Acacia tortilis subsp. heteracantha productivity in the Tugela Dry Valley Bushveld: preliminary results

Abstract

Acacia tortilis Hayne subsp.  heteracantha (Burch.) Brenan dominates secondary succession in the Tugela Dry Valley Bushveld of the Natal midlands. The parts of KwaZulu in this veld type are impoverished, overpopulated and over-grazed. Preliminary results indicate that at a density of 2 700 ± 600 trees/ha there is a standing crop of c.2,87 t/ha (DM) of acacia twigs suitable for hand pruning and milling into fodder, but that this is a costly process. Herbage biomass peaked at 0,73 t/ha (DM). Veld condition assessments suggested a stocking rate of|0,l AU/ha (grazers), but actual grazer stocking rates may be many times this density. It is recommended that the browser/grazer ratio be altered to make use of the c. 1,05 t/ha (DM) of shoot growth produced annually by A. tortilis subsp.  heteracantha.