Study On Soil Organic Carbon And Nitrogen Storage In East Chongming Wetland

The coastal wetland is a complex ecosystem which interacted by water and land, and also it is an importan place that can fix and release greenhouse gases such as CO2, CH4 and N2O. In the background of climate change, wetland has the ability of regulating the content of greenhouse gases because its efficient storage capacity for C and N. Soil is an important pool for C and N in wetland ecosystem. Not only the blance of wetland ecosystem but also the geochemical cycle of the global ecosystem is affected by the contents of C and N in wetland. So it is necessary to study the distribution and dynamic changes in wetland ecosystem.In this study, we choose Dongtan wetland, a typical coastal wetland, which located in the east of Chongming Island, Yangtze estuary as our study area. Based on the plants pattern and the erosion-deposition variation in different areas, we studied the spatial and temporal distribution characteristic of organic carbon and nitrogen storage of 0-50 cm depth in Dongtan wetland in 2013. By considering vegetation types and soil physical-chemical factors, we explored the factors which may affect the carbon and nitrogen storage’s pattern. We want to offer data support for the research of carbon and nitrogen cycle in coastal wetland. The results and main conclusions indicated that:(1)The distribution of soil organic carbon and total nitrogen storage in Dongtan wetland were both in the order of Phragmites australis vegetation zones> Sparitina alterniflora vegetation zones> Scirups mariqueter vegetation zones> Mudflat. Besides the soil organic carbon and nitrogen storage in different sample lines ranked as northern line> middle line>southern line, but there were no significant differences among different sample lines (P>0.05).(2) The results showed that both soil organic carbon and total nitrogen storage in the study area were the lowest in spring,increased over time, and reached the peak in winter. The soil organic carbon storage from spring to winter shows:mudflat (221.66 g/m2-259.73 g/m2); Scirups mariqueter vegetation zone (754.93～929.71 g/m2,); Sparitina alterniflora vegetation zone (1887.60 g/m2～2258.04 g/m2); Phragmites australis vegetation zone (2600.17 g/m2～3029.24 g/m2,).Soil total nitrogen storage also showed the same trend i.e. mudflat (84.95 g/m2～91.98 g/m2); Scirups mariqueter vegetation zone (163.37 g/m2～203.20 g/m2); Sparitina alterniflora vegetation zone 240.93 g/m2～314.33 g/m2); Phragmites australis vegetation zone (230.73 g/m2～ 313.00 g/m2)(3) The vertical distribution of maximum soil organic carbon appeared at 45-50 cm in mudflat (24.57 g/m2～112.71 g/m2); 10-15 cm in Scirups mariqueter vegetation zone (57.58 g/m2～72.65 g/m2); 20-30 cm in Sparitina alterniflora vegetation zone (209.19 g/m2～252.95 g/m2); 25-30 cm in Phragmites australis vegetation zone (298.34 g/m2～392.87 g/m2). And the vertical cistribution of maximum total nitrogen storage appeared at 0-5 cm in mudflat (10.58 g/m2～10.63 g/m2); 10-15 cm in Scirups mariqueter vegetation zone (20.91 g/m2～25.02 g/m2) and Sparitina alterniflora vegetation zone (35.42 g/m2～42.99 g/m2); 25-30 cm in Phragmites australis vegetation zone (27.49 g/m2～40.85 g/m2).(4) There was an extremely significant positive correlation (P< 0.01) between soil organic carbon storage and total nitrogen storage. Vegetation biomass, soil salinity,soil pH showed a significant positive correlation (P< 0.05) with soil organic carbon and total nitrogen storage. And there was a significant negative correlation between soil moisture content and soil organic carbon,total nitrogen storage (P< 0.01).From the above, in Dongtan wetland most of carbon and nitrogen elements are stored in the soils. Because of the vegetation form and environment factors have an influence on the distribution of soil organic carbon and nitrogen storage; different regins have different storage capacity.