1. Southern Swedish Forest Research Centre, Swedish University of Agricultural Sciences, Alnarp, Sweden
2. Institut de recherche sur les forêts, Université du Québec en Abitibi-Témiscamingue, Rouyn-Noranda, Canada
3. Asa Research Station, Swedish University of Agricultural Sciences, Lammhult, Sweden
4. Key Laboratory for Silviculture and Conservation of Ministry of Education, Beijing Forestry University, Beijing, People’s Republic of China