The subcanopy flora in the dynamics of the Kalahari Thornveld

Abstract

Kalahari Thornveld occupies an area of some 390,000 km(2) in Namibia, Botswana and South Africa. It constitutes the southern portion of the arid or fine-leaved savanna on Kalahari sand co-dominated by grasses such as species of Eragrostis and Stipagrostis, and trees and shrubs, especially of the genus Acacia. Microclimatic and edaphic conditions in the subcanopy habitat under trees and shrubs often differ widely from those in the grassland. The subcanopy is unstable and subject to much disturbance, mainly due to its rich and varied fauna. A total of 132 plant species was recorded as typical for, or exclusive to the subcanopy habitat. These species tend to be widely to very widely distributed, and endemism was very low. Almost 50% were hemicryptophytes, 28% annuals and 9% succulents. The most common species were almost exclusively dispersed by animals, especially birds. Leguminosae, the family of most of the pioneer canopy formers, was almost absent from the subcanopy