Changes in the molecular composition of ester-bound aliphatics with depth in an acid forest soil

Changes in the molecular composition of ester-linked aliphatic compounds with depth in an acid andic forest soil are studied. Thermally assisted hydrolysis and methylation (THM) using tetramethylammonium hydroxide in combination with gas chromatography/mass spectrometry revealed a dominance of cutin over suberin-derived THM products in the top 5 cm. From 5 to 20 cm, a strong increase in the contribution of suberin-derived THM products was observed. From 20–50 cm, suberin-derived C22, C24 (and C26) ω-hydroxy acids were found to decrease relatively strongly with depth compared with other suberin building-blocks. Their decrease with depth in the ester-bound fraction is ‘reversely’ linked with a strong increase of these compounds in the free extractable lipid fraction which would justify their use as main indicators of a root-derived input to the free extractable lipid fraction. In addition, their relatively strong decrease in the ester-bound fraction suggests that these compounds are more easily released from the suberin structure in soils than other ester-bound aliphatic building-blocks.