Changes In Soil Microbial Community Structure And Its Seasonal Dynamics In An Alpine Grassland Under Climate Change

The Tibetan Plateau is fragile and sensitive to global climate change,and it is currently experiencing rapid climate warming and precipitation alteration.Soil microbes are an important part of ecosystems and play important roles in soil formation,litter decomposition,nutrient cycling and plant nutrient supply.However,little is known about the response of soil microbes to climate change in the Tibetan Plateau ecosystem.In addition,soil microbial community composition varies from place to place and is still in the process of seasonal dynamic changes.Soil heterogeneity of microenvironment and seasonal variation of soil temperature,moisture contents and nutrients often aggravate the uncertainty of exploring soil microbial responses to climate change.Therefore,it is necessary to study soil microbial responses to climate change at different sites and times in order to fully understand the patterns and internal regulatory mechanisms of soil microbial responses to climate change on the Tibet Plateau.Based on the above research background,this study relies on a long-term warming-by-precipitation experiment platform and a warming experiment platform along the elevation gradient established in the northeast of the Tibetan Plateau.This study took soil microbes as the research object and used high-throughput sequencing technology to comprehensively explore the response of soil microbes to warming or precipitation changes by investigating the community composition of soil microbial communities and its relationship with environmental factors including temperature and moisture.The main ecological processes driving soil microbial community assembly were finally revealed.The main results are as follows:(1)Warming significantly reduced the richness of soil bacteria,increased the complexity,stability and number of key nodes of bacterial networks,and significantly affected the relative abundance of dominant phyla.Warming had no significant effect on the ?-diversity of the fungal community,but significantly affected the ?-diversity of the fungal community,decreased the complexity and stability of the network,increased the number of key nodes in the network.Warming decreased the stochasticity of bacterial and fungal community assembly mechanisms.(2)The increase in precipitation had no significant effect on the ?-diversity of the bacterial community,but had a significant effect on ?-diversity.Precipitation alteration significantly increased the ?-diversity of the fungal community,and significantly affected the ?-diversity.The increase in precipitation increased the complexity,stability and key nodes of the bacterial network;increased the network complexity of fungi and reduced the stability and key nodes of the network.The decrease in precipitation reduced the complexity and stability of the bacterial network,increased the key nodes of the network;increased the complexity and key nodes of the fungal network,and reduced the stability.Decreased precipitation decreased the stochasticity of bacterial and fungal community assembly mechanisms,and increased precipitation increased the stochasticity.(3)The diversity and community structure of soil microorganisms differed significantly in different seasons.The patterns of the effects of warming and precipitation changes on microbial diversity were not consistent across seasons,suggesting the importance of seasonal dynamics in soil microbial responses to climate change.(4)The ? and ? diversity of soil microbial were significantly at different elevations.With the increase in altitude,the bacterial network was simpler and the modularity was higher.The fungal network was most complex at the middle elevation(3700 m)and had the highest degree of modularity.The stability of the soil microbial network was different at different elevations.The stability of the soil bacterial network was the lowest at high elevation(4000 m),and the stability of the fungal network was the highest at middle elevation.This study described the response of soil bacterial and fungal communities to warming or precipitation changes in an alpine grassland of the Tibetan Plateau,considering season and elevation.Soil temperature,moisture contents,season and elevation were important factors shaping soil bacterial and fungal communities in the alpine grassland.However,there are differences between fungi and bacteria.For example,soil p H is the main environmental factor affecting bacterial communities,and the community composition of fungi is also regulated by soil ammonium and nitrate nitrogen content.