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Chestnut Research at Lula Lake: Winter 2004
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 controlled orchard settings.
This allows for conservation of genes from trees that, due to blight
or competition, cannot reproduce on their own. Mark Alexander is a
graduate student at UTC and a research intern for the American
Chestnut Foundation studying the conservation of chestnut genetic
resources. In the winter of 2004, he gathered scion wood from the
Lula Lake Land Trust for inclusion in this year’s scion wood
exchange.
Accompanied by Dr. Hill Craddock and
Chattanooga Chestnut Project researchers, he used the maps
constructed by Jonathan Pewitt in 1999 to revisit the Lula Lake Land
Trust chestnut sprouts. Many of the trees were still surviving and a
few were found to be thriving in the light of canopy breaks caused by
a 2001 tornado. Scion wood was successfully collected, and on
February 21, 2004 at the 2nd annual TN-TACF grafting workshop, the
scions will be grafted. In the controlled environment and full sun of
the breeding orchard at Bendabout Farm, these clones may reach
maturity and bloom. This will allow backcross breeding using locally
adapted Lookout Mountain American parents. The eventual
blight-resistant offspring will retain genetic adaptation for the
unique local Lookout Mountain ecosystem and will thus be suitable for
reforestation plantings. A grafted clone of a Lula Lake Land Trust
chestnut tree was included in the research of UTC masters graduate
Stephen Alexander. Stephen's work involved host-pathogen interactions
and different levels of expression of hypovirulence in the backcross
hybrid population at Bendabout Farm in Cleveland, Tennessee.
New
research opportunities in chestnut conservation are continuing to
surface as a result of the Land Trust's dedication to protect and
preserve the natural beauty and abundant resources within the Rock
Creek watershed. Plans are underway to
investigate a unique genetic phenomenon occurring in the forests of
Lookout Mountain. In 1997, molecular biology techniques were used to
perform genetic analyses on samples taken from Lula Lake Land Trust
chestnut trees visually identified as pure American chestnut. The
results showed evidence of genes from another native chestnut
species, the chinquapin (Castanea pumila). The presence of chinquapin
on Lookout Mountain has been confirmed and a more detailed study of
the possible chestnut-chinquapin hybrids is being planned. Mark
Alexander is also working on a computer mapping project in
conjunction with The American Chestnut Foundation, and the Geographic
Information Systems (G.I.S.) facilities at UTC. A G.I.S. map has been
constructed to catalogue the genetic resources of C. dentata across
the entire region of the southeastern United States. The G.I.S. map
functions also as a database, which spatially references chestnut
breeding information. In 2003 the breeding orchards at Lula Lake Land
Trust were incorporated into this region-wide resource database.
Global Positioning Satellite (GPS) location was used to record
precise coordinates for all trees, which were catalogued and linked
with extensive genetic and ecological information for each tree. In
this way the research conducted at the Lula Lake Land Trust will
benefit not only the local researchers of Lookout Mountain, but also
those of the entire region. The preservation of the invaluable
ecological data gathered at Lula Lake will be thus ensured and its
application will benefit chestnut reforestation efforts for
generations to come.
The return
of the chestnut will require the concerted efforts of university,
government, and private foundation researchers and the work of
dedicated volunteer enthusiasts. Education and public awareness are a
big part of the Chattanooga Chestnut Project and the
resource. Opportunities to learn about the
chestnut project and to get involved are regularly available to the
public.
More
information about the Chattanooga Chestnut Project can be found on
the Lula Lake
Land Trust website:
www.lulalake.org/newsletters
Or visit Hill
Craddock’s Chestnut Links website:
www.utc.edu/Faculty/Hill-Craddock/chestnutlinks.html
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