Abstract

JIMENEZ-MORILLO, Nicasio T. et al. Molecular markers surrogated to water repellency in fire-affected soils. Rev. de Ciências Agrárias [online]. 2022, vol.45, n.4, pp.831-840.  Epub Dec 01, 2022. ISSN 0871-018X.  https://doi.org/10.19084/rca.28639.

Soil water repellency (SWR) is often attributed to the accumulation of hydrophobic organic compounds, mainly lipids. Nonetheless, lipid extraction not always suppress SWR and unextractable soil constituents may be related with residual SWR. Burnt (B) and unburnt (UB) soils (Doñana National Park, Huelva) under two vegetations (cork oak and heather) and two soil fractions, coarse (1-2 mm) and fine (<0.05 mm) were studied. Soil organic matter (SOM) molecular composition was studied by ultra-high resolution mass spectrometry. Partial least squares regression (PLS) was employed to explore SWR in function the abundance of the 1221 common compounds found. An omic approach using various indices (e.g., factor loadings of PLS models, etc,) was applied to identify compounds which could be used as proxies for SWR. In the case of B soils, SWR was related (P< 0.05) to aromatic and condensed compounds, while in UB soils it relied mainly on aromatics and lignins. In the fine fractions, lipids were associated with SWR, and no correlation was found in the coarse fractions. In conclusion, hydrophobicity was related to lipids as expected, but also to lignin and aromatic components. The combination of FT-ICR/MS with graphical statistical approach was effective in finding molecular predictors of SWR.

Keywords : Chemometrics; forest fires; hydrophobicity; mass spectrometry; van Krevelen diagram.

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