(a) A simple biodiversity experiment manipulating three species alone and all three in mixture, and measuring two ecosystem functions (F1 and F2) scaled between 0 and 1. Thresholds for 30%, 50% and 90% of the maximum observed level of functioning are denoted as the blue dotted, green dashed and red solid lines, respectively. A grand mean (dark grey bar) is taken across the two individual functions (white and light grey bars). (b) The number of functions exceeding a given threshold is plotted for each treatment, and regressed against richness. A positive slope (β) represents a positive effect of biodiversity on the number of functions exceeding a selected threshold. Line types correspond to threshold level in a. (c) The linear coefficients (β) from each regression in c are plotted against the corresponding threshold. In this case, all thresholds have been calculated from 1 to 99%, and the three coefficients from b are noted. (d) The grand mean from a is plotted for each treatment, and regressed against richness. A positive slope represents a positive effect of biodiversity on average multifunctionality.