Impact Of The Reservoirs On Biodiversity In The Longyangxia To Liujiaxia Reach Of The Upper Yellow River

The upper reaches of the Yellow River are important hydroelectric energy bases in the country.Currently,most of the development of water elevators has been completed,but research on the impact of water elevator development on plant diversity and aquatic biodiversity around the reservoir area is not in-depth;Moreover,the research methods for aquatic biodiversity both domestically and internationally have adopted e DNA macro barcode technology,which provides a comprehensive background check for aquatic biodiversity.However,the application of this technology in this area is relatively rare.This study is of great significance for revealing the ecosystem functions and service capabilities of the region,improving the background data of biodiversity,providing a theoretical basis for biodiversity conservation,maintaining the welfare of human ecosystems,constructing an independent gene bank in the Yellow River Basin,and carrying out follow-up large-scale river basin biodiversity investigation,ecological engineering and vegetation restoration.In this paper,the terrestrial vegetation diversity of 31 plots around Longyangxia Reservoir,Lijiaxia Reservoir,Gongboxia Reservoir and Liujiaxia Reservoir in the Longyangxia-Lanzhou section of the upper reaches of the Yellow River was investigated,and aquatic biodiversity was measured from water samples at 24 points.The species composition,community structure characteristics and diversity status of land plants and aquatic organisms were analyzed,and the impact of reservoir construction on biodiversity was studied.The results of the study are as follows:(1)According to the survey of land plants,a total of 26 orders,34 families,80 genera,and103 species of plants were identified in four reservoirs.A total of 12 orders,14 families,21 genera,and 26 species of plants were recorded in seven sample plots by Liujiaxia Reservoir.A total of 14 orders,16 families,26 genera,and 31 species of plants were recorded in nine sample plots by Gongboxia Reservoir.A total of 15 orders,16 families,30 genera,and 34 species of plants were recorded in 17 sample plots by Lijiaxia Reservoir.A total of 17 orders,21 families,44 genera,and 50 species of plants were recorded in 32 sample plots by Longyangxia Reservoir.Most plants are Compositae,Gramineae,Leguminosae,Salicaceae,and Chenopodiaceae.There are 17 species of halophytic drought tolerant plants,including typical halophytes such as Tamarix chinensis Lour.,Reaumuria Linn.,elaeagnus angustifolia,Kalidium foliatum(Pall.)Moq.,and Peganum harmala L.,accounting for a large proportion of plant types,with the largest species of drought tolerant plants around the Longyangxia Reservoir.The surveyed plant communities basically belong to drought resistant types and no invasive species have been found.From Liujiaxia Reservoir to Longyangxia Reservoir along the river,drought resistant vegetation types and plant species have become more common.(2)The survey of aquatic organisms used e DNA metabarcoding,selecting 6 pairs of primers,with amplification regions of 12 S r RNA,18 S r RNA,and COI,and performed highthroughput sequencing of water samples at 24 points.A large number of species have been found in all four reservoirs,with similar dominant genera.Phytoplankton is mainly composed of Chrysophyta,Bacillariophyta,and Cryptophyta.Phytoplankton includes the Polyarthra,Strobilidium,and Arthropoda includes the Daphnia and Macrothrix.The fish species in the four reservoirs are basically the same,but there are differences in quantity.Lefua,Eleotris,Herzensteinia,Schizopygopsis,Elopichthys,and other fish species are abundant in the river channel,but few in the reservoir.Attention should also be paid to the special species Phytophthora.(3)Through comparison and analysis with previous research results,the impact of the reservoir on the species diversity of terrestrial vegetation has not changed significantly in recent decades,but the specific species richness and vegetation coverage have changed significantly.The area with greater impact is the reservoir bank fluctuation area,where there is a phenomenon of single genus,single species and single superior community.After the impoundment of the reservoir,the water environment changes from the river ecosystem to the reservoir ecosystem,and the population density and biomass of some algae plants that adapt to the still water environment significantly increase.Due to the appropriate reservoir water temperature,chrysophyceae and Bacillariophyta have become dominant species,while benthic animals and fish groups that adapt to static water environments have become dominant species.Fish species used for aquaculture in the reservoir area have also become dominant species.The impact of cascade reservoirs on biodiversity is mainly reflected in the vegetation and fish species in the reservoir bank’s subsidence zone.It is also necessary to pay attention to the vegetation restoration in the reservoir’s subsidence zone and the protection of indigenous fish species.