The Response Of Waterbird Community To Winter Flood And Its Indication To Poyang Lake Ecosystem

Poyang Lake,the largest freshwater lake in China,is one of the most important wintering areas for waterbirds along the East Asian-Australian Flyway.In recent years,a series of ecological problems has occurred at Poyang Lake,which may lead to the change of waterbird diversity and community structure.Particularly,a severe winter flood struck Poyang Lake in the winter of 2015/2016,potentially threatened waterbird diversity.In this study,we compared waterbird richness and abundances at nine sub-lakes of Poyang Lake in the winters of 2014/2015(normal water level),2015/2016(winter flood),2016/2017(normal water level)and 2017/2018(normal water level)to explore the flood's impacts on waterbird community and its indication to Poyang Lake ecosystem.The correlation between the lake area and the number of waterbird was calculated,and the variation of the number of waterbird in different habitats was compared duiring the four wintering periods,and the results showed that:1.Totally,we recorded 57 species and 368,411 individuals.Spotted Redshank(Triga erythropus),Swan Goose(Anser cygnoides),and Bean Goose(Anser fabalis)were dominant species.Bean Goose and Swan Goose were dominant species in three wintering periods.Among the nine sub-lakes,Dahuchi the largest lake supported the most abundant waterbirds.Correlation analysis between lake area and waterbird abundance indicated that they were significantly positively correlated.2.Waterbird richness,bird diversity and evenness did not change much during the four wintering periods.Waterbird abundances declined by 1/3 in the flood year,and rebounded to pre-flood level within two years.Different foraging guilds responded differently to the flood.The abundances of invertebrate eaters and fish eaters greatly declined in the flood year,indicating that they are vulnerable to water level fluctuations.The impacts of the flood on abundances of tuber eaters,seed eaters and grass eaters were less obvious.3.The numbers of waterbirds in different habitats changed different during the four wintering periods.The numbers of waterbirds inhabiting in deep waters and grassland have changed little,while the numbers of waterbirds inhabiting the shallow waters have decreased greatly.The abundances of grass eaters increased gradually in the four wintering periods,which might be related to expansion of grassland.The abundances of tuber eaters and seed eaters declined gradually.The abundances of two endangered tuber-feeding species,Siberian Crane(Critically Endangered,Leucogeranus leucogeranus)and Swan Goose(Endangered)declined greatly in natural wetlands,with many birds moved from the natural wetlands to adjacent rice paddies and lotus ponds.These results indicate that submerged plants are declining,and the Poyang Lake wetland ecosystem is deteriorating.It is urgent to find out the main driver of the degradation of aquatic vegetation so that effective measures can be taken to recover it.