American Chestnut (Castanea dentata) Restoration Research
- Research Goals
- What happened to the chestnut?
- What's being done to restore chestnut?
- Making history, the first restoration test plantings established on national forests!
- Early Results of Restoration Plantings
- Other chestnut studies
- Publications
Research Goals
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.
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?
- How 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?
The American chestnut (Castanea dentata Marsh. Borkh.) was decimated by an exotic fungus known as the chestnut blight (Cryphonectria parasitica Murr. Barr), 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.
What's being done to restore chestnut?
Restoration of American chestnut to eastern forests largely depends on the development of blight-resistant seedlings. 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 expected to be 15/16 American chestnut with 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, but also requires a prescription for how and where to plant trees once available. To date, planning for American chestnut restoration has emphasized producing a blight-resistant tree, and only limited attention and resources have been specifically given to test procedures needed for successful establishment and growth of resistant seedlings. The U.S. Forest Service signed a Memorandum of Understanding with the TACF in 2004, which designates the Forest Service as the 'most favored recipient' of the TACF's chestnut material, and the resulting seedlings are to be incorporated into management activities on National Forest System (NFS) lands.
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, once they become available. 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!
The first BC3F3 nut collection by the TACF occurred in 2007, with adequate numbers (550 nuts) available for field testing. These chestnuts were transferred to the Southern Region of the National Forest System and in turn given to Dr. Stacy Clark of the Southern Research Station's Upland Hardwood Ecology and Management Research Work Unit for experimental testing. Dr. Clark is working in cooperation with Dr. Scott Schlarbaum, Director of the University of Tennessee's Tree Improvement Program and the Southern Region to implement these test plantings. 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.
The 2009 field tests were established on three national forests in the Southern Region. In 2010, two additional plantings were established on two national forests in the Southern Region using similar experimental design and planting protocols. These experiments are the first testing of the TACF's BC3F3 generation in forest conditions!
Each planting consists of 400-600 trees, and approximately 1/3 of each planting contains trees from the BC3F3 generation. The remaining trees are a mixture of pure American, Chinese, and other less developed generations.
Additional test plantings are planned for 2011. The Southern Research Station's Upland Hardwood Ecology and Management Work Unit is leading the way to provide information on seedling performance of American chestnut in 'real-world' forest conditions. Data collected includes survival, growth, competitive ability, bud-break phenology, and disease, insect, and animal damage. Results will provide guidance to managers on national forests that will soon be receiving chestnuts for large-scale reforestation efforts. The data will also help TACF in making selections of superior families in their breeding program. The test plantings can be used as education and demonstration sites for local citizen groups and professional organizations to illustrate how forest management can be used in the restoration of a native species.
Early Results of Restoration Plantings
Results are preliminary, but test plantings established in 2009 and 2010 are growing successfully. Survival across all 2009 plantings averages 88%, and nearly all trees are in a competitive position with no other trees overtopping them. Deer browse has been a problem in at least one planting, so deer protectors were erected when needed.
Other chestnut studies
Due to the limited availability of advanced breeding material (BC3F3), studies using pure American seedlings and less advanced genetic material have been implemented to test early field performance and growth in a variety of conditions.
Bent Creek Experimental Forest Gall Wasp Resistance Study, North Carolina
This study was implemented in cooperation with Sandy Anagnostakis with the Connecticut Agricultural Experiment Station. In 1995, hybrid chestnuts were planted, and were reexamined in 2006 after a recent gall wasp infestation. The objective of this study was to examine resistant to the gall wasp among four hybrid families of Castanea species. Approximately half of the trees (53/93) survived to 2006. There is segregation for wasp infestation among the surviving hybrids, and we conclude that the genes for resistance to infestation cannot be cytoplasmic. These preliminary results provide some indication that a single dominant gene may be controlling resistance to Asian chestnut gall wasp.
Kentucky Silviculture Plantings
These plantings were established in 2001 and 2002 on the Daniel Boone National Forest, the Tygart State Forest and the Robinson Forest of the University of Kentucky to determine how seedlings would perform when subjected to various site conditions. Seedlings were planted in two-age shelterwood stands (creating high-light conditions) and in stands treated with a midstory reduction treatment (creating low-light conditions). Both silviculture treatments were implemented on xeric (dry soils) and mesic (moist soils) site type, and treatments and site types were each replicated 4 times.
Results indicate that seedlings grew best on mesic sites subjected to the two-age shelterwood harvest. Even in the face of competition from fast-growing species like yellow poplar (Liriodendron tulipifera), the majority of surviving chestnuts were free to grow. Survival was independent of either site type or silvicultural treatment. An exotic soil-borne pathogen, Phytophthora cinnamomi resulted in failure of one replication.
Bent Creek Experimental Forest Silviculture Planting
These plantings were established in 2006 on the Bent Creek Experimental Forest to determine how seedlings would perform when subjected to various site conditions. Seedlings were planted in two-age shelterwood stands (creating high-light conditions) and in stands treated with a midstory reduction treatment (creating low-light conditions). Silviculture treatments were implemented on three replications consisting of xeric, subxeric and mesic site types.
Results indicate that seedlings grew best on mesic sites subjected to the two-age shelterwood harvest. Survival was independent of either site type or silvicultural treatment.
Jackson County, Alabama Silviculture Planting
These plantings were established in 2006 and 2007 on land owned by Stevenson Land Company and by the Alabama Department of Conservation and Natural Resources State Lands Division to determine how seedlings would perform when subjected to two silvicultural treatments. Seedlings were planted in clearcuts (creating high-light conditions) and in stands treated with a midstory reduction treatment (creating low-light conditions). Each silvicultural treatment was replicated three times.
In 2006, seedlings were susceptible to the exotic soil pathogen, ink disease (Phytophthora cinnamomi), killing 80% of all seedlings. Seedlings planted in the clearcuts were more likely to receive rabbit browse than seedlings planted in the midstory treatment. No differences in growth were detected between the two silvicultural treatments. Hybrid seedlings developed by Dr. Sandy Anagnostakis, Agricultural Scientist with the Connecticut Agricultural Experiment Station were planted in dead tree spots in 2007, but mortality exceeded 90% due to the exceptional drought in 2007.
Cherokee National Forest Planting Progeny Test Planting
The planting was established in 2006 in cooperation with The University of Tennessee's Tree Improvement Program on the Ocoee Ranger District of the Cherokee National Forest in Tennessee . The seedlings were planted in a former pine stand (Pinus virginia and P. echinata) treated for the southern pine beetle, resulting in a stand with 0% retention of overstory trees. The seedlings were planted using an incomplete block design to test performance of seven families.
No family differences were detected by the end of the second growing season. Survival was 50% by the second growing season and most trees died due to the exceptional drought that occurred in 2007. The dead tree spots were replanted in 2008 with BC1F3 and BC2F3 material from the TACF and their growth and development will be monitored.
William B. Bankhead National Forest Planting Silviculture Planting
These plantings were established in 2007 and 2008 on the William B. Bankhead National Forest in cooperation with The University of Tennessee's Tree Improvement Program to determine how seedlings would perform when subjected to two contrasting light environments. Seedlings were planted in pine stands (Pinus taeda) that the forest is restoring to native hardwoods. Seedlings were planted in stands thinned to approximately 50 ft2 per acre of basal area (creating moderate-light conditions) or in areas that were group clearcuts treated for southern pine beetle (creating high-light conditions) Early results indicate that seedlings were susceptible to the exceptional drought that occurred in 2007. Seedlings in the thinned areas had significantly better survival than seedlings in the clearcut areas due to higher soil moisture in the thinned stands. Growth did not differ between the two silvicultural treatments. The dead tree spots were replanted in 2008 with BC2F3 seedlings from the TACF and their growth and development will be monitored.
Publications
Anagnostakis, S., S. Clark, and H. McNab. 2009. Preliminary report on the segregation of resistance in chestnuts to infestation by oriental chestnut gall wasp. Acta Horticulturae 815:33-35.
Clark, S.L., C.J. Schweitzer, S.E. Schlarbaum, L.D. Dimov, and F.V. Hebard. 2009. Nursery quality and first-year response of American chestnut (Castanea dentata) seedlings planted in the southeastern United States. Tree Planters' Notes 53(2): 13-21.
Clark,S.L. and S.E. Schlarbaum. 2009. Bringing back a mighty giant: American chestnut restoration. USDA Forest Service, Research and Development 2008-2009 Highlights, USDA FS-942: 18.
Rhoades, C., D. Loftis, J. Lewis, and S. Clark. 2009. The influence of silvicultural treatments and site conditions on American chestnut (Castanea dentata) seedling establishment in eastern Kentucky, U.S.A. Forest Ecology and Management 258:1211-1218.
For More Information
For more information contact Stacy Clark at stacyclark@fs.fed.us or at 865-974-7996