Soil fungal community succession regulates aggregate C sequestration and organic C pool stability following reclamation of Chinese estuarine wetlands.

The conversion of estuarine wetlands into paddy fields has a significant impact on the global carbon (C) cycle. However, existing studies lack comparative analyses of soil fungal community succession, aggregate stability, and organic C pool stability among estuarine wetland-paddy systems distributed across different climatic zones. This study examined estuarine wetland-paddy field systems at the Yellow River Estuary (temperate), Jiulong River Estuary (subtropical), and Dongzhai Port (tropical), measuring fungal communities, soil aggregate stability, and organic C content in the 0-15 cm and 15-30 cm soil layers. The results indicate that the Ascomycota and Basidiomycota phyla dominate the fungal community. Land reclamation generally restructured the fungal community, reduced the abundance of Geomyces, and overall weakened aggregate stability, decreased the proportion of macroaggregates (> 0.25 mm), and lowered soil organic C (SOC) level. Land reclamation in estuarine wetlands disrupts fungal community structure, weakens the C sequestration function of soil aggregates, reduces organic C storage capacity, and ultimately diminishes the stability of the soil C pool. This study provides a scientific basis for the conservation and restoration of wetland blue C.