Total lipid extracts from characteristic soil horizons in a podzol profile

The podzolization process is studied through lipids in nine characteristic podzol horizons. Organic matter accumulates particularly with aluminium in the Bh horizon, while the hard, cemented Bs horizon below this is formed mainly by iron oxides. The low soil pH seems to have no great influence on the preservation of lipids as reflected by the absolute amounts present and the presence of bacterial lipid markers throughout the profile. Independent of soil pH, lipids accumulate in organically enriched horizons. Albeit, high molecular weight organic compounds accumulate to a relatively greater extent than lipids in these horizons. A lipid signal related to the aerial parts, i.e. leaves and flowers, of Calluna is observed only in the O horizon. This ‘n‐alkane, steroid and triterpenoids’ signal is quickly lost in the underlying Ah horizon due to (bacterial) oxidation. The other total lipid extracts obtained are dominated by root‐derived compounds. In subsoil horizons rich in organic matter, i.e. the Ahb and Bh horizons, root‐derived friedooleanan and steroid compounds dominate the total lipid signal. Degraded horizons, poor in organic matter, i.e. the E2, Bhs, Bs and B/C horizons, are dominated by C₂₂ and C₂₄ω‐hydroxy acids, long‐chain (> C₂₀) n‐alkanoic acids with a strong even‐over‐odd predominance and C₂₂ and C₂₄n‐alkanols. Steroid and root‐derived triterpenoids with a friedooleanan structure have been removed from these horizons through degradation. Based on total organic carbon content and lipid composition, the formation of an E1 horizon has started, but is not yet complete. In the Ahb horizon, a contribution from buried vegetation to the total lipid signal is still present, although degradation and an input from roots have significantly altered the original signal. Overall, lipid data indicate that degradation (microbial oxidation) is an important process that should be taken into account, in addition to leaching, when describing podzolization processes in soils.