1. Department of Plant and Environmental Sciences, Faculty of Science; University of Copenhagen; Thorvaldsensvej 40 Frederiksberg C DK-1871 Denmark
2. Department of Ecology, Faculty of Humanities Natural Sciences; Prešov University in Prešov; Ul. 17 novembra 1 Prešov 081 16 Slovakia
3. Department of Agroecology; Aarhus University, PO Box 50; Tjele DK-8830 Denmark