Vegetation-Driven Changes in Soil Properties, Enzymatic Activities, and Microbial Communities of Saline–Alkaline Wetlands

Saline–alkaline wetlands represent critical ecosystems for maintaining biodiversity, regulating hydrological processes, and supporting regional ecological resilience. However, the extent to which dominant vegetation regulates soil functionality and microbial assemblages in these unique saline systems remains insufficiently understood. In this study, we examined five characteristic vegetation types—Phragmites communis Trin., Typha angustifolia L., Bryophytes, Suaeda salsa (L.) Pall., Echinochloa phyllopogon (Stapf) Koss.—across the saline wetlands of Chagan Lake, northeast China, which are embedded in a heterogeneous matrix of forests, grasslands, and agricultural lands. Comprehensive assessments of soil physicochemical properties, enzyme activities, and bacterial communities were conducted, integrating high-throughput sequencing with multivariate statistical analyses. Our results revealed that vegetation cover markedly influenced soil attributes, particularly total organic carbon (TOC) and alkali-hydrolyzed nitrogen (AN), alongside key enzymatic functions such as urease and alkaline phosphatase activities. Proteobacteria, Actinobacteria, and Acidobacteria emerged as dominant bacterial phyla, with their relative abundances tightly linked to vegetation-induced shifts in soil environments. Notably, soils under E. phyllopogon demonstrated elevated bacterial diversity and enzymatic activities, underscoring the synergistic effects of plant selection on soil biogeochemical health. Structural equation modeling further elucidated complex pathways connecting vegetation, microbial diversity, soil quality, and enzymatic functioning. These findings emphasize the pivotal role of vegetation management in improving soil fertility, shaping microbial communities, and guiding the sustainable restoration of saline–alkaline wetlands under environmental stress.