Energetics of surface‐active terrestrial salamanders in experimentally harvested forest

Abstract

Environmental temperatures affect nearly all aspects of ectotherm physiology, including terrestrial salamanders. Therefore, habitat disturbances that alter temperature regimes may interact with physiological processes to affect energy budgets of salamanders or constrain surface activity and possibly lead to changes in population-level parameters. We hypothesized that warmer surface temperatures following harvesting of canopy trees could cause surface-active salamanders to expend more energy for metabolism, potentially leaving a smaller proportion of the energy budget available for reproduction or storage. From 2006 to 2008, we quantified temperature regimes of salamander refugia in a field experiment replicated at 4 sites that included plots subjected to a timber harvest and plots not manipulated during this time period. At each site, we quantified temperature regimes in regenerating forest stands which, approximately 10 years earlier, experienced a range of harvest intensity from shelterwood to silvicultural clearcut. Further, we compared energetic parameters including 1) calories required to maintain homeostasis across an active season, 2) abundance of available potential energy (i.e., invertebrate prey), and 3) a measure of growth and storage (i.e., body condition index) among silvicultural treatments for surface-active salamanders. For surface-active eastern red-backed salamanders (Plethodon cinereus), mean calories required for maintenance were approximately 33% greater in recently harvested forest compared to unharvested controls, but body condition was inconsistent among treatments, and invertebrate abundances were similar among treatments but differed by study site. In contrast, we did not detect a treatment effect in any energetic metric 8-14 growing seasons after harvesting. Given that surface-active salamanders in recently harvested forest may be forced to restrain behaviors associated with foraging and mating or trade-off growth or reproduction for increased basic maintenance costs, energetics may be an important but overlooked short-term contributor to observed changes in abundances, reproductive demography, or surface activities after timber harvesting. Managing for both the rapid recovery of understory vegetation and retention of large stumps and logs may help mitigate warming of microclimate for salamanders and should be considered further. ß 2011 The Wildlife Society.

Effects of timber harvesting on terrestrial survival of pond-breeding amphibians

“…Because CWD serves as refuge to amphibians and can quickly ameliorate forest floor temperature increases in clearcuts (Homyack et al, 2011), it has been suggested as an important mitigating resource in harvested forests (deMaynadier and Hunter, 1995). We expected clearcuts with retained CWD to have greater salamander survival than those without it.…”

“…Because partial harvesting does not increase temperatures or reduce canopy to the degree that clearcutting does (Todd and Andrews, 2008), it has been proposed to be a more benign practice to minimize negative impacts to amphibians (deMaynadier and Hunter, 1995). Although temperatures may still rise as much as 2-5°C in partially harvested stands relative to unharvested forests, some canopy structure and shade is retained and leaf litter is not completely removed (Todd and Andrews, 2008;Homyack et al, 2011). Similarly, retaining $50% canopy cover can result in winter low temperatures similar to those in unharvested forests (Boggs and McNulty, 2010).…”

Effects of Buffering Key Habitat for Terrestrial Salamanders: Implications for the Management of the Federally Threatened Red Hills Salamander (Phaeognathus hubrichti) and Other Imperiled Plethodontids

“…The mechanism behind this pattern is unclear and warrants future research. Two intriguing hypotheses are that leaving habitat unbuffered decreases prey abundance and that increases in temperature at unbuffered sites raise the energetic cost of maintaining homeostasis [34]. …”

Woodland salamanders as metrics of forest ecosystem recovery: a case study from California's redwoods

“…Such interrelationships have been repeatedly demonstrated for amphibians (e.g., Welsh 1990, Karraker and Welsh 2006, Semlitsch et al 2009), many of whom are inextricably linked to mild, stable temperatures and high ambient moisture by their physiological limits (Wieser 1991, Feder andBurggren 1992). The essential role of moisture in the physiology and ecology of plethodontid salamanders is particularly well established (Spotila 1972, Feder 1983, Grover 2000, Homyack et al 2011, and is likely the v www.esajournals.org result of their late Jurassic evolution into a primarily terrestrial clade (Vieites et al 2007); with most members entirely lacking aquatic life stages (Wake and Hanken 1996). Body condition has proven highly informative for examining the relative status of amphibian populations in forested habitats (e.g., Todd and Rothermel 2006).…”