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by Dr. J. Hill Craddock |
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The major focus of the chestnut research at the Lula Lake Land Trust is the restoration of American chestnut to its former position in the forest. The Trust is actively engaged in several aspects of this project in collaboration with the Chattanooga Chestnut Tree Project.
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The Beautiful American Chestnut |
The American chestnut (Castanea dentata) was once one of the most important timber and nut-producing trees of the eastern United States. In the early 1900s, it was eliminated from its ecological niche by chestnut blight; a disease caused by the fungus Cryphonectria parasitica that was accidentally introduced from Japan. They continue to sprout from the bases of blight-killed stems, and Jonathan Pewitt, a recent graduate of the University of Tennessee at Chattanooga, mapped the locations of more than 40 American chestnut sprouts on Lula Lake Land Trust property. In the near future we hope to begin state-of-the-art computer mapping of all of the surviving chestnuts on Lookout Mountain.
The work at Lula Lake Land Trust involves research in three areas of investigation: 1) breeding the trees for resistance to the fungus; 2) biological control of the chestnut blight disease; and 3) research on the ecology of restoration.
Chestnut Breeding
Soon after blight struck, researchers introduced blight-resistant chestnut species from China and Japan into the US in an attempt to replace the American chestnut. Although the Asian species have proven unsuitable as replacements for the American chestnut, great progress has been made toward a hybrid tree that combines the timber form of the American with the blight resistance of the Chinese chestnut. The most promising hybrids to date are the result of the backcross-breeding program of The American Chestnut Foundation (TACF). The breeding strategy employed by the Chattanooga Chestnut Tree Project follows the TACF model; we aim to transfer the genes for blight resistance from the Asian species into the Lula Lake population of American chestnuts while conserving as much as possible of the surviving genetic diversity of the native Lula Lake trees.
Biological Control of Chestnut Blight
A pathogenic fungus that grows in and kills the inner bark of the American chestnut causes chestnut blight. Biological control is based on "hypovirulence," a phenomenon marked by the reduced virulence of the pathogenic fungus, making it less dangerous for its host. A virus transmits hypovirulence. The virus can convert "lethal" cankers into slower-growing "superficial" bark cankers that do not kill the tree. Slowing the growth of the fungus allows the tree to live and bear fruit. UTC Biology student Pearl Hwang has recently isolated Lula Lake strains of the blight fungus in the laboratory where she will convert them to "hypovirulent" by pairing them with virus-containing strains from Connecticut and West Virginia. We plan to use these Lula Lake hypovirulent strains to attempt biological control of blight at the Lula Lake Land Trust as well.
Lula Lake Land Trust Orchards
We have been planting TACF second-backcross and third-backcross hybrids in orchard number one at Lula Lake since 1998. In addition to their value as a breeding orchard, we can learn about the ecology of chestnut restoration from these hybrids. Together with the recently planted seedlings of pure American chestnut trees in orchard number two and the surviving natives already growing on the Land Trust property, we can ask questions about how to best manage the woodland environment to favor the survival and growth of chestnut and discover which factors are essential to success. Sunlight is certainly one of the most important factors in growth of the young trees, but shade may also have a role in establishment of the seedlings during their first delicate years.
Forest ecology is a complex system of interactions among many organisms; plants, animals, fungi and soil microorganisms working together. Jocelyn DeGuzman, who graduated last May with Departmental Honors in Biology, collected and identified more than 200 species of mushrooms and other fungi growing in orchard number one, alone! Some of these fungi are wood-rotting types or disease-causing parasites of trees, but the majority are symbiotic fungi that live in a mutually beneficial relationship with the roots of their host tree. By doing a thorough survey of the fungal diversity in the orchard as it appears today, we will be able to gage some of the ecological changes that may occur to the site as chestnut returns.
The restoration of the American chestnut will be successful if the current rates of progress are maintained in chestnut breeding and in research on biological control of chestnut blight and chestnut restoration ecology. Efforts are underway to conserve threatened Lula Lake Castanea dentata genetic resources. Ecological and sylvicultural studies have been undertaken that will allow us to better plan the actual return of the chestnut to Lookout Mountain. |
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© 2010 Lula Lake Land Trust & Three HD |
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