Figure 5: The biodiversity effect across a range of multifunctionality threshold values in theoretical communities.

Artificial communities were created by randomly drawing species from an artificial, regional species pool. Average correlation coefficients between ecosystem function values of these monocultures are −0.07 (a), 0.00 (b), 0.50 (c) and 1.00 (d), while ϕx values47, which indicate overall correlation strength, range from 0 (indicating lowest possible average correlation coefficients) to 1 (maximally positive correlations, equivalent to a single-function scenario). Linear models (N=100) were used to quantify the biodiversity effect and the 95% confidence interval (grey polygon). The observed average correlation value among functions in monocultures in European forests was 0.027 (=0.265; Fig. 1). The dotted, horizontal line shows the x axis, where the biodiversity effect is zero.