[Effects and mechanisms of marshland reclamation for cropland on the carbon-sequestration function of iron minerals in marsh soils].

Marshes are characterized by strong organic carbon accumulation capacity and important carbon sink functions. However, large-scale marshland reclamation for cropland can lead to substantial depletion of marsh soil carbon pools and impairment of soil organic carbon (SOC) stability. Iron minerals are important carriers of SOC and can form carbon-iron complexes (Fe-OC) through adsorption and co-precipitation, thereby contributing to SOC retention. Here, we summarize the effects of reclamation on SOC content and fractions in marsh soils. We further review how iron mineral forms, Fe-OC association mechanisms, organic carbon molecular composition, microbial processes, and environmental factors regulate the carbon-sequestration function of iron minerals, and evaluate the effects of reclamation on this function in marsh soils. We summarize current knowledge gaps and highlight the need to clarify how reclamation-induced changes in carbon sources affect the stability and thresholds of iron mineral-associated carbon sequestration, to elucidate the succession of Fe-reducing microbial communities and their roles in regulating iron mineral carbon sequestration, and to develop sustainable carbon management strategies for reclaimed marsh soils. This review would provid a better understanding of the mechanisms by which reclamation affects the stability of marsh soil carbon pools and provides a scientific basis for sustainable marsh management.