Is the Japanese walnut (Juglans ailantifolia, Juglandaceae) native to Sakhalin Island?

The Japanese walnut (Juglans ailantifolia Carrière) is considered a very rare native tree species to Sakhalin Island. There is no information about J. ailantifolia records in the natural broad-leaved mixed forests of the island. The valleys of the Uglegorka and the Nadym Rivers in the Uglegorsk administrative district were noted as the main habitats areas of J. ailantifolia in several sources. We found that all walnut trees from these locations belong to artificial forest stands over 95 years old. We conclude that J. ailantifolia is a non-native species to the modern flora of Sakhalin and was introduced from Japan at the beginning of the XX century.