Bird’s-Eye View

In his office on the second floor of Snowden Hall, Forestry Professor Scott Torreano pulls a heavy chunk of wood from a plastic storage tub. He wants to point out a piece of climate-related data that happens to be encoded in the growth rings of the tree that was harvested to create this piece of old lumber. This particular block of wood has quite a history—it came from a shortleaf pine that was a seedling on the South Cumberland Plateau before the Declaration of Independence was signed. When the tree was eventually felled, its wood was used to build a roof to cover the nave of All Saints’ Chapel in Sewanee while the stone building was under construction. And when the chapel was completed in 1959, the wood was repurposed to build a pavilion at Lake Cheston. 

Torreano points to a spot on the cut face of the wood block where the concentric rings are packed tightly together, indicating a period of extremely slow growth. “This area here is just before the Revolutionary War,” he says, “when we know there was a catastrophic spring freeze, followed by two years of historic drought.” While this shortleaf pine was struggling through a late-season freeze, Thomas Jefferson was in Virginia, writing in his garden journal from Monticello and noting the destructive effects of a spring frost on his plants in 1774. These two accounts—one from nature and one from man— line up perfectly to tell a story about what was happening in a remote forest in what would become Tennessee in the years before European settlers arrived in great numbers.

To Torreano’s eyes, every tree in the forest has a story to tell. “Trees and the wood in the trees are environmental proxies,” he says. “They don’t lie. We can sample them and figure out what was going on when they were alive.” Together with Sewanee forestry students as summer interns and colleagues from the University of Alabama and the University of Missouri, Torreano has been working painstakingly to assemble a history of the forests of the South Cumberland Plateau and to document disturbances to the forests—like that 18th-century spring frost—including freezes, droughts, fires, and significant wind events. That history is providing not only a picture of the forest’s past and present composition and behavior, but also an invaluable baseline for the future study of climate change and human interactions with the forests.

Significant wind events are of particular interest to the researchers because so little is known about forest destruction caused by wind in this area. So, when a series of powerful straight-line storms toppled swaths of trees on Sewanee’s Domain and in Savage Gulf State Park 25 miles northeast of Sewanee in March, April, and May 2020, Torreano and his colleagues knew there was much to be learned. “The downed trees—their orientation, their size, where they snapped, which species went down, and the geology underneath the trees—all of that is important,” says Torreano. He wanted to know which species were prone to windfall compared to other species, and he wanted to know what happens after a wind event in an old-growth forest. How do the trees regrow? “Another question is how large of an area does nature disturb?” he says. “What does it put back and can we learn something really important for how we manage our forests?”

But there would be challenges to studying the aftermath of these wind events. March 2020 was also the month when the University informed Sewanee students that classes would not resume in person after spring break due to the emergence of COVID-19, so there would be no students on campus to help with the research and no visits allowed by outside researchers. And Torreano knew the area he would need to survey was thousands of acres, far too vast to do it alone on foot.

Around that time, Torreano was having a conversation with Joe Delozier, C’77, a former chair of the University’s Board of Regents, and mentioned the great research potential represented by the downed trees and the near impossibility of carrying out that research on the ground. Delozier asked Torreano if he could get what he needed by surveying the damaged areas by drone. Torreano agreed that a drone might be able to do the job, but any students who might have drone experience weren’t on campus to help, and it would require some serious equipment and talent. Delozier knew just the person for the task: Nate Parrish was not only an avid and experienced drone pilot, but, as Sewanee’s head golf coach at the time, he also happened to be on campus.

Combined with dendrochronology—examining tree rings to learn about the lives of individual trees—the drone flights help paint a more complete picture of the history of the forest, allowing researchers to assess landscape-scale disturbances to as far back as the late 1600s in the case of the forests being sampled. Since the fieldwork was completed, Torreano and his colleagues at other universities have published two papers about their findings in peer-reviewed journals, and a third is in the works.

Key takeaways from the research will help foresters understand how to manage forests in ways that mimic natural effects. While major landscape-altering wind events happen in forests along coastal plains and in the Great Lakes region, with hundreds of acres flattened at a time, Torreano says the research shows that in this area, wind affects much smaller portions of the forest. “We’re learning that what impacts our forests here in the southern Appalachians tend to be what we call ‘intermediate scale disturbances,’” he says. “It’s not tree by tree falling down, it’s not hundred-acre swaths, it’s the quarter-acre, the half-acre, and so you get this shifting mosaic.” That information can help forest managers decide how to harvest trees in a way that will maximize forest resilience.

“In forestry, we say that we want to mimic nature as best we can,” Torreano says. “No forester is going to argue that we need a 20-acre clearcut to regenerate a stand of shortleaf pine if that’s not true. With the drone footage, we can see those trees and say, ‘See, this is what nature did in this area,’ so when we start logging, we can recreate that.”