Morphological, physical, and chemical properties of Andisols of the Kitakami mountain range, Japan

Abstract

Morphological, physical, and chemical properties of 38 pedons located on the Kitakami mountain range were studied. All the soils showed similar structure and boundaries, and had pH(NaF)>9.4 and bulk density <0.90Mg m-3 However, they differed in almost all the other properties determined. At both the northern and central parts of the mountain range, close to 60% of the sampling locations were under forest vegetation. On the contrary, the dominant vegetation at the southern part was forest with grass undergrowth or grass only. Consequently, organic matter content increased and soil color became darker from the north to the south of the mountain. The amount of sand fraction in the soils decreased from >600 g kg-1 at the north to <400 g kg-l at the south. The amount of oxalate-oxalic acid-soluble components (OSC) extracted from the clay fraction of the soils decreased sharply from the north to the south but increased with soil depth, especially at the northern and central parts of the mountain. The amount of OSC in almost all the soils at the northern part was about 600 g kg-1 in the surface horizons and > 750 g kg-1 in the lower horizons. On the other hand, more than 75% of the soils at the southern part contained < 400 g kg-l OSC in all horizons. The particle size distribution and OSC data of the soils at the central part were intermediate between those of the northern and the southern parts. Furthermore, the soils at the northern and central parts contained small amounts of KCI-extractable AI, and their pH(H20) ranged from 5.1 to 6.7. In contrast, the soils at the southern part contained large amounts of KCI-extractable Al and their pH(H20) ranged from 4.3 to 5.7. From these results, we concluded that: 1) the soils of the Kitakami mountain range were formed from a mixture of tephric and non-tephric materials, 2) the soils at the northern and central parts revealed properties inherited mainly from tephra, 3) the soils at the southern part showed stronger influences of a non-tephric material, and 4) the non-tephric material was probably of tropospheric eolian dust origin.