1. College of Agriculture, Tamagawa University, Tamagawa Gakuen 6-1-1, Machida, Tokyo 194-8610, Japan
2. Northern Oikoscape Research Ateleir, Shimorenjaku 4-16-8-103, Mitaka, Tokyo 181-0013, Japan
3. Department of Forest and Conservation Sciences, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada