Preservation of an ancient grassland biomarker signature in a forest soil from the French Massif Central |
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| Institution: | 1. Centre de recherche du CHU de Québec, Faculty of Medicine, Laval University, Quebec City, Quebec, Canada;2. Quebec Heart and Lung Institute, Faculty of Medicine, Laval University, Quebec, Quebec, Canada;1. Department of Diagnostic Radiology, Montefiore Medical Center of the Albert Einstein School of Medicine, 111 E 210th St., Bronx, NY 10467;2. Department of Diagnostic Radiology, Jack D. Weiler Hospital of the Albert Einstein School of Medicine, 1825 Eastchester Rd., Bronx, NY 10461 |
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| Abstract: | In response to the lack of studies focussing on the residence time of molecular biomarkers in soils, the lipid content of three soil profiles from the French Massif Central with different land use history were examined. The free neutral lipid content of two reference soil profiles developed under grassland and forest vegetation, and of a former grassland soil converted to forest about 60 years ago, was analysed using gas chromatography–mass spectrometry (GC–MS). Wax esters as well as the ratio of major homologues of n-alkanes and n-alkan-2-ones could be used to characterise the overlying vegetation in the reference forest and grassland soil profiles, but failed to distinguish the respective grassland and forest contributions to the profile of the soil that had changed use. For n-alkanes and n-alkan-2-ones, the failure might be attributed either to mixing of the molecular patterns inherited from the former and current plant cover, whereas for compounds such as wax esters simple degradation is likely to be involved. Conversely, iso- and anteiso-C15:0 fatty acid methyl esters (FAMEs; of bacterial origin), steroids (tracing cattle faecal contamination), tricyclic diterpenoids and their oxygenated derivatives, as well as methoxyserratenes (inherited from Pinaceae) and triterpenyl acetates (specific to the Asteraceae), proved to be effective in distinguishing current land use for the reference soil profiles and for the converted soil. The persistence of these compounds in the changed use soil allowed us to estimate their residence time in soil. |
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