Ecosystem functions
A total of 16 ecosystem functions were measured on each plot. Function
data included grassland productivity (above- and belowground), proxies
of energy transfer between trophic levels (herbivory, seed and dung
depletion, litter decomposition, root decomposition, pathogen
infection), biogeochemical cycling (carbon, nitrate and ammonia fluxes,
phosphatase, potential nitrification, N and P retention), and hydrology
(water recharge). Plant shoot biomass was measured in eight 0.5 m x 0.5
m squares and root biomass in 14 soil cores per plot. Herbivory was
calculated by measuring the proportion of leaf area damaged by insects,
on 100 random leaves selected from the biomass sample. Seed and dung
depletion was calculated as the proportion of cattle dung or sunflower
seeds removed after 48 hours exposure. Litter and root decomposition was
calculated as the mass loss from litterbags after 4 and 6 months
respectively. Pathogen infection was estimated by visual inspection and
calculated as the cover weighted mean of pathogen prevalence and
severity per plant species. Proxies of carbon, nitrate and ammonia
fluxes were calculated using composite indices including several
enzymatic activities (Carbon: β-Glucosidase, N-Acetyl-β-Glucosaminidase
and Xylosidase; Nitrate: Denitrification enzyme; Ammonia: Urease) and
functional genes (Nitrate: nitrogenase, nrxA gene fornitrobacter , 16S rRNA gene for nitrospira ; Ammonia:
ammonia oxidation genes for archaea and bacteria). C-cycling enzyme
activities were analyzed using fluorogenic substrate and fluorometric
detection, N-cycling enzyme activities as well as potential
nitrification were photometrically analyzed and the abundance of
functional genes was quantified via real-time qPCR analysis. Nutrient
retention (N, P) was measured as the remaining anion content in resin
bags buried 20 cm deep for 140 days. Water recharge was calculated using
a water balance model using climatic and soil data. Detailed information
about function data collection is included in Supplementary Table S3).
Statistical Analyses