The Mechanism Of Long-term Simulated Warming Affecting Soil Microbial Communities And Ecosystem Multifunctionality

Soil microbial community plays a key role in the biogeochemical cycle and the primary productivity,thus constituting the life support system of the biosphere.In the context of global warming,temperature increasing and its associated changes will regulate biogeochemical cycles by affecting the composition and functions of microbial communities,thus exerting profound impacts on the structure,function and sustainable development of ecosystems.However,our understanding of the response of soil microbes and their dynamic trends in plateau ecosystems in the context of long-term climate warming is still limited.In this study,we focused on the typical ecosystems(plateau meadow and shrub)in Qinghai-Tibetan Plateau.Based on long-term field simulated warming experiment,we analyzed the effects of climate warming on soil microbial diversity,community composition,interaction,function and community dynamic changes.Our study explored the change of ecosystem multifunctionality under climate warming,clarified the relationship between ecosystem multifunctionality and soil microbial community and systematically revealed the biological maintaining mechanisms of ecosystem function.The main results are as follows:1)Differences in the characteristics of above-ground vegetation communities lead to differential responses of microbial community to warming in different ecosystems.Elevated temperature significantly changed soil microbial community structure in the two typical ecosystems and decreased microbial diversity in meadow.Soil microbial interactions differed in response to climate warming in different ecosystems.Warming made the soil microbial co-occurrence network tighter with the more links in shrub(Links of Warmed= 2478;Links of CK=2150),while made the network of meadow looser with the less links among community members(Links of Warmed= 1721;Links of CK=2254).Elevated temperature significantly increased soil microbial respiration rate in meadow(16.52 %),but had no significant effect on microbial respiration rate in shrub.Based on the path model analysis,the changed plant community characteristics under warming conditions can directly or indirectly affect the composition and interaction of microbial community through changing soil physical and chemical properties,and then regulate the response of microbial respiration rate to climate warming.2)Warming-induced selection pressure affects the succession patterns of microbial communities,which in turn leads to significant changes in their diversity and community composition.In meadow,long-term simulation of warming increases relative importance of deterministic processes in shaping community assembly,which bring with the changes of the successional direction and rate,leading to significant changes in the composition and diversity microbial community in meadow.This means that under the long-term simulated warming condition,the soil microbial community in the meadow has been converged to a state with less stochastic processes(with 46.7%,and 52.4% of the community variation explained by neutral community model of warmed and control sites,respectively)and strong adaptability in response to high temperature environment,and this will continue to be the situation.In shrubs,long-term simulation of warming increases relative importance of deterministic processes in driving community assembly(with 52.2%,and 55.6% of the community variation explained by neutral community model of warmed and control sites,respectively),which changed the direction of community succession,leading to significant changes in community composition.Different from meadow,the difference in community composition did not increase linearly with time.The dominant taxa showed lower time-dynamic stability due to the higher proportion of specialists than generalist taxa,and thus it act as a driving taxa in the process of microbial community succession.3)Microorganisms in different ecosystems have different strategies for responding to warming in terms of functional performance.Warming induced the enrichment of genes for the decompositions of easily mineralizable carbon(i.e.starch)and the genes involved in respiration,fermentation and so on in the meadow.In shrubs,relative abundance of genes involved in the decomposition of recalcitrant carbon and easily mineralizable carbon decreased or remained unchanged in response to climate warming,while the relative abundance of genes involved in organic carbon biosynthesis did not respond significantly.4)In the context of climate warming,the biological maintenance mechanisms of ecosystem multifunctionality is related to the response of the microbial community to the disturbances and their driving effect on ecosystem multifunctionality.Warming significantly decreased the ecosystem multifunctionality in plateau meadow,but there was no significant difference between the control and warming sites in shrubs.In the meadow,longterm simulated warming resulted in a significant decrease in whole community diversity by significantly reducing the diversity of dominant taxa and conditionally rare taxa.In shrubs,long-term simulated warming resulted in a significant decrease in always rare taxa diversity,which did not cause a significant decrease in the microbial diversity.The importance of different microbial taxa on the maintenance of ecosystem multifunctionality was different,and the importance broadly follow the order: bacteria > fungi,dominant taxa > conditional rare taxa > always rare taxa.Warming leads to a decrease in ecosystem multifunctionality by reducing the diversity of dominant and conditionally rare taxa of soil bacteria in meadows.These findings highlight that the differentiation in the response characteristics of soil microbial communities and their functions in different ecosystems under warming conditions is the result of the influence of above-ground vegetation communities.The study of community dynamics(succession patterns)found that the response of different ecosystem community succession patterns to warming also varied,and that the dynamic trends of microbial communities were influenced by a combination of environmental conditions.In addition,subcommunity-based studies revealed that different taxa play different roles in driving community succession and maintaining ecosystem multifunctionality,which provided new insights into the mechanisms underlying the response of microbial communities and the stability of ecosystem function in the context of climate change.