3.2 Soil microbial community structure
The relative abundances of major microbial phyla are illustrated
(Fig.2a, b). Proteobacteria, Acidobacteria, Gemmatimonadetes,
Planctomycetes, and Actinobacteria accounted for 83% of the total
bacterial sequences, and Ascomycota, Basidiomycota, and chytridiomycota
accounted for 78% of fungal. Bacteria alpha-diversity Chao1 and ACE
indices did not significantly differ among the slope gradients. Simpson
indices significantly differed among slope gradients and declined with
increasing slope gradient (Table 3). These alpha-diversity indices had
no significant differences between slope positions. Fungi
alpha-diversity indices were not significantly affected by slope
gradient or position. NMDS analysis based on the Bray-Curtis distance
clustered bacterial and fungal communities, and distinct differences
were observed in the communities’ composition (Fig. 2c, d). PERMANOVA
revealed significant differences in bacterial and fungal community
composition, which is significantly lower in the highest slope gradient
level than in the other two levels. However, differences were not
significant among slope positions (Table 4).