Riparian Ecosystem Response to Hemlock Woolly Adelgid (Adelges tsugae) Induced Eastern Hemlock (Tsuga canadensis) Mortality in the Great Smoky Mountains National Park, USA

Hemlock woolly adelgid (HWA)-induced mortality of eastern hemlock in the Great Smoky Mountains National Park has triggered significant ecological shifts in riparian ecosystems. Impacted streams exhibit reduced canopy coverage, increased light availability, and altered vegetative composition, with red maple, yellow birch, sweet birch, and rosebay rhododendron dominating post-mortality landscapes. Aquatic systems show cooler temperatures during colder months, higher concentrations of nutrients like silicon, sodium, potassium, magnesium, chlorine, and copper, as well as increased acid neutralization capacity and pH. While macroinvertebrate diversity and abundance remain largely unaffected, shifts in functional feeding groups (from collector/filter to scraper) and reductions in specific taxa, such as Chironomidae, Ephemeroptera, and Pleuroceridae snails, highlight the ecological disruption caused by hemlock mortality. The study employed a comparative approach, assessing riparian and aquatic impacts across reference sites with initial HWA presence and impacted sites with over 90% hemlock mortality, revealing both short-term and long-term consequences of invasive species on stream ecosystems.

Huddleston, M. D., Clatterbuck, W., Wilson, L., Lambdin, P., & Etnier, D. (2011). Riparian Ecosystem Response to Hemlock Woolly Adelgid (Adelges tsugae) Induced Eastern Hemlock (Tsuga canadensis) Mortality in the Great Smoky Mountains National Park, USA. Unpublished. https://doi.org/10.13140/2.1.3983.6486