Variation in lipid abundance and composition in a fire affected hillside from Lyulin mountain, Bulgaria.

Top soils from a fire-affected catena sequence on the Southern hillside of Lyulin Mountain, Bulgaria were analysed for free lipids with the aim to identify molecular markers of the effect of fire on soil organic matter. The total lipid extract of the unburned control soil was dominated by aliphatic series of alkanes, alkanoic acids, alkanols, diterpenoids and steroids indicating the predominant higher plant input. The alkane patterns as revealed by the carbon preference index (CPI) and the average chain length (ACL) showed higher relative abundance of short chain homologues (C - C ) in the burned soils as 13 20 compared to the control soil and indicated a thermal, but also a microbial input. The fatty acids and alkanols signatures, as well as the typical biomarker signals for pine such as pimaric acid and methyldehydroabietate were lost in the chromatogram of the severely burnt soil on the ridge of the mountain. All samples displayed a particular pattern of short- and long-chain and even carbon numbered n-alkanes (maximum at C and C ). Aromatic hydrocarbons and 29 27 oxygenated acids were more abundant in the burnt soil on the ridge while the pine signals of pimaric acid and dehydroabietic acid disappeared.