1. Warnell School of Forestry and Natural Resources, The University of Georgia, Athens, GA 30602, USA.
2. U.S. Forest Service, Northern Research Station, 11 Campus Blvd., Suite 200, Newtown Square, PA 19073, USA.
3. U.S. Forest Service, Southern Research Station, 1710 Research Center Drive, Blacksburg, VA 24060, USA.
4. Department of Natural Resource Ecology and Management, Oklahoma State University, Stillwater, OK 74078, USA.