Characteristics of soil organic carbon under different karst landforms

The spatial distribution patterns of soil organic carbon (SOC) and its relationship with various environmental factors in different topographic features are of great significance for evaluating SOC reserves and carbon pool management in karst areas. In this paper, SOC from the non-karst landforms and four typical karst landforms (karst canyon, karst peak cluster, karst plateau, and karst trough valley) was selected as the research object. The distribution patterns and the driving factors of SOC in the typical landforms were investigated from the topographical and environmental perspectives. The results showed that the average content of organic carbon in non-karst region was 9.39 g/kg, while that in karst areas was 16.31 g/kg. The vertical changes in SOC content showed different patterns in different topographic features, and each layer of the soil profile showed that SOC content in karst regions was greater than that in the non-karst one. The driving factors for SOC varied in different landforms. Specifically, in non-karst and karst peak cluster areas, slope gradient was the key factor influencing SOC. In karst canyon areas, soil thickness was the key factor influencing SOC. In karst plateau areas, land utilization was the key factor influencing superficial SOC. In karst trough valley areas, rock exposure was the major driving factor for karst SOC. These findings could provide an excellent explanation for the factors influencing SOC in karst and non-karst regions in Southwest China.