| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1988: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1987: ¥1,400,000 (Direct Cost: ¥1,400,000)
|
|---|
| Research Abstract |
The objectives of this study were to elucidate the factors affecting pedogenesis and corresponding patterns and the relationship between the extent of vegetation and the opal phytolith assembleges in soils. In addition, the stability and dissolution of the opal phytoliths derived from different plant species in acidic and alkaline media, and their chemical compositions were determined. Also, the precentage phytolith frequencies of grass and tree origins and their ratio examined.
A relationship between vegetation types and the opal phytolith assembleges isolated from A horizons underneath prersent-day forest was observed. In the podzolic soils underneath coniferous forests the opal phytolith originated from Picea and Abies were detected, while in the red soils, yellow soils, and brown forest soils underneath laural and deciduous forests the opal phytoliths derived from Castanopsis, Quercus, Machilus, Dystylium, and Fagus were identified. However, the forst soils covered densely with Sasa
… More
had a relative lower percentage of opal phytoliths of tree origins. As a general rule, in the soils predominated by forest cover the phytolith frequency of tree origins was more than 10% and the ratios of grass to tree originated phytoliths was less than 5. In the case of climax forests the phytolith frequency of tree origins was greater than 30% while the ratio of grass to tree originated phytoliths was always less than one. On the other hand, in secondary forests the opal phytoliths originated fro Pinus had a comparatively lower frequency, but that of grass origins was high.
In model experiments, leaves of various plant species were mixed at different ratios and their phytolith frequencies from different origins were determined. The results revealed that in order for grass to tree originated phytolith ratio to be one, the leaves from trees must be 2.4-16 times more than that of the grasses. This indicated that in climax forests where the ratio is always less than one a large amount of leaves from trees must be accumulated over a long period of time. The dissolution 3f opal phytoliths were rapid until the end of second week and there after decreased gradually with time. The dissolution rates of the opal phytoliths was about 5 times greater at 60゜C than at room temperature.
Opal phytolith analysis is a powerful tool fo the interpretation of the vegetation history in siols and their analysis was designed in order to understand the role of vegetative factors in pedogenisis. For future studies the percentage of tree origins and the grass: tree phytolith ratio will become important in understanding the pedogenesis under different vegetation. Less
|
