Study On Characteristics And Driving Factors Of Soil Microbial Community In Subalpine Meadows Of Luya Mountain

Soil microorganisms participate in the material cycle and energy flow of soil ecosystems,and play a crucial role in the biogeochemical cycle,maintaining the stability of ecosystem structures and functions.Subalpine meadows ecosystem,an important type of meadows ecosystem,has ecological service functions such as climate regulation,windbreak and sand fixation,water conservation and biodiversity maintenance.Many studies showed that soil physicochemical properties had certain heterogeneity with soil depth gradient,but there were still relatively few studies on soil microbial community characteristics,driving factors and assembly mechanisms in subalpine meadows ecosystems with different depth.In this study,soil samples were collected from the subalpine meadows of Luya Mountain along the soil profile at five depth gradients,that was humus layer(C0),0-10 cm(C1),10-20 cm(C2),20-40 cm(C3),and 40-80 cm(C4).We analyzed the composition,structure,diversity,and function of soil microbial communities at different depths in the soil profile with Illumina Mi Seq high throughput sequencing technology.We also preliminarily explored the assembly mechanisms of soil microbial communities at different depths.The main research results are as follows:(1)There were significant differences in soil physical and chemical properties at different depths of the subalpine meadows in Luya Mountain.Soil nutrient content and water content significantly decreased as the increase of soil depth,while there was no significant difference in soil enzyme activity at different depths.(2)The dominant soil bacteria were Chloroflexi,Actinobacteriota,Acidobacteria and Proteobacteria,while the dominant soil fungi were Ascomycota and Basidiomycota.There were significant differences in soil bacterial community structure(R~2=0.6408,P=0.001)and soil fungal community structure(R~2=0.3975,P=0.002)among different soil depths,and soil microbial richness and diversity significantly decreased with soil depth(0-80 cm).(3)The main factors affecting the bacterial community were soil water content,total phosphorus,nitrate nitrogen and ammonium nitrogen contents at each soil depth.The key driving factors affecting the soil fungal community were soil water content,p H,ammonium nitrogen,total phosphorus content,neutral phosphatase and polyphenol oxidase.Firmicutes,Proteobacteria and Bacteroidota were marked positive correlated with SWC.There was a significant positive correlation between Gemmatimonadetes and p H,and a very significant positive correlation between Chloroflexi and p H.Basidiobolomycota,Basidiomycota and Blastocladiomycota were marked positive correlated with TC and TS,and Basidiomycota and Blastocladiomycota were marked positive correlated with TN.(4)Tax4Fun functional prediction analysis showed that the relative abundances of carbohydrate metabolism and nucleotide metabolism were higher in 0-10 cm soil layer(C1),while the relative abundances of membrane transport,xenobiotics biodegradation and metabolism,cell motility,energy metabolism,and cell growth and death were higher in 40-80 cm soil layer(C4).FUNGuild analysis showed that ectomycorrhizal were the dominant functional group in the upper soil layer(humus layer,0-10 cm layer),and their relative abundance gradually decreased with the soil depth gradient.(5)Co-occurrence network analysis showed that the bacterial and fungal communities in the surface soil were more closely connected.The bacterial and fungal communities in the deep soil had a higher degree of functional differentiation and stronger anti-interference ability,and coexistence was dominant among soil bacterial and fungal communities in the soil.The key soil bacteria were the Thermoleophilia and Acidimicrobiia of Actinobacteriota,and the Methylomirabilia of the methylcreatinobacteria.The key soil fungi were Sordariomycetes and Dothideomycetes of Ascomycoetes,and Actinobacteriota in topsoil and Ascomycota in deep soil had potentially important roles in maintaining the structure and function of bacterial community.(6)The soil bacterial and fungal communities at different depths in subalpine meadows were dominated by random processes.The soil bacterial community was mainly limited by diffusion in the humus layer and 0-20 cm soil.The soil bacterial community in the middle layer(20-40 cm)was mainly controlled by drift.The soil bacterial community in the deep soil(40-80 cm)was mainly driven by homogeneous diffusion.The soil fungal community was mainly confined to diffusion in the humus layer and the surface layer(0-10 cm)soil,but mainly to drift in other soil layers(10-80 cm).The results of this study could provide data supports for the development and utilization of microbial resources at different soil depths in the subalpine meadows ecosystem.