EAGER: Vertebrate mortality and decomposition hot spots: soil microbial community dynamics and nutrient cycling.

University Of Tennessee Institute Of Agriculture, Knoxville TN

Investigators

Abstract

Animals have limited life spans, and mortality is a common occurrence in terrestrial ecosystems. What happens in nature to the body of an animal after it dies? From an ecological perspective, a decomposing animal creates a localized pulse (hot spot) of nutrient-rich organic matter, fertilizing the soil below. Following death of an animal, the environment may be inoculated with microorganisms from the animal's microbiome. Very little is understood about the ultimate fate of these nutrients and microbes - how much is retained in soil, recycled, or released into the atmosphere? These questions are important in terms of understanding how nutrients are produced and consumed in ecosystems, and evaluating the importance of carrion inputs across larger scales, following massive die-offs, for example. The focus of this study will be to determine the impact of decomposing animal carcasses on nitrogen (N) levels in soil. As a result, this research will contribute to our understanding of terrestrial nutrient fluxes, and will inform or expand existing models through the inclusion of carcass-derived inputs. This research will provide foundational knowledge about a natural decomposition process and the abiotic and biotic controls on nutrient recycling. This knowledge has potential applications for agriculture (livestock mortality disposal) and forensic science (time since death estimations). This project will also provide interdisciplinary training for a postdoctoral scholar in microbial ecology, soil biogeochemistry, forensic anthropology, molecular biology, and bioinformatics and will support and undergraduate trainee and the development of new curriculum on soil and environmental science for Tennessee 4-H programs. This research will provide a comprehensive evaluation of N flux in carcass decomposition hotpots. Preliminary research shows that microbial communities in soils below a decomposing carcass include both native soil taxa and introduced taxa from the carcass or insects that visit the carcass. These communities change in both composition and function, shifting to more anaerobic metabolic strategies over time. The objective of this research is to determine the fate of N in carcass decomposition hotspots, and elucidate how abiotic (temperature and oxygen) and biotic (decomposer community composition) factors control the fate of N. The objective will be met using a combination of lab mesocosms and field decomposition experiments with carcasses, manipulating abiotic and biotic controls and documenting the effects on N pools (nitrate, ammonia, nitrous oxide) and fluxes (nitrification and denitrification rates). Decomposer microbial communities will be examined using functional gene expression of N cycling genes and sequencing. This will reveal the types of microbes involved in decomposition and the mechanisms by which they are transforming nutrients. Ultimately this research will provide an understanding of the postmortem fate of vertebrate nutrients in terrestrial ecosystems.