Institution: | aFinnish Forest Research Institute, Muhos Research Station, Kirkkosaarentie 7, FIN-91500 Muhos, Finland bDepartment of Biology, University of Oulu, P.O. Box 3000, FIN-90014 University of Oulu, Finland cDepartment of Ecological and Environmental Sciences, University of Helsinki, Niemenkatu 73, FIN-15140 Lahti, Finland |