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Rocky Mountain Subalpine Deciduous Shrubland

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Provisional State Rank: S5
* (see reason below)

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State Rank Reason
This system is protected through most of its range. Climate effects are uncertain over the long term, but transitions from grassland to shrubland are possible, and this system should rmeina stable in size.
 

General Description

This shrubland ecological system is found within the zone of continuous forest in the upper montane and lower subalpine zones along both sides of the Continental Divide from southwestern to northwestern Montana, and in the island mountain ranges. Soils tend to be moist to wet. It is found on steep mountain slopes, usually on north and east facing aspects. In northwestern and west-central Montana, it forms within upper montane Douglas-fir (Pseudotsuga menziesii) and Engelmann spruce-subalpine fir (Picea engelmanii/ Abies lasiocarpa) forests on steep slopes and ravines. Soils are usually shallow, rocky or gravelly with good aeration and drainage. 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 to the montane zone in places where cold-air ponding occurs, especially on north and east aspects. In northwestern Montana, elevation ranges from 1,525 to 1,950 meters (5,000 to 6,400 feet) west and immediately east of the Continental Divide and up to 2,682 meters (8,800 feet) in southwestern Montana. Common shrub species include rusty leaf menziesia (Menziesia ferruginea), black twinberry (Lonicera involucrata), alder buckthorn (Rhamnus alnifolia), prickly currant (Ribes lacustre), thimbleberry (Rubus parviflorus), sitka alder (Alnus viridis), cascade mountain ash (Sorbus scopulina), Sitka mountain ash (Sorbus sitchensis), and thinleaf huckleberry (Vaccinium membranaceum).


Diagnostic Characteristics
montane, shrubland, broad leaf deciduous shrub, very shallow soils, moderate persistence

Similar Systems

Range
This system is found in the subalpine and upper montane zones along both sides of the Continental Divide from southwestern to northwestern Montana, and in the island mountain ranges.

Ecological System Distribution
Approximately 1,574 square kilometers are classified as Rocky Mountain Subalpine Deciduous Shrubland 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, 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
Large and Small Patch

Environment
In northwestern and west-central Montana, this ecosystem forms within upper montane Douglas-fir and Engelmann spruce-subalpine fir forests on steep slopes and ravines. Soils are derived from a variety of parent materials, but are usually acidic. Soils are usually shallow, rocky or gravelly with good aeration and drainage. 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 to the montane zone in places where cold-air ponding occurs, especially on north and east aspects. In northwestern Montana, these systems are found at elevation from 1,524-1,950 meters (5,000 -6,400 feet) west and immediately east of the Continental Divide and up to 2,682 meters (8,800 feet) in southwestern Montana

Vegetation

These shrubland communities develop on steep mountain slopes, at the heads of cirque basin drainages, and on upper elevation toeslopes within the mesic montane and subalpine forest zones. Common shrub species include rusty-leaf menziesia, black twinberry, alder buckthorn, prickly currant, thimbleberry, Sitka alder, cascade mountain ash, sitka mountain ash, and thinleaf huckleberry. Extensive stands of mountain huckleberry are important summer and fall foraging areas for grizzly and black bears.

On some sites in northwestern Montana, rusty leaf menziesiaand Sitka alder can form nearly impenetrable stands. Drier aspects of this community can also support stands of thimbleberry, Canadian buffaloberrry (Shepherdia canadensis), birchleaf spiraea (Spiraea betulifolia), and deerbrush ceanothus (Ceanothus velutinus).

The herbaceous understory can be sparse on sites with dense shrub cover. Common graminoids include bluejoint reedgrass (Calamagrostis canadensis), pinegrass (Calamagrostis rubescens), sedges (Carex species), and blue wildrye (Elymus glaucus). Common forbs and ferns include beargrass (Xerophyllum tenax), fireweed (Chamerion angustifolium), and bracken fern (Pteridium aquilinum), reflecting the mesic nature of many of these shrublands. Other forb species include baneberry (Actaea rubra), arnica (Arnica species), queen’s cup beadlily (Clintonia uniflora), boreal bedstraw (Galium triflorum), twinflower (Linnaea borealis), clasp-leaf twisted stalk(Streptopus amplexifolius), and western meadow rue (Thalictrum occidentale). Post-fire communities are often dominated by fireweed, yarrow (Achillea millefolium), nettle-leaf giant hyssop (Agastache urticifolia), aster (Symphyotrichum spp.), goldenrod (Solidago spp.), and pearly everlasting (Anaphalis margaritacea).


Alliances and Associations
Alliances
  • (A.962) Alderleaf Buckthorn Temporarily Flooded Shrubland Alliance
  • (A.970) Bristly Black Currant Temporarily Flooded Shrubland Alliance
  • (A.2633) Fool's-huckleberry Shrubland Alliance
  • (A.2632) Square-twig Blueberry Shrubland Alliance

Dynamic Processes
Fire impacts these shrublands, but they typically persist on sites for long periods (up to 500 years). All shrub species regenerate well following low to moderate intensity fires by re-sprouting from the root systems. Under present conditions, the fire regime is of mixed severity and more variable than in the past, with stand-replacing fires being more common in associated forested habitats. Areas that are dry in summer also have occasional high-severity fires. Insects and diseases can play an indirect but major role in the successional direction of these shrublands by killing adjacent associated forests. Throughout Montana, subalpine fir and spruce are affected by spruce bud worm attacks and large stands of these subalpine forests can be killed following several years of drought or unusually mild winters.

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

Restoration Considerations
Restoration in these systems is generally restricted to post-fire efforts, and strategies will depend largely on fire severity. Light to moderately burned areas usually recover quickly from fire; most dominant shrubs resprout from rhizomatous root systems and root crowns. In some cases, severely burned sites on very steep terrain may need to be reseeded to prevent soil erosion. Intense fires occurring during summer months cause considerable damage to these shrublands and seed banks.

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
Natureserve Western Ecology Group

Montana Version Authors
T. Luna and L.K. Vance

Version Date
2/14/2010

References
  • Classification and Map Identifiers

    Cowardian Wetland Classification: Not applicable

    National Vegetation Classification Standard:
    Class Shrubland and Grassland
    Subclass Temperate and Boreal Shrubland and Grassland
    Formation Temperate Grassland, Meadow and Shrubland
    Division Vancouverian and Rocky Mountain Grassland and Shrubland
    Macrogroup Northern Rocky Mountain-Vancouverian Montane Shrubland and Grassland

    NatureServe Identifiers:
    Element Global ID
    System Code CES306.961, Northern Rocky Mountain Subalpine Deciduous Shrubland

    ReGAP:
    5326: Northern Rocky Mountain Subalpine Deciduous Shrubland



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Citation for data on this website:
Rocky Mountain Subalpine Deciduous Shrubland — Northern Rocky Mountain Subalpine Deciduous Shrubland.  Montana Field Guide.  Retrieved on October 24, 2014, from http://FieldGuide.mt.gov/displayES_Detail.aspx?ES=5326
 
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