1. Dep. of Chemical Ecology and Ecosystem Research; Univ. of Vienna; Althanstrasse 14 1090 Vienna Austria
2. Dep. of Forest and Ecosystem Science; Univ. of Melbourne; Water St. Creswick VIC 3363 Australia
3. Dep. of Forest Ecology and Management; Swedish Univ. of Agricultural Sciences; SE-901, 83 Umeå Sweden