Abstract: High primary productivity and slow degradation rate of organic matter in coastal salt marshes result in a substantial carbon sink function. Quantitative research on net carbon sequestration capacity provides important technical support for formulating policies to increase sinks, reduce emissions and achieve carbon neutrality. Many methods of observation, calculation and prediction of wetland net carbon sinks are used, with low comparability among research methods. In this study, we conducted a systematic review from the perspectives of carbon flux observation, ecosystem carbon budget measurement, soil carbon storage variation and carbon cycle simulation. Following an analysis of the knowledge gaps, we proposed future research directions for determining the net carbon sequestration capacity of coastal salt marshes. On the basis of the biogeochemical cycle mechanisms of carbon in wetland ecosystems, combined with satellite remote sensing technology, a carbon source/sink process model should be constructed, and carbon flux observations and carbon budget measurement data should be used for parameter calibration and verification of model suitable for different temporal and spatial scales. The development of such model would provide an effective way to quantitatively evaluate the net carbon sink capacity of coastal salt marshes.

Key words: coastal salt marsh, carbon flux, carbon budget, soil carbon storage, carbon cycle simulation, net carbon sink capacity.