Review Structure and dynamics of grazed vegetation

Abstract- The relationship between vegetation and grazing herbivores is dynamic; the structure and quality of vegetation affect the diet of grazing herbivores and, in turn, the components of grazing (defo-liation, excretal return and treading) affect the structure and species composition of the vegetation. Both the vertical and horizontal distribution of vegetation are important in understanding plant-ani-mal interactions in grazed plant communities. Mechanisms which confer grazing resistance, through avoidance and tolerance strategies, are discussed. The difficulties in addressing scaling issues at the plant-animal interface are addressed; measurements or events at a small scale cannot be directly extrapolated to a larger scale. Moreover, integration of small-scale functions could result in counter intuitive results at the larger scale. The role of modelling in exploring spatio-temporal heterogeneity in plant-animal interactions is developed. Such models allow the exploration of a large number of hypotheses which cannot be tested under experimental conditions because of logistical, time and money constraints, and provide a framework in which to better understand grazing systems. As a man-agement tool, models have value in their predictive capacity and ability to simulate the complex sit-uations in grazed plant communities. @ Elsevier / Inra grazing resistance / heterogeneity / plant competition / plant-animal interactions / scalin