Current disturbance models (predation hypothesis, intermediate-disturbance hypothesis, and the Huston hypothesis) do not adequately account for the wide range of responses by grassland plants communities to grazing by large herbivores. This model looked at data from areas representing the four boundary cases of the moisture gradient and the evolutionary-history-of-grazing gradient. Feedback mechanisms are manifest in the rapid switching capabilities of subhumid grasslands with long evolutionary histories of grazing and divergent selection pressures. Switching capabilities do not exist in semiarid grasslands with long evolutionary histories of grazing and convergent selection pressures. Feedback mechanisms are not well developed in systems with short evolutionary histories of grazing. In these cases, the differences in response to grazing by semiarid and subhumid situations arise mainly from differences in the grazing tolerance of plants adapted to semiaridity or of plants adapted to competition for light and from the different effects of grazing on canopy structure.
Citations and enhanced abstracts for journals articles and documents focused on rangeland ecology and management. RSIS is a collaboration between Montana State University, University of Idaho, and University of Wyoming.