| 摘 要： |
The evaluation of soil organic carbon (SOC) dynamics and its driving factors is important for developing sus-tainable soil C sequestration practices. A key challenge is the lack of a time series of spatially explicit SOC es-timates; most previous SOC estimates are static. In this study, we applied a digital soil mapping framework to model the relationship between SOC and environmental factors based on a combined dataset of 4695 soil samples collected in China from the early 1980 s and during the 2000-2014 period. We predicted the annual SOC distribution at a depth of 0-100 cm at a 1 km resolution for China between 1982 and 2019. We mapped trends of SOC change and identified change hotspots. To obtain the pixel-level association between SOC change and environmental factors, we used a linear function to quantify the contribution of individual predictors to SOC change. The results show that the accuracy of SOC prediction is acceptable, with a mean R2 value of 0.58 for validation. SOC storage in China was estimated to range from 89.03 to 97.41 Pg C and showed a slight increase (slope = 0.024 Pg C/yr) from 1982 to 2019. Specifically, two distinct phases of SOC were identified as follows: (1) from 1982 to 2004, a considerable decline occurred, which was mainly driven by increased temperature; (2) from 2004 to 2019, SOC increased slowly, resulting from the contribution of greening to sustaining C seques-tration in soils under warming conditions. Approximately 17 % of all areas have been characterized by a sig-nificant decrease in SOC since 1982, predominantly in central and western China. Environmental controls exhibited large spatial variation, where approximately 69 % of all areas were predominantly controlled by climate factors. For grasslands, the SOC losses in northern China were largely driven by temperature and pre-cipitation, while the SOC losses were primarily attributed to decreased organic inputs driven by grassland degradation on the Tibetan Plateau. Policy-driven land use change has led to an increase in SOC in some cropland areas (e.g., northeast and east China). The implementation of ecological restoration has shown a positive in-fluence on SOC sequestration. This study highlights the diverse spatial patterns and heterogeneity of SOC changes and their controls. Given this spatial differentiation, spatially explicit assessments of soil C dynamics are important for the formulation of regional soil-based mitigation strategies and guidance for effective restoration interventions based on geographic location. |
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