ArborGen uses various breeding techniques to replant areas from abandoned mine sites to wetlands.  

Blending Old And New In Reforesting

In the spring of 2009, 80 people gathered atop a ravaged, amputated peak deep in Kentucky’s Appalachian Mountains. The mountaintop had been ripped away to strip mine the coal deposits within, leaving a deforested scar amid the lush green hardwood and evergreen that cloak the surrounding razorback ridges. Over that March weekend, an unlikely alliance of volunteers worked elbow-to-elbow in small teams: coal company employees, Sierra Club members, local rural residents, foresters and students from faraway universities. Under the foresters’ watchful eyes, the teams planted native seedlings—5,000 in all—in a biodiverse mix that matched the species in adjacent, intact forests.

This scene was repeated throughout the spring on a dozen abandoned mine sites as far north as Pennsylvania and Ohio, with volunteers planting donated trees and shrubs on a shoestring budget. Ten thousand of those donations came from ArborGen, a South Carolina–based seedling company that regularly helps small and large clients replant wetlands, streambeds, forests or rare groves of longleaf pine and Atlantic white cedar. It also sells seedlings to mammoth commercial wood and paper clients, totaling some 300 million trees each year throughout the southeastern U.S., New Zealand and Brazil.

The strength and hardiness of those seedlings are the result of a half-century’s careful crossbreeding of high performance individuals from more than 80 species. Future varieties might also benefit from advances in 83genetic engineering, allowing ArborGen’s scientists to create faster-growing trees with increased disease resistance, tolerance to cold or drought, greater strength or properties for easier processing into paper and biofuels. “Through innovations in both conventional breeding and biotechnology, we develop trees that contribute to the sustainability of the forest industry as well as our native forests,” says Barbara Wells, ArborGen president and chief executive officer.

The need for trees with enhanced characteristics goes beyond the marketplace. Forests are disappearing at an alarming rate, leveled by development, killed off by insects like the emerald ash borer and the Asian longhorn beetle and diseases like sudden oak death and chestnut blight—and increasing and more destructive wildfires, says Gerry Gray, acting executive director of American Forests. Development alone is expected to level 23 million acres by 2050, he says.

These losses come at a time when the need for tree products is higher than ever. “We can’t keep pulling trees out of native forests,” says Geoff Hill, southeastern seedling sales coordinator for ArborGen. “We’ve got to grow them.” ArborGen’s tagline reflects this goal: “More wood, less land.”
Hill’s colleague, chief technology officer Maud Hinchee, notes that advanced genetic-improvement technologies such as biotechnology can help trees respond better to rapidly changing environmental conditions.

Gently Juggling Genes

One current area of the company’s research focuses on eucalyptus, the towering tropical hardwoods native to Australasia. Although hardier eucalyptus species grow well in southern Florida, their range is limited: one frigid cold snap, and they may be dead, says Michael Cunningham, director of product development. ArborGen researchers have inserted a freeze-resistant gene into a highly productive hybrid currently grown in Brazil. This added plant gene essentially makes a 911 call to the rest of the genome, says Hinchee, prompting other genes in the tree to provide cryoprotection—increasing sugar production, shoring up cell walls and otherwise preventing the tree from freezing.

This transgenic eucalyptus is now in limited field tests in seven southern states, including Texas and Alabama, according to ArborGen. “We think it can survive down to 16 degrees Fahrenheit,” says Cunningham. He points to an encouraging result from January 2008, when the mercury fell to 19 degrees Fahrenheit for a few days running. Come spring, the Alabama study site was a geometric patchwork: green foliage graced the genetically altered trees beside stands of black, dead unimproved ones.

Eucalyptus grows naturally at lightning-fast speed; selective breeding has accelerated maturation of some species from 15–18 years to as little as 6–7, by which time they stand 70 to 80 feet tall. “If you plant a seedling and stand and watch it, you might get poked in the eye,” Cunningham jokes. This capacity makes the tree a premier source for paper and potentially for ethanol. The challenge is to modify the wood fiber so that it gives a higher cellulose yield, pulps more efficiently and requires less energy and chemicals during processing. To do so, scientists must alter the chemical composition of lignin, a compound in the trees’ cell walls that must be removed to extract cellulose.

After selecting for eucalyptus trees with higher cellulose content, ArborGen introduced genes that modify lignin. The resulting trees are in ongoing field trials in Brazil, where researchers are collecting wood data to determine how their lignin has been altered and if that change would translate into improved efficiency.

The goal is to fine-tune eucalyptus as a biomass source that is not only renewable, but sustainable as a U.S.–grown paper source. Perfecting and testing the trees’ freeze tolerance and lignin modification and clearing regulatory hurdles might take a decade, however, says Hinchee.
The company is working with about 20 species in the lab, focusing on those with industrial applications: lumber, paper and bioenergy. “The traits we are testing in these trees relate to productivity, so that more wood can be harvested from less acreage in a shorter amount of time,” Hinchee explains. Among those species are “short rotation” hardwoods such as cottonwood and aspen that mature quickly. The goal of biotech pine is to cut the quarter-century it once took trees to reach maturity to just 18 years.

But some of ArborGen’s bioengineering efforts are not what most would imagine when they envision genetic tinkering. “When people think of transgenics,” Hinchee says, “they think of bringing in genes from other species.” In fact, much of ArborGen’s work involves moving one species’ genes back and forth, making subtle changes. “It’s almost a kind of accelerated breeding that would take 50 years to do in the traditional way,” she says, “but now only takes 10.”

Selective breeding of pine trees goes back to the 1950s. The result: today’s loblolly pine produces up to 40 percent more wood. “Just improving the genetics of what we plant can have a huge impact on sustainability,” says Hinchee, noting that most of the company’s work involves traditional breeding.
With the growing specter of climate change, the rising clamor for sustainable energy sources, and the need to remediate the human ravage of wild lands and conserve those that remain, “we must find ways to dramatically increase the productivity of our land,” says Hill.