Facilitation enhances ecosystem function with non-random species gains

© 2021 The Authors.
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 increase of plant cover was a consequence of the identity of the species enhanced by nurse plants, which were more productive than the average. We discuss these results in terms of sampling effects (i.e. the higher probability of richer communities to harbour hyperproductive species) and complementary effects (i.e. richer communities enhancing productivity through resource partitioning, abiotic facilitation or biotic feedbacks). The enhancement of ecosystem functions that plant facilitation produces by incorporating species with high functional values to the community may reverberate among other trophic levels and propagate beyond the local scale where the ecological interaction is produced.
Financial support was provided by the Spanish Ministry of Economy and Competitiveness (CGL2014-58333-P, CGL2017-89751-R, PID2020-113157GB-I00).