杏吧原创

Plants may be able to help investigators find dead bodies. Botanists believe the sudden flush of nutrients into the soil from decomposition may affect nearby foliage. If scientists can understand those changes 鈥� for instance, the effect they have on leaf colour 鈥� they may be able to identify where remains are buried simply by studying foliage features in aerial images.

鈥淚f we鈥檙e able to use the plants as sensors, at least first as indicators or crude indicators, we can identify whether a missing body may be close by,鈥� says Neal Stewart Jr, a botanist at the University of Tennessee.

Search teams looking for human remains often rely on aerial searches, but these are difficult if a cadaver is buried in a forest. Although pedestrian surveys or teams of trained dogs can help in these situations, in very large forests or in war zones, it becomes impractical to search for human remains this way.

The hope is that features of the foliage can reveal the presence of a body, offering a new way to locate missing bodies 鈥� particularly given that anecdotal evidence suggests visual signals can appear in the leaves of trees and shrubs growing near a body.

Forensic anthropologists at the University of Tennessee have been training members of the FBI for 20 years. This includes rudimentary 鈥渇orensic botany鈥�. For instance, a body can affect the mix of plant species growing nearby and plant leaves may be visibly darker, indicative of higher nitrogen uptake.

Now, the plan is to explore those botanical effects more thoroughly and systematically at a 鈥渂ody farm鈥� at the university, where researchers study the way cadavers decompose with time. The farm was the first of its kind when it was created in the 1980s.

鈥淲e鈥檝e actually built a whole plant imager that can analyse fluorescence signatures,鈥� says Stewart. 鈥淏ut the first steps are going to be very fine scale, looking at individual leaves and measuring how their reflectance or fluorescence changes over time when plants are near human remains.鈥�

An average human body in the US contains roughly 2.6 kilograms of nitrogen, much of which is released and converted into ammonium when the body decomposes. That may see nitrogen in the soil spike to levels up to 50 times higher than from typical fertiliser. The effects can increase soil toxicity or alter leaf fluorescence or reflectance. Other chemicals in a body, like chemotherapy drugs, may also have an impact on leaf fluorescence.

鈥淭hat is why this study is exciting, as we can quantify exactly what is happening in the foliage with hyperspectral and chemical analyses even if we can鈥檛 see a physical change,鈥� says research team member Dawnie Steadman, a forensic anthropologist at the University of Tennessee.

The research is at an early stage at the moment. The team is focusing on the plants available in the body farm, which are predominantly Amur honeysuckles, an invasive plant found across much of the eastern US. The results may be translatable to different climatic zones and ecosystems, but the team is unsure how effects can be generalised between species.

鈥淲hat may be different is the rate at which [nutrient] uptake [from a body] occurs based on soil type and plant species,鈥� says Steadman. 鈥淭hat will be exciting to figure out in the future.鈥�