White Pines, Hemlocks, and Sunlight
The Blue Valley Experimental Forest
The Blue Valley Experimental Forest (Blue Valley) lies in southwest North Carolina in the Nantahala National Forest. Located in Macon County, near the point where North Carolina meets Georgia and South Carolina, the experimental forest was established in 1964. At 1,300 acres, it is the smallest of the three experimental forests in North Carolina and the second smallest of the 19 managed by U.S. Forest Service Southern Research Station (SRS).
Blue Valley’s landscape is dominated by eastern white pine, but also includes mixed hardwood and eastern hemlock stands. Experts believe extensive grazing and logging in the early 1900s contributed to the abundance of eastern white pine. The infertile soil is typical of the southern highlands. Buckberry, a type of huckleberry, is the most prevalent of the ericaceous (acid- loving) shrubs that dominate the forest understory.
Research studies at Blue Valley started in 1995, and included experiments on management practices such as single-tree selection cutting in white pine/hardwoods, shelterwood and prescribed burning in white pine/hardwoods, and dealing with bark beetle populations. Blue Valley continues to provide opportunities to study the fundamentals of white pine ecology (including seed production and dispersal), ericaceous shrubs, and the qualities of low-fertility sites.
Blue Valley is also the site of a more recent field experiment to investigate whether sunlighting – creating gaps to allow more light to reach the tops of trees – improves the health of hemlocks infested with hemlock woolly adelgid, the insect that’s already devastated hemlocks across the southern Appalachian region.
Many infested hemlocks are still alive, and there is hope that biocontrol using predator beetles – insect species that feed almost exclusively on hemlock woolly adelgids — can keep the trees healthy enough to continue to grow in mountain landscapes where they often function as a foundation species, shading streams and providing essential habitat to birds and insects.
Set up by SRS scientists from the Coweeta Hydrologic Laboratory (Coweeta) in mixed hardwood stands with eastern hemlock in the understory on sites at Coweeta and Blue Valley, the experiment tested the effects of sunlighting on hemlocks that were either uninfested or infested with hemlock woolly adelgid, and either with (Blue Valley) or without (Coweeta) predator beetles present.
In the stands at Coweeta and Blue Valley, researchers created 0.3 acre gaps around half of the eastern hemlocks, and them compared different indicators of physiological stress to evaluate tree health in relation to adelgid infestation and the presence of predator beetles. Results show that combining biological control with silvicultural treatments may improve the long-term survival of infested trees and may be an effective restoration treatment.
Read more about Coweeta research on hemlock woolly adelgid.
The SRS Upland Hardwoods Ecology and Management unit manages Blue Valley, which features 22 different camping sites.
For more information on the experimental forest, contact Henry McNab at hmcnab@fs.fed.us.