Abstract: Changes of environmental conditions can affect carbon sink function of wetlands. Understanding the effects of environmental conditions on soil organic carbon and its components in wetlands can provide scientific guidance for soil carbon regulation in wetlands. Here, we investigated the effects of water levels (high and low water level) and vegetation types (Triarrhena lutarioriparia and Polygonum hydropiper) on soil organic carbon and its components in Poyang Lake wetland. We analyzed the relationships between soil physicochemical properties and soil organic carbon components. Results showed that heavy fraction organic carbon was the main component of soil organic carbon, accounting for more than 70% of the total. Water level had significantly stronger effects on soil organic carbon components than the vegetation type. Soil organic carbon, heavy fraction organic carbon, particulate organic, soluble organic carbon and microbial biomass carbon of P. hydropiper community in high water level were 109.2%, 115.5%, 175.8%, 239.4%, and 61.7% higher than those in low water level, respectively. Soil pH was significantly negatively correlated with soil total carbon, heavy fraction organic carbon, and particulate organic carbon. Soil water content and total nitrogen content were significantly positively correlated with organic carbon components. Therefore, increasing water level is beneficial to soil carbon accumulation in wetlands.

Key words: Poyang Lake wetland, organic carbon component, water level, plant community.