| Description: | This widespread alliance is characterized by an open, xeromorphic shrub layer codominated by Larrea tridentata and Ambrosia dumosa. Cover of either species does not exceed the other by more than twice, and no other species greatly exceeds the cover of both combined. Stands occur in the Mojave, Sonoran and Colorado deserts on alluvial fans, bajadas, upland slopes and minor washes on well-drained, sandy soils derived from colluvium or alluvium. |