Based on resource availability models of plant defense investment, several authors have predicted and documented that herbivores tend to accelerate the pace of plant community succession. Davidson did a literature survey of experimental and observational tests of the effects of above-ground, native herbivores on terrestrial plant succession and it revealed a more complex pattern than anticipated from earlier reviews on this subject. Although herbivory tends to hasten succession from grasses, shrubs, and pioneer trees to persistent trees, it typically retards succession from earlier stages, if such seres are present. The dichotomy in herbivore effects early and late in old field succession reflects differentially high herbivory on intermediate seral species, whose principal defense against herbivores is rapid, compensatory growth in comparatively favorable resource environments. Documented patterns in the effects of herbivores and, to a lesser extent, granivores on the course of succession should be useful to management of natural ecosystems and the restoration of disturbed environments. Humans have modified natural ecosystems both through the activities of symbiotic grazers (domestic livestock), and by hunting out granivores or the predators of these granivores. By constructing general models to predict the likely consequences of such intervention in natural communities, Davidson feels it may strengthen arguments for curtailing destructive practices and avoid some of the inherent pitfalls.
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.