A baseline study for controlling the indigenous encroacher Stoebe vulgaris in the natural grasslands of Southern Africa

Abstract

South African natural grasslands are being encroached by Stoebe vulgaris, a hardy, indigenous dwarf-shrub thriving in nutrient deficient soils with a history of poor veld management. This baseline study investigates selected management options and associated costs for controlling S. vulgaris in Bankenveld grassland. Control measures examined include 50% removal, 100% removal, and application of herbicide. Four spatially separated study sites were randomly selected within encroached areas. At each study site, two 25 × 25 m plots were demarcated, one of which was enclosed to prevent access by large ungulates. Sixteen 4 × 4 m sub-plots were placed within each of the eight demarcated plots. Veld condition and density of S. vulgaris were determined in all sub-plots prior to the application of control measures. Various control measures were applied, and after twelve months, the veld condition and density of S. vulgaris were again ascertained for comparison to pre-treatment values. Effects of herbivore presence and slope were investigated for the different control measures. Results indicate that to control S. vulgaris over the short term, either 100% removal or herbicide application is effective. We suggest a combination of these control measures, accompanied by ongoing monitoring and follow up treatments to ensure long-term success.