Classification and dynamics of a Southern African subtropical coastal lowland forest

Abstract

The composition and dynamics of Dukuduku coastal lowland forest were investigated by means of ordination techniques. Size-class distributions on data from 200 plots were analysed and we also interpreted aerial photographs. An initial classification suggested that there were six widespread communities. Ordination of data of potential canopy species, found in the canopy and in the sub-canopy, was done separately for five of the six communities. A successional trajectory became apparent from this analysis. Understorey composition in a particular community was often similar to the canopy composition in the next community in the hypothesized time sequence, than to the composition of its own canopy. Analysis of size-class distributions of canopy species for each community supported the concept of a successional gradient. Common canopy species found in early successional community tended to have negative exponential size-class distributions, whereas these same species were less frequent and had flatter size-class distributions in the later successional stages. Based on the results of the ordinations and size-class analysis, a conceptual model of forest dynamics is presented. It is hypothesized that large-scale disturbances, such as fire, are the dominant forces driving the dynamics of this coastal lowland forest.