日本における陸成腐植質土壌の分類学的試論(<シンポジウム特集>「火山灰に由来する土壌型」,第16回ペドロジストシンポジウム)

抄録

In classifying the humic uplaud soils in Japan, several key horizons are selected which are Kuroboku A horizon (Ak) with allophanic clays and highly humified organic matters, Jun-(para-) kuroboku A horizon (Ajk) with crystalline clays and highly humified organic matters and allophanic (B) horizon [(B)a]. Here (B) is designated as color B, weathered C or Cambic horizon. Soil types are defined by genetically associating the key horizons, (B), C and G horizons with each other as follows ; Ak-(B)a Kuroboku soils (Andosols, Dystrandepts) Ajk-(B) Jun-(para-) kuroboku soils (Vitrandepts or Haplumbrepts) A-(B)a Tan-(pale) kuroboku soils (Entic Dystrandepts) Ajk-C Jun-kuroboku Rankers (Entic Haplumbrepts) Ajk(Ak)-G Kuroboku-Gley soils (Typic Humaquepts) Ak-(B) and Ajk-(B)a have not yet been fouud. The soil types are grouped by their characteristic humic horizons as Kuroboku soils (Humic Upland soils) and subdivided into soil subtypes and soil species. The soil subtypes are set up based on whether the soils are typical or intergrading to other soil types. The thickness of humic horizons and their humus contents are criteria in differentiating the soil subtypes into soil species. The classification system thus obtained was examined by comparison with other systems already published in Japan.