Vegetation patterns and nutrients in relation to grazing pressure and soils in the sandveld and hardveld communal grazing areas of Botswana

Abstract

A major challenge confronting managers of extensive grazing systems is uneven use of erbaceous forage plants by livestock. The concentration of grazing in preferred areas or around foci points (e.g. water points) eventually results in adverse impacts in soil nutrients, vegetation structure, production and composition. In Botswana's communal grazing systems, however, the severity or magnitude of this foregoing problem is little understood. This study therefore investigated herbaceous plant species patterns as a function of grazing pressure and soil nutrients in the sandveld and hardveld communal grazing areas of Botswana. Six boreholes (three in the hardveld and three in the sandveld), with sampling points at distances 50m, 100m, 200m, 400m, 800m, 1 500m and 3 000m formed the investigation. At each sampling distance, two plots measuring 10m x 15m were designated, where soil and herbaceous plant samples were collected for further chemical analysis. Marked differences in soil nutrients, herbaceous plant nutrients, species composition and diversity were prominent between the two land zones. Soils from the hardveld boreholes recorded significantly higher concentration levels for both macro- and microelements relative to the sandveld. Insignificant negative correlations between soil and plant elements were established for the two ecological zones. Herbaceous plant species from the hardveld boreholes contained adequate macro- and microelements to meet dietary livestock requirements relative to the sandveld. The results are here discussed with the view of understanding their management implications for extensive grazing areas.

African Journal of Range & Forage Science 2005, 22(1): 17–28