Water supplementation amplifies prescribed fire effects on soil organic carbon persistence in a degraded saline‐alkaline wetland

Abstract Understanding how restoration and management affect wetland soil organic carbon (SOC) persistence is essential for assessing, predicting, managing and restoring carbon sink function, which is vital for global carbon cycles. Although prescribed fire and water supplementation (also termed ‘rewetting’) are common wetland restoration and management tools, whether they can effectively improve SOC persistence and what the improvement mechanisms are remain unclear, particularly in saline‐alkaline wetlands. Combining 642 published data points and a nearly 2‐year in situ experiment conducted in a degraded saline‐alkaline wetland, we confirm the effects of prescribed fire and water supplementation on SOC, and explore the regulating mechanisms through microbial SOC degradation (metagenomic sequencing), organic carbon components (Fourier transform infrared spectrometry) and exchangeable cations. Published data demonstrate prescribed fire and water supplementation increased SOC by 13.10% and 17.97%, respectively. Our in situ experiment reveals the water supplementation amplifies the enhancement effects of prescribed fire on SOC persistence in the saline‐alkaline wetland: prescribed fire increases aliphatic carbon, driving short‐term SOC changes, whereas water supplementation increases calcium (Ca 2+ ) and magnesium (Mg 2+ ) in burned plots, making prescribed fire improve SOC by approximately 36.68% and Ca 2+ further enhances SOC by inhibiting peptidoglycan degradation. Synthesis and applications : These findings elucidate the synergistic mechanisms of prescribed fire and water supplementation. For degraded saline‐alkaline wetlands, implementing prescribed fire combined with water supplementation is recommended for enhancing SOC persistence. This approach could be a reference for carbon sink restoration in comparable ecosystems.