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A; et al., (2010). Bottom-up effects of plant diversity on multitrophic interactions in a biodiversity experiment. Nature, (468) Bottom-up effects of plant diversity on multitrophic interactions in a biodiversity experiment Abstract Biodiversity is rapidly declining1, and this may negatively affect ecosystem processes, including economically important ecosystem services. Previous studies have shown that biodiversity has positive effects on organisms and processes4 across trophic levels. However, only a few studies have so far incorporated an explicit food-web perspective. In an eight-year biodiversity experiment, we studied an unprecedented range of above-and below-ground organisms and multitrophic interactions. A multitrophic data set originating from a single long-term experiment allows mechanistic insights that would not be gained from meta-analysis of different experiments. Here we show that plant diversity effects dampen with increasing trophic level and degree of omnivory. This was true both for abundance and species richness of organisms. Furthermore, we present comprehensive above-ground/below-ground biodiversity food webs. Both above ground and below ground, herbivores responded more strongly to changes in plant diversity than did carnivores or omnivores. Density and richness of carnivorous taxa was independent of vegetation structure. Below-ground responses to plant diversity were consistently weaker than above-ground responses. Responses to increasing plant diversity were generally positive, but were negative for biological invasion, pathogen infestation and hyperparasitism. Our results suggest that plant diversity has strong bottom-up effects on multitrophic interaction networks, with particularly strong effects on lower trophic levels. Effects on higher trophic levels are indirectly mediated through bottom-up trophic cascades. However, only few studies so far incorporated an explicit food-web perspective 6 . In an 8-50 year biodiversity experiment, we studied an unprecedented range of above-and 51 belowground organisms and biotic interactions. A multitrophic dataset originating from 52 a single long-term experiment allows mechanistic insights that otherwise would not be 53 possible using meta-analysis of different experiments. We show that plant diversity 54 effects dampen with increasing trophic level and degree of omnivory. This finding was 55 consistent both for abundance and species richness of organisms. Further, we present 56 comprehensive above-belowground biodiversity food webs. Both above-and 57 belowground, herbivores responded more strongly to changes in plant diversity than did 58 carnivores or omnivores. Density and richness of carnivorous taxa was independent of 59 vegetation structure. Belowground responses to plant diversity were consistently weaker 60 than aboveground responses. Responses to increasing plant diversity were generally 61 positive, but negative for biological invasion, pathogen infestation and hyperparasitism. 62Our results suggest that plant diversity exhibits stron...

Plant diversity generally promotes biomass production, but how the shape of the response curve changes with time remains unclear. This is a critical knowledge gap because the shape of this relationship indicates the extent to which loss of the first few species will influence biomass production. Using two long-term (≥13 years) biodiversity experiments, we show that the effects of diversity on biomass productivity increased and became less saturating over time. Our analyses suggest that effects of diversity-dependent ecosystem feedbacks and interspecific complementarity accumulate over time, causing high-diversity species combinations that appeared functionally redundant during early years to become more functionally unique through time. Consequently, simplification of diverse ecosystems will likely have greater negative impacts on ecosystem functioning than has been suggested by short-term experiments.