Characteristics and genesis of volcanic soils along a toposequence under a subtropical climate in Taiwan
Journal
Soil Science
Journal Volume
164
Journal Volume
164
Journal Issue
7
Journal Issue
7
Pages
510-525
Start Page
510
End Page
525
ISSN
0038075X
Date Issued
1999-07
Author(s)
Abstract
The development of several unique characteristics of volcanic soils is not yet as fully understood as the influence of topography on the pedogenesis of such soils. This study was conducted to explain the pedogenesis of consolidated volcanic rocks along a southeastern aspect of toposequence in the subtropical region of Taiwan and to evaluate the effects of topography on their genesis. Three pedons were selected representing the following positions in the toposequence: summit at 970 m elevation with 12% slope, backslope at 890 m elevation with 25% slope, and footslope at 800 m elevation and 10% slope. The soils formed on andesitic pyroclastic rocks of relatively the same geochemistry and age and under the same subtropical climate, with a mean annual precipitation of 4800 mm and an average temperature of 16.6 δC. Results revealed that the soils are in their middle stage (<300,000 years) of development and have characteristics that are closely comparable except for depth of solum. They exhibit andic properties and are strongly acidic, with very high A1 saturation. Aluminum toxicity and P deficiency are believed to contribute to humus accumulation. The high porosity of the soils is attributed to high contents of humus and noncrystalline materials as well as to isovolumetric weathering. The noncrystalline forms of Fe and A1 are associated largely with humus, which is related to the little or no allophane formation in A horizons. Kaolinite, halloysite, gibbsite, and quartz dominate the clay mineral assemblage, with minor amounts of 2:1 silicate clays. Kaolinite, halloysite and gibbsite probably formed from the weathering of feldspar, whereas the layer silicates may have formed in cracks and pores in rocks where weathering solutions are held for long periods. Quartz is thought to have come from pedogenic processes and inheritance from parent material. Goethite formation seemed more likely than hematite. Solum thickness seemed to be related to the position in the toposequence. More lateral water flow and surfacial runoff occurred in backslope soils with higher slopes.
Subjects
Andisols
Genesis
Micromorphology
Subtropical climate
Toposequence
Volcanic soils
Publisher
Lippincott Williams and Wilkins
Type
journal article