Land degradation evaluation in a game reserve in Eastern Cape of South Africa: Soil properties and vegetation cover
Scientific Research and Essays
University of Fort Hare, Faculty of Science and Agriculture, Livestock and Pasture Science Department, PB X1314, Alice 5700, South Africa
Land degradation in the agricultural domains of South Africa has attained a scale that requires scientific intervention. To devise an appropriate control measure, we investigated the contribution of vegetation condition and soil properties to observed land degradation conditions. Twenty three degraded sites were identified and classified using a land degradation index derived from six physical degradation indicators, using multidimensional analysis techniques. A veldt condition assessment was also con-ducted on the sites. Soil samples from the sites were analyzed for soil degradation indicators viz., particle size fractions, aggregate stability, organic C, pH, EC, total and exchangeable Na, Mg, K and Ca. The veldt condition score ranged from 26.3 - 50%, which implied that the veldt condition has diminished by up to 50 - 77% of its standard condition. Most of the degraded sites are poorly covered; the percentage basal cover ranged from 12 - 39% with average distance of 0.8 - 30.7cm between plants. The degraded lands consisted of high (69 - 100%) proportion of increaser's species which was caused by selective grazing of palatable species by wildlife herbivores. The stable soil aggregate size ranged from 0.8 - 1.4 mm across the mechanical disaggregation, fast wetting and slow wetting tests. Soils of the degraded sites (poorly, moderately and highly degraded) have low organic carbon content < 13.0 mgkg-1. Higher quantities of Na and Ca were observed in the highly degraded sites, indicating the effects of increased solidification and calcification on the breakdown and erosion of soil aggregates. Soil erosion was the major end occurrence in land degradation episodes at Tsolwana game reserve, which was a result of the integrated effects of the vegetation and soil variables. It is recommended that land degradation control measures should be focused on the alteration of cause-variables rather than the effects variable (soil erosion). © 2008 Academic Journals.