1. Unitat d’Ecofisiologia CSIC‐CEAB‐CREAF, CREAF (Centre de Recerca Ecològica i Aplicacions Forestals), Universitat Autònoma de Barcelona, 08193 Bellaterra (Barcelona), Catalonia, Spain;
2. Present address: Department of Entomology, University of Illinois, 320 Morrill Hall, 505 S. Goodwin, Urbana, IL 61801, USA.
3. Department of Forest Sciences, University of Alaska, Fairbanks, AK 99775‐7200, USA;