1. Department of Geology, PO Box 64, FIN-00014 University of Helsinki, Finland;
2. Karelian Institute, University of Joensuu, PO Box 111, FIN 80101 Joensuu, Finland
3. Climatic Research Unit, University of East Anglia, Norwich NR4 7TJ, UK
4. Department of Geology, PO Box 64, FIN-00014 University of Helsinki, Finland
5. Saima Centre for Environmental Sciences, University of Joensuu, Linnankatu 11, FIN-57130 Savonlinna, Finland
6. Finnish Forest Research Institute, PO Box 16, FIN-96301 Rovaniemi, Finland