Effects of the removal of overstory hemlock from hemlock-dominated forests on eastern redback salamanders

Abstract

Eastern hemlock (Tsuga canadensis) is a common conifer throughout northeastern North America. The species is threatened by the exotic hemlock woolly adelgid (HWA), Adelges tsugae; infestation by this forest pest can result in high levels of mortality of overstory trees with a resultant change in understory vegetation composition and structure. Pre-salvage harvesting of overstory hemlock results in a residual stand compositionally and structurally similar to that resulting from mortality due to adelgid infestation, except for the occurrence of standing or fallen dead trees in adelgid infested stands. The vertebrate fauna of hemlock-dominated forests is poorly studied and the effects of the mortality or removal of overstory hemlock on forest fauna in these stands is unknown. This study reports the findings of a 3-year study of the effects of pre- or green-tree salvage of overstory hemlock from hemlock-hardwood stands on terrestrial salamanders. The residual hemlock stocking was reduced an average of 60% following harvesting and the understory vegetation responded vigorously. The relative abundance of eastern redback salamanders was reduced in harvested stands but the effect was ephemeral and salamander numbers appear to be increasing within a few years of the logging. It appears that hemlock defoliation and mortality due to HWA infestation or pre-salvage harvesting of live hemlock will result in only a brief reduction in the principal terrestrial salamander of hemlock-dominated forests.