1. USDA Forest Service, Pacific Southwest Region 1323 Club Drive Vallejo California94592USA
2. USDA Forest Service, Pacific Northwest Research Station 3625 93rd Avenue Olympia Washington98512USA
3. Department of Mathematics Montana State University 1156‐1174 South 11th Street Bozeman Montana59715USA
4. USDA Forest Service, Rocky Mountain Research Station 800 East Beckwith Avenue Missoula Montana59801USA