Salamander Abundance at Harvard Forest 2003-2004

1. Eastern redback salamander relative abundance Eastern hemlock (Tsuga canadensis), an important late successional tree species, is currently threatened in this region by the hemlock woolly adelgid (Adelges tsugae), a small aphid-like invasive insect from Japan. While many species of birds and mammals have found to be associated with eastern hemlock dominated stands, there have been very few studies examining amphibian relative abundance in this forest type. Eastern redback salamanders (Plethodon cinereus) are important components of the forest ecosystem as they are extremely abundant with a biomass found to be twice that of breeding birds and equal to small mammals in the Hubbard Brook Experimental Forest. In addition, redbacks are positioned in the middle of the food web where they are important predators of soil invertebrates, potentially impacting soil respiration rates, and prey for larger vertebrates such as birds, reptiles, and small mammals. Redbacks have been cited as excellent indicators of forest health due to these characteristics as well as their low annual variation in abundance compared to other forest fauna. The objectives of this study was to 1) establish baseline data on eastern redback salamander relative abundance in eastern hemlock dominated stands and mixed deciduous stands in the Harvard Forest in Petersham, MA using artificial cover objects (ACOs) 2) test for differences in redback relative abundance based on forest type, 3) test for correlations between redback relative abundance and soil pH and forest floor temperature. 2. Juvenile eastern red-spotted newt minimum density This study provides baseline estimates of juvenile eastern red-spotted newt (Notophthalmus viridescens viridescens) or "red eft" minimum density through visual surveys of transects in ten forest stands, five eastern hemlock (Tsuga canadensis) dominated and five mixed deciduous, located in the Prospect Hill, Slab City, Simes, and Tom Swamp tracts of Harvard Forest. The objectives of this study were to 1) acquire baseline minimum red eft density data at Harvard Forest, 2) test for potential differences in minimum density based on forest type, 3) test for correlations between minimum density and soil pH and forest floor temperature, 4) test for seasonal differences in minimum density estimates. 3. Time-constrained intensive searches Intensive two minute searches of 1-m2 were conducted to measure eastern redback salamander (Plethodon cinereus) abundance and juvenile eastern red-spotted newt (Notophthalmus viridescens viridescens) or "red eft" abundance at ten stands, five eastern hemlock (Tsuga canadensis) dominated and five mixed deciduous stands, in the Prospect Hill, Slab City, Simes, and Tom Swamp tracts of Harvard Forest in fall 2003 and spring 2004. The objective of this study was to supplement other studies using artificial cover objects (ACOs) to measure eastern redback salamander relative abundance and transect walks to measure minimum density of red efts at Harvard Forest. 4. Artificial cover objects Plethodontid salamanders are increasingly being cited as important indicators of forest health as they are major contributors to the overall faunal biomass in a forest. In addition, they are positioned in the middle of the food web where they are important predators of soil invertebrates, potentially impacting soil respiration rates, as well as prey for higher vertebrates such as birds, small mammals, and reptiles. Plethodon species also have lower annual coefficients of variation than other animals due to their small home ranges and terrestrial breeding habits. A relatively new technique used in assessing plethodontid abundance is the installation and monitoring of artificial cover objects (ACOs). Wood ACOs of different sizes have been effectively used as terrestrial salamander monitoring tools. However, there is a concern that the quality of habitat under wooden cover objects may change over time as they weather thus altering their ability to track real changes in salamander abundance. More rot-resistant materials such as asphalt shingles may provide more consistent habitat over time. This study compared the observation rates of the most common plethodontid species in this region, the eastern redback salamander (Plethodon cinereus) under artificial cover objects (ACOs) of the same surface area - 1m x 0.25m - but different materials - 2cm thick rough-cut eastern hemlock boards and asphalt shingles.