Abstract:
Throughout the twentieth century many dominant tree species have suffered severe decline due to exotic pests and pathogens, yet little is known concerning the effects of these losses on ecosystem process or associated wildlife populations. Eastern hemlock (Tsuga canadensis) is severely threatened throughout its range by the hemlock woolly adelgid (Adelges tsugae; HWA), an invasive insect pest native to Japan. The unique structure and microenvironment of hemlock-dominated stands create critical landscape level heterogeneity, providing habitat for ninety-six bird species and forty-seven mammal species in the northeast. Eastern red-backed salamanders (Plethodon cinereus) contribute significantly to the overall vertebrate biomass in northeastern forests, but few studies have examined whether red-back populations differ in hemlock-dominated and mixed deciduous forest. To address this question artificial cover objects (ACO) were monitored in fifteen paired hemlock-dominated and mixed deciduous plots throughout north central Massachusetts. Size class distribution differed between forest types with a higher percentage of large red-backs found in hemlock-dominated forests. The best predictor of variation in red-back relative abundance was relative humidity and soil pH in hemlock-dominated forests and soil temperature in mixed deciduous forests. Relative humidity was also the best predictor of red-back body condition in hemlock-dominated forests, while percentage of white pine (Pinus strobus) and black birch (Betula lenta) were the most important predictors of body condition in mixed deciduous forests. Surprisingly, no difference was observed in red-back relative abundance or body condition in the two forest types. This study suggests that red-backed salamander populations differ in hemlock-dominated forests in terms of size class distribution and the factors which are most important in predicting variation in relative abundance and body condition, but that red-back relative abundance and body condition do not differ in these two forest types.
