Fig. 4

Redundancy analysis (RDA) ordination biplot showing relationships between bacterial communities and environmental factors based on sequences abundance assigned at phylum level along altitudinal gradients. Black circles indicate sampling sites in the Tibet Plateau. Ovals drawn with black dashed lines indicate samples from the rhizosphere and roots of S. chamaejasme in different elevations, respectively. The red arrows indicate the types of environmental variables and their relative effects on bacterial communities, and the blue arrows indicate the different bacterial phylum. The distance between black circles reflects their dissimilarity, and the relative position (in perpendicular distance) of a black circle to a red arrow-line indicates the influence of the specified environmental factor on the bacterial communities in different sampling sites. 1, Acidobacteria; 2, Actinobacteria; 3, α-proteobacteria; 4, Armatimonadetes; 5, Bacteroidetes; 6, β-proteobacteria; 7, Chloroflexi; 8, δ-proteobacteria; 9, Firmicutes; 10, γ-proteobacteria; 11, Gemmatimonadetes; 12, Saccharibacteria; 13, Uncultured bacterium; 14, Verrucomicrobia