Not by Salinity Alone: How Environmental Factors Shape Fungal Communities in Saline Soils

Core Ideas Fungal diversity exhibits a longitudinal gradient in saline soils. Soil moisture, then salinity and total potassium, were the main environmental drivers of fungal communities. Environmental variables were more important than geographical distance to variation in trophic guilds. The fungal community assembly was mainly stochastic. Soil salinity is prominent in arid and semiarid regions, especially in local agricultural systems. Fungi play major roles in ecosystem processes, but the determinants of fungal diversity and biogeographical patterns in saline agricultural systems remain poorly understood. Here we performed Illumina MiSeq high throughput sequencing of the fungal ITS1 region from 31 soils covering representative saline agricultural lands in northwest China. The results showed that Dothideomycetes, Eurotiomycetes and Sordariomycetes were the dominant taxonomic groups across all soil samples (>5% of all sequences), while saprotroph, pathotroph-saprotroph-symbiotroph and pathotroph were the main functional guilds across all soil samples. Interestingly, the fungal abundance and α diversity increased with increasing longitudinal gradient from 84°13′ E to 89°11′ E. Soil moisture, followed by salinity and total potassium, were the primary environmental drivers of the fungal community; these soil parameters were significantly (P < 0.05) correlated with longitude, and therefore potentially result in longitudinal fungal gradients. Furthermore, the fungal community assembly was mainly stochastic; fungal community exhibited distance-decay distribution patterns, which were mainly influenced by geographical distance. By contrast, environmental factors (such as salinity pH, soil moisture, or nutrients) mainly contributed to the variation in trophic guilds. These findings enhance our understanding of fungal biogeography in saline agricultural soils.