Decomposition and eDNA: Good for the Environment

Have you ever considered that roadkill might be beneficial to the environment such as providing growth factors for the soil? For most that is not the first thought that comes to mind, nevertheless it’s been backed up by scientific research.

Decomposition plays a major role in the carbon cycle of any given ecosystem. It is organic recycling at its finest: the carbon travels from the atmosphere to be absorbed by plants via photosynthesis, plants get eaten by animals, and animals that eat other animals get carbon through their meal as well. When animals and plants die, their carcasses, leaves and wood are broken down by the process of decay. This process couldn’t be performed without the involvement of decomposers that are made up of communities of bacteria and fungi with the capability to transform the dead plants and animal remains into nutritional elements for the soil to promote growth. Some of the carbon in the soil can also turn into fossil fuel. There are several pathways via which carbon could return back to the atmosphere:

1. via exhalation of living things such as animals or humans

2. by burning fossil fuels such as coal and oil.

There has been a recent study done by the University of California supporting that the way climate is affecting the process of decomposition is dependent upon the makeup of the microbial community involved. The experiment consisted of reciprocally transplanting five leaf litter microbial communities from a cold, high elevation site to hotter, drier locations at lower altitude. The sites chosen for the study were desert, scrubland, grassland, pine-oak, and subalpine terrains respectively. As an engineering control, the inoculants were placed in special nylon mesh bags allowing water and nutrients to enter but prevented the transport of microbial cells. The progression of decay was tracked over an 18 month period by measuring bacterial and fungal biomass, community composition, litter chemistry and mass loss. The sites were sampled at 6, 12, and 18 months respectively. To find out which bacterial and fungal families the microbial communities housed, 16S and ITS sequencing was performed. As many as 135 bacterial and 145 fungal families participated in decomposition of each leaf litter inoculant. The researchers were curious to see whether the way decomposition responded to climate differentiated based on the community, so they measured the initial diversity among the transplanted communities. The site was the primary factor that influenced decomposition rate varying 30-64% in mass loss at all three collection times. There was less mass loss in desert and scrubland sites, finding its peak point at mid-elevation grassland site with intermediate temperature and precipitation. However, in support of their hypothesis, the decomposition rates were in fact dependent on the microbial community specifically the interaction between community and environment. The difference in mass loss of litter bags inoculated with communities from different sites surfaced at 12- and 18-month sampling times. Although the variation is small (3-10%), it reveals that the functionality of communities are not the same. Additionally, the “home field advantage” concept did not enhance the decomposition rate of the leaf litter inoculants. The scrubland microbial communities decomposed more litter in the grassland location and vice versa. Also, the extreme elevation sites (desert, pine – oak and subalpine) responded similarly to one another compared to the midelevation sites. So with all that being said, roadkill might decay faster at locations where there is an optimal interaction between decomposers and the environment.