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The main objective of this research was to study the oxidizability of soil organic matter (SOM). Forty-one surface horizons of forest soils under Fagus sylvatica L. developed on different lithologies (limestones, sandstones, marlstones, and shales) were sampled. The oxidizability of SOM was assessed by reacting air-dried samples with 33 mmol/L of potassium permanganate for different incubation times (1, 3, 6, and 24 h). None of the soil properties analyzed (including organic C content and oxidizability of SOM) showed significant differences (P 0.850). The cumulative amount of OCper increased with time following an asymptotic trend that fitted to a power model (r2 > 0.700); oxidation rates showed that the first hour was the most reactive (0.069-0.094 g of C g-1 of soil h-1). On average, 9% of the total initial organic C was oxidized at 1 h, 12% at 3 h, 15% at 6 h, and 23% at 24 h, which are values comparable to those found in previous studies. Principal component analysis revealed that the samples were composed of two groups of soils. Both groups showed an increase in total soil organic C content (and oxidizability) with increasing contents of reactive soil colloids (clay and metal-SOM complexes) but had different slopes in their relationship to the scores of the first principal component, suggesting different dynamics. Copyright © 2011 by Lippincott Williams & Wilkins. |
