CATASTROPHIC VEGETATION SHIFTS AND SOIL DEGRADATION IN TERRESTRIAL GRAZING SYSTEMS

It has long been recognized that alternative vegetation states may occ ur in terrestrial grazing systems. This phenomenon may be of great imp ortance as small environmental fluctuations may lead to relatively sud den and irreversible jumps between vegetation states. Early theoretica l studies emphasized saturation of herbivore feeding to explain multip le stable states and catastrophic behaviour. Recent studies on semi-ar id grasslands and arctic salt marshes, however, relate catastrophic ev ents In these systems to plant-soil interactions.