Microbial Diversity In Rhizosphere Of Four Species Of Deciduous Oak And Its Relationship With Environmental Factors

The zonal vegetation in China's warm temperate zone is a deciduous broad-leaved forest.Deciduous oak forest is one of the representative vegetation types.In the long history of human development,forests provide an important material basis for human survival and production.Due to long-term human disturbance and changes in the ecological environment,most of the deciduous oak forests are replaced by secondary forests,artificial coniferous forests and other broad-leaved forests.The restoration and reconstruction of warm-temperate forest vegetation characterized by deciduous oak forests has a long way to go.The restoration of forest vegetation involves many aspects such as theory,tree species selection,configuration mode,cultivation and management techniques,among which the tree species selection and planting technology are important.In foreign countries,there have been many studies on the diversity and function of rhizosphere microorganisms in the field of planting techniques,and there have been successful experiences in afforestation of saline-alkali lands and infertile mountainous regions.However,there was only few reports on the study of rhizosphere microbial diversity using deciduous oaks as a native species.Developing related research has theoretical and practical significance.It can provide scientific basis for vegetation restoration and sustainable use of forestsin Shandong Province and warm temperate zone.In the present study,the Laoshan Nature Reserve,which has a more concentrated and typical distribution of deciduous oak forests in Shandong Province,was used as the research area.The four common dominant species of the typical deciduous oak forests in the warm temperate zone:Quercus glandulifera Thunb.var.brevipetiolata Nakai,Q.dentata Thunb.,Q.acutissima Carruth.andQ.mongolica Fisch.ex Ledeb.were used to collect rhizosphere samples.The composition,structure,diversity and spatial distribution of microbial communities in the rhizosphere soil were analyzed.The relationship between microbial diversity in the rhizosphere and environmental factors was analyzed.The community structure and characteristics of rhizosphere soil bacteria and archaea were analyzed using 454 sequencing technology.The principal component analysis(PCA)was used to reveal the spatial distribution pattern of soil microorganisms in the rhizosphere,and the relationship between soil microbes and soil physical and chemical properties was analyzed using the redundancy analysis(RDA)method.The relationship between rhizosphere microbial diversity and major environmental factors was explored.Using the linear discriminant analysis effect size(LEfSe),we identified the populations with significantly different microbial abundances in the three altitude gradient groups,namely a statistically significant biomarker.The study obtained the following results:(1)The rhizosphere microbial diversity of four species of deciduous oaks was abundant.In the study plots,the number of valid sequences of bacteria was also much higher than that of archaea,and the number of operational operational taxonomic units(OTUs)was much higher than the number of archaea,that is,the abundance of bacteria was high.Bacterial phylum:Proteobacteria(27.94%-36.51%),Acidobacteria(25.07%-33.33%)and Actinobacteria(11.72%-18.34%)were the most abundant phyla;Archaea phylum Thraumarchaeotawas the most abundant phylum.(2)Altitude had a significant impact on microbial diversity.Principal component analysis(PCA)and redundancy analysis(RDA)results showed that soil pH and altitude played an important role in the composition of forest rhizosphere microbial communities and soil water content,organic matter,total nitrogen and total phosphorus had no significant correlation with the relative abundance of any microorganism.The number of bacterial OTUs and Chaol diversity index at lower altitude(<500 meters)was significantly higher than that at higher altitude(500-1000 meters);however,the number of OTUs and the Chao 1 diversity index of the two altitude samples had no significant difference.The LEfSe analysis of low-altitude samples,middle-altitude samples,and high-altitude samples showed that Actinobacteriand Gammaproteobacteria had high relatively abundance in low-altitude samples;Burkholderia class was relatively high in the middle-altitude sampes;Gemmatimonas(Gemmatimonadetes)was more abundant in high-altitude samples.(3)The community composition and structure of rhizosphere soil microorganisms of different deciduous oakspecies were not significantly different.Proteobacteria,Acidobacteria,and Actinobacteriawere dominant in all rhizosphere soil samples of deciduous oaks.(4)In the lineage of Proteobacteria,the relative abundance of the class Deltaproteobacteria decreased as soil pH increased.However,the relative abundance of Alphaproteobacteria,Betaproteobacteria and Gammaproteobacteria had no significant relation with soil pH.In the other lineage of Acidobacteria,the relative abundance of the class Holophagae was significantly higher in low altitude sites than that in high altitude sites.The results of this study indicated that therhizosphere microbial diversity of deciduous oaks was rich and abundant,and there were significant differences in the composition and diversity of microorganisms at different altitudes.These results could provide scientific data on the use of microorganisms in artificial planting and cultivation management of deciduous oak species,and provide a basis for screening soil microbial species that contribute to the growth of fleas.It also could provide theoretical supportfor the restoration of vegetation to select reasonable free speciesaccording to the conditions of the local soil microorganisms.This studywas innovative in research methods and research area on rhizosphere microbial diversity.In the future,comparative studies will be conducted in different seasons and vegetation types,and comparative experiments will be conducted under artificially controlled greenhouse conditions to further confirm whether different deciduous oaks have influence on the structure and diversity rhizosphere microbial community.It is expected that theoretical breakthroughs and stronger data and evidence will be obtained.