Effects of land-use change on herbaceous vegetation in a semi-arid Mopaneveld savanna

Background: Low altitude Mopaneveld savanna in the northeastern parts of South Africa is generally well conserved. However, extensive copper mining, agricultural practices and urbanisation in the Phalaborwa region prompted research on the possible effects of land-use change on plant community diversity and function. Species diversity measures are usually considered adequate to assess disturbance effects to inform conservation efforts and management practices. However, diversity measures based on species level accounts often limit the outcomes of these studies as this approach fails to quantify how disturbances affect ecosystem functioning when community assembly, and not species diversity alone, is altered by land-use change. Objectives: The aim of this study was to apply both species and functional diversity measures to a data set derived from various land-use types (i.e. areas exposed to strip mining activities, communal farming practices and conservation) in the Phalaborwa region to examine the effects of land-use change on the community ecology of the herbaceous layer. Results: Land-use change, particularly severe top-soil disturbances through strip mining activities, had a significant filtering effect on all measures of species diversity, though functional evenness was maintained across land-use types. Conclusion: These results suggest that, despite initial species loss, this particular savanna ecosystem is buffered against anthropogenic disturbances through functional stability. Indicator species analyses, as well as relationships between plant functional types and land-use change, revealed that forb species are largely responsible for ecosystem stability in areas exposed to anthropogenic disturbances.