Seed germination and seedling survival of A. adenophora

Seed germination time and rate after inoculation of soil or leaves in the G0 period (a-b) and seedling death rate after inoculation of soil or leaves in the G0 and G21 periods and subsequent growth in Petri dishes (c). Seedling death rate after two weeks when seedlings were transplanted into soil under different feedback conditions (d), under sterile or non–sterile inoculation (e), at different nutrient levels (f) and at different inoculation time treatments(g) based on all the treatments. Ss: sterile soil; Sns: non–sterile soil; Ls: sterile leaf; Lns: non– sterile leaf; G0, inoculated on the day of germination; G21, inoculated on the 21st day after germination; G28, inoculated on the 28th day after germination; G21+28, inoculated on both the 21st and 28th days after germination. * P < 0.05, *** P < 0.001. Error bars depict the standard error.

Effects of feedback (a), nutrient level (b), and inoculation time (c) on the microbial role in A. adenophora growth based on total dry weight

For the abbreviations G0, G21, G28, and G21+28, see Fig. 1. Error bars depict the standard error. The asterisks indicate that the RI is significantly different from zero. Different lowercases represent significant differences among the different inoculation time treatments.

Microbial diversity and community composition at the phylum level in the inocula AAS and AAL

Fungal and bacterial Shannon, Chao 1 and Pielou_e indices of AAS and AAL (a-c). Relative abundances of bacterial (d) and fungal phyla (e) in the AAS and AAL. AAS: A. adenophora rhizosphere soil inoculum, AAL: A. adenophora litter inoculum. Brown stars represent significantly greater relative abundances in the AAS than in the AAL, green stars represent significantly greater relative abundances in the AAL than in the AAS, P < 0.05 at least.

Microbial community composition and potential functional differences between leaf litter (AAL) and rhizosphere soil (AAS)

Correlations between the top 30 bacterial (a) and fungal (f) genera and germination time (GT), germination rate (GR) and death rate (DR). Core bacteria (b-c) and fungi (g-h) in AAS and AAL. The potential functions of core bacteria (d-e) and fungi (i-j) in AAS and AAL. Only the top 10 core taxa and potential functional groups are shown in the figures. The “un” in the figures is the abbreviation for “unclassified”, and the MM is Methylobacterium-Methylorubrum. Red and blue represent negative and positive Spearman’s coefficients, respectively. * P < 0.05, ** P < 0.01, *** P < 0.001. Different lowercase letters in the heatmap represent significant differences in relative abundance between AAS and AAL (P < 0.05). Several bacterial functions classified as N circles related to AAL and AAS are shown in Table S1-2. Several fungal guilds were classified as plant pathogen-related guilds in the AAL and AAS (see Tables S3-4).

Cultivable fungi associated with dead A. adenophora seedlings and their mortality to seedlings

Cultivable fungal community composition at the genus level (a). Isolation frequency from one dead seedling (b). Death rate of 33 fungal strains to seedlings and their phylogenetic signal (c).

Bacterial and fungal communities and functions enrichment in A. adenophora seedlings under different treatments

Nonmetric multidimensional scaling (NMDS) ordinations of Bray–Curtis dissimilarity matrices with permutational analysis of variance (PERMANOVA) of bacterial and fungal communities and function (a-h). Contribution of compartment, feedback and nutrient level to the variation in bacterial and fungal communities and function at each inoculation time based on PERMANOVA (i-l). * P < 0.05, ** P < 0.01, *** P < 0.001. In the figures, F and S represent foliage and soil feedback; L and R represent leaves and roots for different compartments; and H and L represent high and low nutrient levels, respectively.

Correlations between the enriched microbial community, functions and seedling growth

These genera accounted for more than 1% of the total relative abundance in seedling roots or leaves. (a) Correlations between 47 out of 214 genera enriched in roots with RI (left) and the relative abundances of genera under different treatments, i.e., different feedbacks, inoculation time and nutrient levels (right). (b) Correlations between 18 out of 184 genera enriched in leaves with RI (left) and the relative abundances of genera under different treatments (right). (c) Correlations between putative bacterial functions enriched in roots with RI (left) and the relative abundances of functions with negative and positive effects under different treatments (right). (d) Correlations between fungal guilds enriched in roots with RI (left) and the relative abundances of guilds with negative and positive effects under different treatments. (e) Correlations between fungal guilds in leaves with RI (left) and the relative abundances of guilds with positive effects under different treatments (right). No bacterial functions in the leaves showed a significant correlation with seedling growth. “F_” represents fungal genera, “B_” represents bacterial genera, “un” represents unclassified; H: RI of seedling height; AD: RI of aboveground dry biomass; UD: RI of underground dry biomass; TD: RI of total dry biomass. Red and blue represent negative and positive Spearman’s coefficients, respectively. * P < 0.05, ** P < 0.01, *** P < 0.001. For abbreviations of fungal function guilds, please see Table S8.

Schematic diagram of soil or litter inoculation at different growth stages

The abbreviations G0, G21, G28, and G21+28 are shown in Fig. 1.