[Spatial Partitioning and Influencing Factors of Soil Organic Carbon in Karst and Non-Karst Regions of Southeast Yunnan Province].

The difference in soil organic carbon （SOC） between karst and non-karst areas affects the accurate assessment of soil carbon sinks at the county scale， making it a hot and difficult topic in soil carbon research in karst areas. Taking Wenshan County， a typical karst area in southeast Yunnan Province， as an example， a 1 km×1 km grid sampling method was used to conduct the spatial differences in SOC content， density， and storage in the 0-20 cm soil layer between karst and non-karst areas. The impacts of different land use patterns， karst rocky desertification， elevation， and soil physicochemical properties on surface SOC were also explored. The results showed that the SOC storage in the 0-20 cm soil layer was 12.619 million tons， with a distribution pattern of high in the west and low in the central and northern regions in Wenshan County. The mean values of ω（SOC） and SOC density in non-karst areas were 20.88 g·kg^-1 and 4.93 kg·m^-2， respectively， which were 27.94% and 23.55% higher than those in karst areas （P < 0.01）. Significant differences in ω（SOC） were observed under different land use types， with shrubland （24.58 g·kg^-1） > grassland （20.92 g·kg^-1） > forestland （20.52 g·kg^-1） > orchard （19.89 g·kg^-1） > other woodland （18.87 g·kg^-1） > dryland （16.16 g·kg^-1） > paddy field （15.58 g·kg^-1）. The SOC in shrubland， grassland， and other woodland in non-karst areas was 35.95%-66.52% higher than that in karst areas， indicating that abundant plant litter input in non-karst areas contributed to SOC accumulation. Karst rocky desertification was mainly distributed in the northern， central， and eastern regions of Wenshan County， which was consistent with the distribution of low SOC areas （8.0-15.0 g·kg^-1）. The ω（SOC） in mild， moderate， and severe karst rocky desertification areas ranged from 12.98 to 15.55 g·kg^-1， significantly lower than that in non-rocky desertification and potential rocky desertification areas （17.34-17.82 g·kg^-1， P < 0.01）. Geographical detection analysis showed that the single-factor explanatory power of soil total nitrogen （TN） content for SOC spatial differentiation exceeded 0.70， followed by elevation， soil bulk density， and C/P， with single-factor explanatory powers ranging from 0.31 to 0.52. The interaction effects of TN and C/N， as well as TP and C/P， had explanatory powers of 0.73 to 0.95 for SOC， indicating that soil nutrients such as nitrogen and phosphorus had important impacts on SOC. Due to the influence of karst rocky desertification， the ω（TN） in the karst area of Wenshan County was 1.54-2.10 g·kg^-1， which was 11.47%-27.25% lower than that in non-karst areas， resulting in lower explanatory powers of the aforementioned influencing factors and their interactions for SOC in karst areas compared to those in non-karst areas. This study provides a scientific reference for assessing soil carbon sinks at the county scale in karst regions.