Physiognomy and Structure: Stands are dominated by graminoids, the tallest of which rarely reach 1 m. Most of the vegetation is 0.6 m tall or shorter. Vegetation cover is moderate to dense. The depth to the clay layer affects the height and amount of vegetation, i.e., the deeper the clay layer, the denser the vegetation (Hirsch 1985).

Floristics: The herbaceous layer is dominated or codominated by Pascopyrum smithii with Distichlis spicata, Eleocharis acicularis, Eleocharis palustris, or Hordeum jubatum often codominating. Other common graminoids include Bouteloua gracilis, Carex duriuscula (= Carex eleocharis), Hesperostipa comata (= Stipa comata), Juncus arcticus ssp. littoralis (= Juncus balticus), and Koeleria macrantha. Forbs that may be present include Asteraceae spp., Gutierrezia sarothrae, Helianthus petiolaris, Iva annua, Plantago patagonica. Woody plants are rare. Some stands may have scattered woody species such as the dwarf-shrubs Gutierrezia sarothrae or Artemisia frigida, or the shrubs Artemisia cana or Symphoricarpos occidentalis. The temporary flooding regime combined with high evaporation rates in these dry climates causes accumulations of soluble salts in the soil. Total vegetation cover (density and height), species composition, and soil salinity depend on the amount and timing of precipitation and flooding. In playas, growth-inhibiting salt concentrations are diluted when the soil is saturated allowing the growth of less salt-tolerant species such as Pascopyrum smithii. As the saturated soils dry, the salt concentrates until it precipitates on the soil surface (Dodd and Coupland 1966). Vegetation forms zones at some saline sites, where species abundances are stratified by salt tolerance. In playas, the soil salinity at field capacity generally increases from the edge to the center allowing for several different vegetation stands to co-occur (Ungar 1967, 1970). Also within a vegetation type, more mesic or salt-tolerant species such as Eleocharis acicularis, Eleocharis palustris, Juncus arcticus ssp. littoralis, and Alopecurus spp. will be more common at lower topographic levels where flooding is more frequent, than the dry-mesic species such as Pascopyrum smithii. Pascopyrum smithii is rhizomatous and is tolerant of moderate grazing. If severely overgrazed, Pascopyrum smithii will decline and may be replaced by less desirable warm-season grasses and exotic species such as Poa pratensis. Adjacent vegetation is upland mid- or shortgrass prairie often dominated by Bouteloua gracilis, Hesperostipa comata, Pascopyrum smithii, or Schizachyrium scoparium.

Dynamics:  The temporary flooding regime combined with high evaporation rates in these dry climates causes accumulations of soluble salts in the soil. Total vegetation cover (density and height), species composition, and soil salinity depend on the amount and timing of precipitation and flooding. In playas, growth-inhibiting salt concentrations are diluted when the soil is saturated allowing the growth of less salt-tolerant species such as Pascopyrum smithii. As the saturated soils dry, the salt concentrates until it precipitates on the soil surface (Dodd and Coupland 1966). Vegetation forms zones at some saline sites, where species abundance is stratified by salt tolerance. In playas, the soil salinity at field capacity generally increases from the edge to the center allowing for several different vegetation stands to co-occur (Ungar 1967, 1969, 1970). Also within a vegetation type, more mesic or salt-tolerant species such as Eleocharis acicularis, Eleocharis palustris, Juncus arcticus ssp. littoralis, and Alopecurus spp. will be more common at lower topographic levels where flooding is more frequent, than the dry-mesic species such as Pascopyrum smithii. Pascopyrum smithii is rhizomatous and is tolerant of moderate grazing. If severely overgrazed, Pascopyrum smithii will decline and may be replaced by less desirable warm-season grasses and exotic species such as Poa pratensis.