Fire induced transformation of soil organic matter from an oak forest. An experimental approach to the effects of fire on humic substances

Abstract

The effects of forest fire on the organic matter from a Dystric Xerochrept under Quercus rotundifolia were studied. In laboratory experiments carried out to simulate the effects of fire on isolated humic fractions, several physicochemical characteristics were described in the heated samples, as well as in humic substances extracted from samples of control and postfire soil areas. The results suggested that humic and fulvic acids underwent moderate structural modifications, but important changes in their colloidal properties, particularly regarding solubility, were observed. The composition and properties of pyromorphic humus are discussed, using a tentative model for humus transformation on the basis of different fire-induced modifications of the soil organic fractions.