1. Department of Biology; University of Eastern Finland; P.O. Box 111 FI-80101 Joensuu Finland
2. Department of Ecology and Natural Resource Management; Norwegian University of Life Sciences; P.O. Box 5003 NO-1432 Ås Norway
3. The Finnish Forest Research Institute; Vantaa Research Unit; P.O. Box 18 FI-01301 Vantaa Finland
4. Finnish Game and Fisheries Research Institute; Joensuu Game and Fisheries Research; Yliopistonkatu 6 FI-80100 Joensuu Finland
5. Department of Forestry; University of Eastern Finland; P.O. Box 111 FI-80101 Joensuu Finland