Bottom-up effects of plant diversity on multitrophic interactions in a biodiversity experiment

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

Plant Diversity Surpasses Plant Functional Groups and Plant Productivity as Driver of Soil Biota in the Long Term

One of the most significant consequences of contemporary global change is the rapid decline of biodiversity in many ecosystems. Knowledge of the consequences of biodiversity loss in terrestrial ecosystems is largely restricted to single ecosystem functions. Impacts of key plant functional groups on soil biota are considered to be more important than those of plant diversity; however, current knowledge mainly relies on short-term experiments.We studied changes in the impacts of plant diversity and presence of key functional groups on soil biota by investigating the performance of soil microorganisms and soil fauna two, four and six years after the establishment of model grasslands. The results indicate that temporal changes of plant community effects depend on the trophic affiliation of soil animals: plant diversity effects on decomposers only occurred after six years, changed little in herbivores, but occurred in predators after two years. The results suggest that plant diversity, in terms of species and functional group richness, is the most important plant community property affecting soil biota, exceeding the relevance of plant above- and belowground productivity and the presence of key plant functional groups, i.e. grasses and legumes, with the relevance of the latter decreasing in time.Plant diversity effects on biota are not only due to the presence of key plant functional groups or plant productivity highlighting the importance of diverse and high-quality plant derived resources, and supporting the validity of the singular hypothesis for soil biota. Our results demonstrate that in the long term plant diversity essentially drives the performance of soil biota questioning the paradigm that belowground communities are not affected by plant diversity and reinforcing the importance of biodiversity for ecosystem functioning

Effects of plant biodiversity on above-belowground interactions

<p>This graph comes from a manuscript published in <strong>Nature</strong> (http://dx.doi.org/10.1038/nature09492) and shows how<strong> plant species richness</strong> affects <strong>organisms living in the soil and in the vegetation layer</strong>. It was originally published as part of the Supplementary Material and is reproduced here to show it to a wider audience.</p

How biodiversity affects ecosystem processes

<p>This graph shows the effects of <strong>plant species richness</strong> on <strong>ecosystem processes</strong>, e.g.:</p> <p>-effects of plant biodiversity on <strong>decomposition</strong></p> <p>-effects of plant biodiversity on <strong>pathogen infection</strong></p> <p>-effects of plant biodiversity on <strong>herbivory</strong></p> <p>-effects of plant biodiversity on <strong>flower visitation</strong> (pollination)</p> <p>-effects of plant biodiversity on <strong>bioturbation</strong></p> <p>-effects of plant biodiversity on<strong> ant activity</strong></p> <p>-effects of plant biodiversity on <strong>parasitism</strong> and <strong>hyperparasitism</strong>,</p> <p>-effects of plant biodiversity on <strong>biological invasion</strong> and</p> <p>-effects of plant biodiversity on <strong>soil microbial respiration</strong>.</p> <p>The graph comes from the supplementary material of a paper published by Scherber et al. in Nature (http://dx.doi.org/10.1038/nature09492).</p> <p>Biodiversity effects are mostly non-linear, and species richness effects are negative in some cases. For more details, see the Supplementary Material at http://www.nature.com/nature/journal/v468/n7323/extref/nature09492-s1.pdf</p