Natural Environmental Gradients Predict the Microhabitat Use, Fine-Scale Distribution, and Abundance of Three Woodland Salamanders in an Old-Growth Forest

Woodland salamanders (Plethodonidae: Plethodon)---a group of sensitive, direct developing, lungless amphibians---are particularly responsive to gradients in environmental conditions. Because of their functional dominance in terrestrial ecosystems, woodland salamanders are responsible for the transformation of nutrients and translocation of energy between highly desperate levels of trophic organization (detrital food webs and high-order predators). However, the spatial extent of woodland salamanders' role in the ecosystem is likely contingent upon the distribution of their biomass throughout the forest. Therefore, a better understanding of woodland salamander spatial population dynamics is needed to further understand their role in terrestrial ecosystems. The objectives of this study were to determine if natural environmental gradients influence the microhabitat use, fine-scale distribution, and abundance of three species of woodland salamander--- Plethodon richmondi , P. kentucki, and P. glutinosus. These objectives were addressed by assessing microhabitat conditions and constructing occupancy, co-occurrence, and abundance models from temporally-replicated surveys (N = 4) at forty 0.08-ha sample plots within a ca. 42 ha old-growth forest in the Cumberland Plateau region of southeastern Kentucky. This study finds that patterns of microhabitat use, occupancy, and abundance of P. richmondi and kentucki reflected physiological restraints associated with desiccation vulnerability and thermo-osmoregulatory requirements of small to mid-sized salamanders. Plethodon richmondi occupied markedly cooler microhabitats, had the most restricted fine-scale distribution (mean occupancy probability [psi] = 0.737), and exhibited variable abundance, from 1000 N·ha-2, associated with increased soil moisture and reduced solar exposure due to slope face. While more ubiquitously distributed (psi = 0.95), P. kentucki abundance varied from >1000 to <400 N·ha -2 in association with increased solar exposure from canopy disturbance and landscape convexity. Plethodon glutinosus displayed a dramatic tolerance to thermal environments by preferentially occupying warm microhabitats and relying only minimally upon subterranean refugia for thermo-osmoregulation (temporary vertical emigration). Given the critical role that woodland salamanders play in the maintenance of forest health, regions which support large populations of woodland salamanders, such as those highlighted in this study (mesic forest stands on north-to-east facing slopes with dense canopy and abundant natural cover) may provide enhanced ecosystem services and support the stability of the total forest.