There is an urgent need to develop a mechanistic understanding of how site-specific can lead to irreversible vegetation changes. We show, by means of a analysis of two mathematica1 models, how site-specific properties determine resilience of vegetation changes in semi-arid grazing systems. The models that if available soil water limits plant growth, the vegetation supported by soils is generally resilient to herbivore impact and rainfall fluctuations, unlike vegetation on clayey soils. This depends on the capacity of vegetation communities improve the structural and water-holding capacities of the soil. In contrast, if growth is nutrient limited, vegetation on sandy soils is generally not resilient to impact and fluctuations in external nutrient input, unlike the vegetation by clayey soils. This is affected by the nutrient retention capacity of communities. We stress the applicability of the general theory provided by model to the Sahel environment. The model predictions are consistent with field documented in the literature.
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Rietkerk et al. (1997) studied this question.