| Soil microbes is a major part of the soil ecosystem,and the soil is an important foundation of the microorganism survival.Research on soil microbial diversity can be reflected the interaction relationship between microbes and soil environment.Soil microbes play an important role in improving soil environment,optimizing ecological structure,maintaining ecological stability,repairing soil pollution,returning farmland to forest and grassland and controlling desertification and other ecological environment protection.This study analyzed bacterial community and nitrogen-fixing microbial community structure diversity in four different ecoregion soils of Loess Plateau(LP),Mu Us Sandy Land(MU),North Slope of Qinling Mountains(NS),South Slope of Qinling Mountains(SS)in Shaanxi province.We isolated 97 nitrogen fixing bacteria strains from the research of cultivated nitrogen-fixing microbial community diversity,which belongs to 27 genera.The proportion of the dominant genus of Pseudomonas,Arthrobacter,Bosea,Paenibacillus,Massilia,Rhizobium is 11.34%,10.30%,8.25%,7.21%,7.21%,6.1%,respectively.It was found that two strains of LP4.4-SZ4(Arthrobacter)and NS2.1-SZ1(Burkholderia)could promote the growth of wheat root and the strain of NS2.1-SZ1 have the evident growth-promoting effect.According to the separable nitrogen-fixing bacteria colony count analysis,the colonies between the SS and MU show remarkable significant difference(P<0.01),and the colonies between LP and MU,LP and SS show significant differences(P<0.05)of the two groups.According to the correlation analysis between nitrogen fixing bacteria and soil,we find that the samples of MU with maximum similarity in species and uniform distribution,the species is similar within samples of LP,the species of NS/SS samples is neither similar nor uneven in distribution.PCA analysis indicated that two primary axis explains the 88.8%species variation,and the first axis explained 62.1%of the variation of species,the second axis explains 26.7%of variation of species.CCA analysis indicated that the soil properties(such as pH/TC/TN/TP)will affect the nitrogen-fixing bacteria community distribution in different ecoregion soils.There was no significant difference(P>0.05)between effective sequence and OUTs on the research of soil bacteria community diversity among different groups,but the annotation of the top 10 species abundance existd significant differences(P<0.05).In the phylum of bacteria,Actinobacteria,Proteobacteria and Chloroflexi are three of dominant phylum in different ecological regions,and the bacterial population is depend on the ecological region and soil types.The alpha diversity index of microbial analysis showed that SS and MU group exist significant differences(P<0.05)in the diversity of bacteria community composition and the species abundance and eveness and the overall genetic lineage,while the other groups have no significant difference.The beta diversity index of microbial analysis showed that the PC1 axis explains 30.32%of species variation.The microbial community composition in the SS and MU groups with high similarity,while the microbial community structure has significant difference between SS and MU,which are consistent with the alpha diversity analysis.And then,the PC2 axis explains 23.65%of species variation,and there have significant differences in PC2 among the four group samples,and the two principal components have explaind 53.95%of species variation totally.Physical and chemical with the key species correlation analysis(CCA)indicates that the property of soil physical and chemical can change the distribution of microbial community and has an effect on the structure of microbial community to a certain extent. |
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