A soil formed from volcanic ash under a Sasa palmata community at the subalpine zone in central Japan

Abstract

The chemical properties of a volcanic ash soil under a Sasa palmata community at the top of Mt. Neko (alt. 2,195m) of Nagano prefecture, central Japan belonging to the subalpine zone were studied. The soil profile had the black (7.5 YR 2/1-2) and thick A horizons (about 40 cm depth), and was similar to Kuroboku soils profile. Soil textures were light clay to clay loam in A horizons and heavy clay in BC horizon. The values of pH (KC1) were 3 to 4, and the base saturation percentages were very low except A_<11> horizon. The amounts of phosphate absorption were about 7000 mg/100g dry soil in A_3 and BC horizons. TAMM (oxalic acid and ammonium oxalate) solution solble Al_2O_3 (%) was the greatest in BC horizon (14.3 %), in which free alminum was accumulated, indicating the influence of podzolization. The large amounts of humic acid fraction were found in alkali extracts from A horizons. In BC horizon, however, the amounts of fulvic acid fraction were greater than those of humic acid fraction. The type of humic acid determined from absorption spectra was P type in all horizons. From these results, it is apparent that an unique soil was developed under the Sasa community at the subalpine zone and black and thick A horizons containing large amounts of P type humic acid were formed.