Can Chestnuts Survive on Their Own?
by Claire PayneIn spring 2009, the Forest Service (FS) will begin planting a mixture of pure American chestnut, three generations of hybrids, and Chinese chestnut seedlings on national forests in Tennessee, North Carolina, and Virginia. According to Stacy Clark, SRS lead scientist for implementing the first test plantings, the hybrids will include 100 final-generation seedlings and 300 to 400 seedlings from earlier generations.
Clark, research forester with the SRS Upland Hardwoods unit, works closely with Scott Schlarbaum, professor and director of the Tree Improvement Program at the University of Tennessee, to run the science component of the chestnut outplanting project. They also work with Don Tomczak, regional silviculturalist for the FS Southern Region, to locate ideal sites for the first outplanting. They have already secured the nuts from Fred Hebard of The American Chestnut Foundation (TACF), who designed the nursery experiments, and will lay out the test plantings in the field in 2009.
The FS began working with TACF in 2004 when former Chief Dale Bosworth signed a memorandum of understanding to cooperate on restoring American chestnut on national forest land. If nuts germinate and grow as expected, over 100 of the hybrid seedlings will be planted on the Cherokee National Forest in Tennessee, the George Washington-Jefferson National Forest in Virginia, and the National Forests in North Carolina. John Blanton, forest silviculturalist for the National Forests in North Carolina, is working with Clark, Tomczak, regional geneticist Barbara Crane, pathologist Bill Jones from the Forest Health Protection (FHP) unit, and district silviculturalists to determine which districts in North Carolina are best suited for the chestnut seedlings.
In 2010, the FS and TACF intend to extend the experiment to the Daniel Boone National Forest in Kentucky and the Monongahela National Forest in West Virginia. It will take at least 3 to 4 years for the hybrid seedlings to demonstrate how blight resistant they are.
The seedlings destined for national forest lands grow from nuts from trees grown at the TACF farm in Meadowview, VA. The nuts are the result of years of crossbreeding the American chestnut with the Chinese chestnut in an attempt to make them resistant to the Cryphonectria parasitica fungus that causes the chestnut blight. FS scientists and cooperators, FS Southern Region silviculturalists and geneticists, and FHP scientists have been working with TACF to develop a hybrid that is 94 percent pure American chestnut. Seedlings from the nuts are grown for a year in a commercial nursery before they’re outplanted. Clark and Schlarbaum have also implemented a first study of its kind to find out which nursery breeding materials work best, and will be able to determine differences in blight resistance and outplanting performance among pure American seedlings and hybrid seedlings.
What Chestnuts Need
Clark and Schlarbaum have found that chestnut seedlings planted in soils that are not free of Phytophthora cinnamomi, the exotic root-borne ink disease that reduced the chestnutís range in the 1800s, will have little to no chance of survival. That disease persists in wet clay or compacted soils in the Southeastern United States, particularly in lower elevations of the treeís original range.
The national forest sites chosen to grow the chestnut seedlings already include small chestnut trees—sprouts from still living roots that grow to a certain height then succumb to chestnut blight, usually before they can flower. The presence of sprouts indicates the soil is likely free of P. cinnamomi, which completely kills chestnuts. The national forest sites are chosen to insure that site and climatic conditions are similar to those of the seed source of Meadowview, VA, but the outplanted seedlings will have to be able to make it on their own.
“We’re not going to pamper them,” says Tomczak. “TACF wants us to see how they do against natural competition. According to people who have tried to grow them, they should grow pretty quickly, and there’s a good chance they’ll do well. We’ll plant them under two-aged shelterwood systems, with ample but not full sunlight.” Tomczak, retiring after a 30-year FS career, will leave the project in the hands of co-coordinator Crane.
Give Pure A Chance
Clark, along with scientists Henry McNab and David Loftis from the SRS Upland Hardwoods unit, has set up preliminary research plots with pure chestnut seedlings on four sites: timber company land in Jackson County, AL; the Cherokee National Forest in Tennessee; the Bent Creek Experimental Forest in North Carolina; and at the Bankhead National Forest in Alabama. Clark is in charge of analyzing the experiments, and she hopes results will help forest managers understand what’s needed to grow, establish, and outplant chestnut seedlings—as well as provide chestnut breeders with a better understanding of genetic influence on early establishment of forest plantings.
“A lot of attention has been given to producing a blight-resistant tree, but foresters need to know the best methods needed for seedling establishment and growth if there is to be any chance of success for chestnut restoration,” says Clark. “We need to find out how competitive these seedlings are going to be in the face of fierce competition and insect and animal pests.”
The scientists used both clearcut and shelterwood sites to test response to light and competition. Early results indicate a high level of mortality. The scientists report that successful establishment of pure American chestnut seedlings in forest stands will depend on conditions not easily controlled, including animal damage, the presence of ink disease, and other exotic pests such as gypsy moth, the Oriental chestnut gall wasp, and numerous varieties of ambrosia beetles.
It’s been tough going for the young seedlings, with as many as 86 percent dying due to attacks from hungry rabbits and exotic pests; the good news is the survivors grow very fast, keeping up with yellow-poplar and red maple in some test plots.
The project is in its early stages, and survivors will reveal what it takes for chestnuts to reclaim their place. The cost of losing the American chestnut has been too high and the benefits of restoring the species too many to get discouraged. For many people, this effort is a long-term trial with numerous participants and vested cooperators. For some, the restoration of the American chestnut is a life’s work.
For more information:
Stacy Clark at 256–372–4251 or firstname.lastname@example.org
Barbara Crane at 404–347–4039 or email@example.com
Clark, S.L.; Schweitzer, C.J.; Schlarbaum, S.E. [and others]. [In press]. American chestnut (Castanea dentata) restoration research: a genetic and silvicultural approach. In: Stanturf, John A., ed. Proceedings of the 14th biennial southern silvicultural research conference. e-Gen. Tech. Rep. Asheville, NC: U.S. Department of Agriculture Forest Service, Southern Research Station.
McNab, W.H.; Patch, S.; Nutter, A.A. 2003. Early results from a pilot test of planting small American chestnut seedlings under a forest canopy. Journal of The American Chestnut Foundation. 16(2): 32–41.
Oak, S.W. 2002. From the Bronx to Birmingham: impact of chestnut blight and management practices on forest health risks in the Southern Appalachian Mountains. Journal of The American Chestnut Foundation. 16(1): 32–41.
Sisco, P.H. 2007. Southern Appalachian regional breeding summary. Journal of The American Chestnut Foundation. 21(1): 53–60.