1. Department of Economics and Natural Resources, Arboretum, The Royal Veterinary & Agricultural University, Hørsholm Kongevej 11, DK‐2970 Hørsholm, Denmark;
2. Centre for Ecology and Hydrology, Bush Estate, Penicuik, Midlothian EH26 0QB, UK;
3. Norwegian Forest Research Institute, Høgskolevegen 12, N‐1432 Ås, Norway;
4. USDA Forest Service, Rocky Mountain Research Station, 240 West Prospect RD, Fort Collins, CO 80526–2098, and Graduate Degree Program in Ecology, Colorado State University, Fort Collins, Colorado 80523, USA;
5. Biology Program Area, 6237 Craven Hall, California State University San Marcos, California 92096–0001, USA