干旱区生态环境知识资源中心

The spatial grazing pattern of goats around a water point on an arid and semi-arid rangeland system in the Karoo in South Africa was modeled. A dynamic automata model was developed by subdividing a spatial area into subunits called cells and where the dynamics of each cell depends on its present state, the state of its neighbors and external factors such as rainfall. By using a dynamic automata model, the long-term influences on the changes in vegetation composition of two species, namely woody perennials and galenia africana, are investigated.

The model relates a preference equation, which is a combination of two parameters, forage density and distance to a water point, to the total amount of time spent by each animal within a particular cell in a year. The model provides evidence that the total number of animals grazing an area, the number of water points in the system and the weighting factors associated with the preference equation, influence the extent of degradation of the area.