The distribution and degradation of biomarkers in Alberta grassland soil profiles

Recent studies have shown that subsoil (B and C) horizons can store significant amounts of soil organic matter (SOM). Yet the quantity, source, turnover, and chemical composition of subsoil SOM are largely unknown. Biomarker methods were employed in this study to investigate the vertical distribution and degradation of SOM in Alberta grassland soils. Specifically, the composition of solvent extracts, bound lipids, and lignin compounds in the Ah, Bm, and Cca horizons of four chernozemic soils was analyzed using chemolysis and gas chromatography–mass spectrometry (GC–MS) techniques. Suberin, cutin, and lignin compounds were observed to degrade with soil depth. Aliphatic molecules (such as hydroxyalkanoic acids) from suberin and cutin were preferentially preserved in the deeper horizons in comparison to lignin compounds. Trehalose, a carbohydrate found in high abundance in fungal tissues, was detected in significant abundance in the Bm and Cca horizons of three grassland soils, suggesting that non-plant biomass may strongly contribute to the deposition of carbon into the subsoil. It was also demonstrated that soil-forming processes (such as eluviation) played a role in the composition of organic carbon in the lower soil horizons.