The two papers result from a longer-term study on biodiversity and ecosystem functioning in semi-natural grasslands along a gradient in plant species richness (BIOLOG DIVA-Jena). Stein et al. reports results from a 5-year program of applying insecticide and molluscicide to exclude herbivores above- and belowground. Excluding herbivores leds to shifts in the plant community that were stronger when belowground herbivores were excluded. Effects on plant biomass were generally small but depended on plant diversity: the effect of herbivory on biomass tended to be negative at sites of high diversity and positive at sites of low diversity. Unsicker et al. (2010) measured fitness of grasshoppers in the plots and found a positive effect of plant species richness on grasshopper fecundity and grasshopper population size.
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