GSA Annual Meeting in Phoenix, Arizona, USA - 2019

Paper No. 104-14
Presentation Time: 9:00 AM-6:30 PM


KEENAN, Sarah W., Geology and Geological Engineering, South Dakota School of Mines and Technology, 501 East St. Joseph Street, Rapid City, SD 57701 and DEBRUYN, Jennifer M., Biosystems Engineering and Soil Science, University of Tennessee, 2506 E. J. Chapman Drive, Knoxville, TN 37996

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.