Drivers of Soil Organic Carbon Accumulation in Afforestation Ecosystems of China

Afforestation is recognized as a crucial strategy for enhancing the carbon sink capacity of terrestrial ecosystems and mitigating the impact of global greenhouse gases. However, the primary factors influencing soil organic carbon (SOC) accumulation in Chinese afforestation ecosystems remain inadequately understood. We conducted a meta-analysis to identify the temporal patterns and key drivers of SOC accumulation using Structural Equation Modeling (SEM), providing new insights for the planning of timing and locations for afforestation in China. Our analysis revealed that SOC accumulation is positively correlated with stand age, driven by soil fertility, soil moisture, initial SOC stocks, and their interactions over the long term. The temporal pattern of SOC accumulation indicated that losses in SOC stocks can occur not only during the early years but also in the long term (> 20 years) within afforestation ecosystems. Soil fertility emerged as the most significant positive driver of SOC accumulation, followed by soil moisture and their interactions. Mean annual temperature (MAT) and initial SOC stocks were identified as significant negative drivers of SOC accumulation. Overall, these findings underscore the importance of selecting and managing afforestation ecosystems, serving as a scientific reference for maximizing the benefits of soil carbon sequestration and achieving carbon neutrality.