This winter, in collaboration with the North Carolina State University (NCSU) Camcore program, the U.S. Forest Service Southern Research Station (SRS) established plots for the first phase of research to support restoring hemlocks to the forest stands in the southern Appalachians they’ve disappeared from.
Andy Tait, NCSU-Camcore research assistant based at SRS, coordinated the planting of 1600 five-year-old hemlock seedlings in experimental plots on the Cold Mountain Game Lands and DuPont State Forest in western Northern Carolina by crews from the North Carolina Forest Service BRIDGE program, which provides conservation and firefighting training to youth offenders.
Forest Keeper volunteers from MountainTrue planted another set of seedlings on DuPont State Forest on stands where an insect, the hemlock woolly adelgid, killed most of the hemlocks.
First found in the eastern U.S. in the 1950s, the nonnative hemlock woolly adelgid now infests hemlock trees from the U.S.-Canada border south to Georgia, causing widespread decline and mortality in hemlocks across the species’ range. This is particularly devastating in the Southern Appalachians, where eastern hemlock is considered a “foundation” species because of the important role it plays in streamside ecosystems.
So far no one’s come up with a good replacement for the hemlock, so managers focus on retaining existing trees using chemical or biological control or a combination of both. Actually restoring eastern and Carolina hemlocks to the landscape is a relatively new concept, but one attracting increasing interest.
“To date, most research has focused on chemical insecticides, biological control, genetic resource conservation, and resistance breeding, but the specific methods needed to reintroduce hemlocks to forests have received little attention,” said Bud Mayfield, principal investigator for SRS on the study and project leader of the SRS Insects, Diseases, and Invasive Plants unit. “Developing restoration methods is the critical next step.”
The new plots start the first phase of a research study designed to develop the best silvicultural strategy for growing hemlock seedlings in degraded hemlock stands. Once the seedlings are established in the plots, researchers will test for the optimal integrated biological and chemical control strategy to keep the trees growing to maturity.
“Then we’ll use the restoration strategy from phase one to establish new, local-source eastern, Carolina, and eastern-Carolina mixed species hemlock restoration plots and apply the integrated management strategy we developed in phase two,” said Robert Jetton, NCSU research assistant professor and leader for the Camcore hemlock project. “Even though we don’t yet have resistant hemlock varieties, planting native hemlocks back into areas we’re treating can help ensure the persistence of the species and the role it plays in streamside ecosystems.”
Managers on public and private lands will be able to use the strategies developed by the study to restore hemlocks on their lands. The geographic area of potential application will increase as the hemlock woolly adelgid continues to spread through the range of eastern hemlock, and results will inform restoration strategies developed for the northeastern U.S. and Canada.
With funding from Forest Service Forest Health Protection, Camcore, an international tree breeding and conservation program at NCSU, has collected over 2 million seeds representing 70 populations of eastern hemlock and 19 populations of Carolina hemlock since 2003. The program distributes seeds to long-term seed banks and to forest nurseries and seed orchards in Brazil, Chile, and the U.S.