Range, rising to about 9,000 feet, is forested practically to its summit, and Trapper Peak, the highest point of the same range, reaching 10,175 feet, is likewise timbered nearly to the summit. At Gib- bon’s Pass across the Continental Divide from the Bitter Root to the Big Hole the road passes through a dense forest of lodge- pole pine, and where the railway lines cross the divide are scat- tering stands of pine and juniper. The peaks and high ridges of Glacier Park, from 6,000 to 10,000 feet have no perceptible timber line. Under the conditions cf the very short growing season and other adverse aspects of such situations it is inevitable that the increment of woody plants from season to season should be very small, especially in the cases of trees in situations at all exposed to wind. Trees sheltered in the center of a group make fairly rapid growth. Near the top of the Swan Range a small tree (Abies lasiocarpa) about 6 feet in height and about 3 inches in diameter at the ground stood at the edge of a group, but in a sheltered basin with trees back of it rising 40 feet or more. This tree had no limbs on its windward side but to the leeward ex- tended its branches about two feet. A section across the stem CONTINENTAL 9p ELEVATION 7000 FEET ~ cere NY Hh seep 4. bie ii ig. 40. Forest of Lodgepole pine on Continental Divide between Bighole and Bitter Root Valleys. Alt. 7000 feet. August. THE SUMMITS 163 showed 84 rings of annual growth, which could not be counted without the aid of a lens. ‘The accompanying table prepared from observations on the trees of the sub-alpine forest, shows similar conditions, although in neither of these cases were the conditions less than of average advantage, and might have been even better than the usual sites occupied by trees. It will be observed that it required 60 years for the Engelmann spruce to reach a diameter of 314 inches, 80 years for the pine to reach 43 inches, and 108 years for the fir to attain 414 inches in diam- eter. These may be taken as typical figures for most situations in the sub-alpine zone. The altitude in all these cases was about 6,200 feet. The first case cited was in the Swan Range east of Bigfork, the figures in the table are from observations made near Swift-Current Pass in Glacier National Park. The shrubs most common in the sub-alpine forest are: Salix Barclayi Menziesia ferruginea “* vestita Ledum glandulosum ‘* glaucops Kalnua polifolia Alnus incana Phylledoce empetriformis Ribes lacustre Cassiope Mertensiana Sorbus scopulina Vaccinium erythrococcum Crataegus rivularis Me scopartum Pachystima Myrsinites * oreophilum Of these Salix Barclayi forms dense thickets three or four feet in height here and there in basins at the heads of streams in Glacier Park and elsewhere. In the openings in such forma- tion Kalmia microphylla occurs along with Sphagnum and grasses and sedges. The other species of willow are plentiful but are not massed and are only locally conspicuous. Alnus incana, however, forms pure, dense and matted covering on some of the slopes of the Arctic drainage, and in places elsewhere is prominent in the forest undergrowth. 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