Rainfall variability and animal production in the semi-arid savanna of southern Africa.

Ecological systems in the semi-arid savanna of southern Africa are subject to an erratic moisture supply. This results in large and unpredictable fluctuations in plant production and changes in plant cover and botanical composition. Notably in the herbaceous layer. With rapidly increasing pressure on the land there is an urgent need to define land use procedures which will give maximum production over the years and which will minimise stress on livestock and the vegetation during droughts. Present knowledge is inadequate for this purpose, and there is a strong case for comprehensive study of the effects of rainfall fluctuations on plant and livestock production, botanical composition and soil cover. The feasibility of developing models to estimate plant production from simple meteorological, soil-water and plant growth parameters is indicated. It is shown how such models could be used in conjunction with empirical relations between stocking pressure and gain per animal, and stocking pressure and intake, to simulate fluctuations in animal and plant production over a long period of years. With such a model a variety of management options could be examined with particular emphasis on the critical seasons in which plant growth is at a minimum.Keywords: animal production; botanical composition; botany; drought; ecological systems; growth parameters; herbaceous layer; intake; land use; livestock; maximum production; model; models; plant cover; plant growth; production; rainfall; rainfall variability; semi-arid savanna; soil water; southern africa; stress; variability; vegetatio