WOODLAND DYNAMICS UNDER THE INFLUENCE OF ELEPHANTS AND FIRE IN NORTHERN BOTSWANA

Sustained elephant browsing and intense burning could result in the lo ss of woodlands under conditions where elephant densities are high, su ch as in northern Botswana. Three woodland types dominated by Acacia e rioloba, Baikiaea plurijuga and Colophospermum mopane were monitored i n plots and contemporary recruitment rates of woody plants were compar ed with the associated local elephant densities and fire occurrences. Woodland types differed with respect to structure, extent of elephant damage and the occurrence of fire. Canonical correlations indicated th at high extent of fire damage and high elephant densities did not cova ry within the woodland types investigated. Low tree densities in some woodland types were associated with high elephant densities and new el ephant damage to plants increased with high elephant densities during the dry season. Plots with an apparent high fire frequency had lower t ree densities and higher cover abundance of shrubs and seedlings. The annual rates of tree recruitment/loss in each woodland type were estim ated through a model based on observed seedling recruitment, mortality and reversal to lower height classes due to combinations of fire occu rrence and elephant browsing. The model suggested that elephants induc e tree loss in woodlands dominated by plant species which are principa l food sources. Fire however, seems to have a widespread effect across woodlands which could result in extensive tree loss.