ASSESSING CHANGES IN LIPID BIOMARKERS IN SOILS ASSOCIATED WITH ANIMAL DECOMPOSITION OVER DECADAL TIME SCALES

Animal decomposition provides substantial inputs of organic carbon into the environment, which can drive long-lasting shifts in carbon and other biogeochemical cycles. Understanding the fate and transformation of these organic compounds over time is key to understanding the long-term effects of animal decomposition on the soil organic matter pool. Lipids are more recalcitrant than most other types of organic molecules and can be source specific to producer(s), making them an important target for understanding changes in soil organic matter dynamics. We analyzed the solvent extractable fatty acid and sterol composition of soils associated with a ~15-year-old beaver mass grave from a prairie ecosystem near Rapid City, South Dakota, and compared them to control soils not associated with beaver burial. Control soils had lower total extractable lipid contents relative to burial associated soils. Lipid compositions in both control and burial associated soils contained long-chained fatty acids (>C₂₀) and sterols (β-sitosterol, stigmasterol, and campesterol) diagnostic of the waxes of higher plants consistent with previous work from other prairie environments. However, burial associated soils contained relatively higher concentrations of cholesterol, the major sterol in animals, providing evidence of the impact of organic input from animal decomposition on the soil organic matter pool. Additionally, relatively higher concentrations of short-chained fatty acids (<C₂₀), including branched compounds, were also observed in the burial associated soils compared to controls. The changes in fatty acid content of the soils may reflect input from the beaver tissue or increased activity of microorganisms due to the influx of organic carbon during decomposition. Overall, these results indicate that animal decomposition in a burial setting drives changes to the lipid content of soil organic matter over decadal time scales and provides insight into understanding how these changes affect carbon cycling. In addition, understanding the changes in lipid content in soils associated with animal decomposition may also have forensic applications in identifying clandestine gravesites and in paleontological applications where they are used in paleoenvironmental reconstructions.