Hydrological Alteration‐Induced Vegetation Dynamics in the Poyang Lake Wetland and Their Impacts on Waterbird Conservation

ABSTRACT Poyang Lake wetland serves critical ecosystem functions such as water regulation, carbon sequestration, and biodiversity protection. However, the impoundment of the Three Gorges Dam has markedly influenced the local hydrological processes and vegetation growth in recent years. To quantify these changes, we applied 20‐year Landsat and MODIS observations to produce a synthetic normalised difference vegetation index (NDVI) product with 8‐day revisit frequency and 30‐m spatial resolution. Using this product, we depicted a comprehensive 20‐year monitoring picture of the spatiotemporal evolution of hydrological patterns and net primary productivity (NPP) in Poyang Lake. Then, the impacts of early‐water recession on hydrological patterns, vegetation NPP, and phenological characteristics were documented. Finally, we investigated the influence of hydrological alteration‐induced vegetation dynamics on waterbird habitat suitability. The results showed that 22.13% of the lake area experienced a significant increase in the annual emergence duration over 20 years, and this increasing trend was particularly prominent in autumn, with 33.37% area proportion. The annual NPP experienced a consistent increase (6.85 gC·m −2 ·yr −2 , p > 0.05) during 2000–2019. With regard to seasons, autumn NPP presented the largest increasing trend, and the increasing area accounted for 36.65% of the lake's floodplain. Early‐dropped water levels lead to an earlier start of the growing season in Carex communities in the lower lake center, resulting in a significant increase in autumn NPP (7.41 gC·m −2 ·yr −2 , p < 0.05) and high‐quality food resources in October and November. However, the shift to the earlier peak of the growing season accelerated the normal rate of vegetation senescence and caused a significant decrease in food quality when the foraging requirements peaked in December (−0.15 gC·m −2 ·yr −2 , p < 0.01) and January (−0.11 gC·m −2 ·yr −2 , p < 0.01). In addition, the combined effects of a prolonged dry season and extensive fishery may threaten the stability of the Phragmites community, thus reducing the effectiveness of biodiversity conservation in the nature reserves. These results provide a critical reference for local authorities to optimise hydrological management and biodiversity conservation in the Poyang Lake wetland.