Role of Scirpus mariqueter on methane emission from an intertidal saltmarsh of Yangtze estuary

The role of wetland plant (Scirpus mariqueter) on methane (CH₄) emissions from a subtropical tidal saltmarsh of Yangtze estuary was investigated over a year. Monthly CH₄ flux and pore-water CH₄ concentration were characterized using static closed chamber technique and pore-water extraction. Measured chamber CH₄ fluxes indicated that saltmarsh of the Yangtze estuary acted as a net source of atmospheric CH₄ with annual average flux of 24.0 mgCH₄·m^-2·day^-1. The maximum chamber CH₄ flux was in August (91.2 mgCH₄·m^-2·day^-1), whereas the minimum was observed in March (2.30 mgCH₄·m^-2·day^-1). Calculated diffusion CH₄ fluxes were generally less than 6% of the chamber fluxes. Significant correlations were observed between the chamber CH₄ flux and rhizospheric pore-water CH₄ concentration (11-15 cm: p < 0.05, R = 0.732; 16-20 cm: p < 0.05, R = 0.777). In addition, chamber CH₄ fluxes from July to September constituted more than 80% of the total annual emission and were closely correlated with aboveground biomass yield of S. mariqueter. The results indicated that S. mariqueter transportation was the dominant CH₄ emission pathway and it provided an efficient route for the belowground CH₄ to escape into the atmosphere while avoiding oxidation, leading to CH₄ emissions.