The role of red-backed salamanders in ecosystems

Abstract

Ecosystems provide a vast array of services that benefit human societies, which can be divided into provisioning, regulating, cultural, and supporting services. Amphibians provide provisioning services in the form of food and use in medical advances. As one of the major vertebrate groups, amphibians also play an important part in cultures throughout the world. Finally, amphibians can be extremely abundant and play important roles in ecosystem supporting services, including altering both physical structure and ecosystem functions. In aquatic systems, tadpoles can alter sedimentation, water clarity, and filamentous algae growth. Additionally, amphibians affect ecosystem functions, including nutrient cycling, decomposition, and primary production. Amphibians can alter the transfer of nutrients and energy between aquatic and terrestrial systems, but the net direction of flow varies temporally and depends on the amphibian community. After a review of these supporting services, I conducted two experiments to test the role of red-backed salamanders (Plethodon cinereus) in forested ecosystems. I examined the effects of salamanders on five 314-m² plots with reduced salamanders and five reference plots. I found no evidence that salamanders affected litter or wood decomposition rates, nitrogen mineralization, nitrification, or acorn germination. Nor did salamanders affect the densities of predatory litter-dwelling macroinvertebrates. However, there was considerable variability in the density of salamanders among plots, even within treatments. Therefore, I conducted a second experiment where I manipulated the density of red-backed salamanders in enclosures (2 m² x 1 m) and examined the effects on ecosystem functions. Despite the increased control and precision of this experiment, I did not observe effects of salamander density on decomposition, nitrogen cycling, acorn germination, or foliar insect damage. Since the timing of salamander activity could influence their role in ecosystem functions, I also examined the seasonal activity patterns of red-backed salamanders. I found that salamanders were most active in the spring and fall on warm, humid nights, following rain events. Salamander activity remained low through the summer even when conditions were favorable. Overall, red-backed salamanders had no measurable effects on the ecosystem functions I measured; however, future studies should examine the effects of salamanders in various forest types with different nutrient pools