Mesic Spruce-fir Forest
Global Name:
Rocky Mountain Subalpine Moist-Mesic Spruce - Fir Forest
Global Rank:
G4G5
State Rank:
S4S5
(see reason below)
External Links
State Rank Reason
Relatively common and widespread in the higher mountain ranges in the state. Few threats impacting the type and little loss in extent or habitat quality.
General Description
This National Vegetation Classification Group is dominated by Engelmann Spruce and Subalpine Fir, either in mixed stands or individually. Sites in northwestern Montana dominated or co-dominated by Mountain Hemlock (Tsuga mertensiana) are also included here. These forests are similar to G218 Dry Spruce-Fir Forest but occur on more mesic and generally cooler sites such as northerly-facing slopes, areas with cold-air drainage or ponding, or where snowpacks linger late into the summer. They are most abundant in the Flathead, Lolo, Bitterroot and Kootenai National Forests. Elevations range from 3,000-6,500 feet west of the Continental Divide, and 5,000-9,000 feet east of the Continental Divide. This group is more common and extensive west of the Continental Divide but occurs east of the divide in smaller patches in suitable sites such as cool, northerly slopes, near drainage bottoms or areas with cold air drainage. Other conifers are often present within these stands and may include Lodgepole Pine, Whitebark Pine, or Grand Fir, with Lodgepole Pine more typical of earlier successional stands, Grand Fir at mesic, lower elevations west of the divide and Whitebark Pine at higher elevations. The forest understory may be composed of low to tall shrubs, graminoids and/or forbs. Composition varies widely by geography, site characteristics and Association. The herbaceous understory contains mesic forbs, graminoids, and ferns and fern allies on the wettest sites. Moss cover is high in some communities Stand-replacing fires are less common in mesic spruce-fir forests than in dry spruce-fir forests.
This group is equivalent to the Rocky Mountain Subalpine Mesic Spruce-Fir Forest and Woodland Ecological System.
Diagnostic Characteristics
Subalpine Fir (Abies lasiocarpa), Engelmann Spruce (Picea engelmannii), Mountain Hemlock (Tsuga mertensiana) Dominated; Mesic Conifer Forest and Woodlands; Upper Montane and Subalpine Zones; Moderate to Dense Canopies; Long Fire Return Intervals.
Similar Systems
Range
The group occurs both east and west of the Continental Divide in the upper montane and subalpine zones. It is most common in northwest Montana extending east to Glacier NP and the Bob Marshall Wilderness Complex and south to the Bitterroot Mountains but also occurs in sw MT mountains, east to the Beartooth Mountains and the Big Snowy Mountains.
In MT, G218 occurs within these Level III Ecoregions: 15 (Northern Rockies), 16 (Idaho Batholith), 17 (Middle Rockies) and 41 (Canadian Rockies).
In Montana, G218 occurs within these Major Land Resource Areas: 43A-Northern Rocky Mountains, 43B - Central Rocky Mountains, and 44A - Northern Rocky Mountain Valleys.
Density and Distribution
Based on 2025 land cover layer. Grid on map is based on USGS 7.5 minute quadrangle map boundaries.
Mapped Distribution by County
Beaverhead, Big Horn, Broadwater, Carbon, Cascade, Chouteau, Deer Lodge, Fergus, Flathead, Gallatin, Glacier, Golden Valley, Granite, Jefferson, Judith Basin, Lake, Lewis and Clark, Lincoln, Madison, Meagher, Mineral, Missoula, Park, Pondera, Powell, Ravalli, Sanders, Silver Bow, Stillwater, Sweet Grass, Teton, Wheatland
Based on 2025 land cover layer.
Spatial Pattern
Large Patch-Matrix
Environment
This group occurs at relatively low to high elevations west of the Continental Divide and mid to high elevations east of the Divide. Elevations range from 3,000-6,500 feet west of the Continental Divide, and 5,000-9,000 feet east of the Continental Divide. Cold winter temperatures with heavy snowpack are common at these sites. Stands are often found in locations with cold-air drainage or ponding, or where snowpacks linger late into the summer, such as north-facing slopes and high-elevation ravines. They can extend lower in elevation below the subalpine zone in places where cold-air ponding occurs, especially on north and east aspects. Soils are derived from a variety of parent materials. They are usually rocky or gravelly with good aeration and drainage and are usually acidic.
Vegetation
These forests are dominated by Engelmann Spruce and Subalpine Fir, either in mixed stands or individually. Sites in western Montana dominated or co-dominated by Mountain Hemlock (Tsuga mertensiana) are also included here. Other conifers are often present and may include Lodgepole Pine, Whitebark Pine, or Grand Fir, with Lodgepole Pine more typical of earlier successional stands, Grand Fir at mesic, lower elevations west of the divide and Whitebark Pine at higher elevations. This group encompasses the wetter end of the Spruce-fir forest type and site characteristics and the understory vegetation should reflect that in relation to G219 Dry Spruce-Fir.
The forest understory may be composed of low to tall shrubs, graminoids and/or forbs. Composition varies widely by geography, site characteristics and Association. Common shrubs in these mesic Spruce-fir forests include False Huckleberry (Menziesia ferruginea), Common Huckleberry (Vaccinium membranaceum), Grouse Whortleberry (Vaccinium scoparium), Dwarf Huckleberry (Vaccinium cespitosum), Bristly Black Currant (Ribes lacustre), Rocky Mountain Maple (Acer glabrum), Spiraea (Spiraea betulifolia), Thimbleberry (Rubus parviflorus) and Snowberry (Symphoricarpos albus). Subshrubs such as Twinflower (Linnaea borealis) and Oregon-Grap (Berberis repens) are common in some habitats. Forb diversity can be high on some sites and common ones include Arnica (Arnica cordifolia, Arnica latifolia), Beargrass (Xerophyllum tenax), Fragrant Bedstraw (Galium triflorum), One-Sided Wintergreen (Pyrola secunda), Queen Cup Beadlily (Clintonia uniflora) among many others. Graminoids are generally few with Bluejoint Reedgrass (Calamagrostis canadensis) and Smooth Woodrush (Luzula hitchcockii) being two of the most consistently present within certain Associations. Mosses may be common in some understories. Non-native species are typically absent or uncommon in these communities.
Engelmann spruce is more tolerant of extreme environmental conditions than subalpine fir and is usually more dominant in the drier and wettest occurrences within this group. Mountain hemlock occurs as small to large patches within the matrix of mesic spruce-fir forest but only in the more maritime-influenced climate of northwestern Montana.
The understory in Spruce-fir forests of northwestern Montana often supports diverse stands of ericaceous plants. Beyond those mentioned previously, Labrador Tea (Ledum glandulosum), White-flowered Rhododendron (Rhododendron albiflorum) and Pink Mountain-heath (Phyllodoce empetriformis) may be abundant in some understories. In the wettest subalpine fir forests in northwestern Montana, Devil's-club (Oplopanax horridus) is a major shrub associate. These sites are usually restricted to ravine bottoms near streams and seeps where the water table remains near the surface all year.
In Montana, this group is represented by 34 Associations grouped into 5 Alliances within the National Vegetation Classification. These appear to represent the diversity of vegetation types within this group in the state.
National Vegetation Classification
Download the complete NVC hierarchy for Montana
TT2 B02 Temperate-Boreal Forest and Woodland
TT2.b S92 Cool Temperate Forest and Woodland
TT2.b3 F112 Temperate Continental Conifer Forest and Woodland
TT2.b3.Nd D336 Western Cordilleran Subalpine-High Montane Forest and Woodland
TT2.b3.Nd.2 M020 Rocky Mountain Subalpine-Upper Montane Forest and Woodland
TT2.b3.Nd.2.a G218 Rocky Mountain Subalpine Moist-Mesic Spruce - Fir Forest
A0422 Abies lasiocarpa - Populus tremuloides Rocky Mountain Moist Forest Alliance
CEGL005911 Populus tremuloides - Conifer / Spiraea betulifolia - Symphoricarpos albus Forest
A3614 Abies lasiocarpa - Picea engelmannii Central Rockies Moist Forest Alliance
CEGL000295 Abies lasiocarpa - Picea engelmannii / Actaea rubra Forest
CEGL000311 Abies lasiocarpa - Picea engelmannii / Galium triflorum Forest
CEGL000315 Abies lasiocarpa - Picea engelmannii / Linnaea borealis Forest
CEGL000317 Abies lasiocarpa - Picea engelmannii / Luzula glabrata Woodland
CEGL000319 Abies lasiocarpa - Picea engelmannii / Menziesia ferruginea Forest
CEGL000340 Abies lasiocarpa - Picea engelmannii / Vaccinium cespitosum Forest
CEGL000341 Abies lasiocarpa - Picea engelmannii / Vaccinium membranaceum Rocky Mountain Forest
CEGL000346 Abies lasiocarpa / Xerophyllum tenax Forest
CEGL000406 Picea (x albertiana, engelmannii) / Clintonia uniflora Forest
CEGL000415 Picea engelmannii / Maianthemum stellatum Forest
CEGL002174 Picea engelmannii / Galium triflorum Forest
CEGL002689 Picea engelmannii / Linnaea borealis Forest
CEGL005892 Abies lasiocarpa - Picea engelmannii / Clintonia uniflora - Xerophyllum tenax Forest
CEGL005893 Abies lasiocarpa - Picea engelmannii / Menziesia ferruginea / Clintonia uniflora Forest
CEGL005894 Abies lasiocarpa - Picea engelmannii / Menziesia ferruginea - Vaccinium scoparium Forest
CEGL005895 Abies lasiocarpa - Picea engelmannii / Menziesia ferruginea / Xerophyllum tenax Forest
CEGL005896 Abies lasiocarpa - Picea engelmannii / Menziesia ferruginea / Luzula glabrata Woodland
CEGL005897 Abies lasiocarpa - Picea engelmannii / Menziesia ferruginea / Streptopus amplexifolius Woodland
CEGL005898 Abies lasiocarpa - Picea engelmannii / Xerophyllum tenax - Luzula glabrata Woodland
CEGL005908 Populus tremuloides - Abies lasiocarpa - Picea engelmannii / Streptopus amplexifolius Forest
CEGL005912 Abies lasiocarpa - Picea engelmannii / Clintonia uniflora Forest
CEGL005914 Abies lasiocarpa - Picea engelmannii / Vaccinium scoparium / Xerophyllum tenax Forest
CEGL005917 Abies lasiocarpa - Picea engelmannii / Vaccinium membranaceum / Xerophyllum tenax Forest
CEGL005919 Abies lasiocarpa - Picea engelmannii / Vaccinium scoparium / Thalictrum occidentale Forest
CEGL005920 Abies lasiocarpa - Picea engelmannii / Streptopus amplexifolius - Luzula glabrata Woodland
CEGL005926 Picea engelmannii / Vaccinium cespitosum Forest
A3615 Abies lasiocarpa - Picea engelmannii Southern Rocky Mountain Moist Forest Alliance
CEGL000294 Abies lasiocarpa - Picea engelmannii / Acer glabrum Forest
CEGL000331 Abies lasiocarpa - Picea engelmannii / Ribes (montigenum, lacustre, inerme) Forest
A3616 Abies lasiocarpa - Picea engelmannii Rocky Mountain Talus and Scree Woodland Alliance
CEGL005823 Abies lasiocarpa - Picea engelmannii / Valeriana sitchensis Woodland
A3617 Tsuga mertensiana Rocky Mountain Forest Alliance
CEGL000504 Tsuga mertensiana / Clintonia uniflora Forest
CEGL000506 Tsuga mertensiana / Menziesia ferruginea Forest
CEGL000516 Tsuga mertensiana / Xerophyllum tenax Forest
CEGL007383 Tsuga mertensiana / Luzula glabrata Forest
*Disclaimer: Some Alliances and Associations are considered provisional. Some require further documentation to verify their occurrence in the state
and some may be modified or deleted in future revisions after collection of additional data and information.
Dynamic Processes
Major disturbances include occasional blowdown, insect outbreaks (30-50 years), and fire. Fire return intervals are longer in these habitats than in the Dry Spruce-Fir Forest and range between 170 to more than 300 years (U.S. Department of Agriculture 2012). The majority of fires are stand-replacing, although mixed severity fires also occur (U.S. Department of Agriculture 2012). The cool, mesic environment favors greater fuel loading and infrequent fires, however when dry conditions persist over long periods, these characteristics promote intense, stand-replacing fires (Reinhardt and Holsinger 2010). Both Subalpine Fir and Engelmann Spruce are highly susceptible to fire, in part due to their shallow roots, thin bark, and dense stand growth habits (Alexander and Shepperd 1990; Uchytil 1991). Mountain hemlock is also highly susceptible to fire due to its low-hanging branches, although its bark is relatively thick and may provide some protection to low-intensity burning (Tesky 1992). Following fire, spruce is more successful at establishing on mineral soils while subalpine fir is comparatively better at establishing in the shade and on organic substrates. Both mountain hemlock and spruce are generally slow to establish after fire (Alexander and Shepperd 1990; Tesky 1992). In Montana, subalpine fir will often form pure stands with lesser dominance by Engelmann spruce, although Engelmann spruce often outlives subalpine fir in these habitats (Uchytil 1991). Over time, in the absence of fire or in the presence of spruce budworm attacks, subalpine fir will largely replace spruce within most habitats, with the exception of the wettest sites.
Insects and disease influence species composition and successional direction of this group. Throughout Montana, subalpine fir and spruce are affected by western spruce budworm (Choristoneura occidentalis) attacks. Spruce and subalpine fir in this group may be comparatively less vulnerable to spruce budworm outbreak than those in the Dry Spruce-Fir Forest due to higher energy reserves associated with trees on more mesic sites that increase defense potential against spruce budworm attack (Dupont et al. 1991). The spruce beetle (Dendroctonus rufipennis) also causes extensive damage to spruce in this group. Severe wind events that cause extensive blowdown are often followed by spruce beetle outbreaks as downed trees provide an abundant food supply and are favored by the beetles (Lindemann and Barker 2001). Other disturbances that cause an abundance of downed material, including landslides and avalanches, also contribute to increases in local beetle populations (Jenkins et al. 2014). When outbreak conditions occur, or when downed material is unavailable, spruce beetles will also attack live trees, favoring large size classes and overmature individuals (Alexander and Shepperd 1990). Beetle outbreaks have implications for watershed function, wildlife habitat, recreation, and stand species composition (Jenkins et al. 2014). Large stands of these subalpine forests can be killed following several years of drought or unusually mild winters.
Spruce broom rust (Chrysomyxa arctostaphyli) also occurs in this group causing deformation and increased vulnerability to windbreak (Alexander and Shepperd 1990). Subalpine fir is additionally affected by western balsam bark beetle (Dryocoetes confuses), balsam wooly adelgid (Adelges piceae), and the fir engraver beetle (Scolytus ventralis). Root and wood rots also affect the dominant species in this group by weakening their defenses to insect attack and increasing vulnerability to windfall (Jenkins et al. 2014). Root decay is especially problematic for mature subalpine fir in the Northern Rockies (Uchytil 1991).
Management
In the absence of natural fire, periodic prescribed burns can be used to maintain this group, however, fire return intervals are generally quite long where site conditions are more mesic. Maintaining historic fire return intervals in this group may decrease stand susceptibility to spruce beetle outbreak (Bebi et al 2003; Kulakowski and Veblen 2006). Old stands have a greater abundance of downed material and mature individuals that are vulnerable to attack. Moderate to severe fires change the age structure of a stand thereby decreasing susceptibility to future attack (Kulakowski and Veblen 2006).
All species in this group are vulnerable to windthrow. Mechanical thinning for silvicultural or fire risk reduction purposes should therefore consider stand blowdown as a potential result of thinning treatment. Risk of windfall increases in stands with shallow soils and poor drainage, high degree of root and wood rot, and old, dense stand structure (Alexander and Shepperd 1990). Alternatively, thinning may be useful to promote natural regeneration and reduce abundance of overmature individuals in a stand, altering stand age structure, and thereby decreasing susceptibility to future spruce beetle outbreaks. However, logging residue may contribute to beetle population increases, and downed woody material may therefore need to be removed from the site to prevent beetle population growth. In general, increasing forest heterogeneity limits beetle spread and extent of outbreak (Jenkins et al. 2014).
Restoration Considerations
The dominant species in this group are good seed producers and are capable of regenerating well following fire. Spruce is capable of regenerating well on bare mineral soils if adequate moisture is present during the first two years of growth. Subalpine fir and mountain hemlock colonize both sites with mineral soil and those with some organic matter. At the higher elevation occurrences of this group, seedling survival may be greater where duff seedbeds are present as they protect seedlings from harsh climatic conditions, whereas at lower elevations, mineral seedbeds may be more conducive to seedling establishment (Uchytil 1991).
Small-scale prescribed burning during late fall after several hard frosts can facilitate regeneration and increase stand heterogeneity in terms of age structure and species composition, thereby decreasing susceptibility to insect outbreaks (Jenkins et al. 2014). In some cases, nursery stock may be used to expedite regeneration of severely burned areas if seed rain from adjacent stands is not likely to occur, or if bare mineral soil following severe insect outbreak is limited (Jenkins et al. 2014). When supplemental planting is required, cold, moist stratification is necessary for germination of subalpine fir and spruce (Uchytil 1991). Success of seedling establishment may be greater than in the Dry Spruce-Fir Forest since many sites occur on north aspects with cool air ponding where seedling establishment is favored and droughty conditions are less likely to occur (Alexander and Shepperd 1990).
Species Associated with this Community
- How Lists Were Created and Suggested Uses and Limitations
Animal Species Associations
Please note that while all vertebrate species have been systematically associated with vegetation communities, only a handful of invertebrate species have been associated with vegetation communities and invertebrates lists for each vegetation community should be regarded as incomplete. Animal species associations with natural vegetation communities that they regularly breed or overwinter in or migrate through were made by:
- Using personal observations and reviewing literature that summarize the breeding, overwintering, or migratory habitat requirements of each species (Dobkin 1992, Hart et al. 1998, Hutto and Young 1999, Maxell 2000, Werner et al. 2004, Adams 2003, and Foresman 2012);
- Evaluating structural characteristics and distribution of each vegetation community relative to the species' range and habitat requirements;
- Examining the observation records for each species in the state-wide point observation database associated with each vegetation community;
- Calculating the percentage of observations associated with each vegetation community relative to the percent of Montana covered by each vegetation community to get a measure of "observations versus availability of habitat".
Species that breed in Montana were only evaluated for breeding habitat use. Species that only overwinter in Montana were only evaluated for overwintering habitat use. Species that only migrate through Montana were only evaluated for migratory habitat use. In general, species are listed as associated with a vegetation community if it contains structural characteristics known to be used by the species. However, species are not listed as associated with a vegetation community if we found no support in the literature for the species’ use of structural characteristics of the community even if point observations were associated with it. If you have any questions or comments on animal species associations with vegetation communities, please contact the Montana Natural Heritage Program's Senior Zoologist.
Plant Species Associations
Please note that while diagnostic, dominant, or codominant vascular plant species for a vegetation community have been systematically assigned to those communities and vascular plant Species of Concern were systematically evaluated for their associations with vegetation communities, the majority of Montana’s vascular plant species have not been evaluated for their associations with vegetation communities and no attempt has been made to associate non-vascular plants, fungi, or lichens with vegetation communities. Plant species associations with natural vegetation communities were made in a manner similar to that described above for animals, but with review of Lesica et al. (2022) and specimen collection data from the Consortium of Pacific Northwest Herbaria. If you have any questions or comments on plant species associations with vegetation communities, please contact the Montana Natural Heritage Program's Program Botanist.
Suggested Uses and Limitations
Species associations with vegetation communities should be used to generate potential lists of species that may occupy broader landscapes for the purposes of landscape-level planning. These potential lists of species should not be used in place of documented occurrences of species or predicted habitat suitability models (this information can be requested at: https://mtnhp.mt.gov/requests/), or systematic surveys for species and onsite evaluations of habitat by trained biologists. Users of this information should be aware that the land cover data used to generate species associations is based on satellite imagery from 2016 and was only intended to be used at broader landscape scales. Land cover mapping accuracy is particularly problematic when the vegetation communities occur as small patches or where the land cover types have been altered over the past decade. Thus, particular caution should be used when using the associations in assessments of smaller areas (e.g., evaluations of public land survey sections). Finally, although a species may be associated with a particular vegetation community within its known geographic range, portions of that vegetation community may occur outside of the species' known geographic range.
Literature Cited
- Adams, R.A. 2003. Bats of the Rocky Mountain West; natural history, ecology, and conservation. Boulder, CO: University Press of Colorado. 289 p.
- Consortium of Pacific Northwest Herbaria. https://www.pnwherbaria.org/ Last accessed May 30, 2025.
- Dobkin, D. S. 1992. Neotropical migrant land birds in the Northern Rockies and Great Plains. USDA Forest Service, Northern Region. Publication No. R1-93-34. Missoula, MT.
- Foresman, K.R. 2012. Mammals of Montana. Second edition. Mountain Press Publishing, Missoula, Montana. 429 pp.
- Hart, M.M., W.A. Williams, P.C. Thornton, K.P. McLaughlin, C.M. Tobalske, B.A. Maxell, D.P. Hendricks, C.R. Peterson, and R.L. Redmond. 1998. Montana atlas of terrestrial vertebrates. Montana Cooperative Wildlife Research Unit, University of Montana, Missoula, MT. 1302 p.
- Hutto, R.L. and J.S. Young. 1999. Habitat relationships of landbirds in the Northern Region, USDA Forest Service, Rocky Mountain Research Station RMRS-GTR-32. 72 p.
- Lesica P., M. Lavin, and P.F. Stickney. 2022. Manual of vascular plants, 2nd Edition. Brit Press. 779 p.
- Maxell, B.A. 2000. Management of Montana's amphibians: a review of factors that may present a risk to population viability and accounts on the identification, distribution, taxonomy, habitat use, natural history, and the status and conservation of individual species. Report to U.S. Forest Service Region 1. Missoula, MT: Wildlife Biology Program, University of Montana. 161 p.
- Werner, J.K., B.A. Maxell, P. Hendricks, and D. Flath. 2004. Amphibians and reptiles of Montana. Missoula, MT: Mountain Press Publishing Company. 262 p.
- Species of Concern Associated with this Community
Vascular Plants
Mammals
Birds
Reptiles
Amphibians
Invertebrates
- Diagnostic, Dominant, or Codominant Plant Species for this Community
Vascular Plants
- Other Native Species Commonly Associated with this Community
Vascular Plants
Original Concept Authors
K.A. Schulz 2013
Montana Version Authors
S. Mincemoyer, L. Vance, T. Luna, M. Hart
Version Date
12/4/2024
References
- Literature Cited AboveLegend:
View Online Publication
Alexander, R.R. and W.D. Shepperd. 1990. Picea engelmannii Parry ex Engelm. Silvics of North America 1:187-203.- Bebi, P., D. Kulakowski, and T.T. Veblen. 2003. Interactions between fire and spruce beetles in a subalpine Rocky Mountain forest landscape. Ecology 84(2):362-371.
- Dupont, A., L. Bélanger, and J. Bousquet. 1991. Relationships between balsam fir vulnerability to spruce budworm and ecological site conditions of fir stands in central Quebec. Canadian Journal of Forest Research 21(12):1752-1759.
- Jenkins, M.J., E.G. Hebertson, and A.S. Munson. 2014. Spruce beetle biology, ecology and management in the Rocky Mountains: an addendum to spruce beetle in the rockies. Forests 5(1):21-71.
- Kulakowski, D. and T.T. Veblen. 2006. The effect of fires on susceptibility of subalpine forests to a 19th century spruce beetle outbreak in western Colorado. Canadian Journal of Forest Research 36(11):2974-2982.
- Lindemann, J.D. and W.L. Baker. 2001. Attributes of blowdown patches from a severe wind event in the Southern Rocky Mountains, USA. Landscape Ecology 16(4):313-325.
- Reinhardt, E. and L. Holsinger. 2010. Effects of fuel treatments on carbon-disturbance relationships in forests of the northern Rocky Mountains. Forest Ecology and Management 259(8):1427-1435.
- Tesky, J.L. 1992. Tsuga mertensiana. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory.
- U.S. Department of Agriculture, Forest Service, Missoula Fire Sciences Laboratory. 2012. Information from LANDFIRE on Fire Regimes of Rocky Mounatin Subalpine Mixed-Conifer Communities. In: Fire Effects Information System, [Online]. U.S. Department of Agr
- Uchytil, R.J. 1991. Abies lasiocarpa. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory.
- Additional ReferencesLegend: View Online Publication
Do you know of a citation we're missing?- Arno, S. F. 1980. Forest fire history in the northern Rockies. Journal of Forestry 78(8):460-465.
- Pfister, R. D., B. L. Kovalchik, S. F. Arno, and R. C. Presby. 1977. Forest habitat types of Montana. USDA Forest Service. General Technical Report INT-34. Intermountain Forest and Range Experiment Station, Ogden, UT. 174 pp.
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