Data from: 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 nurses,
and further beneath the nurses and their beneficiaries. Litter biomass was
a good predictor of both the reduction in climatic stress and increase in
edaphic stress (likely owing to metal bioaccumulation). We attributed
increments in soil organics and heterotrophic respiration beneath the
nurses and their beneficiaries, compared to nurses alone, to biomass
effects through increased litter deposition. Variation in fertility and
microbial productivity among microsites shaped by the nurses and their
facilitated communities was attributed to both diversity and biomass
effects. In particular, fertility was promoted beneath phenotypically
diverse facilitated communities, as inferred from ten above- and
belowground traits. However, microbial productivity increased at low
levels of root biomass likely due to reduced plant-microbe competition for
nutrients. 4. Synthesis. Our results show that facilitated plant
communities sheltered by nurse species relieve local abiotic stress and
promote plant-microbe interactions, both through biomass and biodiversity
effects. These observations shift the conception of facilitated species
from simple beneficiaries of the nurse’s effects, to co-drivers of
essential ecosystem functions.