This ecological system is found from southern Alberta through northern Montana’s glaciated and unglaciated plains, typically at elevations ranging from 1,220 to 1,524 meters (4,000-5,000 feet). It can occur on all aspects but is more common on mesic sites with moderately shallow or deep, fine to sandy loam soils. Often it is located on slopes near breaklands and on the edge of coulees, or on upper terraces of rivers and streams. It differs from the Northwestern Great Plains Mixedgrass Prairie in that shrub cover is more than 10%, although the grass component is similar, and may occur where fire suppression in grasslands has allowed shrubs to establish. Dominant shrubs include serviceberry (Amelanchier alnifolia), skunkbush sumac (Rhus trilobata), snowberry (Symphoricarpos species), silver buffaloberry (Sheperdia argentea ), shrubby cinquefoil (Dasiphora fruticosa ssp. floribunda), silverberry (Elaeagnus commutata) and horizontal rug juniper (Juniperus horizontalis). Silver sage (Artemisia cana ssp. cana) shrublands may occur on flat alluvial deposits on floodplains, terraces or benches, and alluvial fans.
In Montana, this ecosystem forms within the northwestern Great Plains fescue (Festuca spp.) dominated prairie east of the Continental Divide into the western wheatgrass (Pascopyrum smithii) mixed grass prairie in the north-central Great Plains. Climate is semi-arid, and the growing season is short. It can occur on all aspects but is more common on mesic sites with moderately shallow or deep, fine to sandy loam soils. Often it is located on slopes near breaklands and on the edge of coulees, or on upper terraces of rivers and streams. Soils can be moderately shallow to deep, fine to sandy loam soils.
This system differs from Great Plains Mixed Grass Prairie in that natural shrub cover is greater than 10%, and in some cases may be greater than 50%. It is typically dominated by shrub and dwarf-shrub species such as serviceberry, skunkbush sumac, snowberry, shrubby cinquefoil, silverberry, and horizontal juniper. Silver sage shrublands may occur on flat alluvial deposits on floodplains, terraces or benches, and alluvial fans. Silver buffaloberry or western snowberry shrublands can also be found along stream terraces, rolling uplands, and badlands, or where moisture is more plentiful than on the surrounding landscape, such as in swales, ravines, near streams, and on northwest- to east-facing slopes. Common graminoids include threadleaf sedge (Carex filifolia), Idaho fescue (Festuca idahoensis), rough fescue (Festuca campestris), western wheatgrass, Kentucky bluegrass (Poa pratensis), prairie junegrass (Koeleria macrantha), blue grama (Bouteloua gracilis) and bluebunch wheatgrass (Pseudoroegneria spicata). Kentucky bluegrass (Poa pratensis) and common timothy (Phleum pratense) are common introduced grasses in the northwestern part of the system’s range. Common forbs include yarrow (Achillea millefolium), Indian blanket flower (Gaillarida aristata), prairiesmoke (Geum triflorum), sweetvetch (Hedysarum species), Pennsylvania pellitory (Parietaria pensylvanica), lupine (Lupinus species), scarlet guara (Gaura coccinea), red globe-mallow (Sphaeralcea coccinea), cinquefoil (Potentilla species),and goldenrod (Solidago species).
Erickson, Albert W., and D. B. Siniff. 1963. A statistical evaluation of factors influencing aerial survey results on brown bears. Anchorage, Alaska: Alaska Department of Fish and Game.
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