Red-backed Salamanders as Indicators of Hemlock Forest Health at Harvard Forest 2014

Species that react quickly to ecological changes are useful indicators for assessing forest health. Red-backed salamanders (Plethodontid cinereus) may be used as an indicator species in declining hemlock forests, allowing for assessment of soil quality and forest health. We hypothesized that decline of hemlock stands due to the effect of hemlock woolly adelgid would negatively impact the abundance of red-backed salamanders by altering soil quality. In the Hemlock Removal Experiment at Harvard Forest, eight-0.8ha plots were treated either with girdling to simulate adelgid invasion, logging to simulate preemptive logging strategies, no treatment in hemlock areas, or no treatment in hardwood areas. Within these treatments in June and July of 2014, P. cinereus relative abundance was determined from coverboard surveys. Soil quality was determined from core samples. Bulk density, pH, carbon-nitrogen ratio, moisture, soil temperature, and litter depth were measured, and ordination was used to create an index of soil quality from these. There was a significant correlation between plot treatment and soil quality (p less than 0.05). Temperature, CN ratio, and pH influenced a strong significant negative correlation between soil quality and salamander abundance (pless than 0.05). Soil quality affected by hemlock decline influenced salamander abundance. These data suggest that we could gain an understanding of forest health and soil quality by examining salamander abundance. Assessing adelgid invasion can be difficult and objective, whereas salamander abundances are easily measured; therefore, we suggest that salamander abundances could be useful in assessing the health of hemlock forest ecosystems.