Phylogenetic, functional, and taxonomic richness have both positive and negative effects on ecosystem multifunctionality

Biodiversity encompasses multiple attributes such as the richness and abundance of species (taxonomic diversity), the presence of different evolutionary lineages (phylogenetic diversity), and the variety of growth forms and resource use strategies (functional diversity). These biodiversity attributes do not necessarily relate to each other and may have contrasting effects on ecosystem functioning. However, how they simultaneously influence the provision of multiple ecosystem functions related to carbon, nitrogen, and phosphorus cycling (multifunctionality) remains unknown. We evaluated the effects of the taxonomic, phylogenetic, and functional attributes of dominant (mass ratio effects) and subordinate (richness effect) plant species on the multifunctionality of 123 drylands from six continents. Our results highlight the importance of the phylogenetic and functional attributes of subordinate species as key drivers of multifunctionality. In addition to a higher taxonomic richness, we found that simultaneously increasing the richness of early diverging lineages and the functional redundancy between species increased multifunctionality. In contrast, the richness of most recent evolutionary lineages and the functional and phylogenetic attributes of dominant plant species (mass ratio effects) were weakly correlated with multifunctionality. However, they were important drivers of individual nutrient cycles. By identifying which biodiversity attributes contribute the most to multifunctionality, our results can guide restoration efforts aiming to maximize either multifunctionality or particular nutrient cycles, a critical step to combat dryland desertification worldwideThis work was funded by the European Research Council [ERC Grant Agreements 242658 (BIOCOM) and 647038 (BIODESERT)]. F.T.M., M.B., and Y.L.B.-P. are supported by the ERC (BIODESERT). Y.L.B.-P. was also supported by a Marie Sklodowska-Curie Actions Individual Fellowship within the European Program Horizon 2020 (DRYFUN Project 656035). S.S. was supported by the Spanish Government under a Ramón y Cajal Contract (RYC-2016-20604). N.G. was supported by the AgreenSkills+ fellowship programme, which has received funding from the European Union’s Seventh Framework Programme under Grant Agreement FP7-609398 (AgreenSkills+ contract). This work was supported by the French government Initiatives d’Excellence–Initiatives Science/Innovation/Territoires/Économie (IDEX-ISITE) initiative 16-IDEX-0001 (CAP 20-25).Peer reviewe