Abstract: The understanding of the impact of heterogeneous landforms within river wetland systems on soil organic carbon is rather limited. We conducted plant community surveys and soil sample collection on four main types of micro landforms, namely the Zhuxi River bank slope, edge beach, floodplain, and heart beach of Wannian Zhuxi National Wetland Park in Jiangxi Province. We measured soil physical and chemical properties and the contents of soil organic carbon components at depths of 0-30 cm for different micro landforms. The results showed that the average content of organic carbon (SOC) in the 0-30 cm soil of wetlands was (13.3±0.8) g·kg^-1. There were significant differences in SOC content of 0-10 cm layer between different micro landform types, with the order of floodplain>edge beach>heart beach>bank slope. There was no significant difference in SOC content of 10-30 cm layer between different micro landform types. The average contents of soluble organic carbon (DOC), particulate organic carbon (POC), and mineral-associated organic carbon (MAOC) in the 0-30 cm soil were (0.2±0.0), (1.9±0.1), and (9.2±0.5) g·kg^-1, respectively. The influence of micro landform types on organic carbon components in the 0-10 cm layer was more significant than that in the 10-30 cm layer. The DOC, POC, and MAOC contents in the 0-10 cm soil layer were highest in the floodplain and lowest in the bank slope. There was a significant correlation between soil organic carbon and its component content and environmental factors. Redundancy ana-lysis shows that soil available nitrogen, bulk density, and moisture were key factors regulating the variation of soil organic carbon and its component with different micro landform types in Zhuxi wetland. In summary, micro landforms affected the dynamics of organic carbon in wetland soils by shaping heterogeneous environments such as soil texture and moisture, and altering the availability of soil nutrients. The assessment of carbon sequestration function and ecological management practices in river wetlands should further consider the impact of different types of micro landforms.

Key words: micro-landform, soil organic carbon, organic carbon component, riverine wetland, national wetland park