Research Goals

american chestnut

Figure 1. Large American chestnut in North Carolina. Courtesy of the Forest History Society.

The Upland Hardwood Ecology and Management Research Work Unit (RWU 4157) has been conducting American chestnut research since 1995. The primary goal of the chestnut research program is to develop protocols that managers can implement to restore this species. American chestnut was highly valued for food, rot-resistant lumber, and tannin. The species could attain large sizes and had a fast growth rate (Figure 1.) Primary questions we hope to answer are:

  • How can we develop high-quality nursery seedlings for planting?
  • Is it best to plant chestnut seedlings in open-conditions or under shaded conditions that will be opened up in a few years?
  • does site quality and disturbance history of a stand affect chestnut seedlings?
  • Will chestnuts that are bred to be blight-resistant behave similarly to pure American chestnut while maintaining blight-resistance?

What happened to the chestnut?

american chestnut

Figure 2. Chestnut blight fruiting bodies on base of planted seedling.

The American chestnut (Castanea dentata Marsh. Borkh.) was decimated by an exotic fungus known as the chestnut blight (Cryphonectria parasitica Murr. Barr)(Figure 2), when the blight was introduced into North America in the latter part of the 19th century. American chestnut was a keystone species in the eastern hardwood forests, and its demise has altered forest ecosystems by reducing species diversity, reducing availability of hard mast, and changed soil and litter dynamics.

The loss of the American chestnut as a mature component in eastern forests has resulted in large-scale changes in species composition, particularly on upland well-drained stands where the species was most competitive. Because the chestnut blight affects only the above-ground portion of the tree, the species has managed to exist as short-lived stump and root sprouts, which will occasionally live long enough to flower and bear fruit.

Our Research

The Forest Service does not conduct breeding of blight-resistant trees, but supports efforts of The American Chestnut Foundation (TACF), a private non-profit organization whose goal is to produce blight-resistant chestnut trees through a back-cross breeding program involving the blight-resistant Chinese chestnut (Castanea mollissima Blume). The TACF breeding program's end product is essentially an American chestnut with blight resistance from Chinese chestnut. The first line of material in the TACF's program that is expected to be blight-resistant is the third intercross of the third backcross generation (BC3F3). Seedlings from this generation are 15/16 American chestnut with expected stable blight-resistance. BC3F3 nuts were produced in sufficient numbers for testing for the first time in Autumn 2007.

Chestnut restoration does not end with development of a blight-resistant tree. A prescription for how and where to plant trees is needed. The Upland Hardwood Ecology and Management Research Work Unit of the Southern Research Station is conducting research to develop prescriptions that managers can use for planting blight-resistant American chestnut seedlings. This research is being led by Dr. Stacy Clark, who is working with partners from The University of Tennessee's Tree Improvement Program, the Tennessee Division of Forestry,and the Southern Region of the National Forest System.

Making history, the first restoration test plantings established on national forests!

american chestnut

Figure 3. An American chestnut planting site at the time of planting establishment

The first BC3F3 nut collection by the TACF occurred in 2007, 2008, and 2009. The trees were grown for one year in a commercial tree nursery, and nursery protocols designed to maximum seedling size were tested. After one year in the nursery, the seedlings were lifted and field tests were established in 2009, 2010, and 2011. click for more...

Early Results of Restoration Plantings

Seedlings averaged 3.1-4.4 ft in height at the time of planting, but were highly variable in size. The large size of the nursery seedlings was due to technological advancements in nursery production of hardwood trees, necessary for successful restoration of hardwood trees in upland forest sites of the southeastern United States. Trees were out-planted into shelterwood harvested areas (residual basal area of 10-20 ft2 acre-1) or underplanted in stands where the midstory had been removed with an herbicide hack-and-squirt injection (Loftis 1990). Prior to plantings, we divided trees into Large and Small size classes based on visual assessment due to the high variability in seedling size of the nursery seedlings. click for more...

Selected Publications

For More Information

For more information contact Stacy Clark at stacyclark@fs.fed.us or at 865-974-0932