Soil organic carbon changes following wetland restoration: A global meta-analysis

Wetland restoration has been conducted worldwide due to the important ecological functions provided by wetlands. However, the global patterns of soil organic carbon (SOC) change following wetland restoration are not clear, which has limited the efficacy of the management of restored wetlands. In this study, we synthesized the results from 41 studies and carried out a meta-analysis to examine the SOC dynamics following wetland restoration and the underlying mechanisms. The SOC of restored wetlands was 13.8% (p = 0.017) higher than that of cultivated wetlands and 29.2% (p < 0.001) lower than that of natural wetlands. Wetland restoration facilitated SOC sequestration under certain conditions, including when the wetlands were restored via water supplementation, had seasonal hydrology in their natural status (before cultivation), were peatlands, occurred under a temperate climate, were restored for 6 to 10 years, or had been cultivated no longer than 15 years before restoration. Meanwhile, some conditions had negative effects on SOC sequestration, including wetlands under a tropical climate, those restored using a plantation approach, and those with a tidal hydrology after restoration. Model selection analysis suggested that the hydrological conditions of cultivated wetlands, soil depth, vegetation type, peat condition and restored age were important influential factors affecting SOC after wetland restoration, with the first 2 being the most important influential factors. Our results indicate that wetland restoration is inefficient in terms of SOC recovery and that wetland restoration to recover SOC is urgently needed and should be conducted more appropriately. The results of this study provide theoretical support for wetland management with the aim of SOC sequestration.