Figure 2 A visualization of a Pearson correlation matrix of ecosystem functions, and the effects of different trophic diversity on 15 ecosystem functions through linear models. Line thickness is plotted and the value is labeled as Adjusted R 2 from the linear model. The pink lines indicate positive effects and the blue lines indicate negative effects. A single asterisk (*) and a double asterisk (**) indicate significant relationships via the Pearson test atP < 0.05 and P < 0.001, respectively. Abbreviations: TN, total nitrogen (g·kg−1); OC, organic carbon (g·kg−1); TP, total phosphorus (g·kg−1); AHN, alkali hydrolyzed nitrogen (mg·kg−1); AP, available phosphorous (mg·kg−1); AMN, ammonium nitrogen (mg·kg−1); NN, nitrate nitrogen (mg·kg−1); MC, moisture content (%); C:N, ratio of organic carbon to total nitrogen; C:P, ratio of organic carbon to total phosphorus; N:P, ratio of total nitrogen to total phosphorus; C:N:P, ratio of organic carbon to total nitrogen to total phosphorus; AGB, plant aboveground biomass (g·m−2); BGB, plant belowground biomass (g·m−2); A:B, ratio of plant aboveground biomass to belowground biomass.
3.3 Predictors of major ecosystem functions and multifunctionality
We further grouped these 15 individual ecosystem functions into four major functions and ecosystem multifunctionality (water conservation, soil fertility, nutrition cycling and transformation, and community productivity, figure 3). A Random Forest analysis showed that altitude, plant, and rodent diversity indices as predictors could better explain the four major functions and ecosystem multifunctionality (Figure S11). Moreover, the significant predictors of ecosystem functions and multifunctionality were different (Figure 4 and Table S4). A function-dependent pattern was found among these relationships. For example, plant diversity had positive relationships with water conservation, nutrition cycling and transformation, and community productivity (Figures 4a, c, and d), and rodent diversity had positive relationships with soil fertility, community productivity, and ecosystem multifunctionality (Figures 4b, d, and e). Among these predictors, multitrophic diversity as a critical one to explain the relationships with functions except for community productivity (Figures 4a, b, c, and e). Notably, it was interesting to observe that multitrophic diversity had a more pronounced positive impact on ecosystem multifunctionality when compared to species diversity within any individual group, which could improve ecosystem multifunctionality (Figure 4e). Overall, ecosystem multifunctionality was better predicted by multitrophic diversity than by other types of diversity.