1. Associate Professor, Dept. of Landscape Architecture and Rural System Engineering, Research Institute for Agriculture and Life Sciences, Seoul National Univ., Gwanagno 599, Gwanak-gu, Seoul, 151-921, Republic of Korea.
2. Ph.D. Student, Geography Graduate Group and Information Center for the Environment, Univ. of California, Davis, One Shields Ave., Davis, CA 95616 (corresponding author).