Das Projekt "Short- and long-term effects of fire on soil organic matter along a toposequence on Mt. Etna, Sicily" wird vom Umweltbundesamt gefördert und von Universität Zürich, Geographisches Institut durchgeführt. In Mediterranean ecosystems, soil organic matter (SOM) can be directly affected by wildfires, both in terms of quantity and quality. The combustion is often incomplete, leading to the formation of pyrogenic organic matter (PyOM), a highly heterogeneous material with prevailing aromatic nature and often long residence time in soil. Focusing our attention on PyOM, we investigate a soil toposequence on the north-eastern side of Mount Etna, Italy, with six sites ranging from 500 m to 1800 m asl. A previous study on the same sites based on the radiocarbon dating of charcoal fragments and the most refractory fraction of SOM, supported the hypothesis that fire frequency is historically higher at lower elevations due to a warmer and drier climate regime. In this work, we evaluate the long-term effect of fire on the chemical and physical characteristics of SOM and, to a lesser extent also shorter-term effects using two sites having a different recent fire history. Chemical oxidation of SOM using acid dichromate are performed to evaluate the contribution of pyrogenic organic carbon (PyOC) to total SOC. Furthermore, SOM density fractions are separated and characterised for principal composition, spectroscopic properties (DRIFT and NMR), and particle morphology (SEM).