The influence of soil salinization, induced by the backwater effect of the Yellow River, on microbial community dynamics and ecosystem functioning in arid regions.

Irrigation practices and groundwater levels are critical factors contributing to soil salinization in arid and semi-arid regions. However, the impact of soil salinization resulting from Yellow River water irrigation and recharge on microbial communities and their functions in the Huinong District has not been thoroughly documented. In this study, high-throughput sequencing technology was employed to analyze the diversity, composition, and structure of bacterial and fungal communities across a gradient of salinized soils. The results indicated that the alpha diversity of bacterial communities was significantly higher in slightly saline soils compared to highly saline soils. Soil salinization notably influenced the composition of both bacterial and fungal communities. Highly salinized soils were enriched with bacterial taxa such as Halomonas, Salinimicrobium, Pseudomonas, Solibacillus, and Kocuria, as well as fungal taxa including Emericellopsis, Alternaria, and Podospora. In these highly saline soils, bacterial taxa associated with iron respiration, sulfur respiration, and hydrocarbon degradation were more prevalent, whereas fungal taxa linked to functions such as soil animal pathogens, arbuscular mycorrhizal symbiosis, endophytes, dung saprotrophy, leaf saprotrophy, soil saprotrophy, fungal parasitism, and plant pathogenicity were less abundant. Random forest analysis identified nine bacterial and eighteen fungal taxa as potential biomarkers for salinity discrimination in saline soils. Symbiotic network analysis further revealed that soil salinization pressure reduced the overall complexity and stability of bacterial and fungal communities. Additionally, bacterial community assembly showed a tendency shift from stochastic to deterministic processes in response to increasing salinity, while fungal community assembly remained dominated by deterministic processes. provide robust evidence that soil salinity is a major inhibitor of soil biogeochemical processes in the Huinong District and plays a critical role in shaping bacterial and fungal communities, their symbiotic networks, and their assembly processes.