Distribution of organic carbon storage in different salt-marsh plant communities: A case study at the Yangtze Estuary

The high carbon (C) sequestration potentials of coastal wetlands play an important role in mitigating climate change associated with the greenhouse effect. In the present study, soil samples were collected from the 0-30-cm topsoil layers and from 0 to 100-cm cores for the analysis of the spatial dynamics and vertical distribution of organic carbon (OC) and biomass in different vegetation zones in a small tidal basin in Chongming Dongtan wetland. According to the results, sediments in the region were a mixture of terrestrial and marine sources and the proportions of terrestrial components decreased with an increase in depth. In addition, soil properties were quite similar in the top-soil layer. In the study area, the OC concentration was in the 0.7-10.93 g/kg range, which was positively correlated with halophyte biomass and negatively correlated with soil salinity and particle size. Furthermore, OC content decreased with an increase in depth. The OC content in different halophyte communities was in the order of Phragmites australis community > Mixed community > sedge community, and was consistent with the gross biomass. The total C sequestered of 100-cm depth in the area was 31,177 ton, with the P. australis community, mixed community, sedge community, and water sequestering 57.7, 49.2, 25.5 t/ha, and 8 t/tidal cycle, respectively. Tidal marshes in Chongming Dongtan exhibited a high C sequestration capacity, indicating that they play a major role in the C cycle in the Yangtze Estuary.