Effects of short-term intensive trampling on Karoo vegetation

Abstract

Plant growth forms likely respond differently to disturbances such as trampling. We investigated the trampling effect of 1 600 sheep encamped at night in temporary enclosures (kraals, corrals or pens), which were relocated weekly. To examine trampling effects and regeneration rates of the various growth forms we compared vegetation composition, canopy cover and foliar nitrogen inside and outside kraals, between one and 12 months after the trampling event. We predicted that inside kraals (1) succulent and non-succulent shrubs would be affected more severely than grasses, (2) perennial plant cover would decrease compared with annual plant cover, (3) foliar nitrogen concentrations would increase, and (4) vegetation recovery would be affected by time and rainfall since last use of the kraal. Grasses and shrubs (succulent and non-succulent) responded differently to kraaling. Density and diversity of succulent and non-succulent shrubs decreased, while annual and perennial grass cover inside and outside kraaling areas did not differ. Foliar nitrogen was greater inside kraals. Both succulent and non-succulent shrub cover increased over time after kraaling irrespective of the rainfall. Our study demonstrates that short-term intensive trampling and dunging creates nutrient-rich, heterogeneous patches that may enhance restoration of degraded production landscapes.

Keywords: corral, dung, high-density grazing, kraal, livestock, pen, vegetation change