Plants of Casa Grande Ruins National Monument - NPS Inventory ...

Vegetation Mapping
20
Prosopis velutina / Larrea tridentata
woodland
This alliance exists along two agricultural fencelines to the south and east of
the large mound and ball court at the Adamsville site. These fencelines contain
earthen berms formed by road building and maintenance to support adjacent
agricultural operations. These berms capture and concentrate runoff, allowing
it to saturate the soil. The moist conditions, perhaps augmented by infiltration
of irrigation water from south and east of the fence, results in growth of
velvet mesquite up to 7 m tall and creosote up to 3.5 m. Herbaceous annuals
representative of the adjacent uplands thrive here, contributing more litter
than is typical in adjacent uplands. This alliance resembles a portion of the
creosote shrubland along the boundary of the main unit where runoff from
adjacent roads permits similar concentrations of larger velvet mesquite.