Abstract: In order to provide basic data for further study the wetland carbon cycle in Poyang Lake and to understand the responses of soil organic carbon pool to climate change, sampling belts were installed in Nanji Wetland National Nature Reserve, and soil organic carbon content was analyzed. In the Reserve, the soil organic carbon content in 0-15, 15-30, and 30-50 cm layers was 1.07%-352%, 0.31%-1.96%, and 0.27%-0.92%, respectively, being decreased sharply from top to deep layers. The soil carbon density in 0-50 cm depth ranged in 302-10.19 kg·m-2, and that in 0-15 cm layer accounted for 42.5%-72.6% of total carbon stock. Both the soil organic carbon content and the carbon density were the highest under Carex cinerascens-dominated community. Soil moisture and plant biomass were the two main factors affecting the distribution of soil organic carbon and carbon density. Soil moisture explained 40% of the top layer organic carbon variation, while total plant biomass explained 28% of the variation. By comparison, the soil carbon density in Poyang Lake wetland was closer to that in other lake wetlands in the middle and lower reaches of Yangzi River, but far lower than that in the peat lands in Ruoergai Plateau and Sanjiang Plain.

Key words: TRMM 3B42, categorical statistical indices, spatial distribution, overestimation.