1. School of Forestry and Wood Products, Michigan Technological University, Houghton, MI 49931, USA;
2. Forest Nutrition Cooperative, North Carolina State University, Raleigh, NC 27695, USA;
3. USDA Forest Service, South‐east Experiment Station, Research Triangle Park, NC 27709, USA;
4. Department of Botany, Duke University, Durham, NC 27708, USA;
5. Westvaco, PO Box 1950, Summerville, SC 29484, USA