Abstract: Floodplain wetlands have a signifcant capacity for carbon sequestration but are vulnerable to land use changes. Poplars are extensively planted in wetlands due to the increasing demand for wood products and bioenergy. Although the large biomass of poplar may increase the carbon stock in wetlands, their high transpiration rates may reduce soil moisture, thereby improving the aeration and facilitating the oxidation of organic materials. Therefore, the impact of poplars on wetland carbon stock remains uncertain and unexplored. Here, we investigated the effects of poplar plantations on biomass carbon stock (BCS) and soil organic carbon (SOC) stock in Dongting Lake wetlands, China, using native Miscanthus lutarioriparius vegetation as a control. Our results indicated that the BCS of middle-aged and near-mature poplar plantations (36.47–81.34 t ha⁻¹) was higher than that of M. lutarioriparius (8.31 t ha⁻¹), and it increased with stand age. The SOC stock within the 0–60 cm depth in young, middle-aged, and near-mature poplar plantations (130.32–152.58 t ha⁻¹) were higher than those in M. lutarioriparius (70.48 t ha⁻¹), but they did not increase with stand age. The BCS was positively associated with soil bulk density, while SOC stock was negatively associated with soil sand content. Overall, our fndings indicate that poplar plantations increase carbon stock in the Dongting Lake wetlands. Nevertheless, the longterm effect of poplar plantation on carbon sequestration in foodplain wetlands should be further investigated.

Key words: carbon storage, soil organic carbon, Populus deltoides, forest stand age, Dongting Lake