干旱区生态环境知识资源中心

Soil erosion plays an important role in land desertification in the karst mountain areas of southwest China, but reliable data on rates of surface soil loss in the area are very limited. Hill-depressions are common landforms in the karst areas. The Cs-137 technique was used to date the sediment deposits in six karst depressions, to estimate average rates of surface soil loss from their catchments. The estimates of soil loss rates obtained from this study evidenced considerable variability. A value of 1.0 t km(-2) year(-1) was obtained for a catchment under original dense karst forest, but the erosion rates ranged between 19.3 t km(-2) year(-1) and 48.7 t km(-2) year(-1) in four catchments under secondary forest or grasses, where the original forest cover had been removed in the Ming and Qing dynasties, several hundred years ago. The highest rate of 1643 t km(-2) year(-1) was obtained for a catchment underlain by clayey carbonate rocks, where the soil cover was thicker and more extensive than in the other catchments and extensive land reclamation for cultivation had occurred during, the period 1979-1981, immediately after the Cultural Revolution.