title: Post-fire recovery of soil organic matter in a Cambisol from typical Mediterranean forest in Southwestern Spain.
abstract: Wildfire is a recurrent phenomenon in Mediterranean ecosystems and contributes to soil degradation and desertification, which are partially caused by alterations to soil organic matter (SOM). The SOM composition from a Cambisol under a Mediterranean forest affected by a wildfire is studied in detail in order to assess soil health status and better understand of soil recovery after the fire event. The soil was sampled one month and twenty-five months after the wildfire. A nearby unburnt site was taken as control soil. Soil rehabilitation actions involving heavy machinery to remove burnt vegetation were conducted sixteen months after the wildfire. Immediately after fire the SOM increased in topsoil due to inputs from charred vegetation, whereas a decrease was observed in the underlying soil layer. Twenty-five months after fire soil-pH increased in fire-affected topsoil due to the presence of ashes, a decrease in SOM content was recorded for the burnt topsoil and similar trend was observed for the water holding capacity. The pyro-chromatograms of burned soils revealed the formation of additional aromatic compounds. The thermal cracking of long-chain n-alkanes was also detected. Solid-state13C NMR spectroscopy supported the increase of aromatic compounds in the fire-affected topsoil due to the accumulation of charcoal, whereas the deeper soil sections were not affected by the fire. Two years later, soil parameters for the unburnt and burnt sites showed comparable values. The reduction of the relative intensity in the aromatic C region of the NMR spectra indicated a decrease in the charcoal content of the topsoil. Due to the negligible slope in the sampling site, the loss of charcoal was explained by the post-fire restoration activity, degradation, leaching of pyrogenic SOM into deeper soil horizons or wind erosion. Our results support that in the Mediterranean region, fire-induced alteration of the SOM is not lasting in the long-term.
authors.affiliation: Museo Nacional de Ciencias Naturales (MNCN-CSIC), Serrano 115-B, Madrid, Spain.
authors.forename: Marco A
authors.initials: MA
authors.lastname: Jiménez-González
authors.affiliation: Instituto de Recursos Naturales y Agrobiología de Sevilla (IRNAS-CSIC), Av. Reina Mercedes 10, Seville 41012, Spain. Electronic address: jmrosa@irnase.csic.es.
authors.forename: José María
authors.initials: JM
authors.lastname: De la Rosa
authors.affiliation: Instituto de Recursos Naturales y Agrobiología de Sevilla (IRNAS-CSIC), Av. Reina Mercedes 10, Seville 41012, Spain.
authors.forename: Nicasio T
authors.initials: NT
authors.lastname: Jiménez-Morillo
authors.affiliation: Museo Nacional de Ciencias Naturales (MNCN-CSIC), Serrano 115-B, Madrid, Spain.
authors.forename: Gonzalo
authors.initials: G
authors.lastname: Almendros
authors.affiliation: Instituto de Recursos Naturales y Agrobiología de Sevilla (IRNAS-CSIC), Av. Reina Mercedes 10, Seville 41012, Spain.
authors.forename: José Antonio
authors.initials: JA
authors.lastname: González-Pérez
authors.affiliation: Instituto de Recursos Naturales y Agrobiología de Sevilla (IRNAS-CSIC), Av. Reina Mercedes 10, Seville 41012, Spain.
authors.forename: Heike
authors.initials: H
authors.lastname: Knicker
keywords: (13)C NMR spectroscopy; Analytical pyrolysis; Mediterranean ecosystems; Organic matter; Soil quality; Wildfire