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Knowledge of the evolution of pedogenic processes in the carbonate area is important to understand the dynamics of rock desertification. A precisely-dated stalagmite delta C-13 record between 61.3 and 50.5 ka BP from southwestern China, potentially related to soil biogenic CO2 production, shifts within a narrow range between -9aEuro degrees and -7aEuro degrees, and exhibits a prominent cycle of 350-470 a, independent of the Asian monsoon changes. This indicates that a threshold effect might control the amplitude of calcite delta C-13 variability, likely associated with the vertical soil loss in the carbonate area. The periodic delta C-13 changes reflect that the loss/recovery of soil cover can operate on centennial scale. Thus, the rock desertification in southwestern China might at least initiate 60 ka ago and should be of natural origin.