Decoupling soil community structure, functional composition, and nitrogen metabolic activity driven by salinity in coastal wetlands

Coastal wetlands, being a multifaceted and crucial global ecosystem, are facing significant impacts from diverse environmental alterations, particularly soil salinization. Concurrently, the escalation of extreme climate events, such as global warming, presents complex challenges for the protection and restoration efforts. Previous researches concerning microbial communities in the context of climate with continous line numbering change have predominantly concentrated on their structural aspects, with limited attention given to establishing relationships between community structure and functional attributes. In this study, a two-year investigation was conducted on conventional coastal wetland ecosystems, considering variations in salinity and seasonal temperature. Utilizing high-throughput 16S rRNA sequencing, isotope technology, and other methods to explore the bacterial community, nitrogen cycling functional groups, and nitrogen reduction process. This research aims to assess the holistic impacts of significant global environmental changes on microbial communities. The results suggest that salinity, acting as an environmental filter, has a significant impact on the microbial community composition. It leads to a decrease in species abundance, an increase in deterministic processes and the nesting of community succession, while also reducing the stability of microbial ecological networks. The mechanism by which soil salinity impacts bacterial communities involves three main aspects: direct effects, positive climate regulation, and negative regulation of soil properties. Surprisingly, soil salinity exerts a mild inhibitory influence on microbial functional genes and metabolic activity. The primary factors involved in the nitrogen reduction process include electron donors/acceptors, types of nitrogen sources, and organic carbon. The three processes are interconnected due to the impact of environmental factors and signal transmission among microbial populations. This study offers a novel scientific framework for the rehabilitation and enhancement of saline-alkali coastal ecosystems in the face of impending global changes. It achieves this by investigating the varied response patterns exhibited by microbial communities and ecological functional metabolism under salinity-induced stress.