1. Institute of Agronomy, University of Natural Resources and Life Science, 3430 Tulln an der Donau, Austria
2. Institute of Botany, University of Natural Resources and Life Science, 1180 Vienna, Austria
3. Department of Ecology, Swedish University of Agricultural Sciences, SE-75007 Uppsala, Sweden
4. Faculty of Agriculture, University of Banja Luka, 78000 Banja Luka, Bosnia and Herzegovina
5. Experimental Farm Groß-Enzerdorf, University of Natural Resources and Life Sciences, 2301 Groß-Enzersdorf, Austria
6. Institute of Mathematics, University of Natural Resources and Life Science, 1180 Vienna, Austria