1. a Muhos Research Station , Finnish Forest Research Institute , Kirkkosaarentie 7, FI-91500, Muhos
2. b Department of Biology , University of Oulu , Oulun, FI-90014, Yliopisto
3. c Department of Mathematics , Natural and Computer Science, University College of Gävle , SE-801 76, Gävle
4. d Division of Biology , Kansas State University , 125 Ackert Hall, KS 66506, Manhattan
5. e Department of Ecological and Environmental Sciences , University of Helsinki , Niemenkatu 73, FI-15140, Lahti