Disentangling the Roles of Microbial Traits and Mineral Protection in Regulating Temperature Sensitivity of Soil Carbon Decomposition in Eroded and Depositional Agricultural Soils

Abstract

The temperature sensitivity of soil organic carbon decomposition (Q₁₀) governs the fate of soil carbon under global warming. Although erosion redistributes soil carbon at scales comparable to the terrestrial carbon sink, how erosion reshapes Q₁₀ across large regional scales remains elusive. Here, we quantified erosion-induced changes in Q₁₀ across four erosion-prone regions in China, spanning contrasting soil structures and geomorphic settings. We found that erosion increased Q₁₀ by 3.6% in eroded zones, but decreased it by 8.6% in depositional zones relative to non-eroded controls across regions, revealing an erosion–deposition asymmetry. This pattern reflected a shift in the dominant regulators of Q₁₀ along hillslopes: depositional zones were jointly regulated by carbon quality and mineral–aggregate protection, whereas in eroded zones, reduced mineral protection lowered substrate quality, triggering a microbial shift toward higher oxidative capacity, which elevated Q₁₀. Notably, this erosion-driven response was attenuated and statistically insignificant in the Loess Plateau, which can be attributed to aeolian-induced physicochemical homogenization and weak mineral–aggregate protection. Model projections further indicate that by 2100, the increase in carbon emissions from eroded soils would exceed that from depositional soils by 12.4% under SSP2–4.5 and 26.5% under SSP5–8.5 scenarios. Together, these findings reveal a mechanistic trade-off between mineral protection and microbial functional traits and highlight the necessity of integrating erosion-driven carbon–climate feedbacks into Earth system models in a soil-structure-dependent manner.