The influence of tree thinning on the reproduction dynamics of Colophospermum mopane

Abstract

The reproduction dynamics of Colophospermum mopane, including flowering, fruit bearing, the germination potential of the seed and seedling establishment were studied over a period of three years on six plots where the trees were thinned to the approximate equivalents of 75%, 50%, 35%, 20% and 10% of the tree density of the control plot (2711 trees ha− 1). Thinning of C. mopane reduced inter-tree competition which resulted in marked increases in the flowering and fruit bearing of the remaining trees. Though the percentage reproductive trees were higher in the low tree density plots, the greater number of trees in the high tree density plots ensured that the total number of trees that flowered and produced fruit were of the same order of those in the low tree density plots. The fruit (seed with and without their pod covers) from trees within the low tree density plots were larger and heavier than those from the plots with a high tree density, but this did not have a marked effect on their potential to germinate. Since the greatest germination was achieved from fresh seeds, no dormancy appears to exist in C. mopane seeds. Seedling numbers were low in all plots and a specific pattern of seedling establishment was lacking. At high tree densities severe competition from the established C. mopane trees could account for the low rate of seedling establishment, while in the low tree density plots competition from newly established herbaceous plants, mainly grasses, could account for the tree seedling absence in these plots.