Additive effects of nurse and facilitated plants on ecosystem functions

1. Nurse plants drive the assembly of facilitated communities and commonly promote plant-soil feedbacks, and are thus recognized as key engineers in abiotically stressful ecosystems. The literature neglects however, the role of the communities which benefit from the presence of the nurse as contributors to soil ecosystem functions. We hypothesized that the nurse and its beneficiaries synergistically enhance essential ecosystem functions mediated by soil microbiota. 2. To track how plant-plant facilitation impacts plant-soil feedbacks, we selected three nurse species in semi-arid mine tailings and defined three microsites (open space, nurse canopy, nurse + facilitated canopy). In each microsite, we quantified 18 abiotic and biotic variables associated with four functions: reduction of climatic stress, reduction of edaphic stress, soil fertility and soil microbial productivity (decomposition and nutrient cycling). 3. Litter biomass increased from open spaces to the microsite beneath the n...