The Response Patterns Of Soil Microbes And Multifunctionality In Dryland And Wetland Agricultural Ecosystems To Environmental Disturbances

Understanding and predicting the impact of climate change and anthropogenic disturbance on soil microorganisms and the ecosystem services they provide present a grand challenge and major opportunity.Although the influence of disturbance on soil microorganisms is well documented in natural ecosystems,its effect on soil bacterial communities in agricultural ecosystems remains poorly understood,especially across large scales.Here,we explored the response patterns of soil bacterial community to environmental change in 25 adjacent pairs of dryland(maize)and paddy(rice)agricultural ecosystems across large-scale regions throughout eastern China.Under warming,the bacterial alpha diversity in both maize and rice soils were no significant change.Bacterial beta diversity had a significant increase in maize soil.In addition,the functions of nitrogen fixation,nitrification,denitrification and organophosphorus mineralization decreased in dryland under warming.However,the functions relating to carbon,nitrogen and phosphorus cycles in paddy soil were not significantly changed.Null model analysis revealed that warming increased the proportion of stochastic assembly processes in maize soils,while the proportion was no changed in rice soils.The results showed that dry-wet cycles significantly decreased the bacterial alpha diversity in both maize and rice soils,with more effects in maize soils.Comparing with control treatments,dry-wet cycles increased bacterial beta diversity of maize soils but deceased that of rice soils.Among different sampling sites,community dissimilarity increased with mean annual temperature,indicating that the bacterial communities in agro-soils from warmer regions were more sensitive to dry-wet cycles.Except the abundance of functional gene AOB not significantly changed,other functional genes related to carbon,nitrogen and Phosphorus cycle were significantly decreased under dry-wet cycles in maize and rice soils.In addition,the resistance of functional genes and multifunctionality were higher in rice soils than maize.Null model analysis revealed that dry-wet cycles increased the proportion of stochastic assembly processes in maize soil,while an opposite trend was observed in rice soil.In maize soils,the alpha diversity significantly decreased under only P addition,and NP addition,while the alpha diversity in rice soils significantly increased under N and P addition.In addition,the beta diversity significantly increased under N,P and NP addition in maize soils,but the beta diversity of paddy soil significantly decreased under N and P addition.P and NP addition increased the interaction of bacteria of maize and rice fields,respectively.Besides,the abundance of functional genes relating to carbon cycle significantly increased in both maize and rice soils.The abundance of functional genes relating to nitrogen fixation and nitrification were significantly increased under nutrient addition in maize and rice soils,whereas the change tendency of denitrification was contrary in maize and rice soils.Integrated functional genes resistance indicated that functional genes associated with carbon,nitrogen and phosphorus cycle in paddy fields had higher resistance under nutrient addition.For bacterial community assembly,in dryland the proportion of stochastic assembly processes had a slight increase under nutrient addition.However,in paddy soil the proportion of stochastic assembly processes only increased under NP addition,separate addition of N and P decreased the proportion of stochastic processes.From the perspective of bacterial community and function,we described the effects of climate change and anthropogenic disturbance on bacterial communities and ecosystem functions in agricultural ecosystems.Compared with maize soil,we found that the bacterial community of rice soils had a higher resistance in response to disturbance.In addition,we also provided a theoretical basis for the response of microorganisms and functions of farmland ecosystem under future environmental changes.