The population dynamics and life-history attributes of a Pterocarpus angolensis DC. population in the Northern Province, South Africa

Abstract

This article examines the population dynamics and life-history attributes of a single P. angolensis population in the Northern Province, South Africa. An introduction to the use of matrix models in population biology is presented. A frequency distribution of diameters reveals a bimodal distribution of stems. Yearly diameter growth increases with age. It is, therefore, concluded that this bimodal size distribution is indicative of discrete recruitment events of permanent stems and not of an unstable population. Established trees and seedlings (suffrutices) can persist in the landscape by means of coppicing. A matrix model, combined with an elasticity analysis of the derived transition matrix is used to isolate key life-history stages. Life-history stages lying along the diagonal of the matrix have the highest elasticity values, emphasizing the importance of stem survivorship, as opposed to growth or fecundity, in the survival of this tree. Long-term survival greater than the life-span of a stem depends on seedling recruitment events. The model is also used to predict the outcome of two harvesting strategies on the future of the population. Some suggestions for management and priorities for future research are presented.