Organic matter–mineral associations in organic horizons in high-altitude areas of snowy mountains, northern Japan
Journal
Catena
Journal Volume
269
Start Page
110130
ISSN
0341-8162
Date Issued
2026-07
Author(s)
Kobayashi, Koya
Asano, Maki
Tanaka, Ryoji
Hsiao, Silver Sung-Yun
Tamura, Kenji
Lee, Der-Chuen
Abstract
Organic horizons often dominate the soil profile in cold and hydric environments. In high-altitude areas of snowy mountains in northern Japan, thick organic horizons receive an abundant supply of wind-transported minerals, e.g., volcanic materials and Asian dust. This unique pedogenic factor could affect the pedogenesis of the organic horizons through organic matter (OM)-mineral associations, although these associations are still poorly understood. Therefore, we determined the mineral properties of the organic horizons and investigated the OM–mineral associations using density fractionation into three fractions: a coarse light fraction (>0.5 mm and < 1.6 g cm−3; coarse LF); a fine light fraction (<0.5 mm and < 1.6 g cm−3; fine LF); and a heavy fraction (>1.6 g cm−3; HF). The organic horizons contained large amounts of active Al and Fe phases from volcanic materials and abundant 2:1 phyllosilicate from Asian dust. The isolated fractions showed different OM and mineral characteristics. The HF was observed to contain fine crystalline minerals attached to OM and was enriched in the active Fe phase, but not in the active Al phase. The difference in density distribution between the active Al and Fe phases may result from spatial variation caused by the sensitivity of redox cycling. The key factor in OM sorting into the HF is its association with the active Fe phase and fine crystalline minerals. In the OM, O-alkyl C preferentially forms micro-assemblages with the active Fe phase and fine crystalline minerals, potentially resulting in protection from microbial degradation. These findings highlight the need to focus on OM-mineral associations to better understand the pedogenesis of organic horizons enriched with abundant minerals. © 2026 Elsevier B.V.
Subjects
Asian dust
Density fractionation
Organic horizons
Peat
Volcanic materials
Publisher
Elsevier BV
Description
Article number 110130
Type
journal article