Microbial induced nitrogen recycling in bio-geochemical decomposition sites

Context: The sporadic introduction of deceased plant and animal matter into soils is pivotal in reincorporating organic carbon (C) and nitrogen (N) compounds into biogeochemical cycles. The breakdown of animal remains offers a rich reservoir of C and N, stimulating both local environmental microbial communities and introducing external microbes stemming from the carcasses. Nonetheless, the interactions within these blended microbial communities and the respective impacts of environment- and carcass-originating microbes on C and N cycling remain uncertain. To determine whether environment-derived, carcass-derived, or the merged microbial communities exerted a greater influence on C and N cycling, we conducted controlled laboratory experiments mimicking carcass decomposition hotspots by combining carcass decomposition fluids with soils. We selectively sterilized the decomposition fluid and/or soil to remove microbial communities, creating distinct combinations of environment- and carcass-derived communities, and incubated the treatments at three temperatures (around 15, 25, and 35 °C). Findings: Carcass-sourced bacteria persisted in soils in our simulated decomposition scenarios, albeit in modest quantities. Hybrid communities demonstrated increased respiration rates at around 15 and 35 °C compared to singular soil or carcass communities. Interestingly, at higher temperatures, mixed communities exhibited reduced diversity but higher respiration, suggesting functional overlap. Additionally, mixed community treatments furnished evidence that microbes linked with carcasses might play a role in ammonification and denitrification, while nitrification was mainly carried out by indigenous soil organisms. Conclusions: Our investigation yields valuable insights into the dynamics of microbial communities converging during carcass decomposition and their functions in the recycling of carcasses within terrestrial ecosystems.