Methane emission in the process of wetland vegetation succession in salt marsh of Yangtze River estuary

As important intermediates in the process of carbon cycle in estuarine wetlands, methane (CH₄) is the important greenhouse gas that only seconds to carbon dioxide (CO₂) in the atmosphere. Accurate estimation of CH₄ emission inventory is important in predicting the global warming tendency. The static closed chamber-chromatograph method was used to investigate the monthly CH₄ fluxes from February 2011 to December 2012 in the salt marshes of Yangtze River estuary. The results indicated that salt marshes in Yangtze River estuary acted as a net source of atmospheric CH₄ and the annual average CH₄ fluxes was 1.00 mg·m^-2·h^-1 in 2011 when the Scirpus mariqueter was the dominant species. After the full-scale invasion of the alien Spartina alterniflora, biomass of Scirpus mariqueter decreased greatly in 2012, with the annual average CH₄ fluxes decreased to 0.55 mg·m^-2·h^-1. According to Pearson correlation analysis, sediment organic carbon, solar radiation and the water content were not the main factors of CH₄ fluxes. In addition, CH₄ fluxes were significantly positively correlated with both aboveground biomass of Scirpus mariqueter(p=0.001, r=0.928)and temperature (p<0.01, r=0.432) in 2011. Along with the invasion of Spartina alterniflora in 2012, CH₄ fluxes reached the highest value in May. The total CH₄ emissions also decreased significantly due to the invasion of Spartina alterniflora in 2012.