Alteraciones del humus en bosques mediterráneos continentales afectados por incendios

Abstract

Active fire-induced dynamism of soil humus was found after the analytical comparison of humic polymers from unaltered or burned soil areas, and from laboratory simulated burnings on soil samples or soil humus fractions. In general, the polymer structure of humic and fulvic acids were found to be rather resistant to the destruction by fire, but they often underwent noticeable chemical transformation as revealed by physical and chemical methods (IR spectroscopy, 13C NMR spectroscopy, oxidative degradation followed by combined GC-MS, elementary composition, etc). The most significant alterations -from the soll point of wiew- arose from the selectlve destruction of specific oxygen-containing functional groups, which probably contributed to a condensation of the tertiary structure of the humus polymers. These effects were responsible for the transformatlon of fulvic acid inyo humic acid-like polymers, the latter being also transformed into very stable condensed polymers that quantitatively contributed to the soil humin fraction. To all appearances, the modifications observed in the properties of the humic polymers are responsible for the changes in aggregation, wettability, mobilization of cations, and for the biological activity of the soils under burned areas.