Bacterial Diversity Of Soils And Nodules In Hippophae Rhamnoides Forests And The Relationship With Soil Nutrient In Shaanxi

Hippophae rhamnoides is a perennial deciduous shrub that forms root nodulation with Frankia.The formation of symbiotic nodules between plants and soil microorganisms is an important way to increase plant nitrogen acquisition,and this symbiotic nodule also provides a stable and balanced environment for microorganism.In this experiment using high-throughput sequencing technology,the diversities of bacteria in the soil(in depth of5-20 cm)and nodule of H.rhamnoides growing in the north-central part of Shaanxi Province(from south to north,Mafang Forestry station in Yongshou County,Loess Plateau Test Station in Ansai County,Wuliwan Township in Jingbian County,and Zhuanlongwan in Yulin City),were determined and analyzed.The relationship between the relative abundance of Frankia with mean annual rainfall and main soil nutrition factors was analyzed.The result showed:1.The analysis of bacterial community characteristics in the soils of H.rhamnoides forest showed that:(1)The bacterial composition in the soils of H.rhamnoides growing in different sites was extremely rich and diverse,covering 32 phyla and 83 classes.There were26 Phyla and 66 classes in Mafang site,22 phyla and 65 classes in Ansai site,28 phyla and73 classes in Wuliwan site,30 phyla and 75 classes in Zhuanlongwan.(2)The community richness indexes(Ace index and Chao1 index)of Wuliwan and Zhuanlongwan sites were significantly higher than Mafang and Ansai sites,but there was no significant difference in the community diversity indexes(Shannon index and Simpson index)between the sites.(3)At the level of order and family,the components of bacterial with higher relative abundance in the four sites were highly similar,but their relative abundance obviously differed from the sites.(4)The relative abundances of Frankiales in the four sites were relatively low,0.44%,2.21%,1.21%,and 0.76% respectively.Among the order,the dominant family in the four sites was Geodermatophilaceae,and the dominant genus was Blastococcus.The relative abundance of Frankia in Frankiales was low,Mafang: 5.57%,Ansai: 0.78%,Wuliwan:0.41%,and Zhulongwan: 0.77% respectively,while that in bacterial community of soils only0.011%?0.007%?0.002% and 0.002% respectively.2.The analysis of bacterial community characteristics in the root nodules of H.rhamnoides forest showed that :(1)The bacterial composition in the nodules of H.rhamnoides growing in different sites was rich and diverse,covering 10 phyla and 17 classes41 orders 84 families 139 genus 214 OTUs.There were 8 phyla and 13 classes in Mafang site,8 phyla and 13 classes in Ansai site,9 phyla and 15 classes in Wuliwan site,7 phyla and12 classes in Zhuanlongwan.(2)The bacterial community richness in the root nodules of Mafang site was higher than that in other sites,but there was no significant difference in the bacterial community diversity among the four sites.(2)The dominant bacteria in the root nodules of different sites were Cyanobacteria and Actinobacteria.The relative abundance of the two phyla was as high as 98%.(3)The class Actinobacteria contained 12 orders 32 families 43 genus 70 OTUs in four sites.The genus Frankia were the dominant bacteria in the order Frankiales,the relative abundance accounted for 99% of Frankiales,while that in bacterial community of nodules 36.49%?48.00%?31.54% and 21.44% respectively.(4)The perspective of bacterial community structure of nodules in different months,the number and relative abundance of Frankiales in the growth season(especially in July)was much higher than that in the non-growth season,while the quantity and relative abundance of Cyanobacteria significantly lower in the growing season than the non-growth season.3.Correlation and PERMANOVA analysis:(1)The richness and diversity of microbial community in soil were closely related to the content of alkali-hydrolyzable nitrogen.The richness of bacterial microbial community was closely related to the content of available phosphorus,and its diversity was closely related to the annual average rainfall.(2)The difference of bacterial in soils of H.rhamnoides growing in different sites mainly depended on the content of total phosphorus and total potassium.The difference of bacterial in root nodules of H.rhamnoides growing in different sites mainly depended on the content of total potassium.(3)There was a significantly positive correlation between the relative abundance of Frankia whether in soils or nodules and alkali-hydrolyzable nitrogen,available phosphorus,available potassium with mean annual rainfall.In summary,the bacterial communities in soils of H.rhamnoides growing in different sites were extremely rich and diverse,but the relative abundance of Frankia in soils was extremely low,and there were significant differences in different sites,which mainly correlated with soil organic matter,alkali-hydrolyzable nitrogen,total phosphorus and total potassium.The nodule bacterial community was mainly composed of Frankia and Cyanobacteria,and the relative abundance of the two was significantly changed with the season.The total potassium content in the soil was closely related to the relative abundance of Frankia.Therefore,in forestry production,especially in the growing season,the creation of good soil nutrient conditions and water supply is conducive to increasing the relative abundance of Frankia in the soils and nodules of H.rhamnoides forest land,thereby theinfection of H.rhamnoides roots by Frankia can be improved,promoting the formation of symbiotic nitrogen fixation,improving the nitrogen fixation capacity of H.rhamnoides roots.