Microbial Characteristics Of Loess-paleosol And Its Response To Climate Change

The Loess-paleosol sequence is a good carrier to record the changes of Quaternary climate and environment,and soil microorganisms can well reflect the changes of soil environment.Therefore,clarifying the changes of soil microbial community in loess paleosol sequence can provide new ideas and new indicators for the study of Quaternary paleoclimate,and provide a basis for the study of how microbial community adapts to climate change on a long-term scale.Taking the loess paleosol sequences in four different geographical locations of the Loess Plateau as the research object,this paper investigates the soil properties,paleoclimate substitution indicators,the distribution characteristics and influencing factors of microbial community abundance,diversity and structural composition on the profile,looks for the key species driving the change of microbial community,and explores the relationship between paleoclimate and soil microbial community.The main conclusions are as follows:(1)The fundamental reason for the change of soil properties in loess paleosol is the alternation of dry and cold,warm and wet climate in the process of soil development.The difference of geographical location leads to the different types and intensity of monsoon influence in different soil forming periods of different profiles,and the great difference of soil properties.(2)The soil bacterial communities of the four profiles were significantly different in the loess paleosol alternation,and Proteobacteria and Actinobacteria were the dominant bacteria.The bacterial abundance is Shimao village > Potou village > Jiuzhoutai > Renjiapo.The driving factors affecting bacterial abundance,diversity and community composition were different in different profiles.Some soil properties had no significant effect on bacterial diversity,but changed bacterial characteristics by affecting the composition of the whole community.The functions of key species change from south to north.Due to the differences of soil properties,the key species with corresponding physiological characteristics and environmental tolerance were selected in the loess profiles of different geographical locations,and finally formed a unique network structure.(3)The soil fungal communities of the four profiles had little difference in the loess and paleosol alternation,and Ascomycota,Basidiomycota and Mortierellomycota accounted for more than 80% of the total sequence.Ascomycota maintain their stability in loess paleosol by the joint action of Sordariomycetes,Dothideomycetes and Eurotiomycetes.The abundance of fungi in loess layer is higher than that in paleosol.p H and organic carbon are the key driving factors affecting the composition of fungal community.The network structure of fungal community may be related to soil texture.Different layers of soil drive the change of fungal community by affecting key species.(4)The difference of bacterial network actually reflects the difference of paleoclimate.Under the same climate background,the difference of bacterial community reflects the environmental difference of different geographical locations.Paleoclimate promotes the change of microbial communities by affecting environmental variables and ecosystem characteristics.Some paleoclimate alternative indicators can not only have an indirect impact on microbial communities,but also directly change the characteristics of microbial communities.However,the degree of impact is significantly less than the significance of paleoclimate,which further confirms that paleoclimate plays a major role in the activities of loess paleosol sequence microorganisms.The impact of paleoclimate on microorganisms is mainly reflected in the promotion of microbial communities to meet their nutritional needs by acquiring fixed limiting elements and releasing excess supply elements under nutritional constraints,and the adaptation mechanism.Moreover,bacterial communities are more vulnerable to the impact of soil properties than fungal communities.