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 thresholds. Our findings suggest that declines in trophic complexity will further reduce the capacity of ecosystems to maintain multifunctionality than expected from plant biodiversity loss. Methods This dataset was collected in a mesocosm experiment at Cedar Creek. The experiment was run from the year 2000-2002. The functional and phylogenetic diversity columns were added later using species trait values from the TRY dataset and a super tree from Zanne et al 2014 respectively.