| The Tibet Plateau,known as the world’s "third pole",is rich in biological resources and is the world’s unique alpine germplasm bank.However,in recent years,with the aggravation of climate change and the impact of human activities,the grassland ecosystem on the Tibet Plateau has significantly degenerated,and its stability and function have been seriously damaged.As the main organisms driving element cycling and material transformation,soil microorganisms are the important link between soil,plants and environment,and play an important role in the normal maintenance of ecosystem functions.It is of great significance to explore the distribution characteristics and influencing factors of soil microorganisms on the Tibet Plateau.In this study,different types of grassland(alpine meadow,alpine swamp meadow,alpine steppe and alpine desert grassland)as the research object,through field investigation and experimental analysis,with the help of amplicon sequencing technology,the distribution characteristics of bacterial and fungal communities of alpine meadow ecosystem on the Tibet plateau and its driving factors were systematically analyzed.The main results were as follows:(1)The α diversity of bacteria and fungi in alpine meadow and alpine wetland meadow was significantly higher than that in alpine desert steppe and alpine steppe.The α diversity of rare bacterial group was significantly higher than that of abundant group.The average Shannon diversity index of rare group was 1.24 times higher than that of abundant group,but there was no significant difference between abundant and rare fungal groups.There were significant differences between habitats in the βdiversity of bacteria,and the β diversity of abundant bacterial communities was greater than that of rare bacterial communities.However,there were no significant differences between habitats in the β diversity of fungi,while there were significant habitat differences between abundant and rare fungal groups.(2)The community composition of the total,abundant and rare bacterial groups tended to be consistent,and the phylum with the largest relative abundance is Chloroflexi(19.76%),followed by proteobacteria(16.26%),Bacteroidetes(9.67%)and Acidobacteria(9.29%).The abundance of Proteobacteria and Bacteroidetes in alpine meadow and alpine wetland meadow was significantly higher than that in alpine steppe and alpine desert steppe,while the abundance of Acidobacteria in alpine meadow and alpine plateau was significantly higher than that in desert grassland and alpine wetland meadow.The abundance of Ascomycota was the largest(53.85%),followed by Mortierella(14.23%)and Basidiomycota(10.08%).The abundance of Ascomycota in alpine steppe and alpine desert steppe was significantly higher than that in alpine meadow and alpine wetland meadow.The abundance of Mortierellain alpine steppe and alpine desert steppe was significantly lower than that in alpine meadow and alpine wetland meadow.(3)The diversity of rare bacteria groups was significantly correlated with longitude,annual precipitation,aridity,vegetation height,aboveground and underground plant biomass,plant richness,soil p H,soil bulk density,the content of soil total nitrogen and organic carbon.The abundance of fungi was significantly correlated with longitude,aboveground and underground biomass,the content of ammonium nitrogen and soluble organic carbon,aridity and plant height.Geographical factors contributed the most to the composition of the total,abundant and rare communities of bacteria and fungi.Altitude,underground biomass,clay and available phosphorus content had direct and significant effects on bacterial community composition,while plant height,soil ammonium nitrogen and clay content had direct effects on fungal community composition.Altogether,the microbial communities of soil bacteria and fungi in alpine grassland ecosystem of the Tibet Plateau were systematically studied in this study.The results showed that the diversity of bacteria and fungi in alpine meadow and alpine meadow wetland were higher than that in alpine steppe and alpine desert grassland,but abundant and rare groups exist obvious differences between habitats,which may closely relate to the environmental tolerance of microbial species.Geography,climate,plant and soil factors all have direct or indirect effects on microbial diversity and composition.These results can provide a scientific basis for assessing and regulating the alpine grassland ecosystem functions on the Tibet Plateau. |
