The impact of land use on biodiversity in xeric succulent thicket, South Africa

Doctoral Thesis


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University of Cape Town

Human-induced land management practices are key factors which influence the dynamics of landscapes, land elements and biotic communities in Xeric Succulent Thicket, a notoriously fragile and low resilience ecosystem in the Eastern Cape, South Africa. In its natural state this vegetation type is characterized by a continuous mosaic of clumps of diverse woody shrubs in a matrix of grass, hardy dwarf shrubs and bare ground. When indigenous herbivores are replaced by domestic livestock at unsustainable stocking rates, the ratio of clump to interclump areas decreases. This has impacts on biodiversity at the landscape level, and affects the composition and species richness of plant, arthropod and reptile communities and fungal symbionts. The study has two main objectives: 1) to detennine the local-level effects of different types of land use on biodiversity in Xeric Succulent Thicket; and 2) to better understand the factors which affect biodiversity in different taxonomic groups and at different spatial scales, so that the preservation function of protected areas could be enhanced. The key questions which are addressed in the thesis are what does 'biodiversity' mean, and what are its different dimensions in Xeric Succulent Thicket; what roles do protected areas and other lands play in preserving biodiversity, how are different taxonomic groups affected by different types of land use; and how can biodiversity be monitored and measured? . The regional 'conservation landscape' is seen as the protected area plus the land immediately adjoining it, and is viewed as an integrated mosaic of anthropogenic landscapes (land management units), land elements (patches within landscapes). producer communities (assemblages of interacting plant species), consumer communities (assemblages of interacting herbivores and predators) and soil microorganisms. From a process point of view, the research relates the intensity of disturbance, mainly as a result of herbivory, to landscape complexity, the structure of land elements, and the species richness of producers and consumers within land elements. The patterns which emerge are interpreted in the context of ecosystem functioning, from the point of view of a practicing conservation biologist.

Bibliography: leaves 100-114.