Clay-mineralogical characteristics of soils distributed under warm-temperate forest climate in Nyu Mountains, Fukui Prefecture, Central Japan

Abstract

Hyperdistri-Rhodic Cambisol, Hyperdistri-Chromic Cambisol, and Hypereutri-Chromic Cambisol of WRB was analyzed quantitatively from the viewpoint of pedogenesis. The results are summarized as follows: Smectite originating in pyroxine andesite which had undergone hydrothermal degradation was altered to chlorite-smectite intergrade in the AB and Bwl horizons, and to chlorite in the A and AB horizons of the KNM soil, suggesting that this soil had been formerly affected by the past warm climate. This intergrade mineral, however, reversely changed to smectite in the surface horizon due to the influence of eluviation of the interlayered hydroxy aluminum of the intergrade mineral under the present cool-temperate climate. The TKS, OSI, and MAT soils, Yellow-Brown Forest soils, were characterized by the presence of chlorite-vermiculite intergrade and chloritization in the surface horizon in terms of clay mineralogy. Based on the clay-mineral composition, the zonal soil under the Warm-temperate deciduous broad-leaved forest climate in the surveyed area was a YellowBrown Forest soil. The DAI soil, as paleo-red soil, was formed by the weathering of autochthonous rocks, but the subsurface horizon of the OSI soil, as a paleosol, originated in the loess brought from the Asian continent, based on the clay-mineral composition.

Characteristics of Clay Minerals in Podzols and Podzolic Soils

“…Weak eluviation of aluminum from the surface was also observed in all the soils. Kurihara et al (2003) showed that interlayered hydroxy-aluminum was released from a chlorite-smectite intergrade derived from hydrothermally altered pyroxene andesite on the surface of a Brown Forest soil developed under the Cool-temperate deciduous broadleaved forest climate in Mt. Kunimidake, Fukui, central Japan.…”

“…The amount of chlorite-vermiculite intergrade, however, increased through the pedogenic process in the surface horizons of Yellow-Brown Forest soils developed under the Warm-temperate deciduous broad-leaved forest climate in the Nyu mountains, Fukui, central Japan (Kurihara et al 2003). The increase in the amount of interlayered hydroxy-aluminum of 2: 1 -type minerals in the surface soils characterized the Yellow-Brown Forest soils under the Warm-temperate lucidophyllous forest climate in southwestern Japan, based on the report of Nagatsuka (1975).…”