Great Basin Naturalist


Ecological aspects of desert vegetation in relation to a moisture gradient along an ephemeral stream in central Arizona were investigated. The stream channel, flood plain, and north-, west-, south-, east-facing slopes represent a moisture gradient going from mesic to xeric conditions. Vegetation in some areas of the stream channel intergraded into flood plain vegetation, which in turn intergraded into slope vegetation types. In other areas there were sharp delineations between stream channel and flood plain and between flood plain and slope. Trees and legume species preferred midmoisture habitats, but forbs, shrubs, and succulents preferred dryer areas. Family groups like the Asteraceae and the Poaceae were found to be distributed ubiquitously. Niche widths were broadest for flood plain species. Diversity was highest on the slopes. Negative correlations existed between stand diversity and the Synthetic Stand Moisture Index (i.e., as moisture increased diversity increased). It is believed that disturbance as well as moisture influenced diversity.