QUANTIFYING THE LONG-TERM IMPACTS OF ANIMAL DECOMPOSITION ON SOIL BIOGEOCHEMICAL CYCLING

Nutrient hotspots represent areas of enhanced biogeochemical processes compared to background conditions. In soils, the decomposition of plants, insects, and animal carcasses result in hotspot formation, provide critical mechanisms for returning carbon and nitrogen to the environment ,and perturb soil biogeochemistry. In particular, bulk soil stable isotopic composition (δ¹⁵N) exhibits enrichment, reflecting active microbially-mediated degradation of amino acids and nitrification, and leaves a long-lived (years) enrichment signature. One year after the decay of a 23 kg mammal, soil δ¹⁵N enrichment extended up to 10 cm vertically and 60 cm laterally from the decomposition hotspot. Within the hotspot, surface soil δ¹⁵N was 7.5 ± 1.0‰ with a pH of 6.10 ± 0.3, differing significantly from control soils with a δ¹⁵N composition of 0.1‰ and a pH of 6.29. One of the primary processes transporting isotopically-enriched carcass byproducts (i.e., fluids) is blowfly larvae migration within and on top of soil. Carcass decomposition represents a critical and currently poorly-constrained input to soils that stimulates micro- and macrofauna and promotes carbon and nitrogen mineralization. These results emphasize the importance of the interactions between geological and biological processes in driving biogeochemical cycling in modern ecosystems.