Physiognomy and Structure: This alliance is dominated by mid- and shortgrass species; woody species do not regularly achieve prominence. Total vegetation cover is typically moderate and leaf litter is present but not thick. Few of the species exceed 1 m, while many do not exceed 50 cm in height. Perennial and annual forbs are common but are not abundant in most stands.

Floristics: The most abundant species are Hesperostipa comata (= Stipa comata) and Bouteloua gracilis. On more mesic sites Hesperostipa comata is predominant, while on areas that are drier or subject to light grazing Bouteloua gracilis takes precedence. Other graminoid species that are commonly found in communities of this alliance are Aristida purpurea var. longiseta (= Aristida longiseta), Carex duriuscula (= Carex eleocharis), Carex filifolia, Carex inops ssp. heliophila, Koeleria macrantha, Pascopyrum smithii, and Poa secunda. Festuca idahoensis is generally absent, but may be locally dominant in small parts of the range. Sites in the southern half of the range of this alliance may have significant amounts of Bouteloua curtipendula. Forbs are common but not usually abundant (<10% cover). Forb species that are regularly found are Antennaria parvifolia, Artemisia frigida, Allium textile, Eriogonum umbellatum, Gaura coccinea, Heterotheca villosa, Liatris punctata, Sphaeralcea coccinea (= Malvastrum coccineum), Phlox hoodii, Packera fendleri (= Senecio fendleri), and Sphaeralcea coccinea. The clubmoss Selaginella densa is present in many stands in this alliance (Coupland 1950, Hansen et al. 1984, DeVelice et al. 1995). Scattered shrubs and dwarf-shrubs are sometimes present. These may include Artemisia frigida, Gutierrezia spp., Krascheninnikovia lanata, Prunus virginiana, Rhus trilobata, Rosa spp., and Symphoricarpos occidentalis. In the western and southwestern portions of its range, Cercocarpus montanus may be found where this alliance occurs on slopes (Hanson 1955).

Dynamics:  These mixed grasslands occur in the subhumid/semi-arid steppes in the western Great Plains where high variability of precipitation, both seasonally and yearly allows both short and mid grasses to co-exist (Coupland 1992a). Hesperostipa comata will decline with overgrazing, leaving the more grazing-tolerant Bouteloua gracilis to dominate (Smoliak 1965, Smoliak et al. 1972, Laurenroth et al. 1994a). Fire also can change the species composition of these grasslands. Burning generally kills or severely damages Hesperostipa comata plants. After fire, regeneration of this non-rhizomatous bunchgrass is through seed and may take many years to reach prefire densities (FEIS 1998). Burning Bouteloua gracilis during the growing season will top-kill the plant, but the rhizomes are usually unharmed and quickly regrow (FEIS 1998). Bouteloua gracilis is usually unharmed by fires in years with above normal winter and spring precipitation (soil moisture prevents lethal soil temperatures), but it can be severely damaged by fires that occur during drought years (FEIS 1998). Exotic species such as Taraxacum officinale, Medicago sativa, Melilotus officinalis, or Salsola kali are present in some stands