Phytogeographical structure of the deciduous broadleaved forests in northeastern asia

Phytogeographical structure of the deciduous broadleaved forests in Northeastern Asia was overviewed, to clarify the phytogeographical relationships between Fagus crenata forests which have been considered as major constitutions, and other types of the deciduous broadleaved forests such as Quercus mongolica var. grosseserrata, Q. serrata, Carpinus tschonoskii, C. laxiflora, Castanea crenata which have been considered as subordinate or secondary ones in Japanese deciduous broadleaved forests. Phytogeographical regions, and their representative forest types and tree species elements of the deciduous broadleaved forests in mainland Northeast Asia were reviewed. Four major forest types appeared in mainland Northeast Asia: Q. mongolica-Betula davurica forest in Davuria-Amur region, Tilia amurensis- Acer mono forest in Primorie, Q. serrata- C. laxiflora forest in Northern Korea and C. tschonoskii forest in Southern Korea. The elements of those four forest types occurred also in Japan, differing from their composition among Southwest Japan, Central Japan and Hokkaido. Central Japan has the most diverse elements. Two major streams of geographical changes in the composition of the elements existed from Davuria-Amur to central Japan in phytogeographical structure of the deciduous broadleaved forests in Northeastern Asia. One stream is that from Primorie directly to Hokkaido, and finally to Central Japan. Hokkaido has almost all the elements of Primorie except for A. pseudosieboldianum. Hokkaido shows apparently similar element composition to that of Primorie. Another stream is that from Primorie to Northern Korea and through Southern Korea and Southwest Japan finally to Central Japan. Central Japan joins those two streams together. This overview stressed that the deciduous broadleaved forests other than F. crenata forests, such as the forest from Q. mongolica, Q. serrata, C. tschonoskii, C. laxiflora, C. crenata, should be also important constitution of Japanese deciduous broadleaved forests