Soil organic carbon storage in tidal wetland and its relationships with soil physico-chemical factors: A case study of Dongtan of Chongming, Shanghai

Field investigation was made in March 2013 of Dongtan (East Beach) of Chongming Island to explore carbon sequestrating function of tidal wetlands and its key influencing factors at the Yangtze Estuary. Sampling sites in Dongtan were laid out with the grid sampling method and elevations measured. Soil samples were collected from the 0- 30 cm topsoil layers for analysis of soil organic carbon content, soil salt content, bulk density, soil moisture content, median particle size and p H. Based on the data obtained during the field investigation of Dongtan, spatial distribution of contents of soil organic carbon and their influencing environmental factors in the topsoil layer were analyzed and the soil organic carbon stock therein was assessed through Kriging interpolation with the aid of Arc GIS and through correlation and path analyses with the aid of SPSS. Results show that in the 30 cm topsoil layer, soil organic carbon density varied in the range of 1.02-5.22 kg · m^-2, averaging 2. 32 kg · m^-2, and the soil organic carbon storage reached 1. 15 × 10⁸ kg. Soil organic carbon content, total salt content, soil water content and NDVI index were all quite similar in spatial distribution, being high in the north and low in the south and high in beaches with high tide and low in beaches with low tide, while median particle size and soil bulk density displayed quite reversely in spatial distribution, being higher in the south and beaches with low tide than in the north and beaches with high tide. However, elevation and pH did not follow any rule in spatial distribution and varied slightly spatially. All the 7 investigated environmental factors were found to have close relationships with soil organic carbon content. Total salt content, in particular, which is the most important factor affecting soil organic carbon content in the soil of Dongtan.