ROOT BIOMASS, DEPTH DISTRIBUTION AND RELATIONS WITH LEAF BIOMASS OF COLOPHOSPERMUM MOPANE

On an area covered by dense stands of Colophospermum mopane with littl e or no grass cover: ten sites were randomly selected. In the centre o f each site, a core (monolith) of soil (2.0 m x 0.5 m x 1.0 m deep) wa s excavated and removed in 5 layers of 200 mm. Roots were washed from the soil and sorted into classes (0-1.0 mm, > 1.0-5.0 mm, > 5.0-10.0 m m, > 10.0 mm), dried and weighed. The canopy dimensions of C, mopane a round each excavation were measured and the leaf dry mass estimated us ing a regression equation which relates spatial canopy volume to leaf dry mass. Total root biomass ranged from 9 760 kg ha(-1) to 29 790 kg ha(-1) (mean: 17 354 kg ha(-1)). Of these a mean of 19% were in the 0- 1.0 mm diameter class, and 20.3%, 16.2% and 44.5% in the > 1.0-5.0 mm, > 5.0-10.0 mm and > 10 mm diameter classes respectively. A mean of 66 .1% of all fine roots (< 5.0 mm) was found within the first 400 mm of the soil. The coarse roots (> 5.0 mm) were virtually absent within the 0-200 mm soil layer, with the highest concentration between 200-600 m m, Leaf biomass was found to be significantly lower than the root biom ass.