The effects of rhododendron on salamander communities in the Nantahala Mountains

Rhododendron or great laurel is a common evergreen shrub found throughout eastern North America. Although native, rhododendron has been increasing in the Southern Appalachian Mountains landscape due to fire suppression, logging, and loss of the American chestnut. It now has the potential to affect a larger variety of ecosystems and species that it did historically. Salamanders of the family Plethodontidae are highly diverse in the Southern Appalachian Mountains. They are known to be sensitive to their environment and are often considered to be potential indicators of ecosystem changes. Rhododendron has known effects on plants, soil nutrients, and leaf litter macroinvertebrates. The expansion of rhododendron may play an important role in determining terrestrial and aquatic salamander community structure and population dynamics. This study aimed to see how rhododendron affects salamander communities in sites in the Nantahala Mountains of western North Carolina. Initially, four sites were chosen in the upper Nantahala River watershed to conduct a mark-recapture study. Sites were divided into two plots; one within a rhododendron thicket and one in the larger forest matrix, both alongside small streams. After collecting data in 2009, concerns from highly variable population estimates and differences in detection between rhododendron and non-rhododendron plots with the mark-recapture study led to methods being changed in 2010 to removal sampling to ameliorate these concerns. Population estimates from removal sampling varied greatly amongst sites and were not significantly different between rhododendron and non-rhododendron plots. Overall, red-legged and ocoee salamanders were the most abundant species across all sites. Rhododendron does not appear to have a net effect on salamander population sizes. Rhododendron does appear to reduce people’s ability to find salamanders and may have negative influences in studies that do not account for differences in detection between plots in and outside of rhododendron thickets