Abstract

MINERVINI, Mariana G; MORRAS, Héctor J. M  and  TABOADA, Miguel A. Effects of fire on the soil matrix: Consequences on soil physical and mineralogical properties. Ecol. austral [online]. 2018, vol.28, n.1, pp.12-27. ISSN 1667-782X.

Fires constitute disturbances of very diverse origin and varied implications. In addition to the effects on vegetation, fires can affect the components and properties of soils. Changes in soils, in turn, tend to increase erosion processes, sediment transport and, as a consequence, floods. Most of the studies on edaphic fire impacts have been focused on the effects on organic matter and other chemical properties and to a lesser extent on the effects on physical and mineralogical properties. The purpose of this work has been to review the state of the art in the literature on the latter effects that have been less explored. It has been found that the soil depth affected, as well as the magnitude of the changes, depend on the fire intensity and the temperature thresholds of its organic and mineral components. The physical characteristic of the soil most affected by fire is the structure or organization of aggregates. Likewise, increases in hydrophobicity occur in burned soils. Both effects modify, in turn, the water properties of the soils, reducing the infiltration and increasing the risks of erosion. Longterm heating at elevated temperatures can lead to microaggregation of the mineral particles, resulting in the generation of coarser pseudo-textures in the surface horizon. Under these conditions, clay minerals are also affected, with a decrease in kaolinite content and transformation of the expandable minerals. Although studies are scarce, modifications have also been observed in iron oxy-hydroxides, including modifications in magnetic properties in the topsoil. Effects on iron compounds may lead to changes in soil color, which may be indicative of fire intensity. Recent works also show the cracking of grains of the sand fraction as a consequence of the repetition of high temperature fires. This review highlights research needs regarding the effects of fire on inorganic soil components, which were less considered up to present. The synthesis carried out often shows contradictory results among the different works, which is due to the different constitutive properties of the soils, the different types of fires and their multiple combination possibilities.

Keywords : Fires; Soil structure; Aggregation; Porosity; Hydrophobicity; Texture; Minerals; Color.

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