By Margot Emery
In 1959 Dr. Eyvind Thor planted two white pines outside his University of Tennessee laboratory. Today the Norway-born scientist can scarcely stretch his arms halfway around their girth.
The trees’ rapid growth symbolizes how the University of Tennessee Tree Improvement Program has flourished in the 50 years since Thor’s arrival. The tree geneticist and Fulbright Scholar, who is now retired, was hired to found the program at a time when many state universities, drawn to the value they perceived in their state’s forested lands, were launching similar efforts. Tennessee’s approach differed significantly, however. Instead of hiring a specialist in silviculture or tree management—each of which focus on immediate utilization of forests—UT hired a tree-improvement specialist.
“Tree improvement, you have to wait a while,” says Thor in his precise accented English. The work occurs over generations of trees, the slowest growing crop there is. But there is no question that Thor had immediate positive impacts. Before his arrival, the state of Tennessee had bought big lots of white pine seedlings for reforestation from the lowest bidder. The seedlings came from Pennsylvania and sometimes required 3 years in a nursery to grow large enough to transplant. Thor sought local seed sources—collecting white-pine cones across the southern range of the species—and demonstrated how much faster seedlings from those cones could grow.
“The first thing I had to do was convince these people that they had to look around a bit to see if those seed sources were the best in the sense that they’d grow faster and become good saw timber in a reasonable period of time. So I went out with my crew and we collected seed cones either by shooting down the branches and picking cones off of them or by climbing, using portable ladders. Seedlings from these cones grew twice as fast as those from Pennsylvania.”
This work established two of the precepts of UT’s Tree Improvement Program: (1) develop genetically improved seedlings ideally suited to Tennessee conditions and (2) focus on quality materials.
The shift from importing seedlings to growing them from local sources wasn’t important for speed of growth alone. It also meant that higher-quality genetic material was being reintroduced into the state’s forests where it would have effects throughout the trees’ decades-long breeding cycles. “It’s the kind of thing that’s not necessarily effective in my lifetime,” Thor says, “but it sure as heck will be effective for maybe hundreds and hundreds of years in the future.”
During his career with the program, he worked hard to find or breed blight-resistant American chestnut trees. “I found quite a few nice looking American chestnuts in the woods. They always had some signs of having been affected by the blight, so we were not looking for immunity, but for some form of resistance.”
He established a small chestnut seed orchard at UT’s Plant Sciences Farm in Knoxville. “But it went from bad to worse, really. They were attacked by the blight, and I lost one tree after another. It got a little bit discouraging after a while. I’m kind of a stubborn person, but that was even too much for me.”
Instead he shifted his focus to study the genetic variations of other tree species. With a UT graduate student, he collaborated on Christmas trees, which studies showed were well suited to growing in East Tennessee. There was then only one grower in the area, but as Thor worked with Frasier firs, more potential growers came forth, and eventually a Christmas tree industry took hold in Tennessee.
“Dr. Thor’s greatest contribution was taking the initial steps with a number of tree species, moving them toward domestication, and setting up an organized, well-run, and well-respected program that gave me the basis to build on,” says Dr. Scott Schlarbaum, who succeeded Thor in leading the UT Tree Improvement Program. While other states abandoned their tree improvement efforts over the years, Tennessee did just the opposite.
“The UT program and the cooperating state Division of Forestry’s program have actually strengthened, and this puts Tennessee in a great position for the future,” Schlarbaum says. “Tennessee consistently ranks among the top five hardwood-producing states. With the UT and the division’s tree improvement programs, we’ll be able to respond quickly to changes in products through integrating molecular techniques with conventional tree breeding in years to come. Unlike other states, Tennessee has taken the first or second step toward domestication, and that’s going to give us, I think, a tremendous advantage in the future.”
State forester Steve Scott agrees. “Tennessee landowners have the advantage of genetically improved seedlings that are going to give them the best growth and quality or resistance to pests in their future forests, and therein lies the value of these two integrated state programs,” he says.
Schlarbaum’s work to domesticate species begins with seed collections from native trees, many of them hardwood species. The seeds are grown for 1 year under optimum nursery conditions, then the largest, best-formed seedlings are selected, usually the top 10 percent of the year-old plants. These are planted in a genetic test that is eventually thinned to leave the best trees for a seed-production orchard. The Division of Forestry’s program then begins to manage the seed orchards and collect the seeds for planting at the East Tennessee State Nursery in Delano, Tennessee. The nursery typically produces from 7 million to 17 million seedlings each year for sale to Tennessee landowners for reforestation efforts.
“The diversity of seedlings will allow Tennessee landowners to mold their lands in any way they want after harvest, damage, or fire,” Schlarbaum says. “Depending on the species mix, seedlings can be planted for game or nongame wildlife purposes, timber production in combination with wildlife, or strictly for wood products. The UT and Division of Forestry programs work together to provide landowners with trees that will allow them to get the maximum yield off of their lands.”
Schlarbaum is most proud of two key accomplishments—the Margaret Finley Shackelford Orchards at the UT AgResearch and Education Center at Ames Plantation in Grand Junction, Tennessee, and technology transfer to the Tennessee Wildlife Resources Agency (TWRA) to guide a massive West Tennessee bottomland reforestation effort.
The Shackelford Orchards include seed orchards of 19 species, including oaks, as well as persimmon, American holly, and pecan. “The Shackelford trustees had the foresight to support the idea of developing locally adapted hardwood seedlings that are improved for both nursery and field performance,” Schlarbaum explains. He expects the Shackelford Orchards to be critically important to using molecular biology in years to come. “We don’t know what the full potential of the molecular genetics will be at the applied level.”
He also notes that seedlings from the Shackelford Orchard will feed into precision forestry research, which is a multidisciplinary effort that studies the effects of light, soil, moisture, competition, silviculture, management, and genetics on growth and form. The combination of orchards and precision forestry effort is possible only because of the enormous size (18,400 acres) and diversity of the Ames Plantation land base. “It’s a model that scientists and land managers are really going to watch,” Schlarbaum says.
TWRA’s bottomland restoration is establishing a corridor of forested land along the Mississippi River, stretching from upper northwest Tennessee down to the Memphis area. According to Gary Myers, executive director of the agency, the corridor will attract migrating neotropical songbirds and raptors, as well as deer, wild turkeys, and waterfowl, and thus support the interests of bird-watchers and wildlife enthusiasts. Technology transfer from UT’s Tree Improvement Program has guided this reforestation effort, which now stretches across 4,000 acres, with 700 to 900 acres added each year.
“Trees are like humans,” Schlarbaum says. “They have juvenile and mature phases and a long reproductive cycle. Just like humans, we’ve barely scratched the surface of the genetic variations and possibilities. The years ahead for the Tree Improvement Program will be exciting ones.”