Carrion decomposition causes large and lasting effects on soil amino acid and peptide flux

• Carcasses were a significant source of N, adding an average of 4.4 kg m−2 to soils beneath the remains.
• The input of proteins and amino acids increased soil microbial turnover of these compounds.
• The decomposition of carcasses produced a large and lasting effect on the soil N, C and P pools.

Carrion decomposition is a critical component of the biogeochemical cycling of energy and nutrients within the biosphere. Two important and currently overlooked nitrogen (N) pools likely to be affected by carrion are free amino acid (FAA) and peptide pools, which are a newly recognised point of competition between plants and microorganisms for the N resource. A carcass addition experiment was established using recently (<12 h) deceased kangaroo (Macropus giganteus) carcasses to quantify soil nutrient changes in a box gum grassy woodland ecosystem. Soil samples were taken every 12 weeks, and analysed for available nutrient content and FAA and peptide turnover rates. Carcasses were a source of N, adding an average of 4.4 kg m−2 to the soils directly under the decomposing carcasses in our study, representing a significant redistribution of this resource within the ecosystem. There was also a significant and lasting input of proteins (40 mg/kg) and amino acids (25 mg/kg) into the soil, which increased microbial turnover of these labile N compounds. Dissolved organic N (DON) cycling in rangelands and natural ecosystems is an overlooked part of the N and C cycle despite representing the most important nutrient input into these systems. Based on our results, we argue for a re-think on the removal of carcasses as an ecosystem management tool, as they provide large and lasting resource islands which influence soil N cycling.