Spatiotemporal heterogeneity of inundation pattern of floodplain lake wetlands and impact on wetland vegetation

The inundation pattern is an important ecohydrological indicator for studying floodplain lake wetlands, as it is the key factor affecting the wetland vegetation distribution patterns. Poyang Lake, the largest freshwater lake in China, is a typical floodplain lake wetland. This study presents a hydrodynamic model and vegetation survey of Poyang Lake, analyzed the spatiotemporal heterogeneity of the inundation pattern (inundation duration and depth), assessed the response patterns of wetland vegetation concerning the inundation pattern, and examined the impact of the proposed Poyang Lake Water Conservancy Hub (PLWCH) on the inundation pattern and wetland vegetation. The results revealed that the inundation pattern of Poyang Lake had significant spatial heterogeneity. Inundation pattern was found to have a significant impact on the vegetation succession. The response relationship between the distribution areas of different wetland vegetation types and inundation pattern was in accordance with the Gaussian curve, and the ecological threshold range of the Carex spp. community was the greatest. Owing to factors such as climate change and anthropogenic activities, the inundation pattern of Poyang Lake varied significantly since 2003, with the average inundation duration and average inundation depth decreasing by 15 d and 0.32 m, respectively. Consequently, the spatial distribution of wetland vegetation changed significantly, whereby the Carex spp., Polygonum criopolitanum, and Phalaris arundinacea communities extended down to the lower elevation zone. In the future, the PLWCH may result in increases in the inundation duration and depth, restrain the downward vegetation extension trend, and promote the vegetation to move to higher elevations similar to the status prior to 2003. These findings provide a detailed description of the spatiotemporal heterogeneity of the inundation pattern and the drivers of wetland vegetation distribution patterns in floodplain lake wetlands, serving as a scientific basis for conservation and restoration of these ecosystems.