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By Mark T. Alexander, Lisa Worthen and J. Hill
Craddock
While Georgia may be behind other states in organized
American Chestnut restoration efforts, UTC Biologist Hill Craddock
and his graduate students have created a state-of-the-art chestnut
orchard high atop Lookout Mountain south of the Tennessee border.
What follows is a summary of their important work as published in the
Winter 2004 issue of the Lula Lake Land Trust quarterly newsletter.
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 continues to be actively engaged in
several aspects of this project in collaboration with the Chattanooga
Chestnut Tree Project. The American Chestnut (Castanea dentata) was
once one of the most important timber and nut-producing trees of the
eastern United States. The historical range of the American chestnut
reaches from southern Maine southward into Georgia, Alabama, and
Mississippi and includes the Chattanooga ridge and valley region. The
upland forest habitat conditions on Lookout Mountain, and in much of
the Lula Lake Land Trust property, represent the historical ideal for
a chestnut-based ecology. Habitats typical of the Cumberland Plateau
are represented: oak-pine, oak-hickory, maple-beech-birch forest,
rocky ridgelines, and streams. "There were more chestnut trees on
Lookout Mountain than there were anything else." said the late
William Raoul, American Chestnut Foundation board member, in
describing the woods near his boyhood home. He remembered the local
ridgeline, known as the "hog's back" as being literally spiked with
chestnut. In the early 1900s, the dominant mountain slope tree of
Appalachia was eliminated from its ecological niche by chestnut
blight; a disease caused by the fungus |
Cryphonectria parasitica that
was accidentally introduced from Japan. The trees continue to sprout
from the bases of blight-killed stems, as the roots are unaffected.
In 1997 the Chattanooga Chestnut Project under the direction of Dr. J
Hill Craddock took up chestnut research initiatives at the Lula Lake
Land Trust, continuing the conservation work of William Raoul. 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. Jonathan Pewitt, a recent graduate of the
University of Tennessee at Chattanooga, mapped the locations of more
than 40 American chestnut sprouts on the Lula Lake Land Trust
property adjacent to Rock Creek and Lula Lake. These surviving stump
sprouts require a delicate forest ecosystem, which is in danger of
elimination due to habitat loss at the hands of human development
activities. The protection of the Rock Creek watershed by Mr.
Davenport and the Lula Lake Land Trust has thus preserved a valuable
genetic resource for the future. Much of this protected land
represents ideal chestnut forest habitat.
The opportunity to conduct chestnut research in a protected and
healthy forest ecosystem allows for important observations on forest
ecology, population genetics, backcross breeding, biological control
of chestnut blight, and seedling growth and survivability studies.
Toward these ends and in cooperation with the Lula Lake Land Trust,
the Chattanooga Chestnut Project maintains three chestnut orchards on
the property along Middle Road planted in 1998. Multiple research
projects are underway. The breeding strategy employed by the
Chattanooga Chestnut Tree Project follows The American Chestnut
Foundation (TACF) model. Through a process known as backcrossing,
genes for blight resistance are transferred |
from the Asian chestnut species into the native
populations of American chestnuts while conserving as much as
possible of the genetic diversity of the surviving native Lula Lake
trees.
TACF second-backcross and third-backcross hybrids have been planted
every year since 1998 in Orchard 1. In addition to their value as a
backcross-breeding population, we can learn about the ecology of
chestnut restoration from these hybrids. Together with the pure
American chestnut seedlings planted in Orchard 2 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.
Removal of overstory pine trees damaged by the Southern Pine Beetle
will increase orchard light levels and allow the seedlings to thrive.
Sun versus shade comparison studies will be an important part of the
future research at the Lula Lake Land Trust.
American chestnut trees in the wild rarely, or never, get the chance
to reproduce. To include the genes from these wild trees in breeding
programs, TACF must find a way to reproduce them. One way to
reproduce the trees is by grafting scion wood (winter twigs with
dormant buds) onto rootstocks already growing in a greenhouse. Last
winter, the Tennessee chapter of the American Chestnut Foundation
initiated a statewide scion wood exchange among its members. Genetic
material was collected from important surviving chestnut trees from
across the state in the form of scion wood. These scions were then
grafted onto select chestnut seeds or rootstocks for reproduction
within
American chestnut trees in the wild
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