Fig. 1: A factorial description of plot design.

Number of plant species denotes the plant species richness treatments (monoculture, 2, 3, or 6 species). Phylogenetically under-dispersed combinations of plants are all within one plant family (e.g. 2 grasses, or 3 legumes, or 6 asters). Phylogenetically over-dispersed combinations of plants are from more than one plant family (e.g. 1 grass and 1 aster, or 1 species from each family, or 2 species from each family). Monocultures are inherently under-dispersed. The sets describe the combinations in which each of the 18 plant species are represented once (i.e. within sets species are randomly chosen without replacement from the pool of 18 plant species). There are 18 monocultures, two sets of 9 under-dispersed 2-plant plots, two sets of 9 over-dispersed 2-plant plots, two set of 6 under-dispersed 3-plant plots, two sets of 6 over-dispersed 3-plant plots, three sets of under-dispersed 6-plant plots, and three sets of over-dispersed 6-plant plots. This approach equally represents each plant species in each richness treatment by phylogenetic dispersion combination.