Impacts Of The Hemlock Woolly Adelgid (Adelges Tsugae) On Headwater Stream Wood Loads In The Southern Appalachian Mountains

The hemlock woolly adelgid is responsible for wide-spread mortality of eastern hemlock, a foundation species of southern Appalachian forest ecosystems. Given the hemlock’s high tolerance for shade and adaptation to moist 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 streams. The objectives of this research were to (1) Characterize the health and abundance of hemlock trees in riparian forests of select Southern Appalachian watersheds, (2) Quantify in-channel LW loads in the same watersheds, and (3) Investigate the relationship of forest and geomorphic characteristics to wood load variables in the streams. Analysis of 26 sites located in headwater streams of the Blue Ridge Mountains with varying hemlock decline and composition revealed 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.