Fire and Herbivory in a Great Salt Lake Marsh

The effects of fire and of herbivory by vertebrates on the standing crops and aboveground net primary production of Typha latifolia, Scirpus lacustris, S. maritimus, and Distichlis spicata were investigated in a freshwater marsh adjacent to the Great Salt Lake. Production of T. latifolia, S. lacustris, and S. maritimus vegetation responding after fire was not different from control areas, but flooding following fire eliminated D. spicata. Grazing by wetland vertebrates reduced net primary production of marsh macrophytes. Significant reductions occurred in previously burned areas of T. latifolia (48%), S. lacustris (25%), and S. maritimus (9%), illustrating the importance of the herbivory food chain for inland marshes. Evidence of increased protein in vegetation responding after fire and preferential grazing was consistent with the hypothesis that wetland vertebrates select vegetation of higher nutritive quality. However, alternative hypotheses such as increased foraging efficiency in burned areas could not be dismissed.