Note: (a) Rhizosphere soil fungal topology parameters; (2) nonrhizosphere soil fungal network topology parameters. Different uppercase letters indicate the following: A, average degree; B, average path length; C, clustering coefficient; D, network degree centrality; E, network tight centrality; F, network efficiency; G, network quality; H, information center; I, network vulnerability; J, network stability.
Fig. 5 Topological properties of the soil fungal community networks ofA. spinulosa at different taxonomic levels
Predictive analysis of fungal function
FUNGuild functional prediction analysis revealed that the soil fungi ofA. spinulosa included nine main groups: pathotroph, symbiotroph, saprotroph, saprotroph–symbiotroph, pathotroph–symbiotroph, pathotroph–saprotroph, saprotroph–pathotroph–symbiotroph, pathotroph–saprotroph–symbiotroph, and pathogen–saprotroph–symbiotroph. Soil fungi in both A. spinulosa rhizosphere and nonrhizosphere were predominantly saprophytic trophic (saprotroph), with the proportion of pathotrophs being higher in the A. spinulosa rhizosphere (10.51% vs. 7.76%).
In total, 108 functional groups were detected through functional group identification, and 15 of them had a relatively high abundance (Fig. 6). The main functional groups of symbiotrophs and saprotrophs in the rhizosphere and non-rhizosphere soils of A. spinulosa were identical. The main functional groups of symbiotrophs were arbuscular mycorrhizal, ectomycorrhizal, and endophyte fungi. Saprotrophs comprised undefined saprotroph, soil saprotroph, and wood saprotroph as the main functional groups. The main functional groups of pathotrophs betweenA. spinulosa rhizosphere and nonrhizosphere soils were identical: animal pathogen, phytopathogen, and fungal parasite–lichen parasite. However, the status of the functional groups differed, with the animal pathogen predominating the A. spinulosa rhizosphere soil and the phytopathogen predominating the nonrhizosphere soil. Compared with fungi in the nonrhizosphere soil, the relative abundance of fungi in the rhizosphere soil of A. spinulosa increased for animal pathogens and saprotroph–symbiotroph and decreased for pathotroph–saprotroph.