Topo-edaphic environment and forest plantation disturbance explain patterns of grassland species richness, composition and structure in an agro-ecological landscape, Maputaland, South Africa

Abstract

Grasslands of the Maputaland coastal plain are biologically diverse and provide a variety of ecosystems services. Yet grasslands in this region are vulnerable to continuing development by plantation forestry that provides economic benefits to local communities. In order to provide a framework for land use that maintains grassland heterogeneity in complex agro-ecological systems, this paper characterises the main relations between grassland species composition, the physical environment and forestry plantation disturbance. Grassland species composition corresponded with landscape position and soil organic carbon. Grasslands occurring in infertile, elevated landscape positions were the most diverse having a greater richness of tufted graminoids, herbaceous forbs and geoxylic suffrutices than grassland occurring in low-lying dystrophic sites, which were dominated by rhizomatous and stoloniferous graminoids. Previously afforested grasslands (i.e. secondary grassland) were species poor, lacked keystone grasses, such as Themeda triandra, were dominated by a few species of rhizomatous or stoloniferous grasses and had been colonised by pioneer or ruderal forbs. Grassland species composition affects the provision of ecosystem services so to maintain a full complement of these attributes, grassland landscapes in Maputaland should comprise intact grasslands that cover both elevated and low-lying topographic positions.