Sokoloff, Kaitlyn, Department of Biology, Susquehanna University, 514 University Ave., Selinsgrove, PA 17870, sokoloffk@susqu.edu; Matlaga, Tanya J.H., Department of Biology, Susquehanna University, 514 University Ave., Selinsgrove, PA 17870, matlagat@susqu.edu.
The hemlock woolly adelgid (Adelges tsugae; HWA) is a small, invasive, aphid-like insect that feeds on the sap of hemlock trees. In the northeastern United States, the primary tree impacted by the HWA is the eastern hemlock (Tsuga canadensis), which lose their needles and eventually die due to infestation. This results in a thinning of the canopy, and therefore, more light on the forest floor, as well as a change in leaf litter composition on the ground. Both factors could impact the surrounding ecosystem, including ephemeral pool species such as spotted salamanders (Ambystoma maculatum) and wood frogs (Lithobates sylvaticus). We randomly assigned 20 cattle tanks, designed to mimic ephemeral pools, to different treatments, either a 35% or 70% shade cloth treatment and either mixed leaf litter or eastern hemlock dominated leaf litter. We added 40 tadpoles and five salamander larvae to each tank. After five weeks, we determined the mass (mg), total length (mm), and developmental stage of each individual. The salamander larvae showed no differences in mass or length between treatment groups, while tadpole mass was higher in the mixed leaf litter treatment but showed no difference between shade treatments. We found no difference in survival rates for tadpoles or salamander larvae between treatments. The increase in tadpole mass in mixed leaf litter was likely due to the improved variety of nutrients available compared to hemlock dominated leaf litter. While eastern hemlock did not appear to have a direct impact on the organisms, other indirect effects of its potential loss to northeastern forest ecosystems are yet to be determined.
Eastern Hemlock, Spotted Salamander, Wood Frog, Ephemeral Pools