Study On Mechanism Of Microbial-Driven Nitrogen Migration And Transformation Based On Watershed Water Cycle

The basin ecosystem is a complex large system composed of various subsystems of the basin water cycle process.In the context of climate change,the flux of water cycle elements in the basin ecosystem has undergone profound changes,affecting the environmental factors of the ecosystem.Microorganisms,as the only species in the ecosystem that crosses producers,consumers and restorers and achieve close physical and energy exchange with environmental factors,are important drivers of environmental elemental circulation in the basin and sensitive to climate change.The Qinghai Lake Basin is a typical plateau salt lake basin on the Qinghai-Tibet Plateau.It is located in the transition zone between the arid region of northwest China,the eastern monsoon region and the Qinghai-Tibet Plateau.The basin ecosystem is fragile and sensitive,and its ecological importance is outstanding.In recent years,the Qinghai Lake Basin has a trend of warm and humidification.The water cycle flux and associated environmental factor fluxes in the basin ecosystem have changed.The Qinghai Lake Basin is a phosphorus-poor lake.Therefore,the migration and transformation of nitrogen directly affects the basin.The degree of nutrition.As the main driving factor of element migration and transformation,the distribution pattern of microbial community structure and functional genes interacts with environmental factors,thus affecting the development direction of river basin ecosystems.The research on microbial-driven nitrogen migration and transformation mechanism based on watershed water cycle is a micro-foundation for realizing the benign development of river basin ecosystem and ensuring the normal function of watershed ecological function.It also provides scientific evidence,quantitative tools and solutions for watershed ecosystem conservation and response to global climate change.The main conclusions are as follows:(1)Under the background of climate change,the meteorological elements in the Qinghai Lake Basin are warm and humid,and the runoff is increasing.The inorganic environmental factors in the associated process also show diverse changes.The annual mean rate of change of temperature and precipitation and the annual rate of change of meteorological stations around the Qinghai Lake Basin are quite different and have strong anisotropy.The temperature and precipitation in the basin are in a“warm and humid”trend.The annual temperature tendency rate is 0.356°C/10a,and the temperature increase rate from high to low is winter>autumn>summer>spring,and winter has replaced spring as the season with the highest temperature rise.The most significant increase in the 2010 s,the"warm winter"pattern has been formed.Throughout the year,the growth rate of precipitation from high to low is summer>spring>winter,and the decline is in autumn.Precipitation in the flood season accounted for 94.2%of the total precipitation in the whole year,and contributed greatly in spring and summer.Runoff increased with the increase of temperature and precipitation,and the runoff was concentrated during the flood season,accounting for 84.5%of the annual runoff,of which 57.1 m~3/s in July;the largest increase in 2010s,and a significant contribution in summer and autumn;but the spring showed a downward trend.The inorganic environmental factors involved in the water cycle are diverse.The organic matter content of the slope soil gradually decreased,especially in the high altitude area,which was significantly higher than that in the low altitude area.The Qinghai Lake is surrounded by lakes and lakes.In terms of space,the water quality of lakes and rivers is better than that of surface II water environment standards.The pH value and NH3-N index of lake water are significantly higher than that of river water monitoring points.Permanganate index Slightly lower than the river water monitoring point,the dissolved oxygen is not much different.The permanganate index of Shaliu River is higher than that of other rivers,and the Buha River has the best water quality.(2)Revealed the spatial pattern of microbial communities in the Qinghai Lake basin,and analyzed the consistency and difference of distribution patterns from the geological genesis of the basin and the geophysical and chemical biological effects.From the geological genesis of the Qinghai Lake Basin,the six sedimentary systems of the rivers into the lake were sorted out.Through in-situ observation experiments,the spatial characteristics of multi-element in the estuary and lake waters of Qinghai Lake were analyzed,and four groups were divided into main lake group,satellite lake group,lake tributary group and inverted river group.The similarities and anisotropies of elemental sources in different groups of water bodies are explained from the aspects of watershed geological genesis and geophysical and chemical biological effects.Taking the Buha River Basin as the core,the spatial pattern of microbial communities in the basin is analyzed from the slopes,rivers and lakes in the process of water circulation and production.The proteobacteria of the deformed bacteria is the horizontal advantage of the land and waters of the Qinghai Lake Basin.The genus Pseudomonas sp.is a dominant genus.In the terrestrial soil,the Shannon-wiener diversity index of the lower reaches of the river is significantly higher than that of the upper high altitude.In the river waters,the relative abundance of microbial communities has strong consistency.Proteobacteria and Cyanobacteria are the most dominant species in river waters.The Heima River has a richer bacterial lineage than the Buha River.Proteus is the most important species in lake waters,with a relative abundance of over 40%.In the lagoon,the relative abundance of dominant species is highly consistent,followed by?-Proteobacteria,Bacteroidetes,Cyanobacteria,Verrucomicrobia and Actinobacteria,but the abundance is slightly different.In freshwater lakes,the relative abundance of microorganisms varies widely.(3)According to the hydrological cycle mechanism,the key factors are screened.Based on the distributed hydrological model,the interaction mechanism between microbial community and environmental factors and the response law to hydrological processes are explained.According to the hydrological cycle mechanism,the soil organic matter on the slope surface,the snow-melting runoff in the river section,the proportion of the runoff in the river section,and the salinity of the lake water are the key factors to characterize the water cycle process,and the other water environment factors are related to the analysis of microorganisms and categories.The proportion of snowmelt runoff in the river section is provided by the distributed WEP model-based distributed hydrological model of the Buha River Basin in Qinghai Lake.The model can well describe the hydrological cycle of the basin.The results showed that in the terrestrial slope ecosystem,the microbial genus such as Arthrobacter,Pseudomonas,Bacillus,Flavobacterium,Microbacterium,and Glacier was compared,only Microbacterium and soil.There was a significant negative correlation between organic matter content,and other species were not significantly correlated with soil organic matter content.Among river ecosystems,pH,conductivity,total nitrogen,nitrate nitrogen,dissolved organic carbon,etc.are the main factors affecting microbial OTU;the most significant indicators for microbial categories are high to low.Height,snowmelt runoff ratio,conductivity.The altitude altitude was significantly positively correlated with Cyanobacteria,and negatively correlated with Proteobacteria and Thermi.The ratio of snowmelt runoff Dp was positively correlated with acid bacillus and negatively correlated with Bacteroides.Conductivity was positively correlated with thick-walled bacteria and negatively correlated with actinomycetes.In the lake ecosystem,salinity,conductivity,TN,NO3,NH4 and DOC,these indicators strongly affect the microbes in the lake water.Acid bacillus,actinomycetes,thick-walled bacteria and Thermi have significant correlations with these indicators,while Bacteroides,cyanobacteria,Proteus,mites,no-wall bacteria and water cycle and water environment factors No significant correlation.(4)Contrasting and analyzing the contribution rate of six process genes in nitrogen and nitrogen metabolism in river and lake ecosystems;constructing a model of microbial-driven nitrogen migration and transformation based on distributed hydrological model,and predicting future nitrogen in Buha River Basin of Qinghai Lake And the evolutionary trend of microbial communities.The functional genes and relative abundance of microbial metabolism in water were identified.The six processes of nitrogen transformation were focused on the quantitative analysis of the relative abundance of nitrogen-transformed functional genes in rivers and lakes,and the contribution to nitrogen transformation was determined.The metabolic genes of river water are higher than that of lake water.The relative abundance of nitrogen metabolism in river water is from high to low,followed by dissimilatory nitrate reduction>assimilation of nitrate reduction>denitrification>nitrogen fixation>nitrification>anaerobic ammonium oxidation;nitrogen metabolism in lake water The order of relative abundance from high to low is basically the same as that of river water,followed by assimilation of nitrate reduction>dissimilatory nitrate reduction>denitrification>nitrogen fixation>nitrification>anaerobic ammonium oxidation.A model of microbial-driven nitrogen migration and transformation based on distributed hydrological model was constructed.The coupling of soil erosion equation and river one-dimensional water quality model was used to focus on the identified nitrogen metabolism process,using Mono equation and first-order reaction kinetic equation.The model was improved to quantitatively describe the mechanism of microbial and nitrogen conversion,and to provide quantitative tools for quantitative assessment of microbial migration and transformation.