Differences in Bacterial Community Structure in Rhizosphere Soil of Three Caragana Species and Its Driving Factors in a Common Garden Experiment

Abstract

The soil bacterial diversity and community structures in rhizosphere soil of Caragana microphylla, Caragana liouana, and Caragana roborovskyi in a common garden experiment were measured using the high-throughput sequencing technique, with the aim of investigating the factors driving the variation in the bacterial community structure. The results indicated that 42 phyla, 55 classes, 123 orders, 244 families, and 558 genera were obtained from the rhizosphere soil. The dominant phyla in all sample sites were Proteobacteria, Cyanobacteria, Actinobacteria, Bacteroidetes, Firmicutes, and Acidobacteria (relative abundance>1%). At the genus level, Phenylobacterium, Ensifer, and Chitinophaga were dominant. Two-way analysis of variance showed that species had a significant effect on the Shannon index and Simpson index of rhizosphere soil bacteria of the three Caragana species, whereas the Chao1 index, Shannon index, and Simpson index were significantly affected by the interaction of provenances and species. There was a significant difference among the three species in the composition of bacterial communities, and the cluster analysis indicated that the composition of the soil bacterial community significantly differed among provenances in C. liouana and C. roborovskyi. Based on the redundancy analysis, mean annual precipitation and altitude were the dominant factors influencing the rhizosphere soil bacterial community structure. Overall, the present results indicated that there were intraspecific and interspecific differences in the diversity and community structures of rhizosphere soil bacteria, and the bacterial community structure was mainly affected by the provenance climate. These results provide a theoretical basis for understanding the adaptation strategies and ecological restoration of the three Caragana species.