Summary of the relevant design details for the subsets of compatible data analysed from the grassland biodiversity experiments that replicated both species richness and composition (ordered by increasing aboveground annual net biomass production, ANPP).

The subsets of the species richness gradients used are given by ‘Diversity’ and the number of species compositions (monocultures or polycultures) in each experiment by ‘Compositions’. For comparability we used data from the earlier stages of each experiment (year 2 or 3). Numbers of compositions for each experiment ignore duplication of species mixtures with other experiments but the row titled Total gives the number of compositions ignoring duplicates and discounting duplicates (in parentheses). The version of the variable with 308 levels was used in all analyses, resulting in partially crossed random effects for experimental sites and species composition in the mixed-effects model.