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Montana Field Guide

Montana Field Guides

Aspen and Mixed Conifer Forest

Provisional State Rank: S3/S4
* (see reason below)

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State Rank Reason
The system is at risk from aspen decline in general. Shifting climate may reduce range even more.

General Description

This system occurs in north-central Montana in the Big Snowy Mountain range, at elevations of 2,012-2,195 meters (6,600-7,200 feet). Occurrences are typically on gentle to steep slopes on any aspect. Soils in this mountain range are derived from alluvium, colluvium, and residuum from calcareous parent materials. Most current occurrences represent a late-seral stage of aspen (Populus tremuloides) forest changing to a pure conifer forest. Nearly a hundred years of fire suppression and livestock grazing have converted much of the pure aspen occurrences to the present-day aspen-conifer forest and woodland ecological system, with conifers increasing in dominance. Conifers in this system include Douglas-fir (Pseudotsuga menziesii), subalpine fir (Abies lasiocarpa), Engelmann spruce (Picea engelmannii) and lodgepole pine (Pinus contorta). Common shrubs include serviceberry (Amelanchier alnifolia), creeping Oregon grape (Mahonia repens), chokecherry (Prunus virginiana), Woods’ rose (Rosa woodsii), birch-leaf spiraea (Spiraea betulifolia), and snowberry (Symphoricarpos species).

Diagnostic Characteristics
Forest and Woodland, Aspen and Conifer mixed forest, montane elevation, side and toe slope topography

Similar Systems

This system occurs in north-central Montana in the Big Snowy Mountain range, at elevations of 2,012-2,195 meters (6,600-7,200 feet) on gentle to steep mountain slopes.

Ecological System Distribution
Approximately 200 square kilometers are classified as Aspen and Mixed Conifer Forest in the 2016 Montana Land Cover layers.  Grid on map is based on USGS 7.5 minute quadrangle map boundaries.

Montana Counties of Occurrence
Beaverhead, Big Horn, Blaine, Broadwater, Carbon, Carter, Cascade, Chouteau, Deer Lodge, Fergus, Flathead, Gallatin, Glacier, Golden Valley, Granite, Hill, Jefferson, Judith Basin, Lake, Lewis and Clark, Lincoln, Madison, Meagher, Mineral, Missoula, Park, Phillips, Pondera, Powder River, Powell, Ravalli, Sanders, Silver Bow, Stillwater, Sweet Grass, Teton, Wheatland

Spatial Pattern

In Montana, this system is found on montane slopes, where climate is dry and cold during winter months. Most precipitation occurs during late spring and early summer months. Distribution is primarily limited to areas of deeper soils with adequate soil moisture. Occurrences at high elevations are restricted by cold temperatures, and are generally only found on warmer southern aspects. By contrast, at lower elevations, aspen is restricted by lack of moisture and is found on cooler north aspects and mesic microsites. Soils are typically deep and well-developed, with rock often absent from the soil. Soil texture ranges from sandy loam to clay loam.


The tree canopy is composed of a mix of deciduous and coniferous species, co-dominated by aspen (Populus tremuloides) and conifers, including Douglas-fir (Pseudotsuga menziesii), subalpine fir (Abies lasiocarpa), Engelmann spruce (Picea engelmannii), lodgepole pine (Pinus contorta) and ponderosa pine (Pinus ponderosa). Common understory shrubs include serviceberry (Amelanchier alnifolia), creeping Oregon grape (Mahonia repens), chokecherry (Prunus virginiana), Woods’ rose (Rosa woodsii), birch-leaf spiraea (Spiraea betulifolia), and snowberry (Symphoricarpos species). Graminoid composition varies depending on available site moisture, but often includes mountain brome (Bromus carinatus), pinegrass (Calamagrostis rubescens), Geyer’s sedge (Carex geyeri), blue wild rye (Elymus glaucus), and needlegrasses (Achnatherum and Nassella species). Common forbs include yarrow (Achillea millefolium), heart-leafarnica (Arnica cordifolia), aspen daisy (Erigeron speciosus), northern bedstraw (Galium boreale), silver lupine (Lupinus argenteus), starry Solomon’s seal (Maianthemum stellatum), and meadow rue (Thalictrum species). Exotic species such as Kentucky bluegrass (Poa pratensis), timothy (Phleum pratense) and common dandelion (Taraxacum officinale) are frequentin areas impacted by grazing.

Alliances and Associations
  • (A.425) Limber Pine - Quaking Aspen Forest Alliance
  • (A.424) Lodgepole Pine - Quaking Aspen Forest Alliance
  • (A.118) Lodgepole Pine Forest Alliance
  • (A.399) Ponderosa Pine - Quaking Aspen Forest Alliance
  • (A.426) Quaking Aspen - Douglas-fir Forest Alliance
  • (A.274) Quaking Aspen Forest Alliance
  • (A.422) Subalpine Fir - Quaking Aspen Forest Alliance

Dynamic Processes
Quaking aspen is seral in this system, and in the absence of fire, the system will succeed to conifer-dominated forest (Mueggler, 1988). The natural fire-return interval is approximately 20 to 50 years for seral occurrences, and 100 years for late-seral occurrences (Hardy and Arno 1996). Young conifer species are susceptible to fire, but older individuals can withstand low-intensity ground fires. In Montana, aspen seed production is erratic and infrequent. Natural seedling establishment is rare due to limited years of viable seed dispersal and the long, moist conditions required for initial germination and first-year establishment.

In the absence of natural fire, periodic prescribed burns can be implemented during late fall months to maintain and enhance aspen regeneration (Hardy and Arno, 1996).

Restoration Considerations

Restoration strategies for Inter-Mountain Basins Aspen-Mixed Conifer Forest and Woodland will depend largely on the severity of the fire or other land use impacts. Early successional stages may be dominated by fireweed (Chamerion angustifolium) and other forbs, small amounts of forest graminoids, and by resprouting of dominant shrubs. Quaking aspen will resprout vigorously following fires of low to moderate severity. Some sprouting will occur after higher intensity fires from root suckers that are deeper in the soil profile. However, the ability of aspen to resprout following removal can vary widely among clones (Schier et al, 1985).

Species Associated with this Ecological System
  • Details on Creation and Suggested Uses and Limitations
    How Associations Were Made
    We associated the use and habitat quality (common or occasional) of each of the 82 ecological systems mapped in Montana for vertebrate animal species that regularly breed, overwinter, or migrate through the state by:
    1. 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, Foresman 2012, Adams 2003, and Werner et al. 2004);
    2. Evaluating structural characteristics and distribution of each ecological system relative to the species' range and habitat requirements;
    3. Examining the observation records for each species in the state-wide point observation database associated with each ecological system;
    4. Calculating the percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system 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, and species that only migrate through Montana were only evaluated for migratory habitat use.  In general, species were listed as associated with an ecological system if structural characteristics of used habitat documented in the literature were present in the ecological system or large numbers of point observations were associated with the ecological system.  However, species were not listed as associated with an ecological system if there was no support in the literature for use of structural characteristics in an ecological system, even if point observations were associated with that system.  Common versus occasional association with an ecological system was assigned based on the degree to which the structural characteristics of an ecological system matched the preferred structural habitat characteristics for each species as represented in scientific literature.  The percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system was also used to guide assignment of common versus occasional association.  If you have any questions or comments on species associations with ecological systems, please contact the Montana Natural Heritage Program's Senior Zoologist.

    Suggested Uses and Limitations
    Species associations with ecological systems 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 (this information can be requested at: or systematic surveys for species and evaluations of habitat at a local site level by trained biologists.  Users of this information should be aware that the land cover data used to generate species associations is based on imagery from the late 1990s and early 2000s and was only intended to be used at broader landscape scales.  Land cover mapping accuracy is particularly problematic when the systems 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 ecological system within its known geographic range, portions of that ecological system 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.
    • 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.
    • 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.

Original Concept Authors
K.A. Schulz, mod. M.S. Reid and G. Kittel

Montana Version Authors
L.K. Vance, T.A. Luna, M.M Hart

Version Date

  • Classification and Map Identifiers

    Cowardin Wetland Classification: Not applicable

    National Vegetation Classification Standard:
    Class Mesomorphic Tree Vegetation (Forest and Woodland)
    Subclass Temperate Forest
    Formation Cool Temperate Forest
    Division Western North America Cool Temperate Forest
    Macrogroup Rocky Mountain Subalpine and High Montane Conifer Forest

    NatureServe Identifiers:
    Element Global ID
    System Code CES304.776, Inter-Mountain Basins Aspen Mixed Conifer Forest-Woodland

    National Land Cover Dataset:
    43: Mixed Forest

    4302: Inter-Mountain Basins Aspen Mixed Conifer Forest-Woodland

  • Literature Cited AboveLegend:   View Online Publication
    • Bell, D.M., J.B. Bradford, and W.K. Lauenroth. 2014. Forest stand structure, productivity, and age mediate climatic effects on aspen decline. Ecology 95(8):2040-2046.
    • Cryer, D.H. and J.E. Murray. 1992. Aspen regeneration and soils. Rangelands Archives 14(4):223-226.
    • Durham, D.A. and C.B. Marlow. 2010. Aspen response to prescribed fire under managed cattle grazing and low elk densities in southwest Montana. Northwest Science 84(1):141-150.
    • Howard, J.L. 1996. Populus tremuloides. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory.
    • Shinneman, D.J., W.L. Baker, P.C. Rogers, and D. Kulakowski. 2013. Fire regimes of quaking aspen in the Mountain West. Forest Ecology and Management 299: 22-34.
    • St. Clair, S.B., X. Cavard, and Y. Bergeron. 2013. The role of facilitation and competition in the development and resilience of aspen forests. Forest ecology and management 299:91-99.
    • U.S. Department of Agriculture, Forest Service, Missoula Fire Sciences Laboratory. 2012. Information from LANDFIRE on Fire Regimes of Northern Rocky Mounatin Quaking Aspen Communities. In: Fire Effects Information System, [Online]. U.S. Department of Agri
    • Wooley, S.C., S. Walker, J. Vernon, and R.L. Lindroth. 2008. Aspen Decline, Aspen Chemistry, and Elk Herbivory: Are They Linked? Aspen chemical ecology can inform the discussion of aspen decline in the West. Rangelands 30(1):17-21.
  • Additional ReferencesLegend:   View Online Publication
    Do you know of a citation we're missing?
    • Hardy, Colin C., and Stephen F. Arno. 1996. The use of fire in forest restoration a general session at the annual meeting of the Society for Ecological Restoration : Seattle, WA, September 14-16, 1995. Ogden, Utah (324 25th Street, Ogden 84401): U.S. Dept. of Agriculture, Forest Service, Intermountain Research Station.

    • Mueggler, W. F. 1988. Aspen community types of the Intermountain Region. USDA Forest Service General Technical Report INT-250. Intermountain Research Station, Ogden, UT. 135 pp.
    • Schier GA, Jones JR, Winokur RP. 1985. Vegetative regeneration. In: DeByle NV, Winokur RP, editors. Aspen: ecology and management in the western United States. USDA Forest Service General Technical Report RM-119. Fort Collins, CO: Rocky Mountain Forest and Range Experiment Station; p 29-33.

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Citation for data on this website:
Aspen and Mixed Conifer Forest — Inter-Mountain Basins Aspen Mixed Conifer Forest-Woodland.  Montana Field Guide.  Retrieved on , from