Study On The The Spatial And Temporal Variation Of Carbon And Nitrogen Driven By Soil Microorganisms In The Yellow River Delta

The environment of the Yellow River Delta is complex and rich in biodiversity,which is the most advantageous natural laboratory to study the spatiotemporal changes of carbon and nitrogen driven by soil microbes.This study selected four typical sample plots in the Yellow River Delta,including beach bare land,the S.salsa community,Ass.P.australis and S.salsa communities and Ass.P.australis and T.chinensis communities,collected soil samples of root layer 0-20 cm of four plots in four different seasons.Using 16 S rRNA high throughput sequencing technology and Biolog microplate method,the spatiotemporal dynamic changes of microbial community and carbon-nitrogen cycle by vegetation differences were mainly discussed,the relationship between microbial community composition diversity and function and carbon and nitrogen cycling was further analyzed.It provides theoretical support for the biogeochemical cycle and sustainable development of the Yellow River Delta,and has important scientific and guiding significance for improving the salinized soil in the Yellow River Delta.It is of practical significance to understand the soil quality of the Yellow River Delta and to explore the relationship between carbon and nitrogen source metabolism and microbial diversity.The results show that:(1)Analysis of soil physical and chemical indexes found that the whole quality of root soil was higher than that of other plots in mixed communities of the mixed communities of P.australis and T.chinensis,and the contents of total nitrogen,organic matter and available phosphorus was the highest in this sample.The content of available nitrogen was the highest was the highest in the community of S.salsa,and the content of available potassium,cation exchange(CEC)and pH was the highest in the bare land of beach.It can be seen that there is an interaction between plant root action,plant litter,microbial action activity and soil physicochemical properties.The growth of wetland plants is beneficial to improve the salinization of soil in the Yellow River Delta,enhance soil fertility and promote the circulation of soil carbon and nitrogen,and the soil can react to plants to make it grow better.(2)The results of microbial community structure and composition analysis showed that the composition of microbial in sample soil were significant temporal and spatial differences.In spring and winter,the diversity of soil microorganism in the mixed community of P.australis andS.salsa was the highest,while in summer and autumn,the diversity of soil microorganism in the mixed community of P.australis and T.chinensis was the highest.Microbial composition at the phylum level,the relative abundance of Actinbacteria increased in summer,and gradually decreased in autumn and winter.At the class level,the relative abundance of Actinomycetes and Acidimicrobiia also increased in summer.At the family level,the Anaerolineaceae and Gemmatimonadaceae was dominated.The dominant bacteria at the genus level mainly include Halomonas,Planctomyces and so on.(3)The analysis of the relative abundance results of functional microorganisms showed that the relative abundance of nitrogen-fixing bacteria varied greatly with the change of this season,while the relative abundance of ammonia-oxidizing bacteria(AOB),complete ammonia-oxidizing bacteria(Comammox),nitrifying bacteria(NOB)and denitrifying bacteria(DNB)in the four seasons were the highest in the mixed community plots of P.australis and T.chinensis.The results of the cluster analysis of functional gene prediction showed that the abundance of functional genes related to carbon and nitrogen changed obviously with the seasons.The abundance of functional genes was the highest in the bare land of beach in spring.In summer,the abundance of functional genes was the highest in the mixed communities of P.australis and Suaeda salsa.In autumn,the abundance of functional genes was higher in the beach bare land and the mixed communities of P.australis and S.salsa.In winter,the abundance of functional genes was the highest among the mixed communities of P.australis and S.salsa and the mixed communities of P.australis and T.chinensis.(4)The results of metabolic activity of soil microbial carbon sources showed that the activity was higher in spring and winter and lower in summer and autumn,and the metabolic activity of microbial carbon sources in soil with vegetation growth is greater than that in bare land.In spring,the carbon source metabolic activity of soil microorganisms was the highest in mixed communities of P.australis and T.chinensis.In summer and autumn,the carbon source metabolic activity gap between soil microorganisms was not obvious.While in winter,the carbon source metabolic activity of soil microorganisms in mixed communities of P.australis and S.salsa was the highest.The main carbon source types of microbial utilization in differentsoils were different,in summer,the similarity of carbon source types of soil microbial utilization between beach bare soils and mixed community of P.australis and S.salsa was the highest,while in autumn,the carbon source utilization types were the most similar between the S.salsa and the mixed communities of P.australis and T.chinensis.The results of soil ammonia oxidation rate showed that the ammonia oxidation rate was proportional to the diversity index of soil microbial community in vegetation community sample plots.The ammonia oxidation rate decreased in summer and increased in winter,and soil denitrification rate showed the same trend as the ammonia oxidation rate.(5)The correlation analysis found that the main microorganisms driving the soil carbon and nitrogen cycle in the four seasons were different.In spring,the soil microbial denitrification rate and ammonia oxidation rate were the most correlated with complete ammonia-oxidizing bacteria(Comammox)and nitrite oxidizing bacteria(NOB).In summer,Nitrospira was positively correlated with the soil ammonia oxidation rate and negatively correlated with the denitrification rate.In autumn,the nitrate dissimilation and reduction to ammonium(DNRA)acting bacteria showed a significant positive correlation with the soil ammonia oxidation rate,but negative correlation with the denitrification rate.In winter,the metabolic activity of soil carbon source was positively correlated with Janthinobacterium.