Die immergrünen Laubwälder Japans
[The broad-leaved evergreen forests of Japan]
Rainy climate continues from the subtropics northward to the cool-temperate region in Japan, because the Archipelago holds marginal seas with Asiatic Continent. There were little orographic barriers that prevented the south-north-ward migrations of biota. The broad-leaved evergreen forests of Japan have many characteristics of the rain-forest, as richness in lianas, epiphytes and ferns. Moreover, the dominant genera, within which have differentiated evergreen and deciduous species during the climatic alternations since Tertiary, are for the most part endemic or have specified endemic taxa in Sino-Japanese Region. We can recognize here an endemic class-group of Lauraceo-Fagacea sempervirens. Since Grisebach pointed out, it has been a unique character of this East Asiatic and Southeast Asiatic group of the broad-leaved evergreen forests that the Lauraceae and the Fagaceae grow in community. Very few species of these dominant genera are found from the Pacific side of North America, but they grow there under the winter rain climate and in a quite different type of plant-community. Because the route of migration was only in one way, namely along the axis of the Archipelago, this class-group is monotypic: Only one class and one order as well as only one alliance. The alliance of Shiion sieboldii is the only one of the class-group that has attained down to the sea-shore, because the others are all mountain forests of the southern countries. We can classify the Shiion sieboldii into four suballiances. I. Suballiance of Quercion phylliraeoides is physiognomically a sclerophyllous forest, but it is floristically a suballiance of the Shiion sieboldii. Quercus phillyraeoides itse1f is a relict of the Tertiary warm xerophytic flora. In this suballiance the Lauraceae are separated from the Fagaceae. II. The typica1 suballiance has no clear character species for itself, but is the main part of the alliance. It is composed of five associations. III. Cyclobalanopsion stenophyllae develops near the upper limit of the alliance. It has three associations, among which the Aucubo-Cyclobalapsetum is the only one association differentiated under the snowy climate of the Japan Sea-side. The last IV. Machilion thunbergii is hygrophilous and shade-tolerant. In the South it seems the most thermophilous of the all suballiances, for it makes a subtropica1 stands near the boundary to the Ficus wightiana and F. retusa-forests, but it is the suballiance that can attain the northernmost limit of the alliance, because Machilus thunbergii can utilize more efficiently the lateral light from the lower position of the sun and by the refraction from the sea-surface.