Plant opal analysis was carried out on soils derived from volcanic ashes at the foots of Mt. Fuji and Mt. Amagi, central Honshu, to reveal previous vegetations and clarify soil-vegetation relationships. The Fuji soils derived from basaltic ashes (younger than about 2,700 y. B. P.), were collected from a Brown Forest soil (No. 1) and a Black (Kuroboku) soil (No. 2) belonging to the cool temperate zone. The Amagi soils were Brown Forest soils (Nos. 3 and 5) and a Black (Kuroboku) soil (No. 4), which were developed from dacitic ashes (younger than about 2,900 y. B. P.). The soil (No. 3) was in the cool temperate zone. On the contrary, the soils (Nos. 4 and 5) were in the warm temperate zone. 1) Plant opal assemblage of Black (Kuroboku) soils (Nos. 2 and 4) was characterized by the dominance of non-Bambusoid, Panicoid and Festucoid phytoliths. Brown Foresn soils (Nos. 1 and 3) were doninated by Bambusoid, mainly, from Sasa and jigsaw pazzle shaped phytolith originated from a deciduous broad leaf tree, Fagus crenata. In a Brown Forest soil (No. 5), Y-shaped phytolith of evergreen oak origin was much more abundant than in the other soils. 2) The present plant opal composition suggests that the Black (Kuroboku) soils, the Brown Forest soils in the cool temperate zone, and the Brown Forest soils in the warm temperate zone have respectively been formed under the vegetation of grass, Fagus crenata forest with Sasa, and evergeen oak forest. This implies that vegetations are able to exert respective and signficant influence upon soils developed from similar parent materials in lithology and age under similar climatic conditions.
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