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.
This system extends from South Dakota into the prairie provinces of southern Canada, and west into Montana’s glaciated and unglaciated plains, typically at elevations ranging from 1,220 to 1,524 meters (4,000-5,000 feet).
Approximately 1,728 square kilometers are classified as Great Plains Shrubland in the 2013 Montana Land Cover layers.
Grid on map is based on USGS 7.5 minute quadrangle map boundaries.
Big Horn, Blaine, Carbon, Carter, Cascade, Chouteau, Fergus, Garfield, Glacier, Golden Valley, Hill, Judith Basin, Lewis and Clark, Liberty, McCone, Meagher, Musselshell, Park, Petroleum, Phillips, Pondera, Powell, Rosebud, Stillwater, Sweet Grass, Teton, Toole, Valley, Wheatland, Yellowstone
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).
Fire and grazing constitute the primary dynamics affecting this system, although drought has also been an impact in the past decade. All shrub species regenerate well following low to moderate intensity fires by re-sprouting from the root systems. In areas where this system occurs in patches within a mixed grass prairie matrix, heavy grazing impacts can limit productivity of associated graminoids and forbs, leading to the increasing spread of introduced grasses and invasive forbs.
In the absence of natural fire, periodic prescribed burns can be used to maintain this system.
Restoration strategies will depend largely on the severity of impacts. Many shrub species occurring within this system resprout following disturbance, including fire. Because lightly to moderately burned or grazed areas recover quickly, reseeding and replanting is usually not necessary.
L.K. Vance, T. Luna
