Montane Loamy Outwash Terrace Richardson’s needlegrass (Achnatherum richardsonii)

Description

Richardson’s needlegrass (Achnatherum richardsonii)-rough fescue (Festuca campestris)-Idaho fescue (Festuca idahoensis)/old man’s whiskers (Geum triflorum)-sticky purple geranium (Geranium viscosissimum)
The Montane Loamy Outwash Terrace ecological site is dominated by a mixture of native, perennial, cool-season tufted bunch grasses. These grasses include rough fescue (Festuca campestris), Idaho fescue (Festuca idahoensis), Richardson’s needlegrass (Achnatherum richardsonii), bluebunch wheatgrass (pseudoroegneria spicata), timber oatgrass (Danthonia intermedia), and prairie Junegrass (Koeleria macrantha). These grasses can occur in varying amounts of cover, but generally are dominated by rough fescue, Richardson’s needlegrass, and Idaho fescue. The grasslands in western Montana, in general, are considered unique in that they have similar species to both grasslands of eastern Washington and northern Idaho (Palouse Region grasslands) as well as northern grasslands in Canada (Alberta fescue grasslands). Associated montane forbs include yarrow (Achillea millefolium), sticky purple geranium (Geranium viscosissimum), old man’s whiskers (Geum triflorum), northern bedstraw (Galium boreale), and yellow penstemon (Penstemon confertus). Shrubs with very low cover occur, including kinnikinnick (Arctostaphylos uva-ursi), serviceberry (Amalanchier alnifolia), shrubby cinquefoil (Dasiphora fruticosa), sulphur-flower buckwheat (Eriogonum umbellatum), common juniper (Juniperus communis), creeping barberry (Mahonia repens), Woods’ rose (Rosa woodsii), snowberry (Symphoricarpos albus), mountain big sagebrush (Artemisia tridentata var. vaseyana) and western snowberry (Symphoricarpos occidentalis). Only kinnikinnick occurs in any abundance, forming low-growing clumps. Some tree species occur in very low cover (1 percent canopy cover at 18 percent of the 22 sites visited). Conifer encroachment by lodgepole pine (Pinus contorta) usually occurs along the edges of the prairie.

Big Prairie along the North Fork of the Flathead River in Glacier National Park is an excellent example of this site. This prairie has the highest number of microhabitat types for a grassland in this area, due to differential accumulation of glacio-alluvial material and the mix of subtle river swales and depressions on this former glacial outwash floodplain (Koterba and Habeck, 1971). Koterba and Habeck found in their ordination study of North Fork grasslands that species distribution was grouped by available soil moisture and soil attributes. Drier sites with available soil moisture of 17.7 percent and 60-70 percent sand and 5-10 percent clay had more bluebunch wheatgrass. Bluebunch wheatgrass usually is associated with drier areas and south facing aspects, but has very broad range of osmoregulation and can grow in a variety of sites. Areas with higher available soil moisture of 31.3 percent and less sandy soils (40-50 percent) had a higher proportion of rough fescue. Idaho fescue, timber oatgrass, and prairie Junegrass were found throughout. They surmised that the development and maintenance of the North Fork grasslands are attributed to the local climate (the “rain shadow effect” of the Whitefish Range), soil texture (coarse subsoil materials), and a long history of fire. The U.S. Forest Service (USFS) Fire Effects Information System (FEIS) evaluates the fire regime for northwestern montane and foothill grasslands with a fire interval of 9-66 years, with 43-100 percent of the fires occurring as replacement severity and 0-57 percent of fires as mixed severity, and 0-35 percent of the fires as low severity. The National Park Service (NPS) states that the historic mean fire return interval for the Big Prairie specifically is 9-26 years (Barrett, 1983). The policy of full fire suppression resulted in an absence of fire for 77 years, with a concomitant increase in the encroachment of lodgepole pine (Pinus contorta) upon the prairies during this period. The NPS fire management process is to actively try to return the area to close to the historic fire return interval through the prescribed fire program (NPS Fire Ecology Annual Report (2014) and Prescribed fire in the North fork Grasslands of Big Prairie poster (Fire Effects Program, Glacier NPS). In October of 1996, a prescribed fire was conducted. The NPS objectives are to maintain existing native species without introducing an inordinate number of non-native species, and to reduce overstory and pole sized trees by 30-70 percent within five years postburn. Post fire analysis showed there was minimal change in relative cover of native and nonnative species, the overstory and pole-sized density was reduced, but the seedling establishment was initially reduced and then increased and requires further prescribed burning. This increase in seedling establishment might be expected of a fire adapted species.

Submodel

Description

Current Potential State with weedy species present at a very low canopy cover value.
Richardson’s needlegrass (Achnatherum richardsonii)-rough fescue (Festuca campestris)-Idaho fescue (Festuca idahoensis)/old man’s whiskers (Geum triflorum)-sticky purple geranium (Geranium viscosissimum)

Submodel

Description

This state represents the community with significant increase in weedy species and concomitant decrease in native grass species.

Submodel