The multi-stemmed shrub species of Betula (dwarf birch) are important elements of boreal ecosystems in continental Asia, but their taxonomy is poorly understood. Among such dwarf birch species, B. fusca is found in northern Mongolia and southern Siberia, and B. ovalifolia (Yachikanba) is distributed in northern Far East Asia including Japan. In Japan, the distribution of B. ovalifoila is restricted to only two locations (Betsukai and Sarabetsu) of Hokkaido. These two species may be synonyms of Betula fruticosa which is broadly distributed in Northeast Asia.
I conducted allometric measurement of B. fusca in Mongolia and B. ovalifolia in Hokkaido at both whole plant and shoot levels to examine how much alike the two dwarf birch species are. In whole-plant allometrty, B. fusca had smaller crown area than B. ovalifolia. This may be related to shoot allometry that B. fusca had shorter shoots relative to shoot basal area than B. ovalifolia. Water stress in drier conditions may explain smaller crown area and stouter shoot allometry of B. fusca.