Burcham Zachary M, Weitzel Misty A, Hodges Larry D, Deel Heather L, Metcalf Jessica L
Department of Animal Sciences, Colorado State University, Fort Collins, CO 80525, USA.
Criminal Justice Department, Western Oregon University, Monmouth, OR 97361, USA.
Forensic Sci Int. 2021 Jun;323:110782. doi: 10.1016/j.forsciint.2021.110782. Epub 2021 Apr 21.
Vertebrate decomposition leads to an efflux of fluids rich with biochemicals and microbes from the carcass into the surrounding soil affecting the endogenous soil bacterial community. These perturbations are detectable in soils associated with carcasses (gravesoil) and influence soil bacterial ecology for years after the decomposition event, but it is unknown for how long. Measuring these impacts over extended timescales is critical to expanding vertebrate decomposition's role in the ecosystem and may provide useful information to forensic science. Using 16S rRNA gene amplicon data, this study surveyed bacterial composition in terrestrial soils associated with surface-exposed swine decomposition for 10 years after carcass placement. This pilot study utilizes the increased statistical power associated with repeated measure/within-subjects sampling to analyze bacterial diversity trends over time. Our results demonstrate that the soil bacterial diversity was significantly impacted by decomposition, with this impact being localized to the area underneath the carcass. Bacterial community dissimilarity was greatest 12 months postmortem before beginning recovery. Additionally, random forest regressions were utilized to determine 10 important genera for distinguishing decomposition timepoints, an important component of forensic investigations. Of these 10 genera, four were further analyzed for their significant relative abundance shifts underneath the carcass. This pilot study helps expand the current knowledge of long-term effects of carcass decomposition on soil bacterial communities, and is the first to our knowledge to characterize these communities temporally from placement through a decade of decomposition.
脊椎动物尸体的分解会导致富含生化物质和微生物的液体从尸体流入周围土壤，从而影响土壤中的内生细菌群落。这些扰动在与尸体相关的土壤（墓土）中可以检测到，并且在分解事件发生后的数年里都会影响土壤细菌生态，但影响的时长尚不清楚。在较长时间尺度上测量这些影响对于扩大脊椎动物分解在生态系统中的作用至关重要，并且可能为法医学提供有用信息。本研究利用16S rRNA基因扩增子数据，对猪尸体放置后10年里地表暴露的猪尸体分解相关的陆地土壤中的细菌组成进行了调查。这项初步研究利用了与重复测量/受试者内抽样相关的增强统计能力来分析细菌多样性随时间的变化趋势。我们的结果表明，土壤细菌多样性受到分解的显著影响，这种影响局限于尸体下方的区域。尸体剖检后12个月细菌群落差异最大，之后开始恢复。此外，利用随机森林回归确定了区分分解时间点的10个重要属，这是法医调查的一个重要组成部分。在这10个属中，对其中4个属在尸体下方的显著相对丰度变化进行了进一步分析。这项初步研究有助于扩展目前对尸体分解对土壤细菌群落长期影响的认识，并且据我们所知，这是首次从尸体放置到十年分解期对这些群落进行时间上的特征描述。
