1. Michigan Technological University, School of Forest Research and Environmental Science, 101 Noblet Hall, 1400 Townsend Drive, Houghton, MI 49931, USA;
2. Virginia Polytechnic Institute and State University, Department of Forestry, 304 Cheatham Hall (0324), Blacksburg, VA 24061, USA;
3. Oregon State University, Department of Forest Science, Corvallis, OR 97331‐5752, USA