Document: BER-3-82-25

Effects of experimental perturbations on biodiversity-ecosystem functioning relationships.

SCHMID, B.* and A.PFISTERER

University of Zurich, Zurich, Switzerland ¹

Abstract:
We investigated how simulated trampling (by horse or sheep hooves) and drought (imposed by transparent roofs) influenced the productivity of 1-, 2-, 4-, 8-, and 32-species plant communities at an experimental site of the EU-BIODEPTH network. Community and species biomasses were measured prior, during, and after perturbation over a 2-year period. Further, the invasibility of the communities by weeds was assessed during and after perturbation. To reach a given amount of total biomass, more species were needed in perturbed than in unperturbed communities for both kinds of perturbation. The absolute reduction of community productivity due to perturbation increased with diversity. However, because productivity itself also increased with diversity the proportional reduction was constant across diversity levels. One year after the experimental drought all communities had fully regained their pre-drought productivity values. Shifts in community composition after drought were small, but more weeds invaded in low- than in high-diversity plots. Simulated trampling had small effects on the weed phytometer Ranunculus repens. These results suggest that the shape of biodiversity-ecosystem functioning relationships is relatively insensitive to perturbation. Diverse systems produce more biomass both without and with perturbation, but at least in terms of productivity they may not be more resistant or resilient than less diverse systems.

Keywords: Disturbance, Diversity, Productivity, Stability

This abstract is being presented at: 10:45 AM in session:
Oral Session #2: Conservation Ecology.