1. Department of Forest Resource Management, Swedish University of Agricultural Sciences, Umeå, Sweden.
2. Department of Biological and Environmental Science, P.O. Box 35, 40014 University of Jyväskylä, Finland.
3. Department of Forest Economics, Swedish University of Agricultural Sciences, Umeå, Sweden.
4. European Forest Institute, North European Regional Office, SLU, SE-901 83 Umeå, Sweden.