日本の自然林の植物社会学体系の概観

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The perfect system of the Japanese forest vegetation is yet far from our present state of knowledge in phytosociology. Urgent need, however, demands us to compile the results so far achieved into one system, because the International Biological Programme will be started and followed from this year. Now we have the pro-forma proposed by the committee of Conservation of the Terrestrial Biological Communities of IBP for classification of plant formations. We must secure the survival and prosperity of mankind as long as possible. Production branch will clarify, how much resources are now preserved, and how they are to be utilized in future. Conservation Section in its part must show the line between the nature to be exploited and that to be preserved. System and mapping of vegetation are indispensable for it. The writer classified here the Japanese forest vegetation into three class groups, and two orders out of the class group. Class group of Vaccinio-Piceetea BR. -BL. is the circumpolar boreal vegetation unit, of which two classes, Loiseleurio-Cetratietea, the alpine heath and Vaccinio-Piceetea japonica, alpine and subalpine coniferous shrublands and forest. Only the order of Pinetalia pentaphyllae has the circumpacific floristic re1ationshp. II. Class group of Acero-Fagetea Suz. -TOK., nov. is the cool-temperate beech forest climax group of the northern hemisphere. This group, on account of its segregation by oceans and continental non-forested lands, has scarce common character plants of species rank, but they have vicarious species of generic rank or even sections. Moreover it has prominent floristic unity as the commensal combination of summergreen Aceraceae and Fagaceae. We can therefore recognise this not only as a physiognocical and environmental vegetational unit, but also as a floristic commensal group. III. Lauraceo-Fagaceetea sempervirens is a class group endemic to East and Southeast Asia. It has been restricted to this part of the earth since Tertiary, because few fossils of their character species have been found outside of this area. But it is difficult to settle this large vegetational unit from Himalaya eastward to Malaya, and northward as far as to the coast of northeastern Japan Proper. But it has so many common genera with vicarious species, which are endemic to East and Southeast Asia. Furthermore, it is most characteristic as the commensal assemblage of the evergreen fraga-ceous, lauraceous, theaceaous, symplocaceaous, myrsinaceous woody plants and some dominant ferns of Dryopteris-Sect. Polystichum, Diplazium and Pteris. Besides these three class groups, the order of Tsugetalia sieboldii has circumpacific floristic affinity with North American Continent. Geographically it stands between the two class groups of Acero-Fagetea and Lauraceo-Fagaceetea sempervirens, and the character species are mainly transgressive to the former in East Japan, and to the latter in the Southwest. It retains the combination of Pinaceae and Ericaceae, and in this respect it has circumpolar character, while the dominant species is of cir-cumpacific affinity. Moreover evergreen braoad-leaved subtrees are allowed to prosper under the canopy of coniferous dominant trees. The floristic combination of Pinaceae and Ericaceae also holds in the other order of Pinetalia sensi-florae. This is rather an edaphic or seral communities of the Lauraceo-Fagaceetea sempervirens. Under the rainy climate of Japan, podsolisation is naturally accerelated over the whole cooler regions of Japan. Degradated brown forest soil is not seldom found under the Acero-Fagetea, so that the efficiency of summergreen broad-leaved trees to prevent podsolisation appears here not so prominent as in Europe, while typical podsol profiles tend to be restricted to the Vaccinio-Pinetalia and the Pinetalia pentaphyllae and the subalpine and northern coniferous forests of the Betuletalia ermani do not exhibit apparent podsol structure. The reason will be pursued in relation to the co-existing flora of the temperate climate, and volcanic supply of mineral substance. Broad-leaved evergreens of the Lauraceo-Fagaceetea sempervirens have more effective influence to resist the acidification of upper horizons. The A or A_0-horizons under the broad-leaved evergreen forests shows usually higher pH-values than the underlying. The writer will make the proposal to use following colours in mapping Japanese vegetation in smaller scale so that the whole country is included in one sheet. Violet to the Vaccinio-Piceetea, brown to the Acero-Fagetea, and green to Lauraceo-Fagaceetea sempervirens, to Tsugetalia seiboldii buish green, and red to the Pinetalia densiflorae. The area of the Vaccinio-Pineetea will coinsist with that of the actual range, but near and in the area of hnman activity, the natural vegetation is highly disturbed. The area of the climax community can here only be shown by limiting line, and the residual stands of natnral forests should be drawn in signs of the respective coulors. The ground coulors must be represented by the artificial vsgetation; as Orisetea (paddy field in light blue), Miscanthetea (grassland in yellow). Zonal and zonal communities, and dorsiventral distribution (the communities restricted chiefly to Inner or Outer Arc of Japan) must be recognized to apply the results obtained in well surveyded regions to those not sufficiently investigated.
1966-11-25

著者

鈴木時夫
大分大学生物学教室

日本の自然林の植物社会学体系の概観

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