Saline-alkali gradients reshape soil microbial network complexity and niche breadth

Introduction Saline-alkali soils impose combined osmotic, ionic and alkaline constraints on soil microorganisms, yet how bacterial and fungal ecological strategies vary along saline-alkali gradients remains insufficiently resolved. Methods We analyzed 30 composite soil samples from 10 sites across China using bacterial 16S rRNA and fungal ITS amplicon sequencing, soil physicochemical profiling, co-occurrence network analysis, niche breadth classification and PICRUSt2 -based functional prediction. Results Higher saline-alkali intensity was associated with reduced nutrient availability, lower microbial network complexity and greater network vulnerability. Bacterial specialists showed stronger diversity and compositional responses than generalists, whereas fungal communities displayed comparatively stable patterns across the sampled gradient. Predicted bacterial functional profiles suggested an increased representation of stress-survival-related pathways under high saline-alkali conditions. Discussion These findings identify microbial taxa, network properties and predicted functional features associated with saline-alkali soil degradation and provide candidate targets for future culture-based, metagenomic and experimental validation.