Abundance of Fe/Al Oxides Governs Soil Organic Carbon Stability in Wetlands Under Drying Conditions

Drying of soil accelerates the decomposition of soil organic carbon (SOC) in wetlands, which threatens their function as carbon sinks. However, whether soil mineral protection can mitigate the response of wetland SOC decomposition to drying remains unclear. In this study, using incubation experiments on 37 wetland soils sampling sites across China, we elucidate the role of mineral protection, as represented by iron (Fe) and aluminium (Al) oxides, in regulating the magnitude of wetland SOC decomposition responses to drying across a large geographical scale. The results indicate that, compared with climatic, soil, and microbial properties, soil Fe/Al oxide contents have a stronger influence on the intensity of SOC decomposition responses to drying, with the response intensity decreasing as soil Fe/Al oxide content increases. Moreover, temperature, precipitation, and soil pH indirectly affect the intensity of the response by regulating Fe/Al oxide content. Our findings highlight the critical role of Fe/Al oxides in modulating the response of wetland carbon decomposition to drying, enhancing our understanding of wetland carbon cycling under global climate change.