Tree Rings Reveal Centuries Old Fire Record
A tree’s rings have been able to provide a lot of clues as our understanding has grown, and now a researcher from Texas A&M has shown how they are also revealing the history of fires, sometimes reaching back hundreds of years.
Charles Lafon, an associate professor of geography at Texas A&M has studied the fire history of forests throughout the southern and central Appalachian Mountains. His research – published in the journals Applied Vegetation Science and Physical Geography – has shown that a tree’s rings also show when that tree was in the middle of a fire event.
“We found one tree that has had at least 14 fires, and we found many other trees that had endured multiple fires,” he explains.
Together with his students and collaborators, Lafon has studied the fire-scar record – a disfigurement of the wood which is an unmistakable sign of a previous fire – and learned that fires occurred frequently, about once every 2 to 10 years throughout the southern and central Appalachian Mountains. They have dated the fires back to the mid-1600s, but have not been able to go back any further.
“The fires probably were ignited by a combination of humans and lightning strikes,” Lafon adds.
“We know that Indians often set fires to clear areas, and from records we have learned that the early settlers of the area also set fires so they could clear lands for grazing and planting crops,” he says. “Eventually, by the late 1800s and early 1900s, there was a tremendous amount of logging because America needed a lot of timber at that time. Devastating fires accompanied the logging, and those fires motivated the fire protection campaign of the 20th century.
“The point is, there have always been fires in forests. Sometimes fires are a good thing because they are nature’s way of starting over and producing new growth, and sometimes they are destructive.”
Lafon adds that, interestingly, fires showed a dramatic decrease after the 1930s.
“That’s about the time the U.S. Forest Service and other agencies started to increase public awareness of forest fires, and they introduced the ‘Smokey the Bear’ campaign to tell people that they could prevent forest fires,” he says. “And when a wildfire did occur, they suppressed it to halt its spread. Their efforts worked — the trees show that it did because they are fewer fires in the last 50 to 70 years.”
“The bottom line is that fire scars can tell us a lot about ecological changes,” Lafon notes. “We can tell when a fire occurred and often how severe that fire was, and we can learn how forests changed as fire frequency varied over time. The decline in fire frequency during the 20th century, for example, permitted tree species like red maple to encroach into pine and oak forests. Now the pines, oaks and other fire-associated species like the Peters Mountain mallow are declining in abundance, reducing the commercial value of the timber and diminishing the quality of wildlife habitat.
“Today, agencies like the U.S. Forest Service, the National Park Service, The Nature Conservancy and private landowners use controlled burning to try to restore the fire-associated vegetation. They are applying our fire history research to guide these efforts.”