This ecological system is found in the Columbia Plateau region and forms extensive low shrublands. These xeric shrublands occur under relatively extreme soil-moisture conditions. Substrates are typically shallow lithic soils with limited water-holding capacity over fractured basalt. Because of poor drainage through basalt, these soils are often saturated from fall to spring by winter precipitation but typically dry out completely to bedrock by midsummer. Total vegetation cover is typically low, generally less than 50% and often much less than that. Vegetation is characterized by an open dwarf-shrub canopy dominated by Artemisia rigida along with other shrub and dwarf-shrub species, particularly Eriogonum spp. Other shrubs are uncommon in this system; mixes of Artemisia rigida and other Artemisia species typically belong to different ecological systems than this. Low cover of perennial bunch grasses, such as Danthonia unispicata, Elymus elymoides, Festuca idahoensis, or primarily Poa secunda, as well as scattered forbs, including species of Allium, Antennaria, Balsamorhiza, Lomatium, Phlox, and Sedum, characterize these sites. Individual sites can be dominated by grasses and semi-woody forbs, such as Stenotus stenophyllus. Annuals may be seasonally abundant, and cover of moss and lichen is often high in undisturbed areas (1-60% cover).
Information Source: http://www.natureserve.org/explorer/