Environmental Description:  This shrubland association is found at mid to upper elevations in the Mojave Desert and extends north and east into the Colorado Plateau and southern Great Basin in Arizona, California, Nevada and southern Utah and often forms vast expanses across these environments. It can be seen on a variety of landforms. At lower elevations it occurs on ridgelines in transition areas with Larrea tridentata scrub and in gravelly and cobbly alluvial valleys, alluvial fans and hillslopes at mid to upper elevations, but includes eolian deposits/dunes, along drainage channels, basins, benches, mesas, terraces, plateaus, canyon slopes and rims, and ridges at 850 to 2133 m elevation (Peterson 1984a, Reid and Hall 2010, Evens et al. 2012, 2014). While predominantly found on flat or low-gradient settings (0-15°), this association occasionally occurs on moderate to steep slopes (to 40°) (Reid and Hall 2010, Evens et al. 2012, 2014). Soils are diverse, though primarily rapidly drained sand or loam, and less frequently finer-textured soils such as moderately well-drained to somewhat poorly drained silt loams, silty clay loams, clay loams, silts, or clays (Reid and Hall 2010, Evens et al. 2012, 2014). Sand or bare soil covers most of the unvegetated surface, with low to moderate cover by small rocks, large rocks, litter, and bedrock. Soils are derived from a variety of substrates such as alluvium, eolian deposits, dolostone (dolomite), granodiorite, quartz monzonite, limestone, rhyolite, sandstones of the Navajo, Kayenta, Entrada, or White Rim formations and shales of the Carmel, Halgaito, Moenkopi, Morrison, or Shinarump formations (Peterson 1984a, Reid and Hall 2010, Evens et al. 2012, 2014). Dark cyanobacteria and mosses, if present, have sparse to low cover.