Classification of tephra-derived Spodosols

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.