Rangeland degradation in a semi-arid South Africa—II: influence on soil quality

摘要

The impact of rangeland degradation on soil characteristics (compaction, temperature, soil-water content, infiltrability, root and litter turnover, and the organic matter content), was determined for a semi-arid rangeland. Sampling was from rangeland artificially maintained in three different rangeland conditions, viz. good, moderate and poor. Due to the lower basal cover of rangeland in poor condition, soil compaction increased (p ≤ 0.01) and temperature, water-content, infiltrability and organic matter content decreased (p ≤ 0.01) with rangeland degradation. The mean soil compaction of rangeland in good, moderate and poor conditions was 6.37, 11.51 and 18.34 kg cm~(-2), respectively. The highest temperatures on top of the soil of 55, 49 and 46 ℃ for rangeland in poor, moderate and good conditions respectively, occurred during December. Where rainfall is the biggest determining factor for production in rangeland in poor condition, under higher soil-water conditions, nitrogen is for rangeland in good condition. After only 5 years following degradation, organic C was significantly lower (22.15%) over the first 50mm soil layer and total N significantly lower (12.91%) over the first 100mm in rangeland in poor condition than that of good condition rangeland. Rangeland degradation lengthened the replacement of total root system with about a year and decomposition time of litter with 8 months. The importance of maintaining rangeland in good condition and soil quality to help ensure sustainable utilization of the grassland ecosystem was stressed.