The effects of hemlock removal on rodent community composition in New England forests

Eastern hemlock (Tsuga canadensis) is declining in abundance in New England from logging and the effects of the invasive sap-sucking hemlock woolly adelgid (Adelges tsugae). Hemlocks are foundation species in eastern forests, and their loss may alter the community composition of rodents. To understand how rodent species richness and composition differed among intact forest, logged plots, and invaded hemlock stands, I surveyed rodent communities in the Harvard Forest Hemlock Removal Experiment (HF-HeRE). In 2003, eight 0.81ha plots were established in 2 blocks, each with 4 treatments:

1. Hemlock control, in which hemlocks dominate
2. Hardwood control, in which mid-successional hardwood species dominate
3. Girdled treatment, in which hemlocks were girdled with chainsaws to simulate tree mortality due to the woolly adelgid invasion
4. Logged treatment, in which hemlocks and merchantable hardwoods were removed to simulate a commercial logging operation.

Sampling grids, consisting of 49 Sherman live-traps and covering 0.49ha, were established within each plot in May 2012 and were set from June-July (588 trapping nights per block). Population size of each species was estimated using Schnabel’s mark-recapture methods. To date, six rodent species have been captured at varying abundances among the four treatments. In hemlock and hardwood control plots, deer mice and white-footed mice (Peromyscus spp.) were more abundant than southern red-backed voles (Clethrionomys gapperi); however, in logged and girdled treatment plots voles were more abundant than mice. Collectively, these results suggest that successional transformation within hemlock stands may alter rodent communities.