Trends in savanna structure and composition along an aridity gradient in the Kalahari
Version of Record online: 24 FEB 2009
2002 IAVS - the International Association of Vegetation Science
Journal of Vegetation Science
Volume 13, Issue 3, pages 419–428, June 2002
How to Cite
Scholes, R.J., Dowty, P.R., Caylor, K., Parsons, D.A.B., Frost, P.G.H. and Shugart, H.H. (2002), Trends in savanna structure and composition along an aridity gradient in the Kalahari. Journal of Vegetation Science, 13: 419–428. doi: 10.1111/j.1654-1103.2002.tb02066.x
- Issue online: 24 FEB 2009
- Version of Record online: 24 FEB 2009
- Received 17 January 2001; Revision received 21 January 2002; Accepted 28 March 2002.
- Species number;
- Southern Africa;
- Tree height;
Abstract. The Kalahari sand sheet occupies 2.5 million ha in southern Africa. It is an area with relatively similar deep aeolian soils, and a strong south to north gradient in rainfall, from 200 to 1000 mm mean annual precipitation (MAP) in the region studied. This provides an excellent basis for gradient studies at the subcontinental scale. This paper briefly reviews the literature on the vegetation of the Kalahari and describes the vegetation structure and composition at 11 new sites. There is a clear gradient in woody plant biomass (as indexed by basal area) from south to north. Above the minimum level of 200 mm MAP, the woody basal area increases at a rate of ca. 2.5 m2.ha-1 per 100 mm MAP. Mean maximum tree height also increases along the gradient, reaching 20 m at ca. 800 mm MAP. The number of species to contribute > 95% of the woody basal area increases from one at 200 mm to 16 at 1000 mm MAP. Members of the Mimosaceae (mainly Acacia) dominate the tree layer up to 400 mm MAP. They are replaced by either the Combretaceae (Combretum or Terminalia) or Colophospermum mopane of the Caesalpinaceae between 400 and 600 mm MAP, and by other representatives of the Caesalpinaceae above 600 mm MAP. The vegetation is largely deciduous up to 1000 mm MAP, except for species that apparently have access to groundwater, which may be locally dominant above about 600 mm MAP.