Clayey Spodosols and Andisols showing a biosequential relation occur in the Shimokita Peninsula, northeastern Japan. The Spodosols appear only in association with the Hiba tree (Thujopsis dolabrata var. Hondai Makino), a strong podzolizer, at elevations of 150 to 300 m. They show remarkable eluviation and illuviation and chemical and mineralogical properties common to most Spodosols. We classified them as Haplorthods and Placorthods. Haplorthods do not satisfy the morphological spodic criteria, but the chemical spodic criteria are satisfied when (Fep + Alp)/% clay ≥ 0.1 is employed. Although Placorthods have an albic horizon and a placic horizon, they do not meet the chemical spodic horizon criteria. The Andisols do not have such thick, dark A horizons as those formed under Japanese pampas grass vegetation in northeastern Japan because they are formed under broad-leaved tree vegetation. However, they also show unique properties common to most Andisols in Japan and meet the andic soil properties. We classified them as alic and typic Andisols. The former contain a significant amount of KCl-extractable Al. The transition of Spodosols to Andisols was observed to be caused by the conversion of Hiba vegetation to broad-leaved tree vegetation. Changes in the morphological, chemical, and mineralogical properties are taking place accordingly. It is very important to examine both the morphological and chemical spodic criteria and the implications of the unique parent material of ash-derived Spodosols. The separation of ash-derived Spodosols and Andisols should also be critically studied.
ASJC Scopus subject areas
- Soil Science