1. Faculty of Forestry, University of Toronto, Toronto, Ontario, M5S 3B3, Canada
2. Faculty of Forestry, University of Toronto, Toronto, Ontario, M5S 3B3, Canada; Department des Sciences du Bois et de la Foret, Faculte de Foresterie et Geomatique, Universit6 Laval, Ste-Foy, GIK 7P4, Canada.