Soil organic carbon accumulation and decomposition in coastal wetlands in the changing water and salinity conditions: a review

Coastal wetlands are an important component of blue carbon ecosystems, have great potential for carbon capture and storage, and play a significant role in mitigating climate warming．Soil organic carbon accumulation and decomposition can change greatly along a hydrological and salinity gradient in coastal wetlands．This review summarized the progresses on the soil organic carbon accumulation, carbon emission, microbial mechanisms of soil organic carbon decomposition and the methodology of carbon fluxes in coastal wetlands in a changing water and salinity environment．Finally, the future key researches on the soil organic carbon processes in coastal wetlands under different water and salinity should focus on these following aspects, including (1) the temperature, moisture and salinity sensitivities of soil organic carbon mineralization in coastal wetlands and integrated influencing mechanisms of water, salinity and temperature, (2) the influencing mechanisms of nitrogen and phosphorus inputs and multi-pollutant stresses on soil organic carbon decomposition and carbon emissions from coastal wetlands, and (3) the coupling of microbial carbon metabolism and nitrogen, phosphorus and sulfur metabolisms and the driving mechanisms of water and salinity．This review can provide a scientific and theoretical basis for revealing the influencing mechanisms of changing water and salt conditions on carbon cycle of coastal wetlands, and for evaluating the improvement and management of carbon sink function of coastal wetlands in context to climate change．