1Upland Farming Research Division, Hokkaido Agricultural Research Center, National Agriculture and Food Research Organization (NARO), Shinsei, Memuro, Kasai, Hokkaido, 082-0081, Japan
2Institute of Biological & Environmental Sciences, School of Biological Sciences, University of Aberdeen, 23 St Machar Drive, Aberdeen, AB24 3UU, Scotland, UK
3Natural Resources Inventory Center, National Institute for Agro-Environmental Sciences, 3-1-3 Kan-nondai, Tsukuba, Ibaraki 305-8604, Japan
4Department of International Environmental and Agricultural Science, Graduate School of Agriculture, Tokyo University of Agriculture and Technology, Saiwaicho 3-5-8, Fuchu, Tokyo 183-8509, Japan
5Agro-Environmental Research Division, Hokkaido Agricultural Research Center, NARO, Hitsujigaoka 1, Toyohira, Sapporo, Hokkaido 062-8555, Japan