FOREST REGIONS OF MONTANA 

STEPHEN F. ARNO 

USDA Forest Service Research Paper INT-218 

INTERMOUNTAIN FOREST AND RANGE EXPERIMENT STATION 

Forest Service U.S. Department of Agriculture Ogden, Utah 84401 

This file was created by scanning the printed publication.

Errors identified by the software have been corrected;

however, some errors may remain.
USDA Forest Service 

Research Paper INT-218 

April 1979 

FOREST REGIONS OF MONTANA 

STEPHEN F. ARNO 

INTERMOUNTAIN FOREST AND RANGE EXPERIMENT STATION 

Forest Service 

U. S. Department of Agriculture 

Ogden, Utah 84401 
THE AUTHOR 

STEPHEN F. ARNO is a Plant Ecologist on the Forest Ecosystems 

research work unit at Missoula. He earned a B. S. in forestry 

at Washington State University and a master's degree and a 

Ph. D. in forestry and plant science at the University of Montana before joining the Forest Service in 1970. 

ACKNOWLEDGMENTS 

Robert Pfister (USDA Forest Service Project Leader) gave 

encouragement and advice throughout this study. The following foresters from USDA Forest Service, Northern Region, shared their 

information on the distributions of indicator plants: Robert Bigler, 

Herbert Holdorf (Soil Scientist), John Joy, Bernard Kovalchik, Tom 

Lawrence, Gary Learn, B. John Losensky, and James Schaeffer. 

Similar information was provided by Joseph Antos, James Habeck, 

and Pete Zager from the Botany Department of the University of 

Montana and by Tad Weaver, John Rumley, and Frank Forcella 

from Montana State University. In addition, I would like to thank 

the many people who provided review comments during the development of this manuscript. 
Page 

INTRODUCTION .......................... 

DELINEATING MONTANA FOREST REGIONS .......... 

FOREST REGION DESCRIPTIONS ................ 

Northwestern Montana Forest Region ............ West-Central Montana Forest Region ............ North-Central Montana Forest Region ........... Central Montana Forest Region ............... Southwestern Montana Forest Region ............ South-Central Montana Forest Region ............ Southeastern Montana Forest Region ............ Northeastern Montana Forest Region ............ 

RESEARCH AND MANAGEMENT APPLICATIONS ....... 

PUBLICATIONS CITED ...................... 

APPENDIX A.. DISTRIBUTION OF KEY TREE AND 

UNDERGROWTH SPECIES IN MONTANA .... 

APPENDIX B.. NUMBER OF SAMPLE PLOTS (PFISTER AND 

OTHERS 1977) BY HABITAT TYPE. PHASE. 

AND FOREST REGION IN MONTANA ...... 

APPENDIX C.. NATIONAL FORESTS. INDIAN RESERVATIONS. 

AND NATIONAL PARKS WITHIN EACH FOREST 

REGION IN MONTANA .............. 
The author categorizes forest vegetation across Montana into eight geographic subdivisions called "forest regions. " The regions correlate the influence of climate and general topography to forest vegetation--including the 

distributions of tree and undergrowth species and forest habitat types. The 

vertical zonation of forest series (based on the potential climax tree species) 

also differs from one region to the next. Regional boundaries were fitted to 

distributions of certain tree and undergrowth species, habitat types, and natural climatic barriers such as the Continential Divide and broad grassland 

valleys that separate forest environments. 

(1) The northwestern Montana forest region has major representation by 

Pacific Coast species such as Thujaplicata and Clintoniauniflora; its climate 

is strongly influenced by moist maritime airmasses. (2) The west-central 

region has a generally drier Pacific-influenced climate and only small amounts 

of Pacific Coast species; however, it has major representation of intermountain 

plants like Larix occidentalis and Xerophyllum tenax. 

(3) North-central Montana lies in the severe climate of the "chinook wind 

belt" along the east slope of the Continental Divide. It is distinguished by 

being too cold for Pinus ponderosa, but having extensive Populus tremuloides 

groves and Pinus flexilis woodlands. (4) The central Montana forest region 

has a less severe continental climate and it supports the east-side forin of 

- Pinus ponderosa at lower elevations. However, both coastal and intermountain 

species are essentially absent from its mountain forests. 

Both the (5) southwestern and (6) south-central forest regions have high 

base elevations and are without Pinus ponderosa. The former region's forests are generally drier than the latter's and often have sparse undergrowth. 

(7) Southeastern Montana differs from previously mentioned regions in not 

having prominent mountains. It has extensive Great Plains Pinus ponderosa 

forests. (8) Northeastern Montana is a Great Plains area having no forest, 

except for Populus deltoides groves along major streams. 

The regions may be usefulas a biologically based stratification for forest research and forest management studies. 
INTRODUCTION 

This report describes 'Montana's forests by geographic subdivisions called "forest 

regions. I' It emphasizes pat terns in species composition (trees and undergrowth) and 

the relationship of these patterns to climate and topography. The interpretations are 

based on field experience and data collected during a recent forest habitat type classification (Pfister and others 1977). 

There are two primary reasons for delineating the forest regions of Montana. 

First, the regions serve as a geographic reference for describing patterns of forest 

vegetation across the State. Second, delineating the regions contributes to regional 

classifications that are being developed from a national perspective (Bailey 1976, 1978). 

The geographic subdivisions discussed in this paper are based on the distribution of 

forest vegetation in relation to climate (as influenced by topography). Thus, these 

subdivisions are proposed for use only for interpretations related to forest vegetation. 

After reviewing definitions provided in Kuchler (1973) and Bailey (1976), the term 

" forest region" seemed most appropriate for use here. "Region" is a general term that 

does not necessarily specify a level in the land classification hierarchy, and the term 

"forest region" has been applied in Canada (Rowe 1972). ("Province" was also considered, 

but it has a more precise hierarchical definition related to the dominant vegetative 

types in an area, or to physiography; thus, some of Montana's forest regions occur 

within grassland provinces. j 

Other regional divisions of Montana have been developed from different types of 

information to meet different objectives. Schmidt and Dufour (1975) emphasized geomorphology in designating six regions within Montana. Those regions were used in assessing 

research natural area needs from the following viewpoints: forest vegetation, grass 

and shrubland vegetation, geology, zoology, and aquatics. Crowley (1972) depicted seven 

major environmental regions within Montana based on characteristics of human environments, including landforms, climate, and elevational zonations of vegetation. 

Still others (Kuchler 1964; Payne 1973; Ross and Hunter 1976) have provided maps 

of Montana's natural vegetative types; but the maps are not focused on regional variation in forest vegetation. In contrast to these references, the Montana " forest 

regions" proposed here delineate rather broad areas having similar zonation in forest 

vegetation. These forest regions have general similarities to the forest districts 

designated by the early Montana botanist, Kirkwood (1922), for describing forest distribution in the Northern Rocky Mountains. 

During the Montana forest habitat type study (Pfister and others 1977), 1,500 stands 

were sampled " subjectively without biast' (Mueller-Dombois and Ellenburg 1974). The 

stands represent a spectrum of mature forest communities and sites in each mountain 

range and forested area of the State. As the habitat type classification was being developed from these data, it became obvious that distributions of many tree and undergrowth species (and thus the distributions of the habitat types) are strongly correlated 
to patterns of geography and climate within Montana. It became evident that the State 

could be subdivided into several relatively homogeneous forest regions based on the 

data, field observations, and information on plant species distributions (Herbarium 

collections at the University of Montana, Missoula; Montana State University, Bozeman; 

the USDA Forest Service Forestry Sciences Laboratory, Missoula; personal interviews 

with local foresters and botanists (see acknowledgments) ; Booth and Wright 1966, 

Hitchcock and others 1955-1969, Little 1971, 1976). 

A map of forest regions (called "geographic s~bdivisions~~) was presented by Pfister 

and others (1977), and a brief account of each habitat type's distribution was given by 

region. However, the basis for these regions was not discussed; also, Montana's forest 

vegetation and environments were not described by region. These topics are addressed 

here. 

The Canadian Forest Service (Rowe 1959, 1972) mapped and described "Forest 

Regions of Canada," which provides a precedent. Rowe (1972) explained that the Canadian regional designations are generalized, with the broad perspective of Canada as a 

whole, although the statement was made that it would be possible to designate such 

regions from a detailed knowledge of specific areas if detailed data existed. The 

latter approach is used here with detailed data from the habitat type study (Pfister 

and others 1977) as a basis. 

Kuchler (1973) discussed techniques for designating ecologically based "regions." 

He stated that classifications of natural vegetation types and detailed mapping of their 

distributions are fundamental for establishing such regions. (It appears that the 

Montana forest habitat type classification along with the sample plots and other distributional data can provide this basic information.) Kuchler (1973)~ also concluded that 

vegetation regions should first be designated within a limited study area, such as a 

State or geographic region, and later expanded to surrounding areas. 
Montana's forests are both extensive and diverse. Forest covers nearly one-fourth 

of Montana--about 23 million acres according to Green and Setzer (1974)--and substantial 

amounts of forest are found in all but the northeastern portions of the State (fig. 1). 

At lower elevations these forests range from luxuriant stands of Tsuga heterophylla, 

Thuja plicata, Pinus monticola, and other Pacific Coast species in northwestern Montana 

to open Pinus ponderosa woodlands on the Great Plains of southeastern Montana. The 

high- elevation forests across the Montana Rockies also show substantial variation. 

Differences in climate are primarily responsible for geographic variations in the 

potential climax forest vegetation, expressed in habitat types (Pfister and others 1977). 

The climatic differences across Montana reflect the greater importance of Pacific maritime airmasses west of the Continental Divide versus continental climatic conditions 

east of the Divide. Locally, climate (and thus forest vegetation) also is strongly influenced by changes in elevation, aspect, and landform within the Montana Rockies. 

Soils and underlying geology also affect forest vegetation, but except for certain limestone substrates and extremely rocky sites, the effects do not generally obscure the 

overriding influence of climate and topography. 

The forest regions outlined on figure 1 correlate the influence of climate and 

general topography to forest vegetation--including the distributions of tree and undergrowth species and forest habitat types and the vertical zonation of forest series 

(discussed later). Because tree species serve as indicators of climate (Daubenmire and 

Daubenmire 1968; Pfister and others 1977), their geographic distributions serve as a 

primary determinant of regional boundaries. (Appendixes A-1 through A-6 illustrate how 

the distributions of tree species correlate with Montana's forest regions.) Distributions of undergrowth species that have proved useful as indicator plants in major forest 

habitat type classifications in the Northern Rockies (R. and J. Daubenmire 1968; 

Pfister and others 1977; and Robert Steele and others 1 ), also were used (for examples, 

see appendixes A-7 through A-10) . 

It became obvious that many of the tree, undergrowth plant, and habitat type distributions showed similar patterns, and relate to known climatic differences (U.S. Department of Commerce 1971; USDA Soil Conservation Service 1968). Preliminary regional 

boundaries were drawn to fit these vegetational data. The boundaries then were adjusted 

slightly to correlate with natural climatic barriers such as the Continental Divide and 

broad grassland valleys that separate forest environments. Although these regional 

boundaries were fitted to vegetation data and to topographic barriers as log2cally as 

possible, sometimes the general patterns of forest vegetation change gradually over 

rather broad areas. In these cases, where possible, major topographic features were 

used for final placement of boundaries. Dashed lines were used to designate regional 

boundaries in nonforested areas. 

The occurrence of the approximately 1,500 sample plots by habitat type and forest 

region is summarized in appendix B. Plant composition at these forest sites provides 

basic data for regional boundaries. At a broad level of generalization from this data 

'~eview drafts of "Forest habitat types of central Idaho" (1975) and those of the 

Nezperce National Forest (1976). Intermt. For. and Range Exp. Stn., Ogden, IJtah. 
- FOR

[7 NONFORES

I a WEATHER

Figure 1.--Montana forest regions and forested areas (from Hutchinson and Kemp 1952, Ross and Hu

satellite photo of Montana, GE Space Systems, Beltsville, Md. ,J Circled nwnbers are weather 

table 4. 
Table 1.--Extent (area covered) of forest series (potential climax) in each of Montana's forest regions 

A! = major m = minor r = rare . = absent 

Forest region 

: North- : West- : North- : : South- : Soirth- : South- : NorthSeries : western : central : central : Central : western : central : eastern : eastern 

Tsuga and Thuja M 

Abies grandis M 

Picea m 

Pinus contorta r 

Pinus ponderosa m 

Pinus flexilis 

Pseudotsuga il 

Abies lasiocarpa M 

the extent (area covered) of each climax series can be compared--identified by the most 

shade-tolerant (potential climax) tree species capable of growing on a given site. 

Table 1 shows which series occur in each of the forest regions. For instance, the 

Pacific Northwest coastal forest types (Thuja, Tsuga, and Abies grandis series) are of 

major importance only in northwestern Montana. Low-elevation forest types (Pinus ponderosa climax series) associated with dry, inland climates are abundant only in central 

and southeastern Montana, and are absent or rare in the north- central, southwestern, 

and south- central forest regions. 

Detailed interpretations (from appendix B data) are presented in table 2, which 

shows the major habitat types in each of Montana's forest regions. Additional interpretations and adjustments were made in developing table 2 from the sample plot data 

(appendix B). Certain substrate - oriented habitat types (such as PicealSenecio streptanthifozius and Abies Zasiocarpa/CZematis pseudoaZpina h.t. on limestone substrates) 

were heavily sampled by Pfister and others (1977), and are not as extensive as appendix 

B implies. Also, certain areas near the border of a forest region were heavily sampled; 

thereby more plots were collected from certain habitat types than are indicative of the 

region in general. For instance, several Abies Zasiocarpa/CZintonia and Abies Zasiocarpa/XerophyZZwn h.t. plots were taken in unusual locations immediately east of the 

Continental Divide in north- central Montana. 

The distribution of various tree species and undergrowth plants serving as habitat 

type or climatic indicators is presented in table 3 by forest region across Montana. 

This table is based on the 1,500 habitat type plots, and the field observations and 

published information on plant distributions cited previously. The distributions of 

Pacific Coast and intermountain species are useful for differentiating forests of 

northern Idaho, northwestern Montana, and west- central Montana, but the other forest 

regions are characterized largely by a lack of these species. ("Intermountain species" 

applies to plants found most often between the crest of the Cascade Mountains and the 

Continental Divide.) 

Certain widespread species (like Vacciniwn scopariwn, Juniperus conormnis, Arnica 

cordifo lia, Aster conspicuus, and even Pyro Za secunda) general 1 y are accompanied by 

Pacific Coast or intermountain species west of the Continental Divide; farther east the 

coastal and intermountain competitors drop out. This situation is documented by the 

changes in habitat types depicted in table 2. For instance, Pseudotsuga/Junipems 

cornis, Pseudotsuga/l?rnica cordifozia, and Abies Zasiocarpa/Amica cordifoZia appear 

only east of the Divide. 

Figure 2 shows a summary of the characteristics of each forest region. The rela - 

tionship of forest region and National Forest boundaries is shown in appendix C. 
Table 2.--Major habitat types (Pfister and others 1977) in each of J4mtana's forest 

regions (See appendix B for more detailed information on all habitat types) 

Habitat type Forest region 

Pinus flexilis/Festuca idahoensis 

P. ponderosa/Agropyron spicatum 

P. ponderosa/Festuca idahoensis 

P. ponderosa/Symphoricarpos albus 

P. ponderosa/Prunus virginiana 

Pseudotsuga/Festuca idahoensis 

Pseudotsuga/Festuca scabrella 

Pseudotsuga/Vaccinium caespitosum 

Pseudotsuga/Physocarpus malvaceus x 

Pseudotsuga/Vaccinium globulare x Pseudotsuga/Linnaea borealis 

Pseudotsuga/Syn~phoricarpos albus x 

Pseudotsuga/Calamagrostis, Cal. phase 

Pseudotsuga/Cal., other phases x 

Pseudotsuga/Spiraea betulifolia 

Pseudotsuga/Arctostaphylos uva-ursi 

Pseudotsuga/Juniperus communis 

Pseudotsuga/Arnica cordifolia 

Picea/Clintonia uniflora 

Picea/Physocarpus malvaceus 

Picea/Galium triflorum 

Picea/Linnaea borealis 

All Abies grandis h.t.s x 

Thuja plicata/Clintonia uniflora x 

Tsuga heterophylla/Clintonia uniflora x 

Abies lasiocarpa/Clintonia uniflora x 

Abies lasiocarpa/Galium triflorum 

Abies lasiocarpa/Calamagrostis canadensis . Abies lasiocarpa/Linnaea borealis x 

Abies lasiocarpa/Menziesia ferruginea x 

All Tsuga mertensiana h.t.s x 

Abies lasiocarpa/Xerophyllum tenax x 

Abies lasiocarpa/Vaccinium globulare 

Abies lasiocarpa/Vaccinium scoparium 

Abies lasiocarpa/Arnica cordifolia 

Abies 1as.-Pinus albic./Vaccinium scop. 

Abies lasiocarpa/Luzula hitchcockii 

Pinus albicaulis-Abies lasiocarpa 

Larix lyallii-Abies lasiocarpa 

Pinus contorta community types 
Table 3.--Distribution of selected trees and undergrowth indicator plants by 

forest region across Montana. ?iorthern Idaho data from Daubewnire 

and Daubenmire (1 968) 

x = common 

r = rare or scarce 

. = absent 

Forest region : Northern : 

Species : Idaho : NW : WC : NC : C : SW : SC : SE 

Coastal species 

Adiantum pedatum 

Asarum caudatum 

Tsuga heterophylla x x 

Tsuga mertsnsiana x x 

Thuja plicata 

Pinus monticola 

Taxus brevifolia 

Abies grandis 

Clintonia unif lora 

Intermountain species 

Larix occidentalis x x x Larix lyallii x x x x Pinus ponderosa x x x var . -ponderosal 

Xerophyllum tenax x x x x r r r Menziesia ferruginea x x x x r r r Luzula hitchcockii x x x x r r r 

Widespread species 

Widespread Rocky Mt. x x x x x x x trees2 

Calamagrostis rubescens x x x x x x x 

Carex geyeri x x x x x x x 

Physocarpus malvaceus x x x r x r x 

Eastside species 

Pinus flexilis r x x x x 

Senecio streptanthefolius . r x x x Frasera speciosa r x x x 

Geranium richardsonii x x x x 

Pinus ponderosa x r x 

var . scopulorum3 

Juniperus horizontalis x x x x x 

Fraxinus pennsylvanica r 

(Little 19531, having three-needle fascicles only. 

Pseudotsuga, Abies lasiocarpa, Picea, Pinus contorta, and Pinus albicaulis. 

(Booth 1950 and Little 19531, having many two-needle fascicles. 

7 
MONTANA FOREST REGION 

DOMINANT CLIMATE Modified Maritime Continental *- 

Mountainous Gre

FOREST TOPOGRAPHY 

Average frost-free season 70-110 days 70-110 60-80 90-130 40-70 50-100 100-

in lower elevation forests 

LOWER ELEVATIONS var. ponderosa 4 b - a SUPPORT Pinus ponderosa 

var. scopulorum -var. sc

+-

PERCENT OF LAND FORESTED @ @ 0 

@ @ 0 

90 80 10 20 25 50 20 

DIAGNOSTIC Pacificcoast Intermtn. Eastside Species Great 

FOREST VEGETATION Species Species rl 

aspen E. slope cold dry cold moist P. pon

grovelands P. ponderosa forests forests 

Figure 2. --Sumnary of the major characteristics of Montana's forest regions. (Average frost-fre

with good air circuZation, as interpreted from Caprio 1965.) 
Northwestern Montana 

Forest Region 

The northwestern forest region of Montana includes the Kootenai, Flathead, and 

lower Clark Fork River (as far upstream as Fish Creek and Ninemile Valley) drainages. 

This region is bounded on the east by the Continental Divide, on the north by British 

Columbia, and on the west and southwest by Idaho and the crest of the Bitterroot Mountains. The southeastern border of the region is marked by the Rattlesnake Creek and 

Blackfoot River divTdes. 

Diagnostic forest vegetation 

The northwest forest region has an abundance (in all but the drier valleys) of 

Pacific Coast forest species that are less common or absent elsewhere. Tree species 

largely restricted to this region include Tsuga heterophylla, T. mertensianu, Thuja 

plicata, Abies grandis, Tams brevifolia, and Pinus monticola. Undergrowth largely 

restricted to this region includes Clintonia uniflora, Aralia nudicaulis, Gymocarpiwn 

dryopteris (and other Pacific Coast f ems) , Dispomm hookeri, Tiarella trifoliata, 

Viola glabella, and Oplopam horridwn (nomenclature is from Hitchcock and Cronquist 

1976). 

Forest distribution 

AS is the case in other mountainous sections of Montana, the rugged terrain creates 

an array of habitats and accompanying vegetation, from semiarid grasslands in the rain 

shadow of large mountain masses to moist mountain valleys, subalpine forests, and alpine 

tundra. The generalized distribution of forest trees and climax series for an area in 

the Kootenai River drainage is depicted in figure 3. Major forest habitat types for 

northwestern Montana are listed in table 2. 

About 90 percent of the land in this region is potentially forested (Hutchison and 

Kemp 1952; Green and Setzer 1974). Throughout much of the region, forest covers even 

the lowest elevation valleys (as low as 1,800 feet); in the driest valleys southwest of 

Flathead Lake, grassland prevails below about 3,500 feet elevation. Forest extends over 

all but the highest peaks (and rockiest sites). The average elevation of alpine tree 

line is about 8,000 feet. 
Figure 3.--Distribution of forest trees in an area of the Kootenai drainage in northwestern Montana. Arrows show the relative elevational range of each species; 

solid portion of the arrow indicates where species is potential climax, dashed 

portion shows where it is seral. (Modified from Pfister and others 1977. ) 

Climatic influences 

Northwestern Montana is strongly influenced by moist maritime airmasses that 

typically funnel through this area on their way inland from the Pacific Coast (U.S. 

Department of Commerce 1971; Daubenmire 1969). The airmasses provide abundant rain and 

snowfalls and generally humid, cloudy conditions except in midsummer. The airmasses 

also bring the relatively mild winter temperatures (even at high elevations) that are 

necessary for the survival of many of the coastal forest species. 

The mildest conditions are generally associated with the Kootenai drainage in the 

western part of the region. In the Kootenai drainage, forests most nearly resemble 

those of adjacent northern Idaho, representing a still moister and milder coastal cli - 

mate. Pinus monticola is abundant and is generally the tallest and fastest growing 

tree in northern Idaho. However, eastward through northwestern Montana, Larix occidentalis assumes this role (attaining heights of 150 to 170 feet on favorable sites). 

Farther east, in the upper Flathead Valley, outbreaks of arctic air occur more 

frequently in the winter (1J.S. Department of Commerce 1971). As a result, Tsuga heterophylla and Thuja sustain frost damage and become restricted to special sites. These 

sites either have a climate that is moderated by the presence of a large lake (Flathead 

Lake and Lake McDonald) or represent sheltered "cove" forests in ravines above the 

valley bottom frost zones. Still, even in the upper Flathead Valley, tree and undergrowth flora reflect a Pacific influence extending all the way to the Continental 

Divide itself. 

Weather records for Libby and Trout Creek (table 4) represent the milder, western 

part of this region; whereas the Polebridge station lies in the colder, upper Flathead 
Table 4.--Weather station records from Zower ezevation forested sites in each of E'ontana's forest regions. 

Locations of these stations are shotm by nwnber fat Zeftl on figure I 

Region : Fstimated : : Mean ma. temp. : Ave. length of : Mean annu. : Mean May- : ~ean 

and : climax : : frost- free : precipi- : August : annual 

station : series : Elev. : Jan. July : season - 32'F : tation : precip. : snowfaL 

Feet OF OF Days Inches Inches Inches 

Northwestern 

1. Libby (1NE) PSME 2,080 22 66 79 

2. Trout Creek (2W) ABGR 2,480 23 64 50 

3. Polebridge PICEA 3,690 17 6 1 30 

West - central 

1. Darbv .. f2NNWl , 

2. Greenough 

PIP0 3,815 25 65 99 

PSME 4,000 18 6 3 --45 

North - central 

1. Babb (6NE) POTREM 4,300 19 60 60 

2. Blackleaf (near) PIFL 4,600 21 60 = 60 

Central 

1. Helena near PIP0 3,893 19 68 134 11 5.7 48 

2. Lewistown PIP0 4,130 20 66 107 17 9.6 61 

Southwestern 

1. Lakeview PSME 6,710 10 59 == 30 20 8.4 142 

South - central 

1. Tower Falls dry edge of PSME 6,266 15 5 8 - 90 16 7.7 El00 

Yellowstone N.P. 

2. Mystic Lake PICO-ABLA 6,558 24 64 -- 95 24 10.4 140 

3. W. Yellowstone PICO-ABLA 6,662 12 60 -- 30 21 7.0 145 

Southeastern 

1. Lame Deer PIP0 3,331 22 70 =lo5 15 8.2 5 1 

2. Roundup PIP0 3.227 24 72 129 11 6.5 = 36 

Northeastern 

1. Glasgow no forest 2,277 11 72 124 13 7.8 36 

Valley. Average annual precipitation in most of the subalpine forests of this region 

ranges from about 40 to 65 inche~.~ 

West-Central Montana 

Forest Region 

The west- central forest region includes the Clark Fork River drainage from the 

Missoula-Frenchtown Val 1 ey upstream, except for the Continental Divide range from Nevada 

Peak (northwest of Helena) to California Pass (south of Anaconda). This region is 

bounded on the west by the lofty Bitterroot Range. The Bitterroot Range forms the Montana-Idaho Divide and constitutes a significant barrier to Pacific Coast moisture and 

thus to coastal plants. 

'~hese estimates were based on U.S. Dep. Comm. (1971), U.S. Dep. Comrn. weather 

station data, USDA Soil Conserv. Serv. (1968), Arno (1970), and an isohyetal analysis 

for the Columbia River drainage prepared by the U.S. Weather Bureau River Forecast Center, Portland, Oregon, in 1968. 

11 
Diagnostic forest vegetation 

Although it has a relatively mild, Pacific -influenced climate, this region's forests are generally drier than those of either northwestern Montana or adjacent northern 

Idaho. Thus, the region has only small amounts of Pacific Coast forest species such as 

Thuja plicata, Pinus monticola, Tms brevifolia, Clintonia uniflora, Adenocaulon bicolor, Coptis spp. (of western North America), and Tiarella trifoliata. These species 

are restricted to moist canyon-bottom sites or seepage areas and generally reach their 

southeastern limits within this region (table 3). Abies grandis is locally common, but 

is much less abundant than it is in northwestern Montana. West-central Montana is characterized by an abundance of the intermountain forest species--Larix occidentalis, Larix 

lyallii, Pinus ponderosa var . ponderosa, Xerophyllwn tenax, Menziesia fermginea, and 

Luzula hitchcockii. These species become rare or absent in the remaining regions that 

lie farther east (table 3). 

Forest distribution 

As figure 4 shows, the typical array of forest series here is not as diverse as 

that in northwestern Montana, because of the scarcity of Pacific Coast species. About 

Figure 4.--Distribution of forest trees in an area of west-central Montana. Arrows 

show the relative elevational range of each species; solid portion of the arrow 

indicates where a species is the potential climax and dashed portion shows where 

it is seral. (Modified from Pfister and others 1977). 
80 percent of the land in this region is potentially forested. Most of the nonforest 

land is grassland (Agropyron spieatwn, Festuea idahoensis, and F. scabrella associations 

of Mueggler and Hand1 (In press)) that occur in the broader low-elevation valleys. 

Annual precipitation on these nonforest valley sites is less than 15 inches and soils 

are well-drained. However, this grassland is not extensive, and lower timberline 

generally occurs within 1,000 feet of the valley base elevation; thus it is found 

between about 3,200 and 5,500 feet. Forest extends over all but the highest peaks 

(and rockiest sites). The average elevation of alpine tree line is about 8,800 feet. 

Principal forest habitat types of west- central Montana are shown in table 2. 

Climatic influences 

The comparatively dry, Pacific-influenced climate of this region is illustrated by 

data from the locations of Darby and Greenough (table 4). Average annual precipitation 

in the subalpine forests is generally 35 to 55 inches (footnote 2). 

Sera1 Pinus ponderosa and Larix occidentalis form the largest and most commercially 

important west- central Montana forest trees; they often attain heights of 130 to 140 

feet at maturity. The exception is the southeastern part of this region where valley 

base elevations are high and forests are doninated by Pinus contorts. (However, the 

intermountain undergrowth species dominate.) 

North-Central Montana 

Forest Region 

The north- central Montana forest region includes all the forested terrain along 

the east slope of the Continental Divide from the drainage of the North Fork of the 

Dearborn River north to the Canadian border and east to Havre. Adjacent southern 

Alberta has similar forest environments. 

Diagnostic forest vegetation 

This area supports the most extensive Populus tremuloides groves in the State 

(Lynch 1955) as well as large patches of Pinus flercilis woodland along the lower skirts 

of the mountains. Pinus ponderosa is absent, apparently because of the excessively cold 

and windy winter conditions. A narrow band of Abies lasiocarpa (series) forest along 

the Rocky Mountain front supports the easternmost occurrences of intermountain undergrowth species, Menziesia ferruginea, Xerophyllwn tenax, Luzula hitchcockii, and even 

"cove sites" with Clintonia unifZora barely extending across the Divide from northwestern Montana (appendixes A- 7, -8, and -10); however, the limited tree flora and its 

stunted growth are definitely indicative of the severe eastside climatic conditions. 
ELEVATIONS a.l (approx. 1 L U 

ru 

U 111 

alpine tundra .: I,l 

LAS IOCARPA 

SERIES 

6000 - 

PSEUDOTSUGA SERIES 

5000 

Populus tremuloides grovelands 

4000 - 

Northern Great Plains grassland 

Figure 5.--Distribution of forest trees in an area of north-central Montana. Arrows 

show the relative elevationul range of each species; solid portion of the arrow 

indicates where a species is the potential climax and dashed portion shows where 

it is seral. 

Forest distribution 

Only about 10 percent of the land in this region is potentially forested, most of 

it occurring in a 20 to 30 mile band along the eastern skirts of the Continental Divide 

or Front Range of the Rockies. Figure 5 illustrates a characteristic distribution of 

tree species in this region. A small area of similar forest (8 mi2), lacking only Lap& 

Zyallii, occurs on the Sweetgrass Hills (elev. 6,983 feet) 90 miles east of the nearest 

Front Range stands (Thompson and Kuijt 1976). 

Lower timberline generally occurs between 4,500 and 5,000 feet and forest extends 

up to all but the highest ridges and peaks. Alpine tree line averages about 8,000 feet. 

Most of the nonforest land is potentially grassland dominated by Agropyron, Festuca, 

Bouteloua, and Stipa (Kuchler 1964; Mueggler and Handl, In press). 

Climatic influences 

North-central Montana has a continental climate with severe chinook winds and dramatic fluctuations of winter temperatures that often injure forest trees. On windexposed slopes, tree growth is stunted by "red belt" conditions. Branches, groups of 

trees, or even sizable stands are routinely killed by desiccation of foliage caused when 

warm, dry chinook winds occur while the ground is frozen and little water is available 

to replace transpiration losses. Pinus flexilis (at low and middle elevations) and P. 

albicaulis (at high elevations) are least susceptible to red belt damage. 
Growing seasons are short and cool in the lower elevation forest sites (table 4 

and figure 2). Except in protected valleys, trees seldom reach 70 feet in height. 

Average annual precipitation in the subalpine forests is generally 30 to 40 inches 

(footnote 2), although it is much greater in a few areas along the Continental Divide, 

particularly in Glacier National Park. The severity of winter temperature fluctuations 

is illustrated by the world-record temperature drop of 100" F in 24 hours (from +44" to 

-56°F) at Browning, near East Glacier Park, in January 1916 (McWhirter and McWhirter 

1972). 

Central Montana 

Forest Regioln 

The central Montana forest region includes all the forested terrain from the Helena 

Valley east to Harlowton, Lewistown, and Fort Peck Reservoir, and north to Havre. Specifically, the western edge runs along the Continental Divide from the drainage of the 

Middle Fork of the Dearborn River south to the Boulder River divide. Forests contiguous 

with and west of the divide are included from the Avon Valley south to Deer Lodge (from 

Nevada Peak to Electric Peak along the Continental Divide). Eastward, the area encompasses the Elkhorn Mountains (except for the southwestern portion of that range that 

drains into the Boulder River) as well as the Big Belt, Little Belt, Castle, Big Snowy, 

Little Snowy, Judith, Little Rocky, Bearpaw, and Highwood Mountains. The range also 

contains rather extensive lowland Pinus ponderosa (var. scopulorwn, Booth 1950, Little 

1953) forests in the Helena and Lewistown vicinities and in the Missouri River Breaks. 

Diagnostic forest vegetation 

Most of central Montana has a low- elevation forest belt of Pinus ponderosa (var. 

scopulorwn). In contrast to westside P. ponderosa (var. ponderosa), these have many 

two-needle fascicles and a short growth form. Additionally, central Montana has mountain forests made up of other climax series (table 1). The other eastside region 

containing P. ponderosa (southeastern Montana) does not have additional forest series. 

Coastal and intermountain species are essentially absent, while eastside species, 

including Pinus fZexiZis and Juniperus horizontalis, are prominent (table 3). Great 

Plains grassland elements such as BouteZoua gracilis and B. curtipendula, Yucca glauca, 

and Opuntia fragiZis, and 0. polyacantha are commonly found in the driest Pinus ponderosa and P. flexilis stands. 

Forest distribution 

Approximately 20 percent of the land in this region is potentially forested. Most 

of the nonforest land is potentially grassland dominated by Agropyron, Festuca, BouteZowz, and Stipa (Kuchler 1964; Mueggler and Handl, In press). The forests are 

associated with prominent mountain ranges and the Missouri River Breaks. Forest extends 

from valley base levels or from lower timberlines on the principal mountain ranges (at 

4,000 to 5,500 feet) and covers all but the highest peaks. Alpine tree line averages 

about 8,500 feet. Figure 6 shows a characteristic distribution of tree species on nonlimestone parent materials in central Montana. 
Figme 6.--Distribution of forest trees in an area of central Montana. Arrows show the 

relative elevational range of each species; solid portion of the arrow indicates where 

a species is the potential climax and dashed portion shows where it is seral. 

Extensive areas having limestone substrates occur in the mountain ranges of central 

Montana. The limestone-derived soils drain rapidly and are generally dominated by 

drier site species than the adjacent nonlimestone sites (fig. 53, 54, in Pfister and 

others 1977). For example, at medium elevations the limestone sites often support 

Pseudotsuga with a grass-forb undergrowth, while adjacent granitic sites have Pinus 

contorta and Vacciniwn spp. (Goldin and Nimlos 1977; Weaver and Parry 1978). 

Climatic influences 

This region has a continental climate, but has forests extending to lower elevations and less severe winter conditions than north- central Montana. The warmer July 

temperatures and longer growing seasons (fig. 2) in the lower forest zone are 

indicated by weather station data in table 4. However, except on sheltered sites, 

trees seldom attain 80 feet in height. Average annual precipitation in the subalpine 

forests is estimated to be 25 to 35 inches (footnote 2). 

In the higher valleys and at high elevations in the mountains, extreme temperature 

changes accompanied by strong winds inflict red belt damage. For instance, in midJanuary 1971 such weather conditions (temperatures fluctuating between -30" and +58" F 

at Great Falls, accompanied by strong winds) killed about 20,000 acres of Pinus contorta I 

forest in the Little Belt Mountains. b 
Southwestern Montana 

Forest Region 

Area included 

The southwestern Montana forest region includes the Jefferson, Madison, and Boulder 

River drainages, east of the Continental Divide, as well as the forests on both slopes 

of the Continental Divide range in the vicinity of Butte (specifically from Electric 

Peak, east of Deer Lodge, to California Pass, south of Anaconda). 

As in central Montana, Pacific Coast forest elements are absent and intermountain 

elements are scarce (table 3). Rather short, but stout Pseudotsuga (or Pinus flexilis) 

occupy the warmest forest sites, and Pinus contorta along with Vacciniwn scopariwn 

undergrowth dominate most high- elevation forests. Undergrowth is notably sparse in the 

denser forest stands, and in Pseudotsuga forests undergrowth often consists primarily 

of scattered Festuca idahoensis and even Artemisia tridentata Figure 7 shows a characteristic distribution of tree species in southwestern Montana. Principal forest 

habitat types are shown in table 2. 

V) 

.- - 

TORTA SERIES uncertain) 

MENZIESII SERIES 

- 6000 

grassland 

Figure 7.--Distribution of forest trees in an area of southwestern Montana. Arrows show 

the relative elevationai! range of each species; solid portion of the arrow indicates 

where a species is the potential climax and dashed portion shows where it is seral. 
Forest distribution 

Despite its mountainous terrain, only about one -fourth of this region is forested. 

Most of the nonforest land is semiarid steppe (Artehsia) and grassland (Agropyron, 

Festuca, and Stipa), along with small areas of alpine vegetation (Kuchler 1964; Mueggler 

and Handl, In press) above 9,500 feet elevation. Lower timberline generally occurs 

somewhere between 5,700 and 7,000 feet in elevation. However, some of the mountain 

ranges south of Dillon are so dry that little forest is supported even at 8,000 feet. 

Thus, the entire forest belt (between lower and upper timberline) may span only 1,000 

to 1,500 feet of elevation, and may be locally absent on exposed south- and west-facing 

slopes. Similarly high, semiarid mountain ranges, projecting above an Artemisia 

tridentuta steppe (Kuchler 1964), occur in adjacent east- central Idaho (Steele and 

others (footnote 1)). 

Climatic influences 

As illustrated by weather records from Lakeview (table 4), this is a cold, dry 

forest region having high valley- base elevations, and a continental climate. Average 

annual precipitation in the subalpine forest ranges from about 22 to 35 inches (footnote 2). This forest region evidently has growing seasons too short and cold for 

Pinus ponderosa (fig. 2). The cold, dry conditions are also evidenced by the lack of 

Pseudotsuga/Physocqus habitat type (tables 2 and 3). However, chinook winds and temperature fluctuations are less severe than in north - central and central Montana, and 

red belt damage is less common. 

south-central Montana 

Forest Region 

The south- central Montana forest region includes the Gallatin and upper Yellowstone 

River drainages (along with the Bridger and Crazy Mountains) as well as the Pryor Mountains and the north end of the Bighorn Range. The region encompasses the northern part 

of an extensive, high- elevation forested upland surrounding Yellowstone National Park. 

This upland is capped by large alpine plateaus in Montana and Wyoming. 

Diagnostic forest vegetation 

Most of the forest in south- central Montana is dominated by Pseudotsuga, Pinus 

contortu, Picea, or Abies lasiocqa. The abundance of PicealPhysocarpus, Picea/Galium 

triflorwn, Abies lasiocarpa/GaZiwn triflorwn, and Abies lasiocarpa/CaZwnagrostis canadensis habitat types (table 2) attests to the moistness of many of the forests. Also, 

scattered populations of Xerophyllwn and Menziesia (appendixes A-9 and -10) are found 

here, more than 100 miles east of their usual distributional limits near the Continental 

Divide. In contrast to southwest Montana, one seldom finds extensive stands having a 

grassland undergrowth (except on limestone substrates), nor does one find very sparse 

undergrowth related to dry conditions. 

I 

Forest distribution 

I Nearly half of the land in south- central Montana supports forest, and most of the 

remaining area is potentially grassland--(Agropyron, Festuca, Stipa) according to 
ELEVATIONS 

(approx ) 

Figure 8.--Distribution of forest trees in an area of south-central Montana. Arrows 

show the relative elevational range of each species; solid portion of the arrow 

indicates where a species is the potential climax and dashed portion shows where 

it is seral. (Modified from Pfister and others 1977.1 

Kuchler (1964)--occupying the drier, lower elevation valleys. Lower timberline averages about 5,500 feet and alpine tree line occurs near 9,500 feet. Figure 8 shows a 

characteristic distribution of tree species in an area of south- central Montana. Table 

2 lists principal forest habitat types. 

Limestone substrates are abundant in the Pryor Mountains and occur sporadically 

elsewhere in south- central Montana. These sites, below about an 8,000-foot elevation, 

generally have forests dominated by Pinus flexilis and Pseudotsuga. 

Climatic influences 

South- central Montana has a continental climate, and red belt injury is often 

severe at lower timberline. The valleys have high base elevations and are too cold 

(short growing season, figure 2) for any significant amounts of Pinus ponderosa; however, forests are generally moister than those of southwestern Montana. Weather records 

for three forested sites in this region are found in table 4. Average annual precipita - 

tion in the subalpine forests is generally 30 to 45 inches (footnote 2). 
Southeastern Montana 

Forest Region 

The southeastern Montana forest region includes the extensive pure Pinus ponderosa 

forests on lowlands and hilly terrain (mostly 2,800 to 4,400 fect elevation) in the 

northern Great Plains. It covers the lower Yellowstone River drainage as far upstream 

(west) as Big Timber. The region extends up the Musselshell Valley to Harlowton and 

its northern boundary includes the northernmost pine groves in the vicinities of Roundup, Miles City, and Baker. 

Diagnostic forest vegetation 

Although Pinus ponderosa is the only forest tree, it occurs in rather diverse 

habitat types (table 2). The driest of these forest sites have very open stands of 

short trees (35-60 feet), with grassland undergrowth (e.g., Andropogon gerardii and A. 

scoparius, Agropyron spicatwn, Bouteloua gracilis, Carex filifolia) . Conversely, moist 

north -facing slopes have dense stands of P. ponderosa (70-95 feet tall), with a luxuriant shrub and herb undergrowth including many species characteristic of the mountain 

forests to the west (e. g . , Shepherdia camdensis, Arctostaphylos uva-msi, Berberis 

repens, Linmea borealis, Arnica cordifolia, Dispomon trachycarpwn, PyroZa secunda, and 

Smilacina stellata). 

The presence of Linnaea and some other undergrowth species strongly suggests that 

the more moist habitats would support Pseudotsuga; however, the nearest seed source for 

this species is at least 70 miles away in the Bighorn Range. This conclusion is rein - 

forced by the fact that Pinus ponderosa stands developing on the moister sites are more 

heavily stocked than is characteristic of P. ponderosa habitat types elsewhere in the 

State. 

In addition to having a shorter growth form than its counterpart west of the Continental Divide, the P. ponderosa (var. scopulorwn, Booth 1950 and Little 1953) in southeastern Montana has a majority of two-needle fascicles. These may be manifestations 

of substantial genetic differences between the west slope and Great Plains P. ponderosa. 

Two east ern deciduous - f orest species (Fraxinus pennsy Zvanica and Prunus americana) 

occur along streams and moist lower north slopes in southeastern Montana, and two other 

such species (Ulmus americana and Quercus macrocarpa) reach the eastern edge of this 

region (Little 1971, 1976). Pfister and others (1977) have discussed compositional 

similarities between the P. ponderosa forests of southeastern Montana and those of the 

Black Hills of western South Dakota as sampled by Thilenius (1972). 

Forest distribution 

Approximately 20 percent of southeastern Montana supports forest. This is a region - 

without prominent mountains, or mountain forests; thus, it differs from all other forested regions. (Northeastern Montana does not have mountains, but also is without Great L 

Plains Pinus ponderosa forest.) 
Most of the remainder of the region is Great Plains grassland (BouteZoua-StipaAgropyron, according to Kuchler 1964). Some of this grassland has widely scattered 

pines, and thus can be termed a "savanna." 

Southeastern Montana has a continental climate. Summers are longer, hotter, and 

more humid than those in the mountainous forest regions (table 4 and figure 2). Most 

of the annual precipitation (ranging up to about 18 inches in moist forest areas) 

comes in spring and summer rains. Winters are generally dry and cold, but are not as 

severe as those in the northern parts of Montana east of the Continental Divide. 

Northeastern Montana i-1, 

The northeastern part of Montana includes the area north of Miles City and east of 

the Missouri River Breaks. Potential natural vegetation is Great Plains grassland 

(BouteZoua-Stipa-Agropyron and Agropyron-Stipa, according to Kuchl er 1964) except for 

stands of PopuZus deZtoides lining the principal rivers. This region has no upland 

forest, except for a few widely scattered populations of stunted Pinus ponderosa. (The 

most notable stand is at the Pines Recreation Area south of Glasgow on Fort Peck Reservoir.) The extremely cold continental winters, coupled with desiccating winds, may be 

the factors preventing Pinus ponderosa from growing here. Average annual precipitation 

is between 11 and 15 inches in this region (U.S. Dep. Comm. 1971). Table 4 presents 

climatic data from Glasgow. 
RESEARCH AND MANAGEMENT 

APPLICATIONS 

The forest regions presented here were developed to describe distributions of 

forest habitat types (Pfister and others 1977)--i.e., forest sites and vegetation in 

mature stands. The regions can also be used in describing distributions of individual 

forest species or sera1 forest communities (e .g., Acer gzabrwn-SaZix brushf ields) . The Northern Region of the USDA Forest Service recently adopted forest regions as 

"seed transfer zones" to help insure that nursery-raised seedlings are sent to a 

geographic area similar to the one where the seeds were collected. 

These forest regions may be useful as a biologically based regional stratification 

for forest research and forest management studies. For example, it might be useful to 

stratify productivity estimates (site index and yield capability) of individual habitat 

types by forest region. Similarly, these forest regions logically could be incorporated 

in studies of genetic variation in tree species and in tree improvement programs. 

Responses of trees and other vegetation to management are often stratified by 

habitat type, but it may be useful to analyze them by forest region as well. Forest 

regions offer an additional dimension for interpreting variation in forest vegetation. 

Forest managers may find appendix C useful for determining the location of forest region 

boundaries. 
Arno, Stephen F. 

1970. Ecology of alpine larch (Larix ZyaZZii Parl,) in the Pacific Northwest. Ph.D. 

Diss., Univ. Mont., Missoula, 264 p. 

Bailey, R. G. 

1976. Ecoregions of the United States (map) , USDA For. Serv. , Intermt. Reg. , Ogden, 

Utah. 

Bailey, R. G. 

1978. Ecoregions of the United States (manual to accompany map). USDA For. Serv., 

Intermt. Reg., Ogden, Utah, 77 p. 

Booth, W. E. 

1950. Flora of Montana. Part I, Conifers and Monocots. 232 p. Mont. State Univ., 

Bo z eman. 

Booth, W. E., and J. Wright. 

1966. Flora of Montana. Part 11. Dicotyledons. 305 p. Mont. State Univ., Bozeman. 

Caprio, J. M. 

1965. Average length of freeze -free season. Mont. Agric. Ext. Stn., Bozeman. Folder 

83 (map) . Crowley, J. M. 

1972. Environmental regions of Montana. In Montana Environmental Quality Council, 

First Annu. Rep., Helena, Mont., p. 2-11. 

Daubenmire, R. 

1969. Structure and ecology of coniferous forests of the Northern Rocky Mountains. 

Proc. 1968 Symp. (Coniferous Forests of the Northern Rocky Mountains), Univ. Mont., 

Missoula, p. 25-41. 

Daubenmire, R., and J. B. Daubenmire. 

1968. Forest vegetation of eastern Washington and northern Idaho. Wash. Agric. Exp. 

Stn., Pullman. Tech. Bull. 60, 104 p. 

Goldin, A., and T. J. Nimlos. 

1977. Vegetation patterns on limestone and acid parent materials in the Garnet Mountains of western Montana. Northwest Sci. 51(3):149-160. 

Green, A. W., and T. Setzer. 

1974. The Rocky Mountain timber situation, 1970. USDA For. Serv. Resour. Bull. 

INT-10, 78 p. Intermt. For. and Range Exp. Stn., Ogden, Utah. 

Hitchcock, C. L., and A. Cronquist. 

1976. Flora of the Pacific Northwest. 730 p. Univ. Wash. Press., Seattle. 

Hitchcock, C. L., A. Cronquist, M. Ownbey, and J. Thompson. 

1955-1969. Vascular plants of the Pacific Northwest (5 vols.). Univ. Wash. Press, 

Seattle. 

Hutchison, S. B., and P. D. Kemp. 

1952. Forest resources of Montana. USDA For. Serv., For. Res. Rep. 5, 76 p. North. 

Rocky Mt. For. and Range Exp. Stn., Missoula, Mont. 

Kirkwood, J. E. 

1922. Forest distribution in the Northern Rocky Mountains. Mont. State Univ., Bull. 

247 (ser. 2), Missoula, 180 p. 

Kuchler, A. W. 

1964. Potential natural vegetation of the conterminous United States (map and manual) 

Am. Geog. Soc. Spec. Publ. 36, 116 p. 
Kuchler, A. W. 

1973, Problems in classifying and mapping vegetation for ecological regionalization. 

Ecology 54:512-523. 

Little, E. L., Jr. 

1953. Check list of native and naturalized trees of the U.S. USDA For. Serv. Agric. 

Handb. 41, 472 p. 

Little, E. L., Jr. 

1971. Atlas of United States trees. Vol. 1. Conifers and important hardwoods. USDA 

For. Serv. Misc. Publ. 1146. 

Little, E. L. Jr. 

1976. Atlas of United States trees. Vol. 3. Minor western hardwoods. USDA For. 

Serv. Misc. Publ. 1314. 

Lynch, D. L. 

1955. Ecology of aspen groveland in Glacier County, Montana. Ecol. Monogr. 

25:321-344. 

McWhirter, N., and R. McWhirter. 

1972. Guinness book of world records. 704 p. Sterling Publ. Co., N. Y. 

Mueggler, W. F., and W. P. Handl. 

[In process.] Mountain grassland and shrubland habitat types of western Montana. 

USDA For. Serv., Gen. Tech. Rep., Intermt. For. and Range Exp. Stn., Ogden, Utah, 

and North. Reg., Missoula, Mont. 

Mueller-Dombois, D. , and H. Ellenburg. 

1974. Aims and methods of vegetation ecology. 547 p. John Wiley and Sons, N. Y. 

Payne, G. F. 

1973. Vegetative rangeland types in Montana. Mont. Agric. Exp. Stn., Bull. 671. 

Bozeman, 15 p. and map. 

Pfister, R. D., B. Kovalchik, S. Arno, and R. Presby. 

1977. Forest habitat types of Montana. USDA For. Serv. Gen. Tech. Rep. INT-34. 

174 p. Intermt. For. and Range Exp. Stn., Ogden Utah. 

Ross, R. L., and H. E. Hunter. 

1976. Climax vegetation of Montana based on soils and climate. USDA Soil Cons. 

Serv . , Bozeman . 64 p. and map. 

Rowe, J. S. 

1959 and 1972 editions. Forest regions of Canada. Canadian Forestry Serv. Publ. 

1300. 172 p. Ottawa. 

Schmidt, W. C., and W. P. Dufour. 

1975. Building a natural area system for Montana. Western Wildlands 2(1):20-29. 

Mont. For. and Cons. Exp. Stn., Univ. Mont., Missoula. 

Thilenius, J. F. 

1972. Classification of deer habitat in the ponderosa pine forest of the Black Hills, 

South Dakota. USDA For. Serv. Res. Pap. RM-91, 23 p. Rocky Mt. For. and Range 

Exp. Stn., Fort Collins, Colorado. 

Thompson, L. S., and J. Kuijt. 

1976. Montane and subalpine plants of the Sweetgrass Hills, Montana, and their 

relationship to early postglacial environments of the Northern Great Plains. 

Canadian Field - Naturalist 90(4):432-448. 

USDA Soil Conservation Service. 

1968. Average annual mountain precipitation (map). Soil Cons. Serv., Bozeman, 

Montana. 

U. S. Department of Commerce. 

I 1971. Climates of the States: Montana. Climatography of the United States No. 60: 

24. Environ. Data Serv., Silver Springs, MD. 

Weaver, T., and D. A. Perry. 

I 1978. Relationship of cover type to altitude, aspect, and substrate in the Bridger Range, Montana. Northwest Sci. 52(3):212-219. 
APPENDIX A 

Distribution of key tree and undergrowth species in Montana 
NORTHWESTERN Figure A-].--Natural distribution of Tsuga 

heterophylla in Montana. 

(Species common in 

suitable habitats within 

shaded area. X's indicate small outlying 

populations. ) 

WES 

Figure A-2.--Natural distribution of Pinus 

monticola in Montana. 

(Species common in 

suitable habitats wlthin 

shaded area. X's indicate small outlying 

populations. ) 
Figure A-3. --Natural 

distribution of 

Thuja plicata in 

Montana. (Species 

common in suitable 

habitats within shuded 

area. X's indicate 

sma Z l out l ying 

popu Zations . ) 

NORTHWESTERN 

WES 

Figure A-4. --Natural 

distribution of Abies 

grandis in Montana. 

(Species common in 

suitable habitats 

within shaded area. 

X's indicate small 

outlying populations. ) 
NORTHWESTERN - - - - - . - - . . Fiaure A-5. --Natural distriNORTH-,CENTRAL CENTRAL 

I 

'H* / 

WES 

WES 

" 

bution of Larix occidentalis I 

\ \I I in ~mta&. . - (Species -. common . -. in suitable habitats wzthzn 

shaded area. X's indicate 

smal Z outlying populations. ) 

I Figure A-6.--Natural distribution of Pinus flexilis (plot locations and observations - 

onZy) in Montana. 

28 
Figure A-7. --Natural distribution of Clintonia 

uniflora in Montana. 

(Species comon in 

suitable habitats within 

shaded area. X's indicate small outlying 

populations. ) 

WES 

Figure A-8. --Natural 

distribution of Luzula 

hitchcockii in Montana. 

(Species comon in 

suitable habitats within 

shaded area. X's in- dicate small outlying 

populations. l 

NORTHWESTERN 
NORTHWESTERN 

NORTHWESTERN 

WES 

Figure A-9.--Natural distribution of Menziesia 

ferruginea in Montana. 

(Species common in suitable 

habitats within shaded area. 

X's indicate small outlying 

populations. ) 

Figure A-1 0. --Natural distribution of Xerophyllum 

tenax in Montana. (Species 

common in suitable habitats 

within shaded area. X's in.- 

dicate small outlying 

populations. ) 
APPENDIX B 

Number of sample plots (Pfister and others 1977) 

by habitat type, phase, and forest region in Montana 
Table B-1--Number of sqle plots (Pfister and others 1977) by habitat type, 

phase, and forest region in Montana. (c.t. = cort~mmity type) 

NW = Northwestern Montana 

WC = west-central Montana 

NC = north-central Montarxz 

C = central Montana 

SW = southwestern Montana 

SC = south-central Montana 

SE = southeastern Montana 

Montana forest region 

Series/habitat type/phase : NW : WC : NC : C : SW : SC : SE : Total 

Forested scree 

Pinus flexilis series 

/Agropyron spicatum h.t. 1 2 2 1 6 

/Festuca idahoensis h.t. 

-Festuca idahoensis phase . 1 2 2 2 7 

-Festuca scabrella phase . 1 3 4 

/Juniperus communis h; t . - 1 1 - - 1 4 - - 7 

4 8 5 7 2 4 

Pinus ponderosa series 

/Andropogon spp . h. t . /Agropyron spicatum h.t. 

/Festuca idahoensis h.t. 

-Festuca idahoensis phase 

-Festuca scabrella phase 

/Purshia tridentata h.t. 

-Agropyron spicatum phase 

-Festuca idahoensis phase 

/Symphoricarpos albus h.t. 

-Symphoricarpos albus 

phase 

-Berberis repens phase 

/Prunus virginiana h.t. 

-Prunus virginiana phase 

-Shepherdia canadensis 

phase 

Pseudotsuga menziesii series 

/Agropyron spicatum h.t. 1 4 5 1 2 13 

/Festuca idahoensis h.t. 1 1 . 14 3 19 

/Festuca scabrella h.t. 5 2 6 13 

/Vaccinium caespitosum h.t. 15 9 i 2 2 7 

/Physocarpus malvaceus h.t. 

-Physocarpus malvaceus 

phase 12 23 3 1 6 4 5 

-Calamagrostis rubescens 

phase 1 7 8 

(con. ) 
Table B-1. --(con.) 

Montana forest region 

Series/habitat ty-pe/phase : NW : WC : NC : C : SW : SC : SE : Total 

Pseudotsuga menziesii series 

/Vaccinium globulare h.t. 

-Vaccinium globulare phase 

-Arctostaphylos uva-ursi 

phase 

-Xerophyllum tenax phase 

/Linnaea borealis h.t. 

-Symphoricarpos albus 

phase 

-Calamagrostis rubescens 

phase 

-Vaccinium globulare phase 

/Symphoricarpos albus h.t. 

-Agropyron spicatum phase 

-Calamagrostis rubescens 

phase 

-Symphoricarpos albus 

phase 

/Calamagrostis rubescens h.t. 

-Agropyron spicatum phase 

-Arctostaphylos uva-ursi 

phase 

-Calamagrostis rubescens 

~hase 

-Pinus ponderosa phase 

/Carex geyeri h.t. 

/Spiraea betulifolia h.t. 

/Arctostaphylos uva-ursi 

h.t. 

/Juniperus communis h. t . /Arnica cordifolia h.t. 

/Symphoricarpos oreophilus 

Picea series 

/Equisetum arvense h.t. 3 2 2 1 1 

/Clintonia uniflora h.t. 

-Vaccinium caespitosum 

phase 8 

-Clintonia uniflora phase 16 

/Physocarpus malvaceus h.t. . ti 

/Galium trif lorum h. t . i i i 9 

/Vaccinium caespitosum h.t. 4 i 

/Senecio streptanthifolius 

h.t. 

-Pseudotsuga menziesii 

phase 1 2 2 

-Picea phase 5 

/Linnaea borealis h.t. i 5 4 11 

/Smilacina stellata h.t. - - 1 - - 4 - 1 - 4 

3 1 5 4 19 10 31 

(con. ) 
Table B-1.--(con.) 

Montana forest region 

Series/habitat type/phase : NW : WC : NC : C : SW : SC : SE : Total 

Abies grandis series 

/Xerophyllum tenax h.t. 5 1 6 

/Clintonia uniflora h.t. 

-Clintonia uniflora phase 4 2 6 

-Aralia nudicaulis phase 5 1 6 

-Xerophyllum tenax phase 4 4 

/Linnaea borealis h.t. 

-Linnaea borealis phase 3 2 5 

-Xerophyllum tenax phase 3 - 3 6 - 

2 4 3 0 

Thuja plicata series 

/Clintonia uniflora h.t. 

-Clintonia uniflora phase 13 2 15 

-Aralia nudicaulis phase 8 1 9 

-Menziesia ferruginea phase 6 1 7 

/Oplopanax horridum h.t. - - 11 4 - 38 42 

Tsuga heterophylla series 

/Clintonia uniflora h.t. 

-Clintonia uniflora phase 27 2 7 

-Aralia nudicaulis phase - 11 

3 8 

Abies lasiocarpa series 

(Lower subalpine h.t.s) 

/Oplopanax horridum h.t. 4 4 

/Clintonia uniflora h.t. 

-Clintonia uniflora phase 18 11 3 32 

-Aralia nudicaulis phase 12 4 2 18 

-Vaccinium caespitosum 

phase 8 2 10 

-Xerophyllum tenax phase 13 7 i 2 1 

-Menziesia ferruginea 

phase 12 8 2 2 2 

/Galium triflorum h.t. 10 4 i 3 4 

/Vaccinium caespitosum h.t. . 2 3 i 10 

/Calamagrostis canadensis h.t. 

-Calamagrostis canadensis 

phase 8 1 8 6 23 

-Galium triflorum phase 2 1 2 5 

-Vaccinium caespitosum 

phase 3 1 1 2 7 

/Linnaea borealis h.t. 

-Linnaea borealis phase 1 10 4 2 1 2 20 

-Xerophyllum tenax phase 5 8 13 

-Vaccinium scoparium phase 2 3 i 4 i i 17 

/Menziesia ferruginea h.t. 19 37 5 2 1 64 

(con. ) 
Table R-1.--(con.) 

Montana forest region 

Serieslhabitat tvnelnhase : NW : WC : NC : C : S1.l " SC : SE : 'Total 

Abies lasiocarpa series 

(Lower subalpine h.t.s) 

Tsuga mertensiana/Menziesia 

h.t. 8 2 10 

/Xerophyllum tenax h.t. 

-Vaccinium globulare phase 18 18 3 1 40 

-Vaccinium scoparium phase 3 14 3 1 2 1 

Tsuga mertensiana/Xerophyllum 

h.t. 9 9 

/Vaccinium globulare h.t. i 5 3 11 2 1 

/Vaccinium scoparium h.t. 

-Calamagrostis rubescens 

phase 2 3 5 10 

-Vaccinium scoparium phase 1 ;1 3 4 5 17 

-Thalictrum occidentale 

phase 1 5 4 10 

/Alnus sinuata h.t. i i 2 2 6 

/Calamagrostis rubescens h.t. . 1 i 2 4 8 

/Clematis pseudoalpina h.t. . 1 7 1 6 15 

/Arnica cordifolia h. t. 1 8 15 2 4 

/Carex geyeri h.t. 

-Carex geyeri phase 2 1 3 

-Pseudotsuga menziesii 

phase 2 1 3 6 

(Upper subalpine h. t. s) 

/Ribes montigenum h.t. 3 3 6 

Abies 1as.-Pinus albic./ 

Vaccinium scop. h.t. 4 3 9 15 13 4 4 

/Luzula hitchcockii h.t. 

-Vaccinium scoparium phase 5 18 4 2 29 

-Menziesia ferruginea 

phase 14 9 1 24 

Tsuga mertensiana/Luzula h.t. 

-Vaccinium scoparium phase 2 2 

-Menziesia ferruginea 

phase 2 2 

(Timberline h. t . s) 

Pinus albicaulis-Abies 

lasiocarpa h . t. s 4 6 3 4 6 7 3 0 

Larix lyallii-Abies 

lasiocarpa h.t.s 5 29 2 36 

Pinus albicaulis h.t.s - - 1 - - i - 4 - 

i - 9 

168 221 43 63 94 93 682 

-=->- 

(con. ) 

35 
Table R-1. --(con.) 

-. - Montana forest region Series/habitat type/phase : NW : WC : NC : C : SW : SC : SE : Total 

Pinus contorta series 

/Purshia tridentata h.t. 3 3 

/Vaccinium caespitosum c.t. . 4 i i il 12 

/Linnaea borealis c.t. 1 4 2 6 ;1 17 

/Vaccinium scoparium c.t. 1 6 5 6 2 2 0 

/Calamagrostis rubescens c.t. - - - 1 - 4 1 - - 6 

2 14 1 10 21 10 5 8 

Unclassified stands 11 8 3 12 3 6 4 3 

1 

Total number of plots 399 459 66 217 188 178 24 1,531 

This total includes 35 Pinus contorta community type plots also 

listed under Pseudotsugo, Picea, or Abies Zasiocarpa habitat types. 
APPENDIX C 

National Forests, Indian Reservations, and 

National Parks within each forest region in Montana 

National Forests (fig. C-l), Indian Reservations, and National Parks 

within each forest region. (N.F. = National Forest; R.D. = Ranger District) : 

Forest region 

Northwestern 

West - central 

North- central 

Central 

Southwest ern 

Southeastern 

Northeastern 

Areas incZuded 

Flathead N.F. 

Kootenai N.F. 

Lolo N.F. (Thompson Falls, Plains, 

Superior, and W. and N. portions of 

Ninemile R.D. 's) 

Flathead Indian Reservation 

Glacier National Park (W. slope) 

Bitterroot N.F. (Montana portion) 

Deerlodge N.F. (Philipsburg R.D., W. 

portion of Deer Lodge R.D.) 

Helena N. F. (Blackfoot River drainage 

port ion) 

Lolo N.F. (Missoula, Seeley Lake, and 

S.E. portion of Ninemile R.D.) 

Lewis and Clark N.F. (Rocky Mountain 

Front port ion) 

Blackfeet Indian Reservation 

Glacier National Park (E. slope) 

Helena N.F. (except Blackfoot R. drainage) 

Lewis and Clark N.F. (except Rocky Mt. 

Front and Crazy Mts.) 

Fort Belknap (S. portion) and Rocky Boy 

Indian Reservation 

Chas. M. Russell National Wildlife Refuge 

(W. portion) 

Beaverhead N.F. 

Deerlodge N.F. (except Philipsburg and W. 

portion of Deer Lodge R.D.'s) 

Custer N.F. (Red Lodge R.D.) 

Gallatin N.F. 

Lewis and Clark N.F. (Crazy Mts. portion) 

Crow Indian Reservation (Pryor and Bighorn 

Mts. portion) 

Yellowstone National Park (Montana portion) 

Custer N.F. (Montana portion except Red 

Lodge R.D.) 

Crow (except Pryor and Bighorn Mts .) and 

Northern Cheyenne Indian Reservation 

Fort Belknap (N. portion) and Fort Peck 

Indian Reservation 

Chas. M. Russell National Wildlife Refuge 

(E. portion) 

39 

*LI.S. GOVERNMENT PRINTING OFFICE: 1979-0-677-019/71 
ARNO, STEPHEN F. 

1979. Forest regions of Montana. USDA For. Serv. Res. Pap. 

INT-218, 39 p. Intermt. For. and Range Exp. Stn., Ogden, 

Utah 84401. 

In this paper, Montanais divided into eight geographic subdivisions 

called "forest regions, "based on distributions of tree and undergrowth 

species and the relationship of these patterns to climate and topography. 

The regions serve as a geographic reference for describing patterns of 

forest vegetation across the State. Data on the distributions of plant 

species and habitat types and forest zonation are presented for each 

region. 

KEYWORDS: forest ecology, forest classification, plant geography, 

Northern Rocky Mountains 

ARNO, STEPHEN F. 

1979. Forest regions of Montana. USDA For. Serv. Res. Pap. 

INT-218, 39 p. Intermt. For. and Range Exp. Stn., Ogden, 

Utah 84401. 

In this paper, Montana is divided into eight geographic subdivisions 

called "forest regions, "based on distributions of tree and undergrowth 

species and the relationship of these patterns to climate and topography. 

The regions serve as a geographic reference for describing patterns of 

forest vegetation across the State. Data on the distributions of plant 

species and habitat types and forest zonation are presented for each 

region. 

KEYWORDS: forest ecology, forest classification, plant geography, 

Northern Rocky Mountains