Assembly Patterns and Functional Roles of Bacterial Generalists and Specialists in the Remediation of Saline–Alkali Soils

Saline-alkali soils cover millions of hectares worldwide, severely limiting agricultural productivity. Although various remediation strategies have been applied, the adaptive responses of microbial communities to these interventions remain poorly understood. This study investigated microbial community responses to saline-alkali stress under different remediation treatments, focusing on diversity patterns, community assembly mechanisms, network interactions and functional roles. A randomised block experiment was conducted with three treatments: untreated saline-alkaline (SA) soils, paddy-upland rotation (PUR) and organic fertiliser (OF) amendment. Both PUR and OF treatments increased the relative abundances of Bacteroidota, Acidobacteriota and Firmicutes, indicating enrichment of beneficial taxa. Specialists exhibited higher connectivity with other microbial species than generalists, emphasising their role in stabilising indigenous microbiota and enhancing resistance to saline-alkali stress. Community assembly was dominated by deterministic processes for specialists in SA and PUR soils, while stochastic processes prevailed in other contexts across both generalists and specialists. These results reveal distinct but complementary roles of microbial generalists and specialists in soil adaptation and highlight the mechanisms by which amendments shape microbial community structure and function. Our findings provide mechanistic insights into microbial contributions to saline-alkali soil remediation, informing strategies for sustainable soil restoration.