Soil Conservation Measures Enhanced Soil Organic Carbon Storage Across China

Severe soil erosion accelerates the depletion of soil organic carbon (SOC). While the role of soil conservation measures (SCMs) in mitigating erosion is well-documented, their influence on SOC storage remains insufficiently synthesized. This study incorporates 846 datasets from 55 peer-reviewed studies to evaluate the effects of SCMs on SOC storage across diverse regions of China, with a particular focus on underlying processes and controlling factors. Results show that SCMs implementation increased SOC content by an average of 3.17 g/kg—a 30.3% improvement compared to areas without SCMs. Biological measures (BMs) enhanced plant biomass input and root turnover, promoting SOC accumulation through increased organic matter supply and stabilization in aggregates. These mechanisms were especially effective in the Huang-Huai-Hai Region (HHR), Northern Arid and Semiarid Regions (NAS), Northeast China (NE), and the Sichuan Basin and its surrounding areas (SBS). Engineering measures (EMs) reduced surface runoff and erosion intensity, thereby minimizing SOC loss and promoting in situ retention, which dominated in the Yunnan–Guizhou Plateau (YGP) and Loess Plateau (LP). Combined EMs and BMs enhanced SOC sequestration by simultaneously reducing erosion and boosting organic matter inputs, proving most effective in the Middle-Lower Yangtze Region (MYR) and Southern China (SC). The effectiveness of SCMs for SOC sequestration was modulated by multiple factors, including rainfall, slope, soil moisture content, soil depth, bulk density, and aggregate particle size, with soil moisture identified as the predominant driver. Our findings provide a scientific basis for implementing region-specific conservation strategies to enhance carbon sequestration and promote sustainable land management.