Trophic complexity alters the diversity–multifunctionality relationship in experimental grassland mesocosms

Plant diversity has a positive influence on the number of ecosystem functions maintained simultaneously by a community, or multifunctionality. While the presence of multiple trophic levels, or trophic complexity, affects individual functions, the effect of trophic complexity on the diversity-multifunctionality relationship is less well known. To address this issue, we tested whether the independent or simultaneous manipulation of both plant diversity and trophic complexity impacted multifunctionality using a mecocosm experiment from Cedar Creek, Minnesota, USA. Our analyses revealed that neither plant diversity nor trophic complexity had significant effects on single functions, but trophic complexity altered the diversity-multifunctionality relationship in two key ways: it lowered the maximum strength of the diversity-multifunctionality effect and it resulted shifted the relationship between increasing diversity and multifunctionality from positive to negative at lower function threshol...