THE SPATIAL DISTRIBUTION OF SOIL LOSS TOLERANCE IN CARBONATE AREA IN GUIZHOU PROVINCE

According to the amount of argillaceous material in formations that determines the surface soil thickness,the petrologic assemblages in carbonate area in Guizhou Province can be divided into three types: homogenous carbonate rock,carbonate rock intercalated with clastic rocks,and carbonate/clastic rock alternations.With the average weathering dissolving rate of carbonate rocks in Guizhou being 49.67 mm/ka,the pedogenesis rates of different petrologic assemblages in carbonate area have been calculated and used as the value of soil loss tolerance in carbonate areas.The soil loss tolerance in homogenous carbonate rocks area is lower than 6.84 t/(km~2·a),45.53 t/(km~2·a) in carbonate rock intercalated with clastic rock areas and 103.46 t/(km~2·a) in carbonate/ clastic rock alternations areas.Therefore,this three area are utmost sensitive,severe sensitive and moderate sensitive to soil erosion separately in these carbonate areas.As a result,there exists a spatial heterogeneity of the classification indices for soil erosion intensity in carbonate areas of Guizhou Province.Karst rocky desertification is predominately distributed in homogenous carbonate assemblages whose soil loss tolerance is lower than 6.84 t/(km~2·a),especially,in homogenous limestone assemblage.