Variations in Soil Fungal Community Composition Along A Salinity Gradient in Yellow River Delta, China

The Yellow River Delta (YRD) of China is one of the most active land-sea interaction deltas in the world. However, due to human activities and climate change, it has undergone significant changes, including the degradation of natural wetlands and saltwater intrusion. As an integral part of soil microorganisms, fungi play a crucial role in maintaining and stabilizing the function of wetland ecosystems. To better understand the composition and diversity changes of fungal communities along a salinity gradient in the YRD of China and their relationship with environmental factors, fungal diversity, abundance, and composition in the sediments of four typical vegetation communities spanning from the riverbank to the seaside were investigated. The results showed that the electrical conductivity (EC) increased significantly from the riverbank to the coastal area (P < 0.05), but the levels of total nitrogen (TN), total carbon (TC), total sulfur (TS), available phosphorous (AP), and ammonium (NH₄⁺ -N) increased in Phragmites australis community and then experienced a significant decrease in Tamarix chinensis community and Suaeda salsa community (P < 0.05). The alpha diversity (Shannon and Simpson indices) of the soil fungal community exhibited a negative correlation with EC. There was a significant alteration in the structure of the fungal community, primarily influenced by EC and NO₃⁻-N. Ascomycota was found to be the most abundant phylum, and its relative abundance is positively correlated with pH and TS. The relative abundance of Sordariomycetes, the second-largest class of Ascomycota, reached 38.95%. Salinity was identified as the most important factor driving changes in soil fungal community composition. In summary, the fungal community changed significantly along the salinity gradient, and different environmental factors impacted various tiers of fungal populations differently. The findings of this study lay the groundwork for comprehending soil fungal communities and their primary influencing factors in newly formed wetlands.