Effects Of Extreme Drought On Arbuscular Mycorrhizal Fungi Associated With Different Plant Communities In Typical Steppe Of Inner Mongolia

Global warming and precipitation variability predict that many ecosystems will likely be suffered to more frequent and intense drought in the future,which have a significant impact on the plant and microbial community of grassland ecosystem.Arbuscular mycorrhizal fungi(AMF),as a class of microorganisms that can form reciprocal symbionts with host plants,play an important role in promoting plants absorb water and nutrients and improving their stress resistance.Climate change and host plants may affect their communities.Thus,analyzing the relationship between the characteristics of AMF community and plant community and its response to drought is helpful to understand and predict the plant-AMF interaction in grassland ecosystem under the future climate change,so as to promote the healthy development of grassland ecosystem.However,at present,the taxonomic characteristics of AMF of different plant communities in typical grassland of Inner Mongolia,especially its response to extreme drought,are still unclear.Therefore,based on the extreme drought simulation test platform of maodeng pasture in xilinhot city,Inner Mongolia autonomous region,we selected three kinds of plant communities with two life type,namely,grass type I(Leymus chinensis,Stipa grandis and Agropyron cristatum),grass type II(Leymus chinensis and Stipa grandis)and shrub type(Caragana microphylla and Artemisia frigida).And then Illumina sequencing technology was used to study the diversity and community composition of AMF in plant roots and soil and preliminarily explore the response mechanism of AMF in different plant communities under extreme drought in the earlier,middle and later of grwoing stage.The main conclusions are as follows:(1)On the whole,there was no significant difference between mycorrhizal colonization under extreme drought treatment and the control group,but it under extreme drought treatment in the later growth season was significantly lower than that under other drought treatment.AMF extraradical hyphal length density of different species type was significantly different,and that of grass type II were significantly higher than grass type I and shrub type.Compared with grass type I and shrub type,AMF extraradical hyphal length density in grass type II under control treatment was significantly higher than that under grass type I and shrub type.However,after drought treatment,there was no significant difference in the density of extraradical hyphal length under three plant communities,suggesting that extreme drought may weaken the influence of different species composition on the density of extraradical hyphal length.(2)Extreme drought and plant species composition had no significant effect on the OTU richness of AMF in roots and soil,but had significant effect on the Shannon-wiener index.Extreme drought in late growing season significantly increased the Shannon-wiener index of soil AMF.The Shannon-wiener index of root AMF of shrub type was significantly lower than that of other two types,and Shannon-wiener index of soil AMF in grass type I was significantly higher than that of other two types.(3)144 OTU was detected from the root and soil samples,belonging to 5 families,8 genera.The dominant genus of all treatments was Glomus,but its relative abundance did not change significantly between the extreme drought and the plant communities.NMDS and the multivariate statistical method of AMF community analysis found that the difference between the extreme drought and different plant communities on root AMF community structure had no significant influence.The soil AMF community structure was significantly different under different extreme drought treatments and plant communities,among which the soil AMF community structure under extreme drought treatment in the later growing season was significantly different from other treatments,and soil AMF community structure in grass type I was significantly different from grass type II and shrub type.(4)The correlation analysis between soil factors and AMF extraradical hyphal length density showed that it was significantly positively correlated with soil water content and nitrate nitrogen,and negatively correlated with soil organic carbon and C/N.In addition,we found that SOC,p H and C/N had significant effects on soil AMF community structure under different drought treatment and composition of plant species,but Mantel analysis showed no significant correlation between root and soil AMF community composition and physical and chemical properties.