Biotic and Abiotic Factors Controlling Spatial Variation of Mean Carbon Turnover Time in Forest Soil

Abstract Soil carbon persistence in forests plays a pivotal role in regulating terrestrial feedback to climate change. However, the relative contributions of biotic and abiotic factors in controlling geographic variation of forest soil carbon turnover time ( τ soc ) remains unclear. Here, we first sampled soils from 12 permanent forest plots across eastern China and detected higher radiocarbon‐derived mean turnover time of soil organic carbon in the deep (30–100 cm; 2,087 ± 246 years) than the surface (0–30 cm; 249 ± 80 years) layer. Further analyses based on the partial Mantel test and structural equation model illustrated that the interactions of climate, vegetation, and soil factors are more complex in deep than surface soils. Then, we established a global database of radiocarbon‐derived τ soc from 1897 forest soil samples. On the global scale, τ soc was significantly higher in the deep (3,081 ± 398 years) than the surface (332 ± 56 years) layer. Soil depth alone explained 11.7% of the spatial variation in τ soc , and the interactions between climate, stand age, and soil depth account for 68.6% of the variation. These findings highlight the joint control of climate, vegetation, and soil depth in the spatial variation of soil carbon persistence in global forests.