There are many tephra-derived soils showing characteristic morphology and chemistry of Spodosols in humid cold climates. We reviewed ICOMOD (International Committee on the Classification of Spodosols) Proposal D by the National Soil Quality Survey Assurrance Staff (1989) using 43 tephra-derived soils from Alaska, the State of Washington, U.S.A., and Tohoku, Japan, and we propose classification of tephra-derived Spodosols including the important items as follows: 1) to recognize tephra-derived Spodosols showing characteristic morphology of Spodosols, 2) to key out Spodosols after Andisols, 3) to emphasize morphology over chemical spodic criteria, 4) to modify albic color requirement for tephra-derived Spodosols, 5) to propose a new chemical spodic criterion (oxalate A1 and a half Fe), and 6) to propose a procedure to differentiate a spodic horizon from a buried A horizon. According to our proposal, 25 of 41 pedons of tephra-derived soils which are currently classified as Spodosols will be reclassified as Spodosols, and all of them can be exactly predicted to be Spodosols by field observation.
ASJC Scopus subject areas
- Soil Science