Life after Hemlock: Restoring Riparian Forests in the Southern Appalachians

Posted by Jeff on Dec 6, 2015 @ 10:38 am in Conservation | 0 comments | Last modified: December 6, 2015

In the last decade, the hemlock woolly adelgid, a tiny sap-sucking insect native to Japan, has swept through southern Appalachian forests, leaving dead hemlocks in its wake. Hemlock branches no longer shade streams or tower over shrubs, and their loss has affected streamside, or riparian, forests.

“Without hemlock, more sunlight reaches the forest floor,” says U.S. Forest Service scientist Chelcy Ford Miniat. The species that has benefited the most from the increased light is an evergreen shrub, rosebay rhododendron (Rhododendron maximum), which is now growing twice as fast as expected. Although rhododendron’s showy flowers are appreciated by nature-lovers, its unchecked growth in riparian forests is not so welcome.

Evergreen rhododendron grows so densely that flowering plants, ferns, and seedlings are unable to survive beneath its shade. It also stores essential plant nutrients in its leaves for years, and when the leaves fall off and fragment, they decompose very slowly and nutrients remain locked up in forms that are inaccessible to other plants.

SRS scientists and managers from the U.S. Forest Service Nantahala Ranger District worked closely to plan treatments for study sites in the Coweeta Basin and in the White Oak Creek watershed northwest of Coweeta. “Before treatment, rhododendron and dead hemlock trees dominated the study sites,” says Miniat. “After the treatments are complete, we expect to see more diverse vegetation.” Hardwood trees like black birch, red maple, oaks, and tulip poplar are scattered above the rhododendron sub-canopies, but there are very few tree seedlings, ferns, grasses, or flowering plants.

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