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