Study On The Influence Of Water Level Change On Seed Bank And Aboveground Vegetation Of Three Sub-Lakes In Poyang Lake

Known as the kidney of the earth,the wetland is one of the most abundant types of ecosystems and the largest productive ecosystem with the largest primary productivity on the planet.Wetland vegetation is its main producer.Wetland seed bank plays an important role in the establishment,succession and restoration of wetland vegetation.Its response strategy and response mechanism to water level changes is a hot issue to be analyzed in the field of ecology.Wetland seed banks have different response strategies and response mechanisms to water level changes,thus forming different types of vegetation communities.Studying the dynamic changes of wetland seed bank and aboveground vegetation can provide insight into the possible succession process of Poyang Lake wetland community,and help to answer the hydrological change process,ecological function and structure of Poyang Lake and provide scientific basis for its protection.In this study,Poyang Lake with high water level variation was selected as the research object.The soil seed bank and aboveground vegetation were studied in the three sub-lakes of Wuhu,Dahuchi and Xianghu.The results are as follows:(1)This study found that the seed banks of the three sub-lakes of Poyang Lake accumulate 24 species,belonging to 13 families and 21 genera.Among them,Gramineae and Polygonaceae have the most species,followed by Cyperaceae.Mainly perennial plants and wet plants,the density of soil seed bank is 10190±472.3 grains/m~2,and the dominant species are Carex cinerascens,Heleocharis valleculosa,Vallisneria natans,Najas minor.From the spatial distribution pattern,it can be found that the density of the soil seed bank gradually decreases with the deepening of the soil depth,and also changes regularly along the elevation.It can be found that the vertical distribution and horizontal distribution of the soil seed bank are obvious.(2)In the investigation of the above-ground land,21 species of vegetation on the ground of the three sub-lakes of Poyang Lake were counted,belonging to 14 families and 20 genera.Among them,Gramineae,Polygonaceae,and Asteraceae are the most.Among the 21 germinated plants,there are at least 10 species of germination plants in Wuhu Lake,14 species in the Great Lakes,and 13 species in the germination of the lake.The composition of the plants in the three sub-lakes is similar,and the coincidence degree is similar.high.The ecological type of aboveground vegetation is mainly wet plants,and the life style is mostly annual herbaceous plants.The biomass is mainly perennial herbaceous plants,and the dominant species are C cinerascens and H valleculosa?(3)The similarity of species composition between seed bank and aboveground vegetation is low,and the species that are germinated in seed bank are not found in aboveground vegetation survey.The change of hydrological conditions directly affects the spatial distribution and scale of wetland plant communities,that is,the hydrological rhythm is the main reason for the formation of clusters of soil seed banks and bud banks.(4)Under the interannual variation of water level,the types and quantities of seed banks have decreased significantly in 2017 compared with 2008,and the types and quantity of aboveground vegetation have also shown the same downward trend.The dominant species of aboveground plants changed significantly,and the ash-grass had gradually succeeded to become the dominant species of bare wetland in the dry season of Poyang Lake,which had certain effects on other plants.From the species diversity,the three sub-lakes of Poyang Lake showed vegetation.Signs of species degradation.