Ash-soil interface: Mineralogical composition and physical structure

Abstract

Fires exert many changes on the physical, chemical, morphological, mineralogical, and biological properties of soil that, in turn, affect the soil's hydrology and nutrient flux, modifying its ability to support vegetation and resist erosion. The ash produced by forest fires is a complex mixture composed of organic and inorganic particles with varied properties. This research was conducted to study and characterized ash properties produced at different temperatures and with different soil organic matter combinations. The samples, which included two treatments of soils with underlying mixed leaves and branches composed mainly by Pinus halepensis, Pistacia lentiscus, Cistus salviifolius and typical herbaceous vegetation, versus samples of mixed leaves and branches alone. Both were exposed to 400°C and 600°C heat in a muffle furnace for 2h. The residue ash was generally grayish, consisting of mixed-sized particles that preserved almost none of the original characteristics of the fuel, and was deposited in ash layers with diverse physicochemical and textural properties. The results of this study highlight the differences between all examined samples and strongly support the assumption that ash produced from a complex vegetation-soil system is a new substance with unique structural, textural, and mineralogical properties. Moreover, the ash produced at different temperatures appeared in distinct layering patterns.