Structural variability in the rhizosphere bacterial communities of three halophytes under different levels of salinity-alkalinity

Background and aims Soil alkaline salinity restricts the deep utilization of land resources. Research on the composition and diversity of plant rhizosphere microbial communities in saline-alkaline soils is helpful for identifying important microbial functional groups or functional potential, which is of great significance for vegetation restoration and ecological reconstruction. Methods Bacteria colonized the rhizosphere soil of three halophytes grown in desert grasslands, including Halocnemum strobilaceum (HS), Phragmites communis (PC), and Halostachys capsica (HC), under moderate, heavy, and severe saline-alkaline conditions. Halophytes were then analysed via 16S amplicon sequencing. The relationships between soil physicochemical characteristics and bacterial diversity were determined via redundancy analysis (RDA) and Spearman correlation analysis. Results As the saline-alkali levels increased, the bacterial richness and diversity decreased in the PC and HS groups but were greater in the severe grade than in the heavy grade in the HC group. The bacterial communities in the PC, HS, and HC treatments at different saline-alkali levels were significantly different. Moreover, the rhizosphere bacterial communities were sensitive to changes in the saline-alkaline environment. Proteobacteria, Actinobacteriota, Bacteroidota, and Halobacterota were the predominant phyla for PC, HS, and SC in moderate, heavy, and severe saline-alkaline soils, respectively. EC and pH affected the richness and β diversity of the bacterial communities of all the assayed halophytes, regardless of the saline-alkaline level. Conclusion Our findings suggested that rhizosphere bacterial communities may play a role in halophyte adaptation to saline-alkali land, as well as promoting plant growth and improving ecological performance.