The effects of different environments on diameter growth increments of Colophospermum mopane and Combretum apiculatum

Abstract

Radial cross-sections of 46 wood samples of Colophospermum mopane and Combretum apiculatum trees from four sites were examined for growth increments. Increments were small and sometimes difficult to discern, so measurements were made to the nearest 0.1 mm. The results suggest that rainfall is of little significance in explaining variability in ring size. Combretum apiculatum consistently produced wider rings than Colophospermum mopane (an average of 1.1 mm vs. 0.9 mm, respectively). Significant regressions of total green woody biomass on tree size were found for both species. Significant interactions of species × tree size suggested separate regression equations for each species across sites, whereas the significant site × species interactions would signify different intercepts, which are a measure of site quality. Maximum increments are obtainable on potentially fertile soils but reasonable increments were also achievable on lithosols and halomorphic soils for Combretum apiculatum and Colophospermum mopane, respectively, as these species are well adapted to such abiotic conditions.