Acid‐buffering capacity factors of forest soils

Abstract

Acid neutralizing capacity (ANC) of soil is an acid‐buffering capacity factor and is used to characterize the degree of soil acidification. However, the measured values of ANC are strongly dependent on the procedures employed and there is no standard method. This study develops a new acid‐buffering capacity factor related to extractable aluminum (Al₀). Soil samples under forest vegetation were collected from southwestern British Columbia, Canada for measurement of both ANC and AIQ and for column leaching studies in which simulated organic and mineral acids were used. ANC correlates significantly with Al₀, indicating a possibility of using Al₀ as a capacity factor. The potential mechanisms involved in acid neutralization include the monomeri‐zation of inorganic Al and the dissociation of organic‐Al constituents. Both constituents are the components of Al₀. Aluminum concentrations in soil leachates further support selecting Al₀ as a capacity factor, since the Al concentrations and Al₀ follow the same trend. It is suggested that Al₀ be tested as an acid‐buffering capacity factor because of its advantages of convenience in measurement, correlation with ANC, and suitability as a mechanism for explanation and prediction of Al in soil leachates.

Notes

Financial support from the Natural Sciences and Engineering Research Council of Canada grant number A‐4463 and Fletcher Challenge Fellowship to the senior author are gratefully acknowledged.

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