干旱区生态环境知识资源中心

A model describing two competing species of grass and woody vegetation in a semi-arid savanna grazing system is generalized to include a bounded stochastic variation in the cattle-stocking, rate, and the system behaviour is investigated using, a Monte Carlo-type simulation technique. Some key characteristics of the stochastic system are found to be different from the corresponding deterministic system without the stochastic variation. A single stable state in the deterministic system is diffused into a region of stable states, and a separatrix dividing the two attraction zones no longer exists. Effects of the intensity and the mean frequency of the stochastic variation of the cattle-stocking rate on, the system behaviour are investigated.