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Rocky Mountain Subalpine Dry-Mesic Spruce-Fir Forest and Woodland

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General Description

Engelmann spruce (Picea engelmannii) and subalpine fir (Abies lasiocarpa) make up a substantial part of the montane and lower subalpine forests of the Montana Rocky Mountains and mountain island ranges of north-central and west-central Montana. Spruce is usually associated with fir and occurs as either a climax co-dominant or as a persistent, long-lived seral species in most upper elevation fir habitat types. Dry to mesic spruce-dominated forests range from 884-1,585 meters (2,900-5,200 feet) west of the Continental Divide, and 1585-2,073 meters (5,200-6,800 feet) east of the Continental Divide in the northern and central portions of the state. This system can be found at elevations up to 2,896 meters (9,500 feet) in southwestern Montana. Forests are found on gentle to very steep mountain slopes, high-elevation ridge tops and upper slopes, plateau-like surfaces, basins, alluvial terraces, well-drained benches, and inactive stream terraces. Tree canopy characteristics are relatively uniform. In northern Montana, Engelmann spruce hybridizes with its boreal counterpart, white spruce (Picea glauca). Douglas-fir (Pseudotsuga menziesii), lodgepole pine (Pinus contorta), and western larch (Larix occidentalis) (west of the Continental Divide) are seral but often present in these forests. The understory is comprised of a mixture of shrubs, forbs and graminoids tolerant of warmer and drier soil conditions than those found on the more mesic to wet spruce-fir system. The drier occurrences of this system are especially common on steep slopes at upper elevations throughout the eastern Rocky Mountains, whereas the more mesic occurrences form substantial cover west of the Continental Divide in the Flathead, Lolo, Bitteroot and Kootenai river drainages.


Diagnostic Characteristics

Forest and Woodland, ustic and acidic soils, long persistence, Picea engelmannii, Abies lasiocarpa


Similar Systems

Range
Engelmann spruce and subalpine fir forests comprise a substantial part of the subalpine forests of the Montana Rocky Mountains, including the island ranges of north-central and west-central Montana and southern Montana. In the driest mountain ranges east of the Continental Divide (such as the Bull Mountains, Snowy Mountains, Pryor Mountains, and Dillon area), these forests are restricted to cool exposures, usually on north and east facing aspects. The drier habitats within this system are especially common on steep slopes at upper elevations throughout the Montana Rocky Mountains. The more mesic habitats within this system are very common west of the Continental Divide in the Flathead, Lolo, Bitteroot, and Kootenai river drainages.

Ecological System Distribution
Approximately 12,579 square kilometers are classified as Rocky Mountain Subalpine Dry-Mesic Spruce-Fir 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, BROADWATER, CARBON, CASCADE, 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

Spatial Pattern
Matrix

Environment
This system forms a belt at relatively low to high elevations west of the Continental Divide and mid to high elevations east of the Divide throughout the Montana Rocky Mountains and island ranges of north-central and west-central Montana. Soils are derived from a variety of parent materials, and are usually rocky or gravelly with good aeration and drainage, but are usually acidic. Occurrences are typically 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 down in elevation below the subalpine zone in places where cold-air ponding occurs, especially on north and east aspects. Dry to mesic spruce-dominated forests range from 884 to 1,585 meters (2,900-5,200 feet) west of the Continental Divide, and 1585 to 2,073 meters (5,200-6,800 feet) east of the Continental Divide in the northern and central portions of the state. They can be found at elevations up to 2,896 meters (9,500 feet) in southwestern Montana.

Vegetation

Tree canopy characteristics are relatively uniform, with Engelmann spruce and subalpine fir dominating, either mixed or alone. In northern Montana, Engelmann spruce hybridizes with its boreal counterpart, white spruce. Spruce is more tolerant of extreme environmental conditions than subalpine fir, and is usually more dominant in the drier and wettest habitats within this system. Douglas-fir, lodgepole pine, and western larch (west of the Continental Divide) are seral but often present in these forests. Mountain hemlock (Tsuga mertensiana) occurs as small to large patches within the matrix of this mesic spruce-fir system, but only in the coldest and wettest environments of northwestern Montana.

The understory of these forests often supports diverse stands of ericaceous shrubs, such as rusty leaf menziesia (Menziesia ferruginea), dwarf huckleberry (Vaccinium caespitosum), mountain huckleberry (Vaccinium membranaceum), dwarf bilberry (Vaccinium myrtillus) and mountain heath (Phyllodoce species). Grouse whortleberry (Vaccinium scoparium) is common on mesic sites. Cascade azalea (Rhododendron albiflorum) occurs in association with mountain hemlock and subalpine fir in some mesic occurrences in northwestern Montana.Other common shrubs include Rocky Mountain maple (Acer glabrum), serviceberry (Amelanchier alnifolia),Utah honeysuckle (Lonicera utahensis), ninebark (Physocarpus malvaceus),currant (Ribesspecies), thimbleberry (Rubus parviflorus), birch leaf spiraea (Spiraea betulifolia) and common snowberry (Symphoricarpos albus). On the driest sites in the Bighorn Mountains,big sagebrush (Artemisia tridentata) may be present.Smooth woodrush (Luzula glabrata var. hitchcockii)is the most common graminoid on mesic sites at higher elevations. Pinegrass (Calamagrostis rubescens), Geyer’s sedge (Carex geyeri), and Ross’ sedge (Carex rossi) are common on drier sites. Forb diversity varies depending on moisture conditions. Species includebaneberry (Actaea rubra), arnica (Arnica species),Columbia clematis (Clematis occidentalis), queen’s cup beadlily (Clintonia uniflora), bunchberry dogwood (Cornus canadensis), fragrant bedstraw (Galium triflorum), twinflower (Linnaea borealis), clasp-leaf twisted stalk (Streptopus amplexifolius), western meadow rue (Thalictrum occidentale) and beargrass (Xerophyllum tenax).


Alliances and Associations
Alliances
  • (A.3535) Fireweed Herbaceous Alliance
  • (A.603) Paper Birch Woodland Alliance
  • (A.811) Subalpine Fir - Engelmann Spruce - Limber Pine Krummholz Shrubland Alliance
  • (A.168) Subalpine Fir - Engelmann Spruce Forest Alliance
  • (A.422) Subalpine Fir - Quaking Aspen Forest Alliance
  • (A.190) Subalpine Fir Seasonally Flooded Forest Alliance
  • (A.559) Subalpine Fir Woodland Alliance

Dynamic Processes

Major disturbances include occasional blowdown, insect outbreaks (30-50 years), mixed-severity fire, and stand-replacing fire (150-500 years). The more summer-dry climatic areas also have occasional high-severity fires. Insects and diseases can play a major role in the successional direction of these forests. Throughout Montana, subalpine fir and spruce are affected by spruce budworm attacks, and large stands of these subalpine forests can be killed following several years of drought or unusually mild winters.

Following fire, spruce is more successful at establishing on mineral soils. Subalpine fir, in contrast, is better at establishing in the shade and on organic substrates. In forests undisturbed by fire or subjected to spruce budworm attacks, subalpine fir assumes greater dominance. Over a period of 500 years, subalpine fir will largely replace spruce within most habitats of this system.


Management
In the absence of natural fire, periodic prescribed burns can be used to maintain this system.

Restoration Considerations

Post-fire restoration strategies will depend largely on the severity of the fire.Because lightly burned areas recover quite quickly from fire, reseeding is usually not necessary if an intact, native understory was present before the fire. Early successional stages may be dominated by fireweed, arnica, aster, pearlyeverylasting (Anaphalis margaritacea), mountain hollyhock (Iliamina rivularis) and other forbs, and small amounts of forest graminoids. Both dominant species 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 mostly colonizes sites with some organic matter.

Large, prescribed, stand-replacement fires are not recommended in areas where spruce is in severe decline. Small-scale prescribed burning during late fall after several hard frosts can facilitate regeneration. In some cases, nursery stock may be used to expedite regeneration on severely burned areas if seed rain from adjacent stands is not likely to occur.


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
R. Crawford and M.S. Reid, mod. C. Chappell and G. Kittel (NatureServe ed. date 25Jan2007)

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

Version Date
2/19/2010

References
  • Classification and Map Identifiers

    Cowardian 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 28663
    System Code CES306.828, Rocky Mountain Subalpine Dry-Mesic Spruce-Fir Forest and Woodland

    National Land Cover Dataset:
    42: Evergreen Forest

    ReGAP:
    4242: Rocky Mountain Subalpine Dry-Mesic Spruce-Fir Forest and Woodland


  • Additional ReferencesLegend:   View WorldCat Record   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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Citation for data on this website:
Rocky Mountain Subalpine Dry-Mesic Spruce-Fir Forest and Woodland.  Montana Field Guide.  Retrieved on December 19, 2014, from http://FieldGuide.mt.gov/displayES_Detail.aspx?ES=4242
 
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