Soil Metabolite Succession in Vertebrate Decomposition Impacted Soils

Vertebrate decomposition results in a pulse of critical nutrients such as nitrogen, carbon, and phosphorus into the environment creating a ‘hotspot’ immediately surrounding the carcass. While many decomposition studies have investigated vertebrate decomposition focused on the carcass itself, fewer studies have focused on the impacts of decomposition products on soils. Gaining a greater understanding of soil processes during decomposition could not only aid in better understanding soil biological activities but could also lead to new insights in nutrient cycling in the environment. The assemblage of soil metabolites, also known as the soil metabolome, exposes not only the breakdown products of decomposition, but also the products of microbial metabolism. Identifying these products can reveal insights into the biological processes occurring in soil during decomposition. This study hopes to garner understanding of the effects of decomposition on soil processes through assessing soil metabolite profiles to gain further insights into soil biological functioning and nutrient cycling. To achieve this goal two experiments were conducted; a field experiment (human decomposition study conducted at the Anthropology Research Facility) and a laboratory experiment (mouse decomposition inside a greenhouse). We tested two hypotheses: (i) we hypothesized that carcass decomposition would not only have a significant effect on soil microbial community functional profiles (metabolome) but would lead to variations in metabolite richness and abundance as decomposition progressed, (ii) we hypothesized that increased cadaver mass (dosing pressure) would lead to faster and larger increases in metabolites associated with decomposition. Between the two studies, soils exposed to decomposition underwent significant changes in electrical conductivity and pH, in addition to microbial community functional profiles. In the human decomposition experiment, there were different soil metabolites dominating control and decomposition-impacted soils that changed over time, suggesting a succession of metabolites occurs in the soil due to decomposition. In the mouse decomposition experiment it was found that metabolic concentrations increased 1.3 times with three-fold dosing pressure. However, the timing of the metabolic concentration maxima did not seem to be affected by increasing dosing pressure. Together, these experiments provide insights into soil biological functions as well nutrient cycling in soils during carcass decomposition.