Warming-Induced Plant Species Shifts Lead to Substantial Losses of Wetland Soil Carbon

Wetlands are large reservoirs of soil organic carbon (SOC), storing one-third of global SOC within 6% of the land surface. However, the feedback direction and magnitude of wetland SOC storage to climate warming remain unclear. Here we present results from an 8-year (2014–2022) wetland warming experiment in the Yellow River Delta, revealing that wetland SOC storage responds to warming in a phase-dependent manner. We found that warming initially reduced both carbon input and output but did not change SOC storage. However, SOC storage abruptly decreased by 21.4% in 2020, which persisted over the following 2 years. This occurred mainly due to shifts in the biomass of dominant plant species (P. australis) under warming, reducing carbon input, increasing microbial carbon degradation, and resulting in microbial necromass carbon loss. These results highlight the critical role of dominant plant species in driving the wetland soil carbon cycle and its feedback to climate change.