The Lingering Hemlock Project is made up of a vast team of academic institutions, nonprofit organizations, and government agencies. This enormous effort on behalf of hemlock conservation requires communication and collaboration for its success.
Project Oversight
The project is overseen by The Nature Conservancy and the U.S. Forest Service.
Locating “Lingering” Hemlocks
Most efforts by partners are currently focused on this phase of the project, as resistance testing and breeding cannot occur until we have candidate trees.
The first step in the resistance breeding process is to locate and identify hemlocks exhibiting signs of resistance to HWA. Generally speaking, HWA has already caused widespread hemlock mortality through much of its introduced range in the southeastern United States, while in northeastern North America, this level of hemlock mortality has not yet occurred. However, there is not yet a unified effort to track hemlock mortality; these geographic trends are based on select and sparse field reports, rather than an exhaustive survey of hemlocks throughout their eastern range. Through collaboration with other local partners, such as land trusts, foresters, academic institutions, etc., we hope to track hemlock mortality more systematically so as to better understand hemlock mortality trends and identify HWA-resistant hemlocks.
In locations where hemlock mortality has already reached 80% or higher (primarily the southeastern United States), project partners will search for “lingering hemlocks,” or hemlock trees that are still alive despite the deaths of many of their neighboring hemlock trees. These trees may not be in pristine condition, but even relatively higher survivorship may be important in understanding and breeding resistant hemlocks. If you are interested in learning more about how you can help with the Lingering Hemlock search, visit our Lingering Hemlock page for contact information and protocols for locating, surveying, and reporting lingering hemlocks.
In locations where hemlock mortality has not yet reached 80% (primarily northeastern North America), project partners will set up “hemlock health monitoring plots,” in which hemlocks will be monitored for decline alongside other environmental and site characteristics. Monitoring hemlock decline over time and space in this way will allow us to better understand patterns of hemlock mortality across the landscape. We will be able to understand HWA’s spread and severity across its leading edge and in doing, catch 80% hemlock mortality as it occurs. Once hemlock mortality reaches 80% in these plots, any remaining hemlocks can be documented as “lingering hemlocks.” If you are interested in learning more about how you can help with establishing Hemlock Health Monitoring Plots, visit our Hemlock Health Monitoring Plot page for contact information and protocols.
Project partners contributing to the search for lingering hemlocks are the New York State Hemlock Initiative, Hemlock Restoration Initiative, Blue Hill Heritage Trust, Harvard Forest, Pennsylvania Department of Conservation and Natural Resources, University of Kentucky, and The University of Tennessee Knoxville.
Researching Genetic Resistance in Hemlocks
Once potentially resistant hemlocks have been identified, research partners will run tests on candidate trees to learn more about the mechanisms behind HWA resistance in hemlock trees and to ascertain the degree to which they exhibit resistance to HWA. Through these tests and through cross-breeding of potentially resistant hemlock trees, we hope to accelerate hemlocks’ evolution of HWA resistance.
Partners at institutions such as North Carolina State University and the University of Connecticut will support research into hemlock genetic resistance to HWA.
Breeding HWA-Resistant Hemlocks
Using the knowledge gained by research genetic resistance and the genotypes identified as resistant, we can begin the process of developing nurseries of varied but resistant hemlocks. This genetic stock can be used to re-seed areas that have faced broad hemlock mortality, preventing the loss of the tree from the landscape.
Resistance breeding will be headed by Holden Forests & Gardens and the Ecological Research Institute.
