Plant biomass data (measured from 2012 to 2015) and plant trait data (measured in 2015)

The 48 experimental plant communities included twelve monocultures (of which one was removed from all analyses because it was planted with the wrong species), twelve 2-species mixtures, twelve 4-species mixtures and twelve 8-species mixtures. We used two community-evolution treatments (plant histories); plants with eight years of co-selection history in different plant communities in the Jena Experiment (communities of co-selected plants) and plants without such co-selection history (naïve communities).

Community-level plant productivity was measured each year from 2012 to 2015 by collecting species-specific aboveground biomass at the time of peak biomass in spring, whereas the traits plant height and SLA were measured once in 2015. We harvested plant material 3 cm aboveground from a 50 x 20 cm area in the centre of each half-quadrat, sorted it into species, dried it at 70°C and weighed the dry biomass. At the end of the experiment, in May 2015, we measured plant height and SLA for 30 species in neutral soil.