現世ならびに埋没火山灰土腐植層中の植物起源粒子-とくに植物珪酸体に関する研究 (第II報)

火山灰土の腐植給源植物に関する問題と植物珪酸体を用いた古気候推定

抄録

The amount of plant opals and the constitutions of pollens in humic horizons of present and buried volcanic ash soils distributed in Tohoku, northern Kanto, eastern Tokai and Kyushu districts were investigated.
The results obtained are summarized as follows;
1) It is assumed that the constitutions of plant opals in the humic horizons of volcanic ash soils have an effect on a relationship between the amounts of plant opals (X) and organic carbon contents (Y). In a group having ratios, Panicoid (Pa.)+Festucoid (Fe.) vs. Sasaoid (S.), not less than 0.5, the relationship between X and Y is expressed in the following formula:
Y=1.58X+3.92
In another group having the ratios less than 0.5, the following formula is obtained:
Y=0.63X+3.14
This may be explained by the fact that Sasaoid grasses have higher amount of plant opal production per dry matter than other ones.
2) The constitutions of pollens in the humic horizons of volcanic ash soils are characterized by high content of nonarboreal pollens (NAP), which allows an assumption that herbaceous plants were dominant in the vegetation concerned in formation of the humic horizons of volcanic ash soils.
3) A maximum mean annual production of plant opal is shown by the humic horizons of Kirishima volcanic ash (Ks-d) soils which had been formed during a period from 4, 600y. B.P. to 3, 700y. B.P. (¹⁴C dates), possibly a part of the climatic optimum in the post glacial age. This period nearly agrees with that derived from buried humic horizons of volcanic ash soils in Hokkaido (SASE and KONDO, 1974).