Ecosystem Respiration Does not Differ Before and After Tidal Inundation in Brackish Marshes of the Min River Estuary, Southeast China

Abstract

Respiration in tidal marshes plays an important role in the global carbon cycle, but is little investigated in Asia. In this study, ecosystem respiration in three brackish marshes dominated by Spartina alterniflora (smooth cordgrass), Phragmites australis (common reed) and Cyperus malaccensis (shichito matgrass) were examined monthly during 2009 in the subtropical tidal wetland of the Min River estuary of southeast China. Measurements were taken before and after tidal inundation. Soil porewater CO2 concentrations at soil depths of 5 and 10 cm were also measured. Differences in ecosystem respiration before and after tidal inundation stages were statistically indistinguishable in each vegetation type on an annual scale but differed by month. Monthly variation in ecosystem respiration was apparent and overall respiration in P. australis stand had the highest respiration of the vegetation types. Monthly average CO2 concentration in soil porewater did not differ significantly between the two depths. Ecosystem respiration in P. australis and C. malaccensis stands had a significant positive correlation with soil and air temperature, and a significant negative correlation with soil pH in S. alterniflora and C. malaccensis stands. Our results suggested that the brackish marsh ecosystem of subtropical estuary emits CO2 to the atmosphere at relatively higher level, but the emission pattern did not differ before and after tides.