Figure 1. Results of structural equation modelling to quantify the effects of exogenous variables (water availability, tree functional diversity, functional identity, species richness) and endogenous variables (soil fungal richness, community composition, and guilds) on tree productivity. Effects of A) total fungal richness; B) fungal community composition (NMDS axes 1, 2, and 3), and C) richness of fungal guilds: plant pathogenic fungi (Patho.) and ectomycorrhizal fungi (ECM) on productivity and D) null model with no connection between fungi and productivity. Numbers inside of the boxes indicate the conditional R² for each endogenous variable. Numbers next to arrows represent the standardized coefficient of each path. Blue arrows represent positive effects and red arrows represent negative effects and arrow sizes are scaled to the magnitude of the standardized coefficient. Symbols next to the standardized coefficients indicate the statistical significance of the path (+: P < 0.1; *: P < 0.05, **: P < 0.01, ***: P < 0.001). Paths with P > 0.1 are excluded from the figure (Tables S2-S5).