Seasonal dynamics of microbial diversity in the rhizosphere of Ulmus pumila L. var. sabulosa in a steppe desert area of Northern China

The seasonal dynamics of microbial diversity within the rhizosphere of Ulmus pumila L. var. sabulosa in the hinterland of the Otindag Sandy Land of China were investigated using high-throughput sequencing of bacterial 16S rRNA genes and fungal ITS region sequences. A significant level of bacterial and fungal diversity was observed overall, with detection of 7,676 bacterial Operational Taxonomic Units (OTUs) belonging to 40 bacteria phyla and 3,582 fungal OTUs belonging to six phyla. Proteobacteria, Actinobacteria, and Firmicutes were the dominant bacterial phyla among communities, while Ascomycota, Basidiomycota, and Zygomycota were the dominant phyla of fungal communities. Seasonal changes influenced the α-diversity and β-diversity of bacterial communities within elm rhizospheres more than for fungal communities. Inferred functional analysis of the bacterial communities identified evidence for 41 level two KEGG (Kyoto Encyclopedia of Genes and Genomes) orthology groups, while guild-based analysis of the fungal communities identified eight ecological guilds. Metabolism was the most prevalent bacterial functional group, while saprotrophs prevailed among the identified fungal ecological guilds. Soil moisture and soil nutrient content were important factors that affected the microbial community structures of elm rhizospheres across seasons. The present pilot study provides an important baseline investigation of elm rhizosphere microbial communities.