Fig. 1: Hypothesized relationships among plant species richness, fungal diversity, and ecosystem multifunctionality.

a Green arrows represent the effects of plant species richness on fungal diversity and ecosystem multifunctionality. Brown arrows represent the effects of fungal diversity on plant species richness, ecosystem multifunctionality and the relationship between plant species richness and ecosystem multifunctionality. b The full set of possible linear changes in the relationship between plant species richness and ecosystem multifunctionality with fungicide addition (i.e., reduced fungal diversity), corresponding to the scenarios presented in panel (c). The yellow line represents the hypothesized relationship between plant species richness and ecosystem multifunctionality without any change in fungal diversity (i.e., control communities). The blue, red and brown lines represent how fungicide addition could increase, decrease or have no effect on ecosystem multifunctionality, respectively (represented by straight arrows oriented up and down). Curved arrows represent how changes in fungal diversity could also enhance or inhibit the strength of the relationship between plant species richness and ecosystem multifunctionality. c The range of potential impacts of fungicide addition on ecosystem multifunctionality and the relationship between plant species richness and ecosystem multifunctionality, corresponding to panel (b). Upward arrows represent an increase, downward arrows represent a decrease, and crosses represent no change. Specifically, we hypothesized that reduced fungal diversity (i.e., via the fungicide addition treatment) will decrease ecosystem multifunctionality and weaken the relationship between plant species richness and ecosystem multifunctionality, corresponding to scenario 8.