Plant Life Form Governs Rhizosphere Bacterial Assembly via Direct and Soil-mediated Indirect Pathways in a Saline-alkali Desert Ecosystem

Background and Aims Saline-alkali land represents an important reserve resource for tackling global climate change and ensuring food security. The synergy of plant, soil and microbiome is a key for saline-alkali soil restoration and ecosystem resilience, and is a promising solution for sustainable soil ecosystem functioning agriculture development in arid- and semi-arid regions. However, little is known on how plant life forms function to regulate rhizosphere microbial assembly and the underlying mechanisms. This study aimed to elucidate the effects of different plant life forms on rhizosphere bacterial communities and their potential mechanisms in arid and semi-arid saline-alkali ecosystems. Methods Rhizosphere soils of annual herbs and perennial shrubs were collected from saline-alkali ecosystems in Xinjiang, China. High-throughput sequencing, soil physicochemical analyses, co-occurrence network analysis, and structural equation modeling were used to explore bacterial community characteristics and drivers. Results Perennial shrubs harbored more diverse and stable bacterial communities than annual herbs, with higher soil organic carbon and total nitrogen contents. Shrub rhizosphere networks showed greater complexity, with more links (497 vs. 443) and triangles (3696 vs. 2650), but lower modularity (0.385 vs. 0.651). Keystone taxa, including Actinobacteriota, Proteobacteria, and Chloroflexi, were strongly associated with soil pH, carbon, and nitrogen availability. Plant life forms regulated bacterial communities through direct effects on diversity and indirect effects via soil properties. Conclusion Perennial shrubs enhance rhizosphere microbial stability and functional potential through microbial recruitment and soil improvement, highlighting their importance for saline-alkali ecosystem restoration in arid and semi-arid regions.