Jack-of-all-trades effects drive biodiversity-ecosystem multifunctionality relationships in European forests

Abstract

There is considerable evidence that biodiversity promotes multiple ecosystem functions (multifunctionality),thus ensuring the delivery of ecosystem services important for human well-being.However, the mechanisms underlying this relationship are poorly understood, especially in naturalecosystems. We develop a novel approach to partition biodiversity effects on multifunctionality intothree mechanisms and apply this to European forest data. We show that throughout Europe, treediversity is positively related with multifunctionality when moderate levels of functioning are required,but negatively when very high function levels are desired. For two well-known mechanisms, 'complementarity'and 'selection', we detect only minor effects on multifunctionality. Instead a third, so faroverlooked mechanism, the 'jack-of-all-trades' effect, caused by the averaging of individual specieseffects on function, drives observed patterns. Simulations demonstrate that jack-of-all-trades effectsoccur whenever species effects on different functions are not perfectly correlated, meaning they maycontribute to diversity&-multifunctionality relationships in many of the world's ecosystems.