1. Research Group Aquatic Ecology and Environmental Biology, Department of Ecology, Radboud University Nijmegen, Toernooiveld 1, NL‐6525 ED Nijmegen, The Netherlands
2. Centre for Ecosystem Studies, Alterra, Wageningen University and Research, P.O. Box 47 NL‐6700 AA Wageningen, The Netherlands;
3. E‐mail
4. Section of Landscape Ecology, Institute of Environmental Biology, Utrecht University, P.O. Box 80084, NL‐3508 TB Utrecht, The Netherlands
5. Community and Conservation Ecology Group, University of Groningen, P.O. Box 14, NL‐9750 AA Haren, The Netherlands
6. Institute of Botany, University of Regensburg, DE‐93040 Regensburg, Germany
7. Institute of Botany, Department of Plant Ecology, Dukelská 135, 379 01 Třeboň, Czech Republic