(i) Changes of abiotic and biotic factors along elevational gradients
For soil properties, the first principal component (Soil PCA1 ) explained 41.63% of the total variance and Soil PCA1 was positively correlated with pH, C, and NO3- and negatively correlated with W and NH4+ (Fig. S1.2).
We found 73 plant species in total along the elevational gradient in the alpine meadow. Elevation had a strong correlation with MDTrather than MDH , showed a highly collinearity between them (Fig. S1.3). Due to this collinearity, we feel confident interpreting elevation as a proxy for temperature. Besides, increasingElevation was associated with a significant decrease in AGB(P = 0.006, MarginalR2 = 0.733), SR (P = 0.028, Marginal R2 = 0.482) and Soil PCA1(P = 0.038, Marginal R2 = 0.610) (Fig. S1.5).
At the plant population-level, fungal leaf spot was the most commonly identified symptom, compared with others (e.g. rusts, blight, smuts and downy mildew; Table S1.3). Multiple species belonging to several genera (i.e. Alternaria , Ascochyta , Peronospora ,Puccinia , Trichometasphaeria , Urosystis andUstiligo ) were identified as pathogens associated with the observed foliar fungal diseases (Table S1.2). Host species varied inVi from 0 to 27.78 (Deschampsia caespitosa ) (Table S1.2). With respect to soil pathogens, we identified putative plant fungal pathogens belonging to 106 genera. Soil plant fungal pathogens occupied an average of about 7.72% relative abundance, compared to all soil fungi across all plots.
For foliar fungal diseases and soil pathogens, increasingElevation was associated with a significant reduction in sfpOTUs (P = 0.020, Marginal R2 = 0.433), but not PL(P = 0.403, Marginal R2 = 0.034) orsfpRA (P = 0.973, Marginal R2< 0.001) (Fig. S1.6). PERMANOVA results indicated that the composition of soil fungal pathogens varied with elevation (F 4,25 = 2.744, P < 0.001) (Table S1.3).