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Differentiation of Spodosols and Andepts in a Western Washington Soil Climosequence
Author(s) -
Nettleton W. D.,
Goldin A.,
Engel R.
Publication year - 1986
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1986.03615995005000040031x
Subject(s) - podzol , geology , soil water , soil horizon , colluvium , horizon , udic moisture regime , silt , tephra , soil science , mineralogy , geochemistry , geomorphology , loam , volcano , mathematics , geometry
Five Spodosols were sampled on mountain slopes about 20‐km southwest of Mount Baker in the Cascade Range of western Washington. The soils have formed in colluvium derived from Darrington phyllite and an admixture of 1 to 30 dag tephra kg −1 . Four of the pedons form a climosequence on steep, south‐facing slopes. The fifth is at the foot of the mountain, on an east‐facing slope, and is more weathered than one would have predicted from its low elevation. The three pedons sampled above 700 m have horizons that meet the chemical criteria for Spodosols. These three, as well as the fourth of the climosequence, have silt‐size pellets and cracked coatings. The fifth, at low elevation, has a horizon that meets both the chemical and morphological criteria for Spodosols. All of these pedons have one or more horizons that have the high NaF pH, high 15‐bar to clay and CEC to clay ratios, and the smeary feel characteristic of horizons that contain amorphous material. However, unlike Andepts these pedons have E horizons that contain crystalline silicate clays, mostly smectite, have low NaF pH, and lack the smeary feel. Except for the fourth pedon of the climosequence, the pedons meet the humic acid color criteria recently proposed for Spodosols. Some of the B horizons have >2 dag kg −1 of (NH 4 ) 2 C 2 O 4 extractable Al and ≥1.5 dag kg −1 of 4 M KOH extractable Al, but are not thick enough for the soils to be placed in the proposed Andisols.