American Chestnut Restoration

Research Issue

The American chestnut is a tree species of unique ecological and economic value that was virtually eliminated following a blight caused by the fungal pathogen, Cryphonectria parasitica (Murr.) Barr that was accidentally introduced about a century ago.  In order to restore this economically and ecologically valuable species, multiple approaches to decrease the virulence of the pathogen or increase the resistance of the tree have been evaluated.  However, only one technique – producing highly resistant trees via the hybridization of American and Chinese chestnuts with backcrosses to American chestnut – shows promise for near-term restoration.  The American Chestnut Foundation (TACF) is a leader in this breeding effort, and we are collaborating with TACF to extend this work into the Northern Forest. 

Our Research

Our collaborative group has identified at least three issues that should be addressed to help restore American chestnut to the north: 1) the low representation of germplasm from north-adapted trees in the current restoration breeding program; 2) uncertainty of the role that inadequate cold hardiness plays in limiting the success of the species at its northern limit; and 3) limited knowledge of whether silvicultural and other management techniques may improve the growth and survival of American chestnut seedlings and trees under northern conditions.  

To date, most research and breeding efforts to restore American chestnut have occurred in the central portions of the species historic range.  However, for full species restoration, efforts must be extended to additional geographic regions, including northern extremes of the species range.  Indeed, restoration at the northern range limits may actually be one of the most important locations for population recovery because climate change may favor the extension of oak-hickory cover types (that once included chestnut) into the Northern Forest.  Restoration in the north would provide a range of ecosystem services (e.g., wood products, wildlife mast, etc.) that would be beneficial at a time of shifting forest types.

Although our work is still evolving, significant progress has been made toward addressing these research areas.  So far we have located and verified 15 additional mature American chestnut trees for controlled pollinations in Vermont.  We have also conducted controlled pollinations of five Vermont American chestnut trees.  Nuts collected from these pollinations will be grown in TACF plantations, tested for disease resistance, and included in later breeding efforts.  We have also assessed the cold tolerance of American chestnut seed and shoots.  We are also establishing plantings of American chestnut from different genetic sources under various silvicultural treatments on the Green Mountain National Forest to test whether limitations in cold hardiness can be overcome through either 1) genetic selection (identification of hardier sources that could be introduced into the breeding program), or 2) silvicultural management (determination of cultural regimes that either increase seedling growth and sugar storage and improves cold hardiness). 

Expected Outcomes

Our research team, in collaboration with TACF scientists and managers on the Green Mountain Nationals Forest, hopes to restore American chestnut in Vermont and elsewhere in the Northern Forest.

Research Results

Gurney, Kendra M.; Schaberg, Paul G.; Hawley, Gary J; Shane, John B. 2009. Inadequate cold tolerance as a possible limitation to American chestnut restoration in the northeastern United States. Restoration Ecology.

Schaberg, Paul G.; Gurney, Kendra M.; Janes, Benjamin R.; Halman, Joshua M.; Hawley, Gary J; 2009. Is nut cold tolerance a limitation to the restoration of American chestnut in the northeastern United States? Ecological Restoration 27:266-268.

Research Participants

Principal Investigator

• Paul Schaberg, US Forest Service - Northern Research Station, Research Plant Physiologist

Research Partners

• Kendra Gurney, The American Chestnut Foundation - New England Regional Science Coordinator
• Gary J. Hawley, The University of Vermont - Senior Researcher
• Green Mountain National Forest

For further details log on website :
https://www.nrs.fs.fed.us/disturbance/climate_change/american_chestnut/