Supplementary file 1_Spatial patterns of soil multifunctionality trade-offs and their relationships with microbial diversity in warm-temperate mountain forests of North China.docx

Among the three pairwise relationships, the SCSS–SNM trade-off was the strongest, reaching its maximum intensity at 1,300 m in the topsoil and 1,500 m in the subsoil. Bacterial and fungal diversity showed contrasting relationships with individual SEFs and nonlinear responses to trade-off intensity. VPA showed that altitude and soil depth explained the largest independent fraction of variation in individual SEFs, whereas soil properties explained the largest independent fraction of variation in SEF trade-offs.

Among the microbial variables, bacterial diversity had the greatest relative predictive importance for individual SEFs and their trade-offs, while fungal diversity provided complementary predictive information. SHAP analysis further identified bacterial diversity as the most informative microbial predictor of overall soil multifunctionality and the soil N/P ratio as the strongest predictor of mean trade-off intensity.</p>Discussion<p>These findings indicate that soil multifunctionality and its trade-offs covary with soil depth, hydrothermal conditions, microbial diversity, and stoichiometric constraints.

Within the sampled Dongling Mountain transect, this study provides quantitative evidence for spatially structured soil multifunctionality trade-offs and establishes a basis for testing the generality of these relationships across replicated mountain systems under global change.</p>