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This article in SSSAJ

  1. Vol. 75 No. 1, p. 267-279
    Received: Feb 23, 2010

    * Corresponding author(s): mkimsey@uidaho.edu
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Characterization of Volcanic Ash-Influenced Forest Soils across a Geoclimatic Sequence

  1. Mark J. Kimsey *a,
  2. Mariann T. Garrison-Johnstonb and
  3. Leonard Johnsonc
  1. a Intermountain Forest Tree Nutrition Cooperative, Univ. of Idaho, PO Box 441133, Moscow, ID 83844-1133
    b Intermountain Forest Tree Nutrition Cooperative, Univ. of Idaho, PO Box 441133, Moscow, ID 83844-1133
    c State Univ. of New York, College of Environmental Science and Forestry, PO Box 48, Wanakena, NY 13695


The pedogenic development of volcanic ash mantles within the interior U.S. Pacific Northwest is thought to be a function of the interaction between climatic regimes, plant communities, eolian reworking, and colluvial mixing with subsurface soil parent materials. Little research, however, quantitatively characterizes the extent of these interactions on soil property expression and nutrient retention. This study examined soil physical and chemical properties associated with volcanic ash mantles overlying extrusive and metasedimentary geologic parent materials across an array of precipitation zones. The results were then correlated with NO3, SO4, and BO3 sorption isotherms to assess parent material influence and degree of mineral weathering on nutrient retention. Analyses indicated that ash-mantled extrusive soils had ∼25 to 50% more plant-available water, two to three times greater volcanic glass, two to five times less quartz, and up to five times more short-range-order Fe in the Bw1 and 2Bw2 horizons than ash-mantled metasedimentary soils. Mean annual precipitation zones showed a strong positive correlation with the development of short-range-order Al minerals. Anion sorption isotherms were in the order of SO4 > BO3 ≥ NO3 for surficial Bw1 horizons, and SO4 ≥ NO3 > BO3 for subsurface Bw2 and 2Bw2 horizons. Anion retention mechanisms were positively correlated with the presence of short-range-order Al and Al-substituted Fe oxides. Soil property characterization indicated that surficial ash soils often reflect the physical and mineral characteristics of subsurface soils, but climatic conditions control their chemical expression through the degree of mineral weathering.

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