3.4 Diversity and composition of soil fungal community
A total of 2,625,602 fungal sequences were obtained from the complete data set, of which 2,446 fungal OTUs belonged to 12 phyla, 36 classes, 89 orders, 226 families, and 417 genera. The rarefaction curves of fungal showed clear asymptotes, which indicated a near complete and true sampling of the community. The dominant phyla were in the ranking order: Ascomycota (85.66%-51.53%), Basidiomycota (31.75%-1.64%), unclassified Fungi (18.34%-3.45%), unidentified (18.07-2.53%), and Chytridiomycota (2.93%-0.01%), together accounting for > 98% of fungal sequences across all samples (Fig. S1b). Notably, the relative abundance of Chytridiomycota (p<0.05) decreased significantly with addition of amendments, in which C-M-N decreased the most. No significant differences were observed in Ascomycota and Basidiomycota (except for unclassified Fungi and unidentified) at all amended treatments, and Ascomycota decreased with the N addition. Basidiomycota increased after M addition and decreased in C and C+N treatments(Table 3).
Alpha-diversity estimated by Chao1 estimator, and Shannon indices showed significant differences in species richness and diversity of soil fungal community between different treatment(P <0.05). Chao1 estimator was significantly higher in C (C-N0), C+M2+N (C-M2-N0, C-M2-N1, C-M2-N2, C-M2-N3) treatments in CK (P <0.05), in which M2 level supported higher value (highest in C-M2-N0 treatment). Simpson indices had no significant difference between amended and CK treatment. Shannon indices were significantly higher in C+M1+N2 and C-M2-N2 treatment(Table 4).
PCoA analysis based on Bray-Curtis distances accounted for 42.8% of total variance among the fungal communities, with axes 1 and 2 explaining 23.7 and 19.1% of the variance, respectively (Fig. 4b). PCoA analysis showed that fungal communities also were divided into three major groups. All M2-level treatments (C-M2-N0, C-M2-N1, C-M2-N2, C-M2-N3) tended to group together, M1 level (C-M1-N0, C-M1-N1, C-M1-N2, C-M1-N3) clustered into another group, and treatments without M addition (C-N0, C-N1, C-N2, C-N3) were grouped together with CK(R2 = 0.504 > 0.5,P < 0.001;PERMANOVA,Test statistic= 2.203,P = 0.001). Overall, three groups exhibited significant differences in fungal community composition and were separated mainly by M level.