Effect of plant and soil community history on biodiversity–ecosystem functioning relationships

Background/Question/Methods

Mechanisms underlying biodiversity–ecosystem functioning relationships are closely linked to mechanisms underlying community assembly. Positive biodiversity–productivity relationships have been consistently observed in grassland experiments, with increasing effects of biodiversity noted over time. However, the mechanisms underlying the development of such increases in biodiversity effects remain unresolved. Here we hypothesize that both plant–soil feedbacks and plant community history each and interactively may act to drive the increase in biodiversity effects in grassland plant communities. In a large biodiversity experiment in Jena, Germany, we re-established communities of varying plant species richness and composition, taking advantage of history of the past 8 years to establish the plant and soil communities. We re-assembled the same experimental communities with seeds from plants of the same plot (common plant history) or from the supplier which provided the original seeds. We used unsterilized or sterilized soil taken from the same plots, and in the case of sterilized soil either re-inoculated with the original (common soil history) or with a neutral soil community. We hypothesized that biodiversity effects on productivity, based on complementarity resource use and interaction with soil organism, would be stronger in re-assembled communities with common plant and soil history.

Results/Conclusions

Our initial results show a positive biodiversity–productivity relationship across all soil and plant community treatments. Plant communities grown on sterilized soil exhibited markedly increased productivity. Under the non-sterilized soil treatment with common soil community history, productivity was low, presumably due to negative feedbacks from soil pathogens that had accumulated especially in the low diversity plots. In nearly all cases, plant communities without common plant community history were more productive initially than plant communities with common plant community history. Our results demonstrate that plant and soil community history may explain in part the strengthening of biodiversity–productivity relationships commonly observed during the course of biodiversity experiments.