Hemlock Woolly Adelgid (Adelges tsugae) Induced Decline of Eastern Hemlocks (Tsuga canadensis) and Consquences for Southern Appalachian Headwater Streams

Authors: Burke McDade*, Appalachian State University
Topics: Geomorphology, Landscape
Keywords: Hemlock, Streams, large, wood
Session Type: Paper
Day: 4/11/2018
Start / End Time: 8:00 AM / 9:40 AM
Room: Iberville, Marriott, River Tower Elevators, 4th Floor
Presentation File: No File Uploaded


The Hemlock Woolly Adelgid (Adelges tsugae) is responsible for wide-spread mortality of Eastern Hemlock (Tsuga canadensis), a foundation species of southern Appalachian forest ecosystems. Given the Hemlock’s high tolerance for shade and adaptation to moist and well drained soils, this species of tree preferentially grows in riparian zones. Conceptual models suggest that Hemlock mortality could serve as a forest disturbance event that will increase the large wood (LW) load found within headwater streams. Further, it is well known that elevated LW loads induce geomorphic change and consequently impact ecological functions of aquatic systems. The objectives of this research are to: 1) characterize the health and abundance of Hemlock trees in riparian forests of Southern Appalachian watersheds, 2) quantify in-channel LW loads within the same watersheds, and 3) investigate physical and forest variables that could predict quantities of LW in the streams. These objectives will be achieved by sampling 34 different sites within 3 headwater watersheds of the Blue Ridge Mountains in North Carolina with varying degrees of hemlock decline. Commonly used methods for quantifying LW in streams, and for quantifying and characterizing terrestrial vegetation were implemented. Although fieldwork is on-going, initial field observations suggest that streams draining watersheds with elevated levels of hemlock decline have greater quantities of in-channel LW. Findings from this research could result in beneficial contributions to the management of the Hemlock Woolly Adelgid as well as headwater mountain streams of the region.

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