Multitrophic interaction networks mediate biodiversity effects on ecosystem multifunctionality

Biodiversity loss threatens the multifunctionality of ecosystems on which human well-being ultimately depends. Multitrophic species interactions may be key to explaining the ecological consequences of biodiversity loss, but research explicitly linking species interactions and ecosystem multifunctionality remains rare. To fill this gap, we synthesize data from a large-scale biodiversity experiment established in 2009 in subtropical China that manipulates tree species richness (1-24 species). We integrate 11 types of antagonistic and mutualistic species interaction networks, and 34 ecosystem functions associated with a diverse set of species and trophic levels. Our analysis highlights that characterizing the structure of species interaction networks is invaluable for assessing interaction-mediated biodiversity effects and underlying mechanisms. Positive effects of network size align with expected benefits of multitrophic diversity for ecosystem multifunctionality. Positive effects of niche overlap among interacting species and negative effects of highly connected species (i.e. high linkage density) reveal additional, interaction-mediated drivers. The effects of niche overlap suggest benefits of functionally similar species, and the effects of linkage density underscore the importance of specialized interactions in promoting ecosystem multifunctionality. These findings emphasize that ecosystem service provisioning does not only rely on biodiversity across trophic levels, but to a similar degree on how species interact.