1. Department of Environmental and Biological Sciences, University of Eastern Finland, P. O. Box 1627, 70211 Kuopio, Finland
2. Department of Biology, Terrestrial Ecology Section, University of Copenhagen, 2100 Copenhagen Ø, Denmark
3. Department of Biology, Center for Volatile Interactions (VOLT), University of Copenhagen, 2100 Copenhagen Ø, Denmark
4. Natural Resources Institute Finland, Halolantie 31 A, FI-71750, Maaninka, Finland
5. Department of Technical Physics, University of Eastern Finland, P. O. Box 1627, 70211 Kuopio, Finland
6. Natural Resources Institute Finland, Juntintie 154, 77600 Suonenjoki, Finland