Revisiting molecular-level research on the impact of fire on soil organic matter: Progresses in the 21st century

J.M. de la Rosa, H. Knicker, J.A. González-Pérez, F.J. González-Vila, N.T. Jiménez-Morillo, G. Almendros


Wildfires represent an important disturbance in many ecosystems, especially in Mediterranean areas. It is well known that forest fires exert dramatic changes in soil organic matter (SOM) quality and quantity that in turn affect relevant and closely related characteristics like soil runoff and erosion response, through changes on factors like soil wettability and aggregation. The effects of severe heating in SOM are highly variable and depend on many interrelated factors. Therefore, SOM content may be impacted from its almost total removal to significant increases as a consequence of external inputs, mainly from forest necromass. Additionally to C losses or exogenous increases, pre-existing C forms in the soil may be transformed into recalcitrant pyrogenic material such as black carbon presumably contributing to the long-term C and N sequestration in soils. This paper presents a practical revision of the progresses during the last decade on the studies of the fire impacts on the SOM. During this period, several analytical methodologies have been improved to characterise molecular changes into the SOM due to fire. Other tools have appeared to predict soil recovery indexes after a wildfire event. On the other hand, recent studies have reported that pyrogenic SOM resulting from fires may be less recalcitrant than previously assumed.


soil organic matter, wildfire, pyrogenic carbon, fire intensity, soil carbon sequestration.


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