1. Dept. Natural Resources, Fernow Hall, Cornell University, Ithaca, NY 14853, U.S.A.
2. School of Biology and Ecology, University of Maine, 5572 Deering Hall, Orono, ME 04469, U.S.A.
3. Vermont Department of Environmental Conservation, Air Quality & Climate Division, Davis Building - 2nd Floor, One National Life Drive, Montpelier, VT 05620-3802, U.S.A.
4. U.S. Forest Service-Watershed, Fish, Wildlife, Air & Rare Plants, 201 14th Street SW, Washington, DC 20250, U.S.A.
5. U.S. Forest Service, Eastern Region Air Program, 71 White Mountain Drive, Campton, NH 03223, U.S.A.
6. U.S. Forest Service, Northern Research Station, 81 Carrigan Dr., Burlington, VT 05405, U.S.A.