ABSTRACT
Plant communities of semiarid lands and deserts have spatial and temporal patterns that are characteristic of these ecosystems. Climate and topography are the main driving forces that create these patterns, either directly by limiting plant productivity. density, and composition or indirectly by dictating patterns of soil formation and fertility (Fig. 1). The soil and vegetation resources of deserts are closely integrated; soils not only determine plant species, but plants affect nutrient cycling and the spatial characteristics of the soils (Crawford and Gosz. 1982). Because low precipitation typically results in low plant cover, the soils are subject to erosion on any slight slope or if they are coarse textured (Dorn, 1988). Rocky uplands and depositional lowlands create characteristic spatial patterns of plants across landscapes (Shmida et al.. 1986). The plants themselves tend to be widely spaced and therefore impose a smaller scale spatial organization nested within the elements of the landscape. Finally. deserts are subject to disturbance. and the consequent plant succession. or temporal changes, are often unique to deserts.
