Vegetation patchiness and implications for landscape function: the case of Pteronia incana invader species in Ngqushwa Rural Municipality, Eastern Cape, South Africa.

摘要

Patchy vegetation patterns are an expression of soil surface conditions, water redistribution on the soil surface and landscape function. Their origin is attributed by many a scholar to the degradation of the original plant cover due to human disturbances and climatic fluctuations. In this study, aerial photographs were analysed to benchmark the onset of the invasion by Pteronia incana. The soil moisture dependencies of the invader shrub and grasses were also investigated. The invasion assumed varying trajectories on abandoned and grazing lands. The different soil moisture dependencies between P. incana and grass species were noted to underpin the competitive advantage and eventual replacement of the latter by the former. Soil surface crusting inherent to P. incana, the loss of patchiness and associated expansion of bare zones promote runoff generation and connectivity, and erosion intensification, leading to conversion of hillslopes to dysfunctional systems. Despite its runoff enhancing role, to some extent, P. incana tussocks act as sink areas for some of the runoff generated on the bare zones. Recognition of this resource capture capability should provide the starting point for the rehabilitation of degraded hillslopes.