The influence of soil chemistry on fine root aluminum concentrations and root dynamics in a subalpine Spodosol,Washington State,USA |
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Authors: | Randy A. Dahlgren Kristina A. Vogt Fiorenzo C. Ugolini |
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Affiliation: | (1) Department of Land, Air and Water Resources, University of California, 95616 Davis, CA, USA;(2) School of Forestry and Environmental Studies, Yale University, 06511 New Haven, CT, USA;(3) Dipartimento di Scienza del Suolo e, Universita degli Studi, I-50144 Firenze, Italia |
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Abstract: | The relationship between root Al concentrations and Al fractions in the soil solution was examined in a mature Abies amabilis ecosystem in the Cascade Range of Washington State. The naturally acidic soils in these ecosystems lead to high concentrations of aqueous Al in soil solutions and contribute to the biocycling of Al by the A. amabilis/T. mertensiana stand. Root concentrations of Al were very closely related to aqueous Al3+ activities, but poorly correlated with total aqueous Al concentrations. The solution Al/Ca molar ratios followed a seasonal cycle with low values during the fall and high values during the spring. Ratios remained <1 throughout the year in the Oa horizon while they varied between 2 and 14 in the E and Bhs horizons. The vertical distribution of roots and the mortality of fine roots may be linked to the soil solution Al/Ca ratio. Root cation exchange capacity ranged between 180 and 225 mol g-1 and the exchangeable Al fraction represented from 12–17% of the total Al content in the root. Evidence for solid-phase co-precipitates of Al with PO4 and oxalate was indicated from selective dissolution of the root tissue. Sufficient quantities of PO4 and oxalate exist in the roots to tie up 20–40% of the Al present in the roots of the Oa and E horizons, but only 9% of that present in the Bhs horizon. Species differences in the distribution of Al between the above-ground and below-ground components may be dictated by these retention processes in the fine roots. |
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Keywords: | Abies amabilis Al fractionation Al toxicity fine roots organic acids Spodosols soil solutions |
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