Impacts of high utilisation pressure on biodiversity components in Colophospermum mopane savanna

Abstract

This study aimed to quantify and evaluate the effects of heavy land utilisation, mainly grazing, on plant species richness and diversity, species abundance,  vegetation structure and soil characteristics in a communal area in Colophospermum mopane dominated savanna in southern Africa. The treatment was benchmarked against a relatively lightly stocked neighbouring farm. An assessment of termite richness across the contrasting land-use areas was also made. Significant differences were found mainly in plant structure, with reduced plant canopy cover and plant height on the communal land, thus transforming a woodland to a predominantly shrubland physiognomy. There was no significant effect of heavy utilisation on richness or diversity of plant or termite taxa. Species compositional shifts were reflected by significant species associations with either land-use type. Forb species formed an important component of the vegetation irrespective of grazing intensity. Cover of annual plants did not increase with heavy utilisation owing to the increase of ‘weedy’ annual species being counterbalanced by declining cover of palatable annual plants. Biological soil crusts were markedly less common on the communal land, which may result in an increased hydraulic conductivity of the soil. Other soil properties measured appeared to be insensitive to the intense level of land utilisation.

Keywords: communal rangeland, degradation, grazing, plant species richness, termites

African Journal of Range & Forage Science 2012, 29(1): 1–11