The role of competition in the spacing of savanna trees

Abstract

Past and present research on savanna rangeland has emphasized the role of tree - grass interactions as the limiting factor in the woody - grass balance. The present study examines tree - tree interactions in savannas through the use of nearest neighbour analysis. Results of the study show both a regular dispersion pattern and a positive correlation between the size of trees and the distance to nearest neighbour (tree) for acacia communities, suggesting competition among trees as a mechanism controlling their size and density. In the analysis of data from a mixed acacia broadleaf-evergreen thicket, the dispersion of acacia species was found to be regular even though acacia species accounted for only 36 per cent of the individuals present. However, results of the spatial analysis of all individuals regardless of species show a random dispersion of trees in the thicket community. Results from the analysis of seedling establishment relative to canopy cover suggest possible mechanisms for these findings. Show more