1. European Forest Institute, Yliopistokatu 6, 80100 Joensuu, Finland.
2. Department of Forest Sciences, University of Helsinki, Latokartanonkaari 7, 00790 Helsinki, Finland.
3. European Commission, Joint Research Centre (JRC), Via E. Fermi 2749, I-21027 Ispra, Italy.
4. Department of Chemistry, University of Eastern Finland, Yliopistokatu 7, 80130 Joensuu, Finland.