日本の土と植物

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In Japan pedology and phytosociology have started nearly at the same time little before or after 1930. Owing to the climate characterized by the heavy precipitation, the influence of climate upon soil and vegetation is predominating, so that the mutual relationships between the two latters are concealed behind the controling effects of the former, and to our regret the two sister sciences have developed rather independently in Japan. It will be worth while now to show a vision of a phytosociologist over the mutual influences between the Japanese soil and vegetation. This is not a conclusion, but a forecast. I have induced some not yet firmly proved phenomena into the treatise, which will be later proved substantially. Any advise and criticism from the pedologists' side is welcomed. The warm-temperate broad-leaved evergreen forest of Japan, the alliance of Shiion Sieboldi by the writer is a characteristic plant-community in the Northern Hemisphere, because it has no corresponding community both in Europe and in America. It is a temperate rain forest connecting the deciduous beech-climax to the North and the subtropical rain-forests in the Southeastern Asia. The soil under these broad-leaved evergreen forest, both in the warm-temperate and the subtropical, has in general A-horison with higher pH-value than the underlying B. Consequently we shall call it the Shiia-type soil, separating from the soil under the beech forests in the cool-temperate climate, although the two types are included into the same type of brown forest soils by the other authors. The precipitation increases southward along the archipelagoes lying along the eastern coasts of Asiatic Continent, but the hydrothermal relationship sometimes tends drier, thus we can find local drier districts. In Setouti districts Quercus phillyraeoides A. GRAY, vicarious species of European Q. ilex L. makes a sclerophyllous forest and olive is cultivated in Syodo Island. To the leeside of the winter monsoon, which brings rain or fog between 22° and 31° N we can find drier climates characterized by the Cycas revoluta scrub, Pinus liukiuensis-Cyacas revoluta savannah-like vegetation and deciduous forests of Acacia and Bombax. Although belonging to the group of brown forest soils, the soils under the Japanese beech forest, the alliance of Fagion crenatae, has the acid raw humus and Japanese beech, Fagus crenata BLUME seems not prevent the podzolization tendency of the underlying soil. It is not surprizing, however, when one thinks of the high amount of rainfall in Japan, that the actual amelioration of acidity was concealed by the leaching of heavy rainfall. Nevertheless, the amelioration effect do exist, because in the area of the warm temperate forest we can find the Shiia-type forest soil with A-horison containing less acid humus. In Japan, serpentine and lime plants or plant-communities are also studied, but there exist characteristic plants on volcanic ash. Small-leaved dwarf bamboo, Arundinaria chino MAKINO in East Japan and A. pygmaea MITFORD in the West and bracken fern, Pteridium aquilinum KUHN indicate deep accumulation of volcanic ash. On the contrary Pinus densiflora SIEB. et ZUCC. is not vigorous on the volcanic ash, while P. Thunbergii PERL. sometimes shows preference to it. Among the broad-leaved evergreens, Shiia species are sometimes lacking on the volcanic ash. They may be called negative indicators of volcanic ash.
1963-12-30

日本の土と植物

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