[Soil microbial diversity of artificial peashrub plantation on North Loess Plateau of China].

Peashrub (Caragana korshinskii Kom) is a kind of excellent shrub used for dune-fixation in Loess Plateau of China. In order to explore relationship between peashrub and soil microorganisms, microbial communities diversity associated with rhizoplane, rhizosphere and bulk soil of peashrub in Loess Plateau of China were characterized based on a culture-independent approach. Three 16S rDNA gene libraries were constructed, respectively, and each different profile was used to define an operational taxonomic unit (OTU). The numbers of microorganisms decreased as root proximity decreased and a few OTUs became dominant. Phylogenetic analyses indicated that Proteobacteria was the predominant group in rhizoplane, which included many alpha-Proteobacteria, partially consisted of rhizobia, and gamma-Proteobacteria beneficial to plant growth. In bulk soil, the most frequent OTUs were closely related to Archaea, while Acidobacteria was the dominant group in rhizosphere of peashrub. The diversity index (H') was higher in rhizosphere than in rhizoplane and bulk soil, whereas microbial populations in rhizoplane and bulk soil had the greater dominance indices (D). It was shown that there was a significant change in microbial species composition along the root gradient, shifting from complex plant-associated bacterial community in the root habitats to a simple bacterial community in the bulk soil. These results showed that plant roots and soil conditions created a selective environment for microbial populations.