Abstract: To understand the diversity of soil bacteria in the rhizosphere of Picea crassifolia and its response to environmental changes, and to reveal the mechanism of soil microbiome of P. crassifolia in adapting to alpine and drought stress, Illumina Miseq high-throughput sequencing technology was used to analyze the community composition of soil bacteria. The results showed that Proteobacteria, Actinobacteria and Acidobacteria were the main dominant phyla, with relative abundances of 34.9%, 28.0% and 13.9%, respectively. At the genus level, the relative abundances of Sphingomonas (4.5%), RB41(3.0%) and Bradyrhizobium (3.0%) were more than 1.0% and were the dominant genera. The bacterial diversity and richness increased with the increasing altitude. The analysis of the co-occurrence network of bacterial communities showed that the modularity index of the network was 0.939, indicating a high modularity level. Stochastic processes accounted for 70.4% of assembly processes, indicating that the ecological construction of the bacterial community in the rhizosphere soil of P. crassifolia was dominated by the stochastic processes.

Key words: bacterial community, co-occurrence network, stochastic assembly process, Picea crassifolia