American Chestnut
( Castanea dentata )
Restoration Research
- How can we develop high-quality nursery seedlings for planting?
- Is it best to plant chestnut seedlings in open-conditions (clearcuts, low residual tree shelterwoods) or under shaded conditions that will be opened up in a few years (high residual tree shelterwoods)?
- How will the seedlings compete on a range of sites that vary in quality and disturbance history?
- Will the advanced breeding material behave similarly to a 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 19 th 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. (insert range map you have on the website pdf file with title ‘Historical range of American chestnut') The loss of the American chestnut as a mature component in eastern forests has resulted in large-scale shifts 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. (insert picture 2.jpg-titled ‘Natural American chestnut stump sprout in Jackson County , AL ') .
What's being done to restore chestnut?
Restoration of American chestnut to eastern forests depends on the development of blight-resistant seedlings. The Forest Service does not conduct breeding research, 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 final breeding generation produced in the TACF's program will be the third intercross of the third backcross generation (BC 3 F 3 ). Seedlings from this generation will be 15/16 American chestnut with stable blight resistance.
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 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 . Dr. Clark uses material from TACF and works with partners from The University of Tennessee's Tree Improvement Program and the Southern Region of the National Forest System to conduct her research.
Making history, the first plantings of blight-resistant seedlings is happening in 2009!
Field testing of seedlings from the final generation (BC 3 F 3 ) of the American Chestnut Foundation's (TACF) breeding program will be established on three National Forests in the Southern Region (Region 8) in the winter of 2009. The first BC 3 F 3 nut collection by the TACF occurred in 2007, with adequate numbers (550 nuts) available for field planting. 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. These experiments will be the first testing of the TACF's BC 3 F 3 generation in field conditions.
As part of the test plantings, a study was also established to determine if size of the chestnut affects seedling development in the nursery. This is a question of interest to nursery managers, because size of other seed, including acorns, has been found to affect seedling development. BC 3 F 3 chestnuts along with chestnuts from all phases of the breeding program (pure American, Chinese chestnut, BC 1 F 3, and BC 2 F 3) were sown at the Georgia Forestry Commission's Flint River Nursery in January 2008. The chestnuts from each seed lot were first divided into ‘Large' and ‘Small' size classes to test if chestnut size affects seedling development. The seedlings will be lifted in early 2009 to establish experimental plantings on three National Forests in the Southern Region. Prior to planting, each site will be tested for presence of Phytophthora cinnamomi an exotic fungus that will kill chestnut seedlings by attacking the root system of the tree. P. cinnamomi testing is being conducted in assistance with Bill Jones with U.S. Forest Service, State and Private Forestry. Each planting will consist of approximately 400 trees, including 150 seedlings from the BC 3 F 3 generation.
Early surveys of 2008 nut crops indicate that adequate experimental material will also be available for 2010 test plantings. Dr. Clark and Dr. Schlarbaum will oversee testing of seedling performance in ‘real-world' forest conditions, and results will guide the 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.
Studies
Due to the limited availability of advanced breeding material, 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 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 and mesic 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. (insert picture 4.jpg titled ‘Seedling on mesic site in two-age shelterwood stand) 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. Phytophthora cinnamomi resulted in failure of one replication.
Bent Creek Experimental Forest Planting, North Carolina
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 Planting, Alabama
These plantings were established in 2006 and 2007 on land owned by Steve
nson 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 ink disease ( Phytophthora cinnamomi ), (insert picture 4.jpg titled ‘Seedling on mesic site in two-age shelterwood stand') 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. Results from this study will be published in the Proceedings for the 14 th Biennial Southern Silvicultural Research Conference (in press). Hybrid seedlings developed by Dr. Sandy Anagnostakis, Agricultural Scientis 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, Tennessee
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 BC 1 F 3 and BC 2 F 3 material from the TACF and their growth and development will be monitored.
William B. Bankhead National Forest Planting, Alabama
These plantings were established in 2007 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 ft 2 per acre (creating moderate-light conditions) (insert picture 6.jpg title ‘Seedlings being planted in thinned stands') or in areas that were group clearcuts treated for southern pine beetle (creating high-light conditions) (insert picture 7.jpg titled ‘Seedlings being planted in group clearcuts').
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 BC 2 F 3 seedlings from the TACF and their growth and development will be monitored.
Publications
Anagnostakis, S., S.L. Clark, and H. McNab. In press . Preliminary report on the segregation of resistance in chestnuts to infestation by Oriental Chestnut Gall Wasp. Proceedings of the 97th Annual Report of the Northern Nut Growers Association, August 12 th -15 th , 2007 .
Anagnostakis, S., S.L. Clark, and H. McNab. In press . Preliminary report on the segregation of resistance in chestnuts to infestation by Oriental Chestnut Gall Wasp. Proceedings of Chestnut Management in Mediterranean Countries, Bursa , Turkey , October 23 rd -25 th , 2007 .
Clark , S.L., C.J. Schweitzer, S.E. Schlarbaum, L.D. Dimov, and F.V. Hebard. In press. American chestnut ( Castanea dentata ) restoration research: a genetic and silvicultural approach. In Proceedings of the 14 th Biennial Southern Silvicultural Research Conference, Athens, GA. February 26th-March 1 st , 2007.