Fig. 2. Venn diagram of fungal communities in different grassland types based on OTU abundance. Different colors represent grassland types. The letter G denotes grazing, and the letter E denotes grazing exclusion.
3.3. Soil fungal community composition as affected by grazing exclusion and grassland type
At the phylum level (Fig. 3A), Ascomycota and Basidiomycota were the dominant fungi in the three grassland types in the 0-5 cm soil layer before exclusion. After exclusion, Ascomycota decreased by 14.72% and 9.74% in temperate deserts and mountain meadows respectively, and increased by 4.82% in temperate steppes. Basidiomycota increased by 238.8% and 47.68% in temperate deserts and mountain meadows respectively, but decreased by 23.12% in temperate steppes. In the 5-10 cm soil layer (Fig. 3B), the main fungi of the three grassland types were the same as those in the 0-5 cm soil layer. It is worth mentioning the changes in Mortierellomycota , which we found to be significantly lower after grazing exclusion in the 0-5 soil layer in mountain meadows (P < 0.05), and highly significant higher in the 5-10 soil layer in temperate deserts(P < 0.001). At the class level in the 0-5 cm soil layer (Fig. 3C), Regardless of grazing or grazing exclusion, Dothideomycetes, Archaeorhizomycetes, Sordariomycetes and Agaricomycetes were dominant in three grassland types studied, while in the temperate desert Archaeorhizomycetes almost disappeared. This result illustrates the different responses of fungi to environmental changes. In the 5-10 cm soil layer (Fig. 3D), Sordariomycetesincreased significantly by 279.32% in the temperate desert before exclusion compared to the 0-5 cm soil layer. Grassland type had a highly significant effect on Ustilaginomycetes (P < 0.001) and a significant effect on Eurotiomycetes andOrbiliomycetes (P < 0.05). In addition, grassland type had a highly significant effect on Dothideomycetesand Archaeorhizomycetes in both the 0-5 cm and the 5-10 cm soil layers (P < 0.001) (Supplementary Tables 6 and 7).