Patterns And Drives Of Rhizosphere Microbial Community Of Pinus Taiwanensis Along Elevation Gradients And Seasons In Wuyi Mountain

Rhizosphere microbial community play a crucial role in plant growth and health.However,despite the importance of rhizosphere microbial community,the combined effect and relative importance of the driving factors that influence rhizosphere microbial community remain poorly understood.Climate,plant traits and soil physical and chemical properties vary greatly over short spatial distances and elevational gradients.Seasonal variation has major direct and indirect influences on the rhizosphere microbial community due to the seasonal dynamic variation of soil temperature and humidity and the input of plant litter.In this study,Samples were collected from three forest plots of Pinus taiwanensis with altitude gradients(1200 m,1700 m,2100 m)in August and December 2020,respectively in Wuyi Mountain National Nature Reserve,Jiangxi Province.We used high-throughput sequencing to examine rhizosphere fungi and bacteria of Pinus taiwanensis at different elevations.Soil physical and chemical properties,soil microbial biomass,soil enzyme activity and fine root function traits of Pinus taiwanensis were measured to explore the patterns and drives of rhizosphere microbial community of Pinus taiwanensis along elevation gradients in Wuyi Mountain.The main results of this study are as follows:(1)For soil physicochemical properties,altitude significantly affected the physicochemical properties of the soil in the Pinus taiwanensis forest in Wuyi Mountain.The contents of total soil organic carbon,total nitrogen and total phosphorus in summer increased with the increase of altitudes.There was a significant difference in soil microbial biomass between altitudes in summer,the microbial biomass phosphorus at an altitude of 1200 m was significantly higher than that at 1700 m in winter.Soil enzyme activities decreased with increasing altitudes,but did not have statistical significance.There were significant seasonal differences in soil acid phosphatase,soluble organic carbon and water content.While there was no significant difference in microbial biomass phosphorus between seasons,soil microbial biomass carbon and nitrogen showed significant low in summer and high in winter.Soil physicochemical properties are weakly regulated by seasonal changes and more influenced by elevational gradient.(2)In terms of fine root functional traits,there was a significant effects on the main functional traits of fine roots in season and elevation.Season had a greater effect on fine root phenotypic traits,while altitude had a greater effect on fine root nutrient traits.The fine root P content of Pinus taiwanensis at 2100 m was significantly higher than that at 1200 m.While there was no significant difference in fine root carbon content along altitude gradients in winter,the fine root C content of Pinus taiwanensis in summer was significantly different at altitude gradients.The specific root length and specific root area of Pinus taiwanensis were significantly higher in summer than that in winter,but the root tissue density was larger in winter than in summer.(3)In terms of elevational and seasonal variation of rhizosphere microbial community,the most abundant fungal phyla in Pinus taiwanensis forest are Ascomycota and Basidiomycota,and the dominant bacterial phyla are Proteobacteria and Acidobacteriota.The dominant fungal phylum Basidiomycota shows a decreasing pattern with altitude,while Ascomycota shows an increasing pattern with altitude.There were significant differences in Shannon index and Simpson index of rhizosphere fungi between summer and winter,while Shannon index and Simpson diversity index of rhizosphere bacteria showed significant differences only in winter.The PCoA results showed that there were significant difference in the rhizosphere fungal and bacterial microbial community structures.However,the effect of elevational gradient on rhizosphere microbial community was greater than the seasonal change.(4)At the OTU classification level,the RDA analysis showed that the first and second axes explained 6.07% and 4.32% variation of fungal community composition,respectively,and 30.67% and 14.27% variation of bacterial community composition.Soil total nitrogen content and carbon to nitrogen ratio significantly affected the fungal community structure,and microbial carbon and nitrogen and the ratio of microbial nitrogen to phosphorus had significant effects on the structure of the rhizosphere bacterial community.The RDA analysis of fine root functional traits on rhizosphere microbial communities showed that the first and second axes of RDA explained 3.90% and 3.35%variation of fungal community composition,and 14.55% and 7.70% variation of bacterial community composition,respectively.The fine root tissue density,root carbon content and phosphorus content had significant effect on rhizosphere bacterial and fungal community structure.The specific root length,specific root area and root nitrogen content of fine root had significant effects on the rhizosphere fungal community structure,and the fine root diameter significantly affected the rhizosphere bacterial community structure.Structural equation modeling(SEM)analysis showed that the distribution pattern of rhizosphere microbial community was mainly affected by soil physicochemical properties.In summary,rhizosphere fungal and bacterial alpha diversity and community structure varied significantly along altitude,but have no difference in rhizosphere microbial alpha diversity between summer and winter.The rhizosphere bacterial and fungal communities were affected by specific soil factors and root traits,and soil physicochemical properties are key factors of variation in rhizosphere microbial community.