Quantifying indices of potential competitiveness and browse productivity of single-stemmed Acacia karroo trees in South-Eastern Africa.

Abstract

The prediction of indices of potential competition with grass and browse productivity of single-stemmed Acacia karroo trees, using various trunk and canopy parameters, was evaluated on the basis of the variance accounted for by each of four operators and the repeatability for all operators. Potential competitiveness and browse productivity was measured as total dry weight of leaf-bearing twig and that occurring below a height of 1.5 m, respectively. While trunk measurements and measurements based on canopy volume and twig densities accounted for the greatest variance in competitiveness, trunk circumference and maximum tree height produced the highest levels of repeatability, with maximum errors of c. 7 and c. 17%, respectively. The variance in browse productivity accounted for and the repeatability of predictions of browse productivity were lower than those for potential competitiveness. Browsing units calculated from partial spherical canopy volumes gave predictions of browse productivity with the lowest error (c. 25%). Indices of competitiveness and browse productivity of single-stemmed A. karroo trees can be predicted within c. 25% error using maximum tree height, maximum canopy radius and height of the canopy bottom as basic measurements.Language: English

Keywords: Acacia karroo; botany; browse; Browse units; browsing; canopy volume; competition; dry weight; grasses; measurements; productivity; Repeatability; south africa; technique; Tree equivalents; tree height; Trees