Pedro Flombaum and Osvaldo E. Sala. 2012. Effects of plant species traits on ecosystem processes: Experiments in the Patagonian steppe. Ecology 93:227–234.

Appendix B. Example of construction of a trait richness gradient.

In this example, the species-richness gradient was 1, 2, and 3 species. With three species (Stipa speciosa, Poa ligularis, and Mulinum spinosum) there are seven possible assemblages. To redefine this species-richness gradient into a trait-richness gradient we needed to (1) assign species to trait levels, (2) combine the trait-richness gradients, and (3) count the numbers of levels on each species assemblage.

(1) Stipa speciosa and Poa ligularis belonged to the 12 month level for plant phenology, and to 30–60 cm and 60–90 cm level for rooting depth respectively; Mulinum spinosum belonged to 7 month and 90–120 cm level for plant phenology and rooting depth respectively.

(2) We combined 2 trait richness gradients (a) plant phenology alone, and (b) plant phenology with rooting depth.

(3) We counted the number of levels for each species assemblage (Table B1).

The plant-species-richness gradient was redefined into various trait-diversity gradients. The plant-phenology gradient ranged from 1 to 2 levels. The assemblage “Stipa speciosa and Poa ligularis” had the same trait-diversity level as monocultures, while the other two-species plots had similar trait diversity levels as the three-species mixture (Table B1). The gradient of plant phenology combined with rooting depth ranged from two to five levels; two-species assemblages had intermediate richness levels between monocultures and three-species mixture.

TABLE B1: Table used to redefine species richness gradient into a trait-richness gradient. Level identities replicated in an assemblage (in gray) did not add to the number of levels.