Iron-Organic Carbon Interactions in Wetlands: Implications for Wetland Carbon Preservation Under Global Changes

As a tremendous global carbon reservoir, wetlands play a pivotal role in mediating climate change. Organic carbon (OC) stored in wetlands is usually considered to be dominated by particulate organic carbon (POC) devoid of mineral protection. However, recent studies have revealed that reactive iron (Fe) (hydr)oxides are more abundant than previously recognized in wetlands and may stabilize up to 40% of soil organic carbon (SOC). Yet the significance of Fe-OC interactions in wetland carbon preservation and their responses to global changes remain insufficiently understood. Here this review summarizes recent advances in three key aspects related to Fe-OC interactions in wetlands: microbe- and plant-mediated biogeochemical processes regulating the formation and accumulation of reactive Fe (hydr)oxides in wetland soils; characteristics of Fe-OC interactions and their implications for wetland carbon preservation; and the response of Fe-OC interactions to global changes including drainage and warming. We also highlight future research directions and potential strategies related to wetland Fe-OC interactions, which warrant better recognition in the protection and restoration of wetland carbon reservoirs. These advances underscore that mineral protection by reactive metal oxides is an underappreciated mechanism of SOC preservation in wetlands, potentially improving our understanding of wetland carbon dynamics under global changes.