Responses of soil organic carbon cycle to land degradation by isotopically tracing in a typical karst area, southwest China.

Background: The loss of soil organic carbon (SOC) under land degradation threatens crop production and reduces soil fertility and stability, which is more reflected in eco-sensitive environments. However, fewer studies simultaneously compared SOC variations and Methods: Soil profiles from two agricultural lands and a secondary forest land were selected to analyze SOC contents and their stable isotope composition ( Results: The mean SOC content was found to be the lowest in abandoned cropland (6.91 g/kg), followed by secondary forest land (9.31 g/kg) and grazing shrubland (34.80 g/kg), respectively. Meanwhile, the Conclusions: The findings indicate that the cycling of SOC and soil stability in the calcareous soil of southwest China are largely regulated by different land uses and the presence of vegetation cover. The depletion of SOC and soil physical degradation pose significant challenges for abandoned cropland, particularly in the karst area, where land degradation is inevitable. Nevertheless, moderate grazing enhances SOC levels, which is beneficial to the land fertility maintenance in the karst region. Therefore, more emphasis should be placed on the cultivation methods and management strategies for abandoned cropland in the karst area.