Sybil Gotsch has spent her career climbing trees in some of the world's most remote rainforests - from Costa Rica to Brazil to Mexico. Now, one of the hardest questions in her career is rooted in Eastern Kentucky.
It's been coined "the white oak problem" and has been worrying foresters, ecologists and bourbon distillers for years. White oak seedlings sprout just fine on the forest floor. Mature white oaks tower overhead in the canopy. But the middle-sized trees - the teenagers of the oak world - keep disappearing. Something is preventing young oaks from growing, and nobody is quite sure what.
"The stakes go well beyond the forest," said Gotsch, an associate professor of forest ecophysiology in the Department of Forestry and Natural Resources (FNR) in the Martin-Gatton College of Agriculture, Food and Environment. "White oak acorns are a food source for deer and turkey, and the trunks provide roosts for bats. The wood is also essential for furniture, flooring and cabinetry."
And then there's bourbon. By law, bourbon must be aged in new, charred white oak barrels. Kentucky's bourbon industry alone is valued at $10.6 billion. According to the White Oak Initiative's 2021 assessment, an estimated 60% of surveyed mature white oak acres had no white oak seedlings present, and about 87% had no white oak saplings.
Gotsch, along with fellow researchers John Lhotka and Lance Vickers, have described the situation as two bottlenecks: one where seedlings fail to develop into saplings, and another where saplings fail to climb into the canopy overhead. If the next generation of white oaks doesn't break through, the ripple effects could last decades.
As an ecophysiologist, Gotsch studies how plants function in their environment - how they take in water, handle stress and spend their energy. Most of the researchers tackling the white oak problem have been foresters and ecologists, tracking which trees survive and which don't. Gotsch is asking a different kind of question: What is happening inside the tree that causes it to stall out?
"There are several possibilities," Gotsch said. "One is drought stress. Young oaks stuck beneath the shade of taller trees may not be getting enough water or light to push through to the canopy, especially during dry summers. Another possibility is what scientists call an allocation problem - the tree might be putting its energy into roots or defenses instead of growing taller. Then there is a third factor, which could be competition."
From rainforests to oaks
Gotsch's hands-on approach is something she has been refining for over two decades. She got her start in 1998 in the dry forests of Costa Rica, studying how plants survive months without rain. She was supposed to stay six months. She stayed two years.
"I was doing a good enough job that my adviser kept finding money for me to stay," Gotsch said.
Later, while working in the cloud forests of Mexico, Gotsch learned to climb towering oaks and place instruments right next to the leaves, measuring how trees absorb water directly from fog. It was painstaking, physically demanding work hauling sensors and data loggers into the canopy by rope. But it also gave her something most forest researchers never get: a direct read on what a tree is doing in real time, high above the ground.
Those same techniques are what she's now bringing to Kentucky's white oak stands. She's collaborating with Lhotka, a UK FNR professor of silviculture, on a project based in Berea. Because the work involves tracking trees across seasons and years, she expects to return periodically to run new rounds of physiology measurements and build a clearer picture over time.
Gotsch said the canopy is where the real answers tend to hide. Plenty of scientists study forests, she said, but very few actually climb into them. According to her, most of the biologists who do are studying animals such as birds, bats and primates. Tree physiologists like her are rare up there.
"It feels like this secret world that I have the great honor to be able to study," Gotsch said.
The best part, she said, are the surprises - the moments when the data doesn't match what the textbooks predicted.
"You think it works a certain way, and then you get up there and realize you were completely wrong," Gotsch said. "That's what I love about this work - it never stops raising new questions."
That curiosity is now aimed squarely at the white oaks of Appalachia. If Gotsch and her colleagues can figure out exactly why young oaks are stalling, it could help land managers across the region make smarter decisions about which trees to protect and how to give the next generation of oaks a fighting chance.
Gotsch's broader research on cloud forests and canopy ecology will be featured in an upcoming episode of "Overview," a PBS series of short science documentaries, expected to air this summer. Check local PBS listings for air dates.
This material is based upon work that is supported by National Institute of Food and Agriculture, U.S. Department of Agriculture, McIntire-Stennis Capacity Grant under award number 7008893. Any opinions, findings, conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the Department of Agriculture.
