Figure 2.

Factors shaping the structure of microbial communities in 66 soil samples and 4 habitats

(A) Bray-Curtis similarity-based dendrogram showing average bacterial (left) and fungal (right) community compositions. OTUs with relative abundances >1% were considered. Levels of degradation are represented by colored squares (pink: lightly degraded grassland (L); gray: moderately degraded grassland (M); green: degraded sown grassland (S); and black: heavily degraded grassland (H)). For each sample, the community composition of bacteria and fungi at the class level is indicated by bar plots, and microbial α-diversity is represented by gray bars according to the number of observed OTUs.

(B) effect of compartment (n = 2), habitat (n = 4), plant species (n = 11) and habitat × plant species on bacterial and fungal community compositions. The explained variance for each factor is shown for bacteria and fungi, based on PERMANOVA (p < 0.001 in bacteria and p > 0.05 in fungi), habitat × plant species (Adonis: degrees of freedom (d.f.) = 21; bacterial: coefficient of determination (R²) = 0.53, p < 0.001; fungal: R² = 0.32, p = 0.59), compartment (d.f. = 1; bacterial: R² = 0.04, p < 0.001; fungal: R² = 0.01, p = 0.62), degradation level (d.f. = 3; bacterial: R² = 0.16, p < 0.001; fungal: R² = 0.05, p = 0.91), plant species (d.f. = 10; bacterial: R² = 0.27, p < 0.001; fungal: R² = 0.15, p = 0.29). Compartments include bulk soil and rhizosphere.

(C) PCoA based on Bray-Curtis distances between samples across 66 samples in 4 levels of degradation. Nr, bulk soil, that is, non-rhizosphere soil. Al, Ajuga lupulina; Ef, Euphorbia fischeriana; Sg, Sphallerocarpus gracilis; Oo, Oxytropis ochrocephala; Mk, Morina kokonorica; Pk, Pedicularis kansuensis; An, Artemisia nanschanica; Ad, Artemisia dubia; Ap, Aconitum pendulum; Lv, Ligularia virgaurea.