Effects Of Reduced Microbial Diversity On Soil Multifunctionality And Wheat Growth

Soil microbial diversity plays an important role in promoting biogeochemical cycle,decomposing organic matter,inhibiting soil borne diseases and promoting plant growth.Soil microbial diversity has been reduced due to land intensive production,nitrogen deposition and climate change,but the impact of soil microbial diversity on ecosystem function is not clear.Here,the soil microbial diversity gradient was successfully constructed by the dilution-to-extinction approach,and wheat "Yannong 999"(YN999)and "Linmai 4"(LM4)were planted in different gradient soils,and no wheat was planted as control(CK).Through the artificial indoor simulation test,this paper explores the impact of the reduction of microbial diversity on the soil multifunctionality and wheat growth,and the driving mechanism of different genotypes of wheat on microorganisms under the background of the reduction of microbial diversity.Soil and wheat samples were collected two months after wheat planting.Soil bacteria,fungi and protists were characterized by high-throughput sequencing,and the content of soil available nutrients,soil biological activity,wheat biomass and nutrient content were measured.Analyze the relationship between microbial diversity and soil multifunctionality and wheat growth,provide direct evidence for the impact of microbial diversity reduction on ecosystem,and also provide new insights into the relationship between microbial diversity and ecosystem.The main results are as follows:(1)The gradient of microbial diversity was successfully constructed by dilution-to-extinction approach,and it was found that there were significant differences in microbial community diversity and composition in different treatments,and wheat genotypes also affected the community composition.Compared with OS(original soil),the Richness index and Shannon index of soil bacteria,fungi and protists decreased significantly in sterilization treatment.According to the Beta diversity analysis,the response to sterilization treatment was bacteria > fungi > protists.With the increase of dilution gradient,the relative abundance of bacterial Bacteroidota,Verrucomicrobiota,Proteobacteria and fungal Ascomycota increased gradually.Through network analysis,found that with the increase of dilution gradient,the number of nodes,edges,average degree and average weighting degree of microbial community gradually decrease,and the microbial community tends to be simplified.In the low microbial diversity treatment of YN999,the number of keystone species and the proportion of protists in keystone species increase.And the relationship between microbial communities in the soil environment was closer,and protists community gradually occupy the dominant position.(2)In YN999,the diversity of bacteria and fungi was significantly negatively correlated with the soil available nutrients multifunctional index,and the diversity of protists was significantly negatively correlated with the biological activity multifunctional index.In LM4,the diversity of microorganisms(including bacteria,fungi and protists)was significantly negatively correlated with the soil available nutrients multifunctional index and positively correlated with the biological activity multifunctional.In CK,the relationship between microbial diversity and soil available nutrient multifunctional and biological activity multifunctional index were not significant.Microbial taxa closely related to the soil multifunctional were selected at the genus level.In YN999,protists Aphanomyces and Deasonia,bacteria Aquicella and Armatimonadales and fungus Conioscypha were closely related to soil available nutrients and biological activity multifunctionality.In LM4,bacteria Rhodoplanes and Nitrosopira were significantly negatively correlated with soil available nutrient multifunctionality.Bacteria Pantoea,bryobacter and fungi Talaromyces had significant effects on soil biological activity multifunctionality.In CK,the fungus solicoccozyma was significantly negatively correlated with the soil available nutrients multifunctionality,and the fungus Fusarium was significantly positively correlated with the soil biological activity multifunctionality.(3)Microbial diversity was negatively correlated with wheat biomass and nutrient content.The microbial taxa closely related to wheat growth were screened: in YN999,protists Aphanomyces and Deasonia,bacteria Candidatus udaeobacter and Rhodoplanes were closely related to wheat biomass and nutrient content.In LM4,bacteria Rhodococcus,fungus Trichoderma and protists Chlorosarcinopsis were closely related to wheat biomass;bacteria edaphobaculum and protists Sandona mainly affect the nutrient content of wheat.(4)Compared with LM4,the biomass and nutrient content of resistant variety YN999 responded more strongly to the decrease of soil microbial diversity,especially the decrease of protists diversity.Through linear regression analysis,it was found that compared with LM4,YN999 biomass and nutrient content had more significant correlation with microbial diversity.In YN999,protists,a microbial group closely related to wheat biomass and nutrient content,occupied an important position,while bacteria and fungi played a key role in LM4.Comprehensive calculation showed that the relative impact value of protists diversity on wheat growth was higher in YN999,while the relative impact value of fungal diversity on wheat growth was the highest in LM4.