Drewa and Havstad examined the responses of herbaceous and suffrutescent species to fire, grazing, and presence of Prosopis glandulosa, in a Chihuahuan desert grassland in southcentral New Mexico. Following fires in June 1995, unfenced plots were exposed to livestock grazing over 4 years. Plots were established that either included or excluded P. glandulosa. Grazing did not increase species diversity, richness, or induce changes in evenness, neither did it interact with fire to effect these variables. Grazing generally decreased cover and frequency of perennial grasses, but increased frequency of perennial forbs (although not cover). Only frequency and not cover of perennial forbs and annual grasses increased more following grazing. Presence of P. glandulosa had no differential effect on responses of non-shrub species. Grazing affected individual species differently; Bouteloua eriopoda (black grama, the most important perennial forage) cover and frequency decreased, D. wislizenii increased, while S. flexuosus, G. sarothrae, and A. ramosissimus were unaffected. Precipitation immediately following fire may be critical for recovery of B. eriopoda-dominated desert grasslands; relationships between fire and post-fire precipitation patterns require future investigation.
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