Characterization Of Nutrient Elements And Bacterial Community Structure In Rhizosphere Soils Of Dominant Plants In Phosphorus-enriched Soils In Lake Dian Basin

There are a lot of phosphorus-enriched regions in Lake Dian basin.In the rainy season,large amounts of nutrient elements with phosphorus are lost in runoffs,causing a serious threat to the surrounding water environment and eutrophication in Lake Dian.Previous researches about phosphorus-enriched soils considered that vegetation restoration economical and effective way and focused on key role of vegetation in nitrogen,phosphorus and other nutrient output.But a sustainable ecosystem not only required vegetation coverage,but also need to restore quality and function of soils.On the one hand,vegetation can reduce the loss of nutrients in the soil,on the other hand,microbes involved in the transformation of nutrients in the soil,thereby promoting the plant's nutrients fixation.In this study,the rhizospheric soils of dominant plants in phosphorus-enriched area were sampled,and soil physical and chemical properties were measured.Meanwhile,the bacterial community structure of the soils were analyzed by high throughput Illumina Micseq sequencing technology.At the same time,we analyzed the relationship between the soil nutrients characteristics and bacterial community structure based on rhizospheric soil of different plants and different levels of phosphorus of the same plant.Finally the relationships among plant-nutrient-microbe were explored in this thesis.Major results of this research are:(1)Physicochemical analysis of rhizospheric and non-rhizospheric soil samples of different plants in phosphorus-enriched area showed that carbon(C),nitrogen(N),phosphorus(P)in the rhizospheric soils present more than non-rhizospheric soils and there is obviously rhizospheric effect.Soil organic matter(SOM),total nitrogen(TN),alkali-hydrolyzable nitrogen(A:N),total phosphorus(TP),quickly available phosphorus(QAP)in the soil samples are mainly Pinus yunnanensis>Erianthus rufipilus,Coriaria nepalensis>grassplot.High-through sequencing analysis showed that rhizosphere soil of Pinus yunnanensis has smallest richness and diversity index among different plants in dry season and rainy season.The composition of bacterial taxonomy are dominated by Proteobacteria,Acidobacteria,Verrucomicrobia Planctomycetes,Firmicutes.Venn showed that bacterial OTUs in rhizospheric soils are more than non-rhizosphere.So bacterial communities have rhizospheric effect.(2)The nutrient contents in different levels of phosphorus sampling area Erianthus rufipilus rhizospheric and non-rhizospheric soils,The content of carbon(C)and nitrogen(N)are middle P,low P>high P.The nutrient contents(C,N,P)in the rhizospheric soils present more than non-rhizospheric soils.By high-throughput sequencing analysis,in dry season,rhizospheric soil of Erianthus rufipilus in middle P sampling area has lowest richness and diversity index.In rainy season,rhizosphere soil of Erianthus rufipilus in high P sampling area has lowest richness and diversity index.The composition of bacterial taxonomy are dominated by Proteobacteria,Acidobacteria,Verrucomicrobia and Planctomycetes.Venn showed that bacterial OTUs in rhizosphere soils of middle P sampling area are more than non-rhizosphere.Low P and high P sampling area have lower rhizospheric effect.(3)Compared with physical and chemical properties and bacterial community structure of soil samples between dry season and rainy season,in general,the rhizosphere enrichment ratio of nutrient elements and bacterial community in soil samples in rainy season are lower than dry season,the rhizospheric effect of rainy season is lower than the dry season.(4)The Physical and chemical properties of and bacterial community diversity index correlation analysis in soil samples showed that in most of the soil samples,bacterial community indexes have significant negative correlation with soil organic matter(SOM),nitrogen(N),phosphorus(P)in soils,but positive correlation with nitrogen/phosphorus(N/P).RDA analysis showed bacteria community structure among rhizospheric soil samples of different plants in dry season are mainly influenced by temperature and soil water content.In the rainy season,bacteria community structure among rhizospheric soil samples of different plants are mainly influenced by soil organic matter and total nitrogen.