Characteristics of soil carbon density distribution and influencing factors in typical karst regions of China

As a typical area with widespread karst landforms in China, Hunan Province has rich karst landforms. The karst regions in Xiangxi have a significant carbon storage potential, which plays a crucial role in China's carbon neutrality goals. Based on multi-objective regional geochemical survey data, the distribution characteristics of soil carbon density and carbon storage in the surface (0-20 cm), middle layer (20-100 cm), and deep layer (120-170 cm) of the study area were calculated, and the main influencing factors of soil organic carbon density changes were analyzed. The study reveals that most of the carbon in the soil carbon reservoir of Xiangxi karst region, exists in the form of organic carbon. The composition of the soil carbon reservoir is mainly controlled by soil forming factors such as geological background, soil types, and land use types. The distribution of soil carbon density and carbon storage in the study area is closely related to the geological background, with soil carbon mainly distributed in marine carbonate rock formations. Limestone soil, yellow loam, and red-yellow soil have the widest distribution range and the highest organic carbon density, making them more suitable for carbon sequestration. Different land use types in the study area, due to varying degrees of human impact, exhibit significant differences in soil organic carbon density. Grasslands and forests, which are less affected by human activities, have higher soil organic carbon density and the strongest carbon sequestration capacity. Therefore, it is evident that grasslands and forests have significant potential for soil carbon sequestration. This information is crucial for assessing the current state of soil carbon density in Hunan and its potential for carbon storage, as well as for mitigating greenhouse gas effects. It provides more accurate data to support Hunan Province's contribution to global climate change mitigation efforts.