Tyree, Melvin T, INRA, UMR-ECOFOG, BP 709, F-97387 Kourou, French Guiana; Department of Renewable Resources, Faculty of Agricultural, Life and Environmental Sciences, 442 Earth Sciences Building, University of Alberta, Edmonton, Alberta, Canada T6G 2E3; United States Forest Service, 709 Spear St, PO Box 968, Burlington, Vermont 05402 USA;