HETEROGENEITY IN SHORTGRASS PRAIRIE VEGETATION - THE ROLE OF PLAYA LAKES

We examined the role of playa lakes in promoting regional heterogeneit y on the southern High Plains. The goals of this paper were to: (1) de scribe vegetation types and zonation patterns within playas, (2) evalu ate patterns of species distribution and abundance within and among pl ayas, and (3) assess patterns of heterogeneity within and among playas on a portion of the southern High plains. Perennial grasses were the most abundant species in playa vegetation. Playa vegetation exhibited distinct and repeatable vegetation zones at the majority of sites, but the number of distinct zones varied from site to site. Agropyron smit hii, Buchloe dactyloides, and Panicum obtusum were the most important species of playa interior zones, and Bouteloua gracilis, Buchloe dacty loides, and Schedonnardus paniculatus were important upland species ou tside of playas. Species distribution and abundance were positively co rrelated at 38 of 40 sites. The distributions of species occurrences a mong sites were unimodal both locally and regionally. The degree of he terogeneity varied from playa to playa. Local heterogeneity within pla yas was found to increase regional heterogeneity; therefore, playas in crease both local and regional heterogeneity of vegetation. Longterm m onitoring will be necessary to understand the spatial and temporal res ponse of vegetation within and among playas to stochastic climatic fac tors on the southern High Plains of North America.