sealPurdue News

February 2001

Purdue researchers work hard to save hardwood

WEST LAFAYETTE, Ind. – Purdue University researchers are using genetic research to save some of the most valuable trees in the world, and they are found in Indiana.

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"The mixed hardwood forest – located in the Midwest – is the number one forest sustainability issue right now facing our country," says Jeanne Romero-Severson, assistant professor of quantitative genetics in forestry and natural resources.

Romero-Severson says oak, walnut and cherry trees are a valuable commodity both for economic and environmental reasons.

The forest products industry contributes more than $4 billion each year to the state's economy, according to the Indiana Department of Natural Resources. The industry employs more than 59,000 people.

Romero-Severson says the oak trees harvested today were acorns a century ago. "Growing trees to maturity is not like growing corn or soybeans," she says. "It takes 100 years or more to grow them and just a few hours to cut them down."

Some northern red oaks, with a maximum life expectancy of 250 years, were here during colonial times. Due to the demand for fine hardwoods, these trees and other oaks are being used up faster than they can be replaced.

Loggers also are concerned that high-grading, a practice of constantly harvesting the best trees and leaving inferior trees behind, may be lessening the quality of future hardwood trees. "Younger trees may not be as good genetically because they are not being grown from the best stock," Romero-Severson says.

Because little previous work has been done to study the DNA of trees, researchers are starting at ground zero in investigating hardwood genetics.

Purdue researchers are using genomics, or the study of the trees’ genetic makeup, to learn more about their qualities. Scientists are focusing their efforts on finding the genes responsible for traits such as straightness, growth rate, branch angles and the ratio of sapwood versus heartwood in a tree. These qualities determine the value of the timber for fine veneer, cabinetry and furniture.

Charles Michler, director of the Hardwood Tree Improvement and Regeneration Center at Purdue, says studying trees at the genetic level allows researchers to determine the best trees before they are planted. "We are developing genetic technology that will let us identify superior trees at the seedling stage, rather than waiting 15 to 20 years for the tree to mature," he says.

Once trees with the best traits are identified, they are cloned for further development and testing. These improved varieties will eventually be sold to nurseries. Michler says some of these newer varieties may grow twice as fast as trees in the wild.

Purdue researchers also have found that Pioneer Motheršs forest and the Donaldsonšs Woods, two of Indianašs old-growth forests, carry oak genotypes that are rare or absent elsewhere in the state. These findings were presented in January at the International Conference on the Status of Plant & Animal Genome Research in San Diego.

"We need to preserve these old-growth trees, collect their acorns and save them for breeding stock," Romero-Severson says.

Purdue’s genetic studies are showing that red oak trees in Southern Indiana are genetically different from those in Northern Indiana.

"Glaciers obliterated trees in the northern two-thirds of the state. The vast hardwood forest that greeted pioneers did not exist after the glacier retreated," she says. "Small groups of acorns, stashed away from the forest edge by squirrels and birds, were the tree pioneers that reforested Indiana 10,000 years ago."

Researchers know that when plants or animals recolonize an environment, the survivors and their descendants may become genetically distinct from their parent populations. The DNA evidence shows this has happened in Indiana’s oak forests. The removal of vast tracks of trees, and the practice of taking out the best trees, may be responsible for some of the differences.

"This is a complicated problem to address, but we are working to ensure that Indiana has quality hardwood trees for centuries to come," she says.

Romero-Severson is assisted in her research by Preston Aldrich, a U.S. Forest Service molecular geneticist located at Purdue; Weilin Sun, Purdue laboratory manager; and Yi Feng, a forestry graduate student.

Sources: Jeanne Romero-Severson (765) 496-6801;

Charles Michler, (765) 496-6016

Writer: Beth Forbes, (765) 494-2722;

Purdue News Service: (765) 494-2096;

Purdue researchers are using genomics to study and improve hardwood trees. Charles Michler and Jeanne Romero-Severson use the black-boxed thermocyclers on the counter to replicate and amplify DNA. They are developing technology to identify superior trees at the seedling stage. (Purdue Agricultural Communications photo by Tom Campbell)

A publication-quality photograph is available at the News Service Web site and at the ftp site. Photo ID: Severson.hardwood

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Related Web site:
Genomics Backgrounder

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