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Montana Field Guides

Aspen Forest and Woodland

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General Description

This widespread ecological system is more common in the southern and central Rocky Mountains, but occurs in the montane and subalpine zones throughout much of Montana north into Canada. It is similar to the Inter-Mountain Basins Aspen Mixed Conifer Forest-Woodland found in the Big Snowy Mountains, but lacks the conifer component. Distribution of this system is primarily limited by adequate soil moisture required to meet its high evapotranspirative demand, length of growing season, and temperatures. Mean annual precipitation where these systems occur is generally greater than 38 centimeters (15 inches) and typically greater than 51 centimeters (20 inches), except in semi-arid environments where occurrences are restricted to mesic microsites such as seeps or areas below large snow drifts. Stands can occur on gentle to moderate slopes, in swales, or on level sites. At lower elevations, occurrences are found on cooler, north aspects and mesic sites. Soils are usually deep and well developed with rock often absent from the soil. Soil texture ranges from sandy loam to clay loams. This system describes mesic forests and woodlands dominated by quaking aspen (Populus tremuloides) without a significant conifer component (<25% relative tree cover). This aspen system can be stable and long-lived with little encroachment of coniferous species. The understory structure may be complex with multiple shrub and herbaceous layers, or simple, with just an herbaceous layer. The herbaceous layer may be dense or sparse, dominated by mesic grasses or forbs. Occurrences of this system often originate, and are likely maintained, by stand-replacing disturbances such as crown fire, disease, windthrow, elk and beaver activity.


Diagnostic Characteristics
Northwestern Great Plains Aspen Forest and Parkland and Inter-Mountain Basins Aspen-Mixed Conifer Forest & Woodland

Similar Systems

Range
In Montana, this system is found throughout the Rocky Mountains and island ranges of eastern and south-central Montana. Elevations generally range from 1,493 to 2,743 meters (4,900-9,000 + feet), but occurrences can be found at lower elevations in some regions.

Ecological System Distribution
Approximately 1,710 square kilometers are classified as Aspen Forest and Woodland in the 2013 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, 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, POWELL, RAVALLI, SANDERS, SILVER BOW, STILLWATER, SWEET GRASS, TETON, WHEATLAND

Spatial Pattern
Large patch and Small patch

Environment
Climate is temperate with a relatively long growing season, typically cold winters and deep snow. Mean annual precipitation is greater than 38 centimeters (15 inches) and typically greater than 51 centimaters (20 inches), except in semi-arid environments where occurrences are restricted to mesic, microsites such as seeps or areas below large snow drifts. Stands can occur on gentle to moderate slopes, in swales, or on level sites. At lower elevations, occurrences are found on cooler, north aspects and mesic sites. Soils are usually deep and well developed, with rock often absent from the soil. Soil texture ranges from sandy loam to clay loams.

Vegetation

This system includes aspen stands with a relatively closed canopy of trees 5-20 meters (16 to 66 feet) tall. In Montana, most aspen clones are smaller than in the Central Rocky region. Clones can be stable and long-lived or seral to Douglas-fir (Pseudotsuga menziesii), subalpine fir (Abies lasiocarpa) or spruce (Picea species) dominated forests (Habeck, 1967). Stable climax aspen forest also occurs in southwestern Montana (Pfister et al, 1977). Conifers that may be present but are never codominant include subalpine fir, Engelmann spruce (Picea engelmannii), white spruce (Picea glauca), ponderosa pine (Pinus ponderosa), and Douglas-fir. Conifer species may contribute up to 25% of the tree canopy before the occurrence is reclassified as a mixed occurrence. This system can be interpreted in some instances to be the seral phase of the Inter-Mountain Basins Aspen-Mixed Conifer Forest & Woodland. In Glacier County, this system differs in height growth, which is controlled by recurring Chinook winds.

Depending on available soil moisture and other factors like disturbance, the understory structure may be complex with multiple shrub and herbaceous layers, or simple with just an herbaceous layer. The herbaceous layer may be dense or sparse, dominated by graminoids or forbs. Common shrubs include Rocky Mountain maple (Acer glabrum), serviceberry (Amelanchier alnifolia), creeping Oregon grape (Mahonia repens), chokecherry (Prunus virginiana), rose (Rosa spp.), thimbleberry (Rubus parviflorus), and snowberry (Symphoricarpos spp.). The herbaceous layers may be lush and diverse. Common graminoids may include mountain brome (Bromus carinatus), pinegrass (Calamagrostis rubescens), Ross’ sedge (Carex rossii), blue wildrye (Elymus glaucus), slender wheatgrass (Elymus trachycaulus) and bearded fescue (Festuca subulata). Common mesic understory forbs include yarrow (Achillea millefolium), sharptooth angelica (Angelica arguta), Engelmann aster (Eucephalus engelmannii),larkspur (Delphinium species), aspen daisy (Erigeron speciosus), Richardson’s geranium (Geranium richardsonii), common cow parsnip (Heracleum maximum), western sweet cicely (Osmorhiza occidentalis), western meadow rue (Thalictrum occidentale), stinging nettle (Urtica dioica) and western valerian (Valeriana occidentalis). Bracken fern (Pteridium aquilinum) is present in some stands.Exotic grasses such as the perennials Kentucky bluegrass (Poa pratensis), common timothy (Phleum pratense) and smooth brome (Bromus inermis) are often common in occurrences disturbed by grazing.


Alliances and Associations
Alliances
  • (A.610) Aspen Woodland Alliance
  • (A.274) Quaking Aspen Forest Alliance
  • (A.300) Quaking Aspen Temporarily Flooded Forest Alliance

Dynamic Processes

Occurrences in this ecological system often originate with, and are likely maintained by, stand-replacing disturbances such as crown fire, disease and windthrow, or logging by humans or beaver. Boles are killed by ground fires, but they can quickly and vigorously resprout by root suckers in high densities. Stems are relatively short-lived (70-120 years), and the system will generally succeed to longer-lived conifer forest if undisturbed. Occurrences are favored by fire in the conifer zone (Mueggler, 1988). In Montana, seed production is erratic and infrequent. Natural seedling establishment is limited to years of viable seed production. Seedling recruitment is limited to sites where there is adequate soil moisture following dispersal in early summer. Following the Yellowstone fires of 1988, quaking aspen seedlings established on many suitable sites. These sapling and young tree stands are subjected to heavy elk browsing and will not reach full maturity.

Quaking aspen is dioecious; clones are either male or female. Reproduction is largely clonal. Some clones are thought to be centuries old and have the potential to be large in size. Stems are produced from a common root system; new stems are produced on the outside, advancing in front of the clone, with older trees in the center. The root system persists as stems die and are replaced. Clones can be distinguished by morphological differences in flowering and leaf emergence phenology, leaf size and shape, branching habit, bole character, and gender. Quaking aspen reproduces vegetatively by sprouting from stumps and root crowns, and by forming suckers (adventitious shoots on roots). The ability of Populus to regenerate by suckers can vary widely among clones (Schier et al, 1985).

In recent years, many aspen stands have exhibited mortality from biotic vectors. These pathogens mainly infect clones already stressed by drought, insects, wind damage, heavy livestock and wildlife use and similar factors.


Management
In the absence of natural fire, periodic prescribed burns can be implemented during late fall months to maintain and enhance regeneration.

Restoration Considerations

Restoration strategies for will depend on fire severity, grazing or other land impacts. Because lightly burned areas regenerate vegetatively following fire, additional restoration practices are not required. Early successional stages may be dominated by fireweed (Chamerion angustifolium) and other forbs, small amounts of forest graminoids such as mountain brome, blue wildrye, and pinegrass, and by resprouting of dominant shrubs. 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.


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 (high, medium, or low) 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 2001, 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 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 associated as using 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 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.  High, medium, and low habitat quality was assigned based on the degree to which the structural characteristics of an ecological system matched the preferred structural habitat characteristics for each species in the 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 assignments of habitat quality.  If you have any questions or comments on species associations with ecological systems, please contact Bryce Maxell at bmaxell@mt.gov or (406) 444-3655.

    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: http://mtnhp.org/requests/default.asp) 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.  2001.  The wild mammals of Montana.  Special Publication No. 12.  Lawrence, KS: The American Society of Mammalogists.  278 p.
    • 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
M.S. Reid, mod. G. Kittel

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

Version Date
2/15/2010

References
  • Classification and Map Identifiers

    Cowardian Wetland Classification: Not applicable

    National Vegetation Classification Standard:
    Class Forest and Woodland
    Subclass Temperate Forest
    Formation Cool Temperate Forest
    Division Western North America Cool Temperate Forest
    Macrogroup Northern Rocky Mountain Lower Montane and Foothill Forest

    NatureServe Identifiers:
    Element Global ID 28649
    System Code CES306.813, Rocky Mountain Aspen Forest and Woodland

    National Land Cover Dataset:
    41: Deciduous Forest

    ReGAP:
    4104: Rocky Mountain Aspen Forest and Woodland


  • Additional ReferencesLegend:   View WorldCat Record   View Online Publication
    Do you know of a citation we're missing?
    • 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.
    • 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.
    • 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.
    • Sisson, L. 1976. The sharp-tailed grouse in Nebraska. Neb. Game and Parks Comm. Lincoln. 87 pp.

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Citation for data on this website:
Aspen Forest and Woodland — Rocky Mountain Aspen Forest and Woodland.  Montana Field Guide.  Retrieved on September 30, 2014, from http://FieldGuide.mt.gov/displayES_Detail.aspx?es=4104
 
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