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Posted on March 4th, 2016 in Forestry, Forests and Street Trees | 1 Comment »
10 year old American chestnut tree

10 year old American chestnut tree. Photo: Jim McKenna, USDA Forest Service, Purdue HTIRC

Juvenile American Chestnut

Juvenile American chestnut (Castanea dentata) tree. Photo: Dr. Shaneka Lawson, USDA Forest Service, Purdue FNR

When you hear about endangered species, most of us think about the plights of our furry or feathered friends. This article describes the plight of some of the less cuddly members of the endangered species list. Indiana is home to a number of endangered and threatened tree species. In this multi-part series, we will identify some of the tree species and describe some of their unique characteristics.

Our first species is the American chestnut (Castanea dentata) sometimes called the “Sequoia of the East”. This species was once found thriving throughout eastern forests from central Maine west to southeastern Michigan, and south to northern Mississippi, Alabama, and Georgia.

American chestnut fruit (nuts) inside an opened bur

American chestnut fruit (nuts) inside an opened bur. Photo: Jim McKenna, USDA Forest Service, Purdue HTIRC

American chestnut fruit protected by a spiny bur.

American chestnut fruit protected by a spiny bur. Photo: Dr. Shaneka Lawson, USDA Forest Service, Purdue HTIRC

Early 20th century estimates indicated that these trees numbered closed to 4 billion with the finest, most productive stands found in the Appalachian Mountains and southern New England. American chestnut is a fast growing species that can reach a pinnacle of 120 feet high and 10 feet or more in diameter. The majority of the mature trees were between 3 and 5 feet in diameter and 60 to 90 feet high. The fruit from this tree has been a valued food source for humans, wildlife, and livestock alike. Timber from this former giant is naturally rot-resistant and nearly as durable as oak yet lighter.

American chestnut populations went into decline after the introduction of chestnut blight.

Mature American chestnut leaves

Mature American chestnut leaves. Photo: Dr. Shaneka Lawson, USDA Forest Service, Purdue FNR

Immature American chestnut leaves

Immature American chestnut leaves. Photo: Dr. Shaneka Lawson, USDA Forest Service, Purdue FNR

Chestnut blight is caused by the fungal pathogen (Cryphonectria parasitica), and was accidentally introduced into the American population by imported Asian chestnut trees a century ago. American chestnut is highly susceptible to the fungus which enters the tree through any small wound or crack in the bark. The fungus replicates beneath the bark and produces toxins which lead to plant cell death. The fungus continues to grow until it has circumnavigated the tree and effectively stopped the flow of nutrients. Everything above the girdled circle of fungus will die. The primary symptoms of chestnut blight disease are a sunken canker and orange spores covering the bark.

Chestnut blight canker four months after inoculating a susceptible chestnut tree.

Chestnut blight canker four months after inoculating a susceptible chestnut tree. Photo: Jim McKenna, USDA Forest Service, Purdue HTIRC

12 year old resistant 15/16 American chestnut after direct challenge with (Cryphonectria parasitica) fungus.

12 year old resistant 15/16 American chestnut after direct challenge with (Cryphonectria parasitica) fungus. Photo: Dr. Shaneka Lawson, USDA Forest Service, Purdue FNR

Loss of American chestnut on the landscape has resulted in reduced species diversity and severely reduced fall mast for woodland animal species. In addition, leaves of American chestnut contain greater nutrient concentrations (nitrogen [N], phosphorus [P], potassium [K]) than most other co-occurring trees therefore its loss affects soil nutrient cycling.

American chestnut has survived thus far because it has the ability to sprout from roots and stumps of diseased trees. However, these trees rarely live to maturity thus are often unable to flower and bear fruit. Numerous efforts to restore the tree to its former glory have been and are currently being attempted. Thus far, two of the most effective methods of breeding for resistance are hybridizing with resistant Asian parents and attempting to intercross surviving pure American chestnuts. The HTIRC within the Forestry and Natural Resources Department at Purdue University is working on hybridization of American chestnuts with Asian chestnuts for future restoration of resistant American-like chestnuts for Indiana.

Resources:
The American Chestnut Foundation
A New Generation of American chestnut Trees May Redefine America’s Forests – Scientific American
Consequences of Shifts in Abundance and Distribution of American Chestnut for Restoration of a Foundation Forest Tree – Forests Open Access Forestry Journal
Transgenic American chestnuts show enhanced blight resistance and transmit the trait to T1 progeny – Science Direct (Plant Science)
Chestnut’s Last Stand – Wisconsin Natural Resources Magazine

Shaneka Lawson, USDA Forest Service and HTIRC Research Plant Physiologist & Adjunct Assistant Professor
Purdue University Department of Forestry and Natural Resources

Jim McKenna, USDA Forest Service and HTIRC Biologist
Purdue University Department of Forestry and Natural Resources


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One thought on “Endangered Trees of Indiana: Part 1 – American Chestnut (Castanea dentata)

  1. Tom Work says:

    My Mom always talked about what magnificent trees the American Chestnuts were. As a graduate of Purdue, I was pleased to learn that you are working on a hybird of this tree and wondered if the trees are available on campus or where I can find some small trees to plant on my properties in Michigan.

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