A SALINITY gradient extends from the highly saline beaches of the Great Salt Lake of Utah to the surrounding non-halomorphic soils, with a correlated vegetation gradient in which a succession of plant communities grows in concentric zones. The chief communities, in decreasing order of soil salinity, are dominated by (1) Salicornia–Allenrolfea; (2) Sarcobatus vermiculatus; (3) Atriplex–Eurotia; and (4) Artemisia tridentata1. Within these communities are perplexing local distributions of co-dominant species. Typical communities within the Atriplex–Eurotia zone include pure Atriplex confertifolia, Atriplex–Eurotia, pure Eurotia lanata, A. confertifolia Artemisia spinescens–Eurotia grass, and pure Atriplex nuttallii. Although these communities are separated by sharp ecotones, local soil variations are insufficient to explain the distribution of the different plant communities2.