In areas of the Appalachian Mountains before the turn of the 20th century it is estimated that one in every four hardwood trees was an American chestnut. Once mature, American Chestnut trees grew straight and branch-free for the trunk’s first fifty feet. The trees, sometimes referred to as the “Redwoods of the East”, towered up to 200 feet tall with trunk diameters of 14 feet at a man’s chest height. For hundred’s of years most barns and homes built by settlers east of the Mississippi River were made from American chestnut. The American chestnut played an important role in daily American life but that all changed when a blight destroyed nearly 4 billion American chestnut trees between 1900 and 1940 and decimated the tree’s population throughout the East Coast. However, a local tree scientist recently told a gathering of students and community members at Shenandoah University that reintroduction of the American chestnut into forests may be just around the corner.
Dr. Heather Griscom, a forest ecologist at James Madison University in Harrisonburg, Virginia, presented her research on how best to maximize survival rates for reintroduction of blight-resistant American chestnut hybrids into forests and said that she is optimistic that the tree may someday regain a foothold in Appalachian forests.
“The American chestnut was very important economically to people throughout its range” Griscom told a gathering of over 75 students and community members who attended her lecture “Forest Trials: Restoration of the American Chestnut”. “The nuts were used by farmers to feed livestock, the timber was rot resistant and the nuts provided an abundant source of food for wildlife.”
Griscom’s talk was jointly sponsored by the Shenandoah University Department of Environmental Studies and the State Arboretum of Virginia located in Clarke County.
The American chestnut killer is a wind-borne fungus known as Cryphonectria parasitica. Since infection of American chestnuts by the fungus is local in range, some isolated American chestnuts survive where there are no other trees nearby. Also, two naturally occurring viral pathogens that weaken the fungus have helped a few isolated groves of trees survive. Griscom described a breeding method called “back-crossing” to create a fungus-resistant tree that is a cross between fungus-resistant Chinese chestnuts and native American chestnuts.
“Back-crossing creates a hybrid species that is more like the American chestnut than the Chinese variety” Griscom said. “In the field it’s nearly impossible to tell the new species from the original American chestnut.”
The fungus which led to the demise of the American chestnut was accidentally introduced into North America around 1900 either through imported chestnut lumber or through imported chestnut trees. Asian chestnut trees with the chestnut blight fungus were discovered on Long Island in 1904 and today scientists believe that the blight was originally introduced from either China or Japan.
Griscom explained that unlike the American chestnut, Japanese and Chinese chestnut trees show some susceptibility to infection by C. parasitica, but the fungus does not usually kill them. Because the root collar and root system of the American chestnut tree are fairly resistant to the fungal infection a large number of small American chestnut trees still exist as shoots from old root bases. However, the shoots seldom grow large enough to reproduce before the blight attacks them. Fortunately, the shoots preserve the American Chestnut’s genetic material which is now being used to genetically engineer the new American chestnut tree with the minimal necessary genetic input from the disease-resistant Asiatic species.
Efforts to create the new American chestnut species began in the 1930s and continue today in hopes of repopulating American forests with the trees. Today, the Virginia State Arboretum and the American Chestnut Foundation are working together with an aim of reintroducing a blight-resistant American chestnut into its original forest range sometime during the early decades of the 21st century
“It takes ten years between each backcross to determine if the change was successful” Griscom said. “The overall process takes a very long time.”
American chestnut shoots still grow and sprout leaves each year at the Virginia State Arboretum. Isolated bunches of shoots can be seen growing from old stumps. Nearby, new plantings of back-crossed American chestnuts stand in groves that will evaluated over coming years for blight resistance.
While plant geneticists work to create a blight-resistant strain of American chestnut, Griscom’s research focuses more on the practicalities of successfully re-introducing the new trees back into American forests. Griscom has conducted years of field experiments near Massanutten Mountain to evaluate how landscape shapes where best to re-introduce the American chestnut.
During her field research, Griscom planted American chestnut seedlings at different elevations on the Massanutten Mountain in order to observe factors like competition for sunlight and moisture from other dominant trees species that American chestnuts will compete with, most notably the tulip poplar. Factors like the impact of wildfires and browsing by whitetail deer and voles were not intentionally tested. However, Griscom suspects that clearing forest areas for her seedling plantings and the use of fencing to protect the young trees from deer may have promoted low vegetation growth that created perfect cover for small animals to gnaw at the base of some of the chestnut seedlings.
Griscom’s research findings determined that re-introduction of the American chestnut will be most successful on dryer, upper mountain slopes where there is less competition from tulip poplars.
Using a less scientific approach, Griscom and her husband have also planted American chestnuts on property that they privately own in West Virginia. “We were surprised that the trees did fine even without deer protection” Griscom said. “Trees on the south facing slope are already one meter high after just four years.”
Griscom said that she is very excited about the progress being made toward re-establishing the American chestnut into American forests and believes that people may begin to see the tree again in forests within the next 50 years.
“This is a tree that humans pushed to near extinction” Griscom said. “It’s our responsibility to do everything that we can to bring it back. The American chestnut is a very beautiful tree.”
For more information on the American chestnut please contact the American Chestnut Foundation by phone at 802-447-0110, e-mail firstname.lastname@example.org or on the web at http://www.acf.org