Resilience of South African communal grazing lands after the removal of high grazing pressure

A paired site study was conducted of communally grazed eutrophic and dystro phic grasslands and adjacent ungrazed areas of varying periods of exclusion from communal grazing. This allowed determination of the rate and extent o f change of a number of vegetation and soil variables following the removal of high and continuous grazing pressure characteristic of communal lands. Similarity indices for grass species composition between the grazed and adj acent ungrazed areas showed a significant exponential decrease with increas ing time since protection from continuous grazing. Most change in grass spe cies composition occurred within four to nine years of protection from comm unal grazing in eutrophic grasslands, and in six to nine years in dystrophi c grasslands. In both grassland types palatability increased with time sinc e protection. In eutrophic sites the abundance of perennials showed a signi ficant increase with time since protection, while the abundance of annuals showed a concomitant decrease. This relationship was not evident in dystrop hic grasslands. Grass species diversity, basal cover and density showed no relationship with time since protection in the eutrophic sites, but a gener al increase with time since protection was found in dystrophic sites. Soil bulk density, field capacity, pH and soil nutrients showed no evidence of a relationship with time since protection for either grassland type, while s oil porosity increased significantly with time since protection at eutrophi c sites, but not dystrophic sites. These relatively rapid changes following the removal of the high grazing pressure indicate that these systems are c haracterized by relatively high resilience. Copyright (C) 1999 John Wiley & Sons, Ltd.