Chihuahuan Semi-Desert Grassland [M087] is found at 870-2,200 m (2,850-7,220 ft) elevation throughout the Chihuahuan Desert ecoregion and extends into the Madrean Archipelago and limited areas of the Colorado Plateaus and High Plains and Tablelands ecoregions. This diverse habitat is characterized by an open to dense herbaceous layer dominated by perennial grasses, but shrubs and subshrubs are typical components. In lowland settings of broad alluvial plains and flats and swales, dominant species may include tobosagrass, alkali sacaton (Sporobolus airoides), giant sacaton (S. wrightii), or vine mesquite (Panicum obtusum). Grasslands of sandy sites are characterized by black grama and mesa dropseed (Sporobolus flexuosus), often with soaptree yucca (Yucca elata) and/or Torrey’s jointfir (Ephedra torreyana) shrubs. Black grama, blue grama, hairy grama (Bouteloua hirsuta), curly-mesquite (Hilaria belangeri), bush muhly (Muhlenbergia porteri), and curly leaf muhly (M. setifolia) are representatives of upland piedmonts and foothills along with shrubs such as lechuguilla (Agave lechuguilla), sotols (Dasylirion spp.), beargrasses (Nolina spp.), and Torrey’s yucca (Yucca torreyi). This habitat also includes Madrean lower montane grasslands dominated by bullgrass (Muhlenbergia emersleyi) and New Mexico muhly (M. pauciflora). Grasslands on gypsiferous soils include gypsum grama (Bouteloua breviseta) and gyp dropseed (Sporobolus nealleyi), along with herbaceous gypsophiles such as Hartweg’s sundrops (Calylophus hartwegii) and hairy crinklemat (Tiquilia hispidissima). Soils range from deep, fine-textured loams or clay loams (incipient mollisols) to sandy loams and also include rocky and shallow alluvial fans and hill slopes. Impermeable caliche and argillic horizons are common. Periodic fires are prevalent in some of these grasslands with 10 to 30 year, or longer, return intervals.