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Rocky Mountain Foothill Woodland-Steppe Transition

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Provisional State Rank: S4
* (see reason below)

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State Rank Reason
Fire is the greatest threat, but given the proximity of this system to residential areas, fires are likely to be controlled.
 

General Description

This inland Pacific Northwest ecological system occurs in the foothills of the Montana Rocky Mountains, where it forms a broad ecotone between true forests ad true steppe, shrublands, or grasslands, typically on warm, dry, exposed sites too droughty to support a closed tree canopy. This is not a fire-maintained system. The "steppe" character results from a climate-edaphic interaction that results in a graminiod-dominated landscape with widely scattered trees; even in the absence of fire, a "woodland" or "forest" structure will not be obtained. Occurrences are found on all slopes and aspects; however, moderately steep to very steep slopes or ridgetops on southerly or western aspects are most common. They can be found on glacial till, glacio-fluvial sand and gravel, dune, basaltic rubble, colluvium, deep loess or volcanic ash-derived soils, with characteristic features of good aeration and drainage, coarse texture, and an abundance of mineral material. Ponderosa pine (Pinus ponderosa) or Douglas-fir (Pseudotsuga menziesii)are the predominant conifers. Limber pine (Pinus flexilis)may be present in some occurrences. In fire-protected transition areas with big sagebrush steppe systems, antelope bitterbrush (Purshia tridentata), Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis), big sagebrush (Artemisia tridentata ssp. tridentata), and three-tip sagebrush (Artemisia tripartita) may be common. Deciduous shrubs such as common ninebark (Physocarpus malvaceus), commonsnowberry (Symphoricarpos albus), or birch leaf spiraea (Spiraea betulifolia)may be abundant in occurrences west of the Continental Divide. Important grass species include bluebunch wheatgrass (Pseudoroegneria spicata), Sandberg’s bluegrass (Poa secunda), needle and thread (Hesperostipa comata), needlegrass (Achnatherumspecies), and bottlebrush squirreltail (Elymus elymoides). This system is very similar to Northern Rocky Mountain Ponderosa Pine Woodland and Savanna, but with more widely scattered trees.


Diagnostic Characteristics

woody and herbaceous, aridic and shallow soils, short disturbance interval, Pinus ponderosa, Pseudotsuga menziesii


Similar Systems

Range
This system is found in the foothill to montane elevations east of the Continental Divide in northwestern Montana, in the Missouri river breaks and in central Montana on soils derived from shales. Elsewhere it is found from Idaho to the Columbia Plateau region of Oregon and Washington and west along the foothills of the Modoc Plateau and eastern Cascades into southern interior British Columbia.

Ecological System Distribution
Approximately 2,457 square kilometers are classified as Rocky Mountain Foothill Woodland-Steppe Transition in the 2013 Montana Land Cover layers.  Grid on map is based on USGS 7.5 minute quadrangle map boundaries.



Montana Counties of Occurrence
Blaine, Carbon, Carter, Cascade, Chouteau, Dawson, Fallon, Fergus, Garfield, Golden Valley, Hill, Judith Basin, Lewis and Clark, Liberty, McCone, Meagher, Musselshell, Park, Petroleum, Phillips, Pondera, Prairie, Rosebud, Stillwater, Sweet Grass, Teton, Toole, Treasure, Valley, Wheatland, Wibaux, Yellowstone

Spatial Pattern
Large patch

Environment
In Montana, this system is found at scattered locations throughout northwestern and west central Montana, at elevations of 914-1,829 meters (3,000-6,000 feet) (Pfister et al, 1977; Mueggler and Stewart, 1980). Occurrences are found on all slopes and aspects; however, moderately steep to very steep slopes or ridgetops on southerly or western aspects are most common. This system can occur in association with cliff and canyon systems. It generally occurs on glacial till, glacio-fluvial sand and gravel, and loamy soils derived from a variety of parent materials. Soils are coarse with good aeration, often thin, and with slightly acidic to slightly basic pH. There is usually an abundance of mineral material consisting of fine and coarse rocks. Consequently, this system is subjected to droughty soil conditions during the growing season. Annual precipitation ranges from 36 to 56 centimeters (14 to 20 inches).

Vegetation

Ponderosa pine (Pinus ponderosa) or Douglas-fir (Pseudotsuga menziesii) are the most common conifers. Limber pine (Pinus flexilis) may be present in some occurrences. In transition areas with sagebrush steppe systems, antelope bitterbrush (Purshia tridentata), Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis), big sagebrush (Artemisia tridentata ssp. tridentata), and three-tip sagebrush (Artemisia tripartita) may be common in fire-protected sites such as rocky areas. Common ninebark (Physocarpus malvaceus), common snowberry (Symphoricarpos albus), or birch leaf spiraea (Spiraea betulifolia) can be abundant in occurrences on northern or eastern aspects, or sites west of the Continental Divide in northwestern Montana. Important grass species include bluebunch wheatgrass (Pseudoroegneria spicata), Sandberg’s bluegrass (Poa secunda), needle and thread (Hesperostipa comata), needlegrass (Achnatherum species), prairie junegrass (Koeleria macrantha) and bottlebrush squirreltail (Elymus elymoides).

Common forbs include yarrow (Achillea millefolium), nodding onion (Allium cernuum), rosy pussytoes (Antennaria rosea), hairy golden aster (Heterotheca villosa), elk thistle (Cirsium undulatum), fleabane (Erigeron species), buckwheat (Eriogonum species), Indian blanket flower (Gaillardia aristata), stoneseed (Lithospermum ruderale), silky lupine (Lupinus sericeus), silky crazyweed (Oxtropis sericea), and Hood’s phlox (Phlox hoodii). Arrowleaf balsamroot (Balsamorhiza sagittata) can be abundant in some occurrences.


Alliances and Associations
Alliances
  • (A.552) Douglas-fir Woodland Alliance
  • (A.533) Ponderosa Pine - Douglas-fir Woodland Alliance
  • (A.530) Ponderosa Pine Woodland Alliance

Dynamic Processes

Dry conditions and droughty soils that limit tree establishment are the driving factors in this system. Tree growth is likely episodic, with regeneration episodes in years with available moisture. Tree density is limited in some areas by available growing space due to the rocky conditions of the site. Tree canopy will never reach woodland density due to the interaction of climate and edaphic factors, even in the absence of fire. This system burns occasionally, but the vegetation is sparse enough that fires are typically not carried through the stand. Fire frequency is estimated to be 30 to 50 years. However, the invasion of cheatgrass (Bromus tectorum) is changing fire frequency, spread, and severity. Trees that occupy this edge environment and exhibit resistance to abiotic and biotic stressors are important genetic resources to maximize adaptive potential to current and continued environmental change.


Management

In the absence of natural fire, periodic prescribed burns can be used to maintain and restore this system to similar pre-settlement conditions. Periodic burning is used to expose mineral soils, provide nutrient availability, reduce competition, and stimulate native grass and forb production.

Excessive grazing can result in the depletion of the most common perennial grasses and lead to an abundance of exotic grasses in this system.


Restoration Considerations

Successful restoration of native grasses within this system may be limited to sites where pre-fire cheatgrass (Bromus tectorum) cover was low. Cheatgrass establishment in low-elevation ponderosa pine and Douglas-fir forests can be enhanced by disturbance that opens the understory, removes litter, or both. (Mack and Pyke1983). Fall germination and rapid elongation of roots provide cheatgrass with a competitive advantage over native perennial species (Harris, 1967). Prolific seed production also contributes to the competitive advantage of this grass over native grasses and associated perennial forbs.


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
L.K. Vance, T. Luna

Version Date
1/21/2010

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
    System Code CES306.958, Northern Rocky Mountain Foothill Conifer Wooded Steppe

    National Land Cover Dataset:
    42: Evergreen Forest

    ReGAP:
    5426: Northern Rocky Mountain Foothill Conifer Wooded Steppe


  • Additional ReferencesLegend:   View WorldCat Record   View Online Publication
    Do you know of a citation we're missing?
    • Aguirre, Lucrecia, and Douglas A. Johnson. 1991. "Influence of Temperature and Cheatgrass Competition on Seedling Development of Two Bunchgrasses". Journal of Range Management. 44 (4): 347-354.
    • Harris, G. A. 1967. Some competitive relationships between AGROPYRON SPICATUM and BROMUS TECTORUM. Ecological Monographs 37:89-111.
    • Mack, Richard N., and David A. Pyke. 1983. "The Demography of Bromus Tectorum: Variation in Time and Space". The Journal of Ecology. 71 (1): 69-93.
    • Mueggler, W. F. and W. L. Stewart. 1980. Grassland and shrubland habitat types of western Montana. USDA Forest Service Gen. Tech. Rep. INT-66, Intermountain Forest and Range Exp. Sta., Ogden, Utah. 154 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.

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Citation for data on this website:
Rocky Mountain Foothill Woodland-Steppe Transition — Northern Rocky Mountain Foothill Conifer Wooded Steppe.  Montana Field Guide.  Retrieved on April 16, 2014, from http://FieldGuide.mt.gov/displayES_Detail.aspx?ES=5426
 
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