What controls the concentration of various aliphatic lipids in soil?

• The concentration of lipids in leaves and roots determines their abundance in soil.
• Lipid preservation is influenced by chain length and chemical functional groups.
• Root-derived lipids are only slightly better preserved than leaf-derived lipids.
• The use of simple statistical methods will advance understanding of SOM composition.

The composition of lipids in soil offers clues to the origin and stabilization of soil organic matter, but the descriptive nature of prior research makes quantitative interpretations problematic. We statistically evaluated potential predictors of the concentrations of aliphatic lipids in mineral soils beneath plantations of 11 tree species. Lipids were recovered from leaves, roots, and soils from each plantation using base hydrolysis and solvent extraction. Nearly 70% of the variation in individual soil lipid concentrations was explained by lipid concentrations in tree leaves and roots. Less variation in soil lipid concentrations was attributed to lipid properties such as functional group composition, chain length, and whether a lipid was most abundant in leaves or roots. Surprisingly, although the chemical and biological compositions of soils were highly variable for plantations of different tree species, the tree species identity had little impact on soil lipid concentrations and the effects of lipid properties were similar for all plantations.