1. a Institute for Environment and Sustainability , EC Joint Research Centre , Ispra , 21020 , (VA) , Italy E-mail:
2. b Institute for Environment and Sustainability , EC Joint Research Centre , Ispra , 21020 , (VA) , Italy E-mail:
3. c Center for Forest Ecology and Productivity of Russian Academy of Science , 84/32 Profsoyuznaya Str., Moscow , 117810 , Russia E-mail:
4. d Center for Forest Ecology and Productivity of Russian Academy of Science , 84/32 Profsoyuznaya Str., Moscow , 117810 , Russia E-mail: