大山礫崖の植物群落

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1) Mt. Daisen (1713m, 35°20′. N., 133°30′L.E.), which is the highest mountain in the Chugoku district, is an extinct volcano and its volcanic rock is andesite. The northern side, which makes up the wall of the crater, is on the leeward side, while the southern side is to the windward and is piled up with volcanic lave, ashes and rock scraps. The cliffs of the S-side are crumbled mainly through the agency of the wind or rain. It is softer in composition than the N-side where the curmbled condition is due to the agency of water freezing produced in the rock fissures and not to wind and rain. 2) On the slopes surrounding the peak lie scattered many alluvial cones which differ from one another in their shapes. The cones on the N-side assume a fan-shape form and at the lower region they show more gentle slopes than at the upper region, and at a transvers of the slope they are convex in form. On the W-slope the cones show the form which is almost same with the N-side, but at a transvers of the slope they are concave. On the S-slope the lower regions are steep sloping and at a transvers they are plane. The surface layers of the W-, the S-cones, being composed of more gravels and debris when compared with the N-side, are in continuous movement by the wind and rain. 3) The investigation of the vegetation of the cliffs discloses that there are the characteristic plants such as those which possess long subterranean parts, differential anchoring roots, short terrestrial part with their crowded stems, or rhizomes having strong revival features, etc. On the N-cliff due to the more favorable conditions for development of the vegetation, there are more plants, ordinarily, than on the N-cliff. 4) The degree of stabilization of the ground surface causes the differential development of the plant community, and so from the aspect of the communities we divide the alluvial cones in to three parts, viz : (1) "Unstable region" ("U-R") : the region where only herb comunity (Polygonum cuspidatum) is developed. (2) "Half-stable region" ("H-S-R") : the region where shrub comunity (Salix vulpina)is developed (3) "Almost-stable region" ("A-S-R") : the region where the community of Alunus pendula with young trees is developed. The N-, the W-alluvial cones contain these three regions from upper to lower, but on the S-alluvial cones these three regions arrange side by side. 5) On the N-alluvial cones in the "U-R" Polygonum cuspidatum is pionner and dominant species, which has the short stems and long rhizomes, and so can stand against the ground surface movement, not to be destroyed. In this region at the more stable parts Artemisia princeps more dominates than P. cuspidatum. In the "H-S-R" occurs the S. vulpina-Calamagrostis arundinacea comm., and in the "A-S-R" the A. Pendula-S. vulpina comm. appears. On the S-alluvial cones in the "U-R" P. cuspidatum dominates with Clematis stans. In the "H-S-R" occurs the S. vulpina-Calamaglostis longiseta comm., and in the "A-S-R" the A. pendula-S. vulpina comm. appears. On the W-cones the striped vegetation is distinctly seen, especially in the "U-R" and the "H-S-R". and it is considered that various plants may invade into the striped pattern. From upper to lower the P. cuspidatum-C. longiseta comm., the S. vulpina-P. cuspidatum comm. and the A. pendula-S. vulpina comm. are situated in that order. 6) From statistical studies of the vegetation developing on the cones, that compositional species of the cones are very similar to the vegetation of the cliffs, but with the stabilization of the ground surface The composition becomes more dens and increases the companion which is many young trees or shrubs invading from near forest. Especialy the composition of vegetation and life form of all the plants in the "A-S-R" resemble to thatoof the Quercus mongolica var. grosseserrata-Fagus crenata comm. and from this fact it is surmisedtthat the community in the "A-S-R" will be succeeded, in the furture, by the Q. mongolica var.
日本生態学会の論文
1954-06-30

大山礫崖の植物群落

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