Facilitation enhances ecosystem function with non-random species gains

Facilitation, an ecological interaction assembling plant communities worldwide, has been shown to modulate both species richness and ecosystem functions. Such a Biodiversity-Ecosystem Functioning (BEF) relationship can be decomposed into different components not only related to species losses and gains but also to the identity of the species and the context in which they live. Using an extension of the classical BEF approach named CAFE (Community Assembly and the Functioning of Ecosystems), we quantified the contribution of these components to the BEF relationship in a Spanish semiarid plant community shaped by facilitation. We used species richness as a measure for biodiversity and plant cover as a proxy of multiple ecosystem functions including plant productivity, soil protection, soil fertility and microbial productivity. Nurse plants doubled the number of species that live beneath them relative to open ground, but caused a five-fold increase in plant cover. The disproportionate incr...