Influence of saltmarsh vegetation and sedimentation on the distribution of soil carbon and nitrogen in the Chongming Dongtan wetlands

The distribution of carbon and nitrogen storage in coastal wetlands is hypothesized to be regulated by saltmarsh vegetation and sedimentation. In this study, the spatio-temporal changes of TOC and TN accumulation in the vegetation and soil were investigated for the three dominant saltmarsh vegetation (Phragmites australis, Spartina alterniflora, Scirpus mariqueter) along three sampling transects located in the northern, central and southern parts of the coastal wetlands of Chongming Dongtan in the Yangtze River Estuary. The results showed that the northern and central parts of the study area showed a sediment accretion, while the southern part showed an erosion. The TOC and TN accumulation in the zones of Phragmites australis and Spartina alterniflora was significantly higher than that of Scirpus mariqueter. The soil TOC and TN storage in the northern and central transects was significantly higher than that of the same vegetation types in the southern transect. The soil TOC storage of Phragmites australis in the higher intertidal zone was higher than that of Spartina alterniflora in the middle intertidal zone. While the soil TN storage in Spartina alterniflora zone was marginally higher than that of Phragmites australis zone. The soil TOC and TN storage in the zones of Scirpus mariqueter and mudflat was the lowest. The spatio-temporal changes of TOC and TN storage in soil profiles were affected by the interactions between salrmarsh vegetation types and sedimentation, especially in the 0~10 cm soil profile.