What are the long-term effects of high-density, short-duration stocking on the soils and vegetation of mesic grassland in South Africa?

Abstract

High-density, short-duration stocking (HDG) is gaining popularity amongst farmers in the South African mesic grasslands, but little is known about its potential impact on natural resources. Using a fence-line contrast approach, this study compared the long-term effects of HDG with those of other rotational grazing systems at lower densities (LDG) on soil properties and vegetation composition at two sites. Soils at Kokstad and Cedarville were 31% and 19% more compacted under HDG than LDG, respectively, but did not differ in total nitrogen, total carbon, available phosphorus or pH. At Kokstad, HDG had promoted unpalatable grass species at the expense of palatable grass species. Forb species composition differed substantially between HDG and LDG, with HDG having 13 and LDG having 16 unique species. A radical prostrate forb growth habit was favoured over a cauline erect habit under HDG. At Cedarville, few grass or forb species showed differences between HDG and LDG, possibly because of an overriding influence of the absence of burning in both grazing systems. These results suggest that HDG potentially has negative impacts on soil health and vegetation composition of South African mesic grassland.

Keywords: biodiversity, forbs, grazing management systems