| Soil Organic Carbon Density (SOCD) is a key indicator of the terrestrial carbon cycle and sustainable agricultural development, and its spatiotemporal changes are of great significance for maintaining regional carbon balance and ensuring soil health. Taking the topsoil (0~20 cm) in major counties and districts of Liangshan Yi Autonomous Prefecture, Sichuan Province as the research object, this study systematically analyzed the spatiotemporal variation patterns and driving factors of SOCD by comprehensively applying methods including regression kriging interpolation, correlation analysis and structural equation modeling, aiming to provide a scientific basis for regional carbon pool management and sustainable ecosystem development. The results showed that: over the past 40 years, the SOCD in the topsoil of farmland in Liangshan Prefecture has shown an overall significant downward trend, with the mean value decreasing from 3.52 kg·m?2 to 3.19 kg·m?2, an average reduction of 9.38% and an annual decrease of 0.0083 kg·m?2. There were significant differences in the changes among various counties and districts, among which Puge County had the largest reduction, followed by Xichang City, and only Huili County showed a slight increase. The spatial differentiation pattern of SOCD remained stable, always showing the zonal characteristic of "high in the northwest and low in the southeast".
Correlation analysis indicated that SOCD was extremely significantly positively correlated with temperature, precipitation, Normalized Difference Vegetation Index (NDVI) and precipitation change rate, and extremely significantly negatively correlated with elevation, temperature change rate and NDVI change rate. The fitting results of the structural equation model showed that the spatiotemporal variation of SOCD in the topsoil of farmland in Liangshan Prefecture over the past 40 years was the result of the combined action of topography, climate, vegetation and initial SOCD. Topographic factors indirectly affected SOCD by regulating regional hydrothermal distribution, vegetation growth and initial SOCD, among which the indirect effect through annual average temperature was the strongest. |
