In late November 2016 the Chimney Tops 2 wildfire was reported in the Great Smoky Mountains National Park (GSMNP). Because the fire originated in a remote area of the park, in an area comprised of steep terrain and cliffs, firefighters struggled to access and contain the fire. The fire spread throughout the surrounding area, including nearby towns of Gatlinburg and Pigeon Forge, burning more than 17,000 acres.
After the fires, the university and the Office of Research, Innovation, and Economic Development (ORIED) hosted FUSION: Wildfire Research. As part of a series of events devoted to forging cross-disciplinary partnerships among the campus community, this FUSION event encouraged researchers to consider how their expertise might be applied to some of the potential questions developing from the Chimney Tops 2 fire and its aftermath.
This meeting eventually led Jennifer Schweitzer, professor in Ecology and Evolutionary Biology (EEB), and graduate student Kendall Beals to their current research, in collaboration with researchers in EEB and the Department of Civil and Environmental Engineering. Schweitzer and Beals are investigating the effects of the fires on the soil microbial communities of impacted areas.
“Even though you can’t see them, soil microbes are crucial,” said Beals. “They drive a lot of ecosystem processes like cycling nutrients and filtering ground water. They’re the invisible players behind a lot of important things that nature is doing that we don’t see, and they really influence plant biodiversity.”
Greater plant biodiversity not only helps stabilize ecosystems, but also moderates the climate, stores more carbon, and supports more animals. The Great Smoky Mountains region currently has the greatest plant biodiversity in the contiguous United States, making it a critical resource in Tennessee and beyond.
The Chimney Tops 2 fires presented a unique opportunity to study the regional soil microbial community because of the varied impact microbes had on the surrounding ecosystems. Both within the park and beyond, the fires burned unevenly. This created a patchwork of burn patterns, providing Beals and Schweitzer the ability to compare microbiomes in no-burn, low-burn, and high-burn areas.
After collecting samples, Beals and Schweitzer identified the bacteria and fungi present in the samples in partnership with the UT Genomics Core, then divided the bacteria and fungi into categories based on their relationship to fire.
“What we did here was look at the difference in how abundant the bacteria and fungi were between the burned and unburned sites,” said Beals.
“The majority of bacteria were resistant to the fire. More than 97 percent of bacterial species were actually equally abundant in burned and unburned sites after just one year but there were unique groups in each burn category that were not found in others.” She noted that fungal communities in the sample reflected similar patterns of abundance and unique species.
These results were not what Beals and Schweitzer were expecting. The majority of research looking at soil response to wildfires has been conducted in the western U.S., in places like California where wildfires are often an annual occurrence. That research has shown microbial communities taking nearer to 10 years (or longer) to recover. In the GSMNP samples, Beals and Schweitzer noted that within three years the microbial populations after the fires looked much like those from prior to the fires in unburned sites.
Schweitzer, whose research takes a holistic approach to the study of microbiomes, suggested these unique results could potentially be influenced by differences in both climate and plant life between the eastern and western U.S. Forests; eastern U.S. forests are wetter, have large percentages of deciduous trees, the leaves of which break down quickly, providing nutrients to the soil. Wooded areas in the western U.S. are often much drier and are filled with coniferous trees whose leaves or needles take longer to break down. Additionally, others in the Papeş lab in EEB saw rapid regrowth of plants even in GSMNP high-burn sites.
“When you get plants that cover a landscape and there’s not very much bare soil, that also changes the soil temperature and it changes the amount of water that’s in the soil. Plant recovery sort of creates its own microclimate and that can stabilize the soils and microbial communities,” said Schweitzer.
Beals and Schweitzer plan to continue collecting samples from fire-impacted areas for the foreseeable future to investigate the longer-term effects on microbial communities in the burned and un-burned sites. Thus far their team has included multiple graduate students aside from Beals and two undergraduate students who received invaluable experience and training in microbial analysis as well as colleagues from other UT departments. Continuing to build on a century-long relationship between the university and the GSMNP, Schweitzer and Beals’ work is contributing to broader understandings of soil microbial communities and their associated ecosystems.