Hydrological alterations induced lakeward expansion of wetland vegetation in Dongting Lake, China's second-largest lake

Dongting Lake (DTL), one of China's largest freshwater lakes and a critical wetland ecosystem, has shrunk rapidly due to both natural and human factors. This study presents one of the longest continuous analyses of wetland vegetation dynamics from 1989 to 2023 by combining long-term hydrological data with high-resolution remote sensing imagery, explicitly examining the impacts of hydrological alterations before and after the construction of the Three Gorges Dam (TGD). Results revealed that the vegetation area of DTL increased at a rate of 5.08 km²/yr, with regional rates of 1.88 km²/yr (East), 2.54 km²/yr (South), and 1.46 km²/yr (West), advancing lakeward at average rates of 27.56 ± 27.03 m/yr (East), 13.74 ± 14.45 m/yr (South), and 22.45 ± 20.67 m/yr (West), corresponding with water retreat and a downward shift of vegetation zones. Hydrological alterations caused by the TGD, including lower water levels (∼0.6 m) and longer dry seasons (35 days), strongly shaped wetland vegetation dynamics, with East DTL mainly responding to water level decline and South and West DTL being more sensitive to dry season duration. Sediment input supported vegetation expansion, and vegetation-sediment feedback accelerated wetland evolution by trapping sediments and raising floodplain elevation. Local reclamation and sand mining resulted in a substantial wetland loss of 117.7 km². This study provides a comprehensive understanding of the coupled effects of hydrological drivers and ecological feedback on wetland evolution, offering critical insights for the sustainable management and restoration of lake ecosystems.