Abstract:

Human activities have induced severe soil and water loss and gave rise to rocky desertification in Karst region of southwest China. The recovery of rocky desertification is extremely difficult because there’s very little residue after the weathering of carbonate rocks. Therefore, the key issue of karst rocky desertification is the contradiction between soil formation and soil loss. Currently, the rate of soil formation from carbonate rock is calculated based on the dissolution rate of carbonate rock in soil profile. The dissolution rate of carbonate rock is determined by the dissolution experiment of standard test piece of carbonate rock. This method only considers the soil formation on the contact surface between soil and rock, but not the soil formation between rock layers and rock interior. However, the method of watershed’s geochemical balance which contains the above soil formation types is based on the granite region. It must be modified when applied to carbonate rock watershed. The most important difference of the soil formation between carbonate and granite rocks was the weathering of carbonate rocks diametrically divided into two processes, namely the weathering of carbonate rock to form residual material, and the further weathering of residual material to form soil. In this paper, we propose to modify the method of watershed’s geochemical balance by considering the weathering process of residual material to distinguish these two processes.

Key words: Southwest China, Karst rocky desertification, weathering of carbonate rock, soil formation rate, granite, dissolution rate, method of watershed’s geochemical balance