Responses Of Soil Microbial Community In Tibetan Alpine Grassland To Warming And Altered Precipitation

Tibetan alpine grassland is a fragile ecosystem highly sensitive to climate change,which has experienced warming with the speed over global average,precipitation increase in the south and north and decrease in the central region during past decades.Climate change influenced ecosystem stability and soil carbon turnover of Tibetan alpine grassland.As the major decomposer,microbial community played a vital role in soil biogeochemical cycling.However,it remained unclear how microbial community respond to warming and altered precipitation due to complexity of soil microbiome and traditional technique limitation.Experiments were conducted in Haibei Station of Northeastern Tibet Plateau,with warming simulated by soil downward transplant and altered precipitation achieved by interception and irrigation.Combined with network biology technology,GeoChip and high-throughput sequencing were used to reveal microbial responses to warming and altered precipitation.We found that?1?Microbial communities in alpine grassland were sensitive to warming and altered precipitation.Under warming or altered precipitation condition,both microbial functional gene structure and bacterial composition changed.Nonetheless,the interactive effect of warming and altered precipitation on microbial community was distinct,indicating different effects of warming and precipitation on microbial community.?2?Microbial mediation mechanisms in alpine grassland biogeochemical cycling were distinct under warming or altered precipitation condition.Warming reduced abundances of genes mostly related to recalcitrant carbon degradation and nitrogen cycling,thus preserving soil carbon and nitrogen stocks through negative mediation mechanisms.Decreased precipitation reduced CO₂ flux by decreasing recalcitrant carbon degradation gene abundance,and increased precipitation stimulated CO₂ flux by increasing soil microbial biomass,suggesting positive microbial mediation mechanisms under altered precipitation condition.?3?Microbial network is an important method commonly used to reveal connections between microbial genes.Warming made microbial network tighter while increased precipitation made it looser,implying that microbial connections became closer under warming condition and less under increased precipitation condition.?4?Abundance of microbial functional genes in alpine grassland could provide explanations to corresponding microbe-driven processes and be incorporated into estimation method of Tibetan soil carbon flux.In warming plots,abundance of ammonification and nitrification genes all correlated significantly with N₂O flux,and in altered precipitation plots,abundance of methanogenesis gene mcrA correlated significantly positively with CH₄ flux.Furthermore,plant-microbe-soil model showed that microbial community explained at least 37%of CO₂ flux and 80%of CH₄ flux variation.Our research comprehensively explores responses of microbial communities to warming and altered precipitation,elucidates microbial mediation mechanisms of greenhouse gas variation,and provides fundamental information to improvement of model estimation on greenhouse gas flux and soil carbon stock.