Studies On Soil Microbial Community Characteristics And Their Influencing Factors Under Different Land-use Patterns In The Xiong'an New Area

Soil is the foundation of ecosystem function.Soil microbiomes regulate almost all ecological processes and play an irreplaceable role in maintaining ecosystem function and stability.With the continuous development of high-throughput sequencing technology(HTS)and bioinformatics analysis methods,the study of soil microbiomes has become a current international ecological research hotspot.Existing studies have shown that the community characteristics of soil microbiomes vary significantly among different land-use types,especially different plant types.However,the research on the soil microbial community response to landuse change is not deep enough,and the relationship between soil microbiomes and the functional genes cycle of carbon,nitrogen,and phosphorous is still unclear.The Xiong'an New Area adheres to the concept of ecological priority and green development.Since its establishment on April 1st,2017,it has been in the stage of large-scale construction.Land uses have changed rapidly,providing an ideal platform for studying soil microbial community characteristics and their influencing factors in different land-use patterns.Therefore,the comprehensive use of soil physical and chemical properties,soil enzymatic method,soil microbial high-throughput sequencing and high-throughput q PCR(HT-q PCR)of functional genes,combined with the network analysis and community assembly theory,we comprehensively and in-depth assessed soil microbial community characteristics under different land-use patterns including plant species in the Xiong'an New Area.Moreover,we clarified the regulation mechanisms of soil microbiomes that participated in soil ecological processes.The study will provide scientific supports for improvement of soil ecosystem function and ecological security in the New Area.1.The diversity of the microbial compositions of the root-zone soil(the rhizospheresurrounding soil)and root endosphere(all inner root tissues)of Pinus tabulaeformis Carr.and Ginkgo biloba L.were evaluated in the Xiong'an New Area using soil physical and chemical properties,and HTS technologies;the influence of the soil edaphic parameters was also messured on microbial community compositions.Our results showed that the ?-diversities of the root endosphere were remarkably lower than those of the root-zone soil,but the variation in the endosphere microbial community structure was higher than that of the root-zone soil.Spearman correlation analysis showed that the soil organic matter,total nitrogen,total phosphorus,total potassium,the ratio of carbon to nitrogen,and p H significantly explained the?-diversity of the bacterial community.Variation partitioning analysis showed that plant species had a greater influence on microbial structure variations than did any other soil properties,although soil physicochemical parameters explained more variation when integrated.Together,our results suggest that both plant species and soil physicochemical parameters played a critical role in shaping the microbial community composition and variation.2.We assessed edaphic variables and soil biota compositions among five habitat types:human-made forests,crop cultivations,arid rivers,Baiyangdian(BYD)Lake,and around oil wells with typical plant species belonged to aquatic and terrestrial ecosystems with twelve experimental plots in the Xiong'an New Area by physical and chemical properties,HTS,and real-time quantitative PCR technologies.The relationship between soil biota and edaphic conditions in various land-use types was analysed.Our results showed that the abundance of bacterial and protist communities was higher than fungi,indicating fungi prefer acidic soil conditions and likely have a greater susceptibility to anthropogenic activities.Across all experimental plots,land-use types contributed the most to the ?-diversity of soil biota,followed by soil moisture.The bacterial and fungal ?-diversity of the aquatic ecosystem was higher than the terrestrial ecosystem.Diversity and richness were significantly higher in aquatic habitats than in terrestrial habitats.Functional gene annotation analysis of trophic groups predicted a relatively high frequency of functional genes from bacterial metabolism pathways(carbohydrate and amino acid);contrary to expectation,phototrophic protists,but not fungal symbionts and protistan consumers,were the dominant group at the aquatic ecosystem.Moreover,soil-microbiome relationships were more complex and more intense at crop habitats.Links between protist and fungal taxa were the highest at the petroleum-contaminated sampling sites,indicating the importance of these two soil microbiomes in polluted soil.Thus,our findings suggest that human manipulation and land-use types are crucial factors for soil biota structure and composition across our sampling sites.3.To explore the effect of land-use and ecosystem type conversions on soil microbial community structure and functional genes,and further network analysis and community assembly theory were conducted to elucidate the microbiological mechanism and driving factors of carbon-nitrogen-phosphorus cycling,we assessed edaphic variables and soil microbial community characteristics among six land-use conversions: the rice paddy into the grassland,the rice paddy into the constructed wetland,the harvested maize land into the constructed wetland,the grassland into the urban infrastructure constructure,and the wheat and maize rotation farmland using soil enzymatic method,HT-q PCR,and HTS technologies.Samples were taken from July in 2019 and 2021,respectively.Our results showed that the greatest C limitation happened after the conversion of the rice field and harvested maize into constructed wetlands.Furthermore,the greatest P limitation occurred after converting of the harvested maize into the constructed wetland,and the conversion of the grassland into the human construction.Other types of land conversions showed relatively higher N limitations.Among six land-use changes,the soil ecoenzymatic C:N activity ratio decreased significantly after the conversion of the rice field into the constructed wetland,and soil microbiomes changed from the slow-growing oligotrophic groups to fast-growing symbiotic trophic groups.The conversion of the harvested maize land into the constructed wetland contributed the most to the?-diversity of soil microbiomes.Land-use change had great impacts on the process of microbial community assembly.In archaea and protists,stochastic processes explained large proportion of community assembly variation,and the homogenous dispersal was mainly responsible for the assembly of the archaeal communities,whereas the dispersal limitation was primarily responsible for the assembly of the protistan communities.Bacterial communities were dominated by deterministic processes and influenced by homogeneous selection.Both deterministic processes and stochastic processes simultaneously played important roles in structuring fungal community assembly regardless of land conversion types.