Soil Salinization Increases the Stability of Fungal Not Bacterial Communities in the Taklamakan Desert

• Bacterial richness declined but fungal richness increased under salinization. • Bacteria did not become interactively compact or facilitative under salinization. • Fungi exhibited more compartmentalized and competitive patterns under salinization. • Fungal stability showed steeper increases under salinization than bacterial stability. Soil salinization is a typical environmental challenge in arid regions worldwide. Salinity stress increases plant convergent adaptations and facilitative interactions and thus destabilizes communities. Soil bacteria and fungi have smaller body mass than plants and are often efficient against soil salinization, but how the stability of bacterial and fungal communities change with a wide range of soil salinity gradient remains unclear. Here, we assessed the interactions within both bacterial and fungal communities along a soil salinity gradient in the Taklamakan desert to examine (i) whether the stability of bacterial and fungal communities decreased with soil salinity, and (ii) the stability of which community decreased more with soil salinity, bacteria or fungi. Our results showed that the species richness of soil fungi increased but that of soil bacteria decreased with increasing salinity in topsoils. Fungal communities became more stable under soil salinization, with increasing compartmentalization (i.e., modularity) and proportion of competitions (i.e., negative:positive cohesion) as salinity increased. Bacterial communities exhibited no changes in modularity with increasing salinity and smaller increases in negative:positive cohesion under soil salinization compared to fungal communities. Our results suggest that, by altering interspecific interactions, soil salinization increases the stability of fungal not bacterial communities in extreme environments.