Notes from the Field Station: Chestnut Orchard Proposed for MacLeish

9 Apr

Paul Wetzel, Environmental Monitoring Coordinator for CEEDS, has proposed a partnership between Smith College and the American Chestnut Foundation to aid in the re-establishment of the American Chestnut (Castanea dentata).

Once a dominant forest tree throughout the east coast of the United States, the American Chestnut has almost entirely disappeared from our temperate deciduous forests as a result of a pathogenic fungi, rendering it “effectively extinct”. This large, fast growing tree was incredibly rot resistant and hence supported a lucrative lumber industry essential to rural economies. The nuts were a valuable food source for wildlife, people, and their livestock. Lastly, the tannins from the bark were used in tanning leather.

Chestnut Blight (Cryphonectria parasitica)

In 1904, what would become known as the “chestnut blight” was identified at the Bronx Zoo in NYC. Thought to be imported to the U.S. on Asian chestnut trees in the late 19th century, this sac fungi, Cryphonectria parasitica, forms large cankers and girdles the tree, severing the vascular connections between the tree canopy and root system. As it is a wind dispersed pathogen which enters the tree through wounds on the bark, the blight quickly spread, eliminating 99.9% of the American Chestnut population by 1950, or about four billion trees. The sudden downfall of this keystone species decimated associated wildlife and deprived humans of this priceless resource, destroying local economies.

In 1983, a concerned group of plant scientists who recognized the severe impact the loss of the American Chestnut inflicted on forest ecology and the local economy of many rural communities formed the American Chestnut Foundation (TACF). The overall goal of the foundation is to develop a blight resistant chestnut, which would allow it to be restored it to its native range. Experimental research farms were established to test the backcrossing breeding program, aimed at breeding a hybrid chestnut tree with blight resistance through a minimum of six generations. This would be achieved by crossing the American Chestnut with the naturally resistant Chinese Chestnut, and then backcrossing with an American Chestnut repeatedly, in order to produce an American Chestnut with no Chinese characteristics other than blight resistance.

Under the proposed plan, Smith would contribute to the efforts of TACF through the production of blight resistant chestnuts to be cultivated in a chestnut seed orchard at the MacLeish Field Station. If approved, preliminary installations, such as the deer-proof fence and drip irrigation system, will be installed next fall to prep the site for the orchard. The following spring, the area will be planted with 3,000 B3-F2 nuts. The seeds will be divided into “blocks” of 50 trees, each block containing seeds from the same B3 parent tree. After two years of growth, the saplings will be infected with the chestnut blight fungus (Cryphonectria parasitica). Of the 3,000 nuts planted about 20 are predicted to survive infection from the blight. Those 20 saplings will be protected and maintained so that they may grow to maturity. One third of the nuts these trees produce will produce viable resistant trees, the B3F3 generation, which is genetically comprised of 94% Castanea dentata and 6% Castanea mollissima (the naturally resistant Chinese Chestnut).

The proposed 30-year commitment from Smith College to the American Chestnut Foundation would allow TACF total access to the orchard for assessment, harvesting, and other purposes. The local TACF chapter will supply Smith with all necessary materials for the orchard (nuts, fencing, and pipe, etc.), while Smith will provide all labor for the project.

Student interns will be integral to the project, participating in the initial installation and attending to routine maintenance such as weeding and mowing. Additionally, the orchard would be installed proximal to the new Bechtel Environmental Classroom (BEC), making it a highly accessible teaching opportunity for biology and environmental science classes. Although we will be unable to produce resistant nuts ourselves for a number of years, there is a possibility Smith College would be able to acquire the rare blight resistant B3F3 nuts for teaching purposes in the mean time.

This proposed partnership serves as a perfect opportunity to combine conservation and restoration ecology with teaching opportunities for the college and greater public. Thanks for reading and stay tuned for more field station updates.

Jessa Finch (’12)

CEEDS MacLeish Intern

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