Terrestrial Salamander Abundance Research Articles

The Value of Residential Forests for Plethodontid Salamanders on the Cumberland Plateau, USA

The southeastern United States contains the largest area on Earth devoted to intensive pine growth and represents an area experiencing rapid forest conversion for residential development. This region also harbors the highest lungless salamander diversity in the world. Studies repeatedly demonstrate that this taxon responds negatively to forest conversion. In this study, we evaluated terrestrial salamander abundance in four forest types commonly found on the southern Cumberland Plateau, USA: unmanaged, residential, burned, and harvested. Our results indicate that terrestrial salamanders occur in low surface abundance in this landscape but are found at their highest abundance in residential forest patches. Although we are unable to assess if these areas have always harbored higher abundances of terrestrial salamanders, these residential forest fragments have high conservation value to retain terrestrial salamanders in a heavily managed landscape.

Influence of prescribed fire and forest structure on woodland salamander abundance in the central Appalachians, USA

Prescribed fire is used in the central Appalachians to promote and maintain mixed-oak and pine forests, create open forest conditions, improve habitat for wildlife, and to reduce the risk of impact of higher intensity wildfires on human development. Few studies have investigated responses of terrestrial salamander populations to habitat management using fire, and estimated responses have been neutral, negative, and positive depending on geography, species, and fire-severity. We examined woodland salamander (genus Plethodon) population responses to habitat management using prescribed fire on Shenandoah Mountain in the George Washington National Forest in West Virginia and Virginia, USA. We focused on responses of the Cow Knob Salamander (P. punctatus), a talus specialist and species of high conservation concern, but also examined responses of the Eastern Red-Backed Salamander (P. cinereus), a widespread habitat generalist. Three burn units were subjected to two low-severity burns and one unit was burned five times with ca. 40% tree mortality. Using a combination of nighttime visual encounter surveys and coverboard surveys, we compared terrestrial salamander abundance and body condition in unburned and burned areas. We also measured habitat characteristics at sampling sites to determine if prescribed burn histories were correlated with habitat conditions important to woodland salamanders. Mean abundance for P. punctatus was lower at sites that were burned, but there was not a strong burn effect for P. cinereus. Abundance of both species was positively correlated with canopy cover. Mean and median body condition index (BCI) score was higher for P. punctatus and lower for P. cinereus on the West Virginia side of Shenandoah Mountain, and lower in burned areas for both species. However, the most parsimonious BCI models did not contain the burn predictor. Management using prescribed fire altered microhabitat conditions that are important for woodland salamanders, such as canopy cover, leaf litter depth, and vegetation groundcover. Our study suggests that woodland salamanders in the central Appalachians can persist in forests managed using prescribed fire, but also indicates that prescribed fire can result in reduced habitat quality for some woodland salamander species.

EFFECT OF RECREATIONAL TRAIL TRAFFIC LEVEL ON EASTERN RED-BACKED SALAMANDER (PLETHODON CINEREUS) RELATIVE ABUNDANCE

The effects of roads and trails on terrestrial salamanders, primarily plethodontids, can be important. The abundance of terrestrial salamanders often increases with distance from roads. Less is known about the effects of recreational or hiking trails on terrestrial salamanders than is known about the effects of roads. We explored how low and high traffic trails in a suburban biological reserve affect the relative abundance of Eastern Red-backed Salamanders (Plethodon cinereus). We found more salamanders under cover objects next to low traffic trails compared to either high traffic trails or wooded areas without trails. At wooded sites, we found only striped morphs whereas at high traffic sites we found only unstriped morphs. Low traffic sites included a range of color morph frequencies. The proportion of females found in each site did not differ, nor did the mean size of the salamanders. Our results suggest that the impact of recreational walking trails needs to be examined more closely to see how and why the distributions of P. cinereus, and potentially other woodland salamanders, are affected and what trail characteristics are important in driving the apparent effects. Such information will contribute to the design and maintenance of walking trails in natural areas that minimize effects on terrestrial salamanders, and likely other organisms.

Effective Use of Trails for Assessing Terrestrial Salamander Abundance and Detection: A Case Study at Great Smoky Mountains National Park

ABSTRACT: The conservation and management of wildlife species is contingent on estimating distribution and abundance. Sampling of wildlife requires repeated visits to accurately determine species occurrence and to quantify abundance across temporal and spatial scales. The use of trails to sample wildlife populations is increasing and offers opportunities to potentially sample more frequently, with increased ease of access, and less disturbance to habitats, which can be important in sensitive natural areas. We examined capture data of terrestrial salamanders within Great Smoky Mountains National Park to determine if detection and abundance estimates from trail and non-trail transects were significantly different. Across two, 3-week periods during June and July 2012, we sampled 195 transects (70 along trails and 125 within non-trail habitat) on multiple occasions. We found that most microhabitat variables associated with salamander detection and abundance did not differ between trail and non-trail transects...

Prescribed fire and timber harvest effects on terrestrial salamander abundance, detectability, and microhabitat use

Prescribed fire and timber harvest are anthropogenic disturbances that modify resource availability and ecosystem structure, and can affect wildlife both directly and indirectly. Terrestrial salamanders are effective indicators of forest health due to their high abundance and sensitivity to microclimatic conditions. Given their ecological importance, it is critical to understand how forest salamanders respond to management-related disturbances. We predicted that timber harvest and prescribed fire would decrease salamander abundance and availability, and increase salamander cover object use. We surveyed for southern red-backed salamanders (Plethodon serratus) over 9 sampling periods from 2010 to 2014 in a Missouri Ozark (USA) forest, and used binomial mixture models to estimate abundance and detectability in a large-scale Before-After, Control-Impact (BACI) experiment. Five replicate 5-ha units were randomly assigned to each treatment (prescribed burn, shelterwood harvest, midstory herbicide) and control. We compared abundance, surface activity, detectability, and microhabitat use among treatments. Abundance and surface activity decreased post-treatment in shelterwood, midstory, and burn units. Abundance estimates in midstory and burn units rebounded in the second post-treatment year but declined further in shelterwood harvest units. Overall, treatments had stronger effects on salamander availability than on actual abundance. We also found a higher proportion of salamanders under cover objects after prescribed fire, further illustrating the importance of accounting for imperfect detectability. Our findings foster a more robust understanding of the mechanisms underlying population-level responses to management practices, ultimately increasing our ability to manage terrestrial salamanders effectively.

Effects of timber harvests and silvicultural edges on terrestrial salamanders.

Balancing timber production and conservation in forest management requires an understanding of how timber harvests affect wildlife species. Terrestrial salamanders are useful indicators of mature forest ecosystem health due to their importance to ecosystem processes and sensitivity to environmental change. However, the effects of timber harvests on salamanders, though often researched, are still not well understood. To further this understanding, we used artificial cover objects to monitor the relative abundance of terrestrial salamanders for two seasons (fall and spring) pre-harvest and five seasons post-harvest in six forest management treatments, and for three seasons post-harvest across the edge gradients of six recent clearcuts. In total, we recorded 19,048 encounters representing nine species of salamanders. We observed declines in mean encounters of eastern red-backed salamanders (Plethodon cinereus) and northern slimy salamanders (P. glutinosus) from pre- to post-harvest in group selection cuts and in clearcuts. However, we found no evidence of salamander declines at shelterwoods and forested sites adjacent to harvests. Edge effects induced by recent clearcuts influenced salamanders for approximately 20 m into the forest, but edge influence varied by slope orientation. Temperature, soil moisture, and canopy cover were all correlated with salamander counts. Our results suggest silvicultural techniques that remove the forest canopy negatively affect salamander relative abundance on the local scale during the years immediately following harvest, and that the depth of edge influence of clearcuts on terrestrial salamanders is relatively shallow (<20 m). Small harvests (<4 ha) and techniques that leave the forest canopy intact may be compatible with maintaining terrestrial salamander populations across a forested landscape. Our results demonstrate the importance of examining species-specific responses and monitoring salamanders across multiple seasons and years. Long-term monitoring will be necessary to understand the full impacts of forest management on terrestrial salamanders.

Predicting Variation in Microhabitat Utilization of Terrestrial Salamanders

Understanding patterns of microhabitat use among terrestrial salamanders is important for predicting their responses to natural and anthropogenic disturbances. The dependence of terrestrial salamanders on cutaneous respiration limits their spatial distribution to moist, humid areas. Although many studies have shown negative effects of canopy removal on terrestrial salamander abundance, some have shown potential ameliorating effects of retaining coarse woody debris (CWD) as moist refugia (critical resources in the landscape). Because cover objects like CWD retain moisture longer than fine debris, terrestrial salamanders are often more locally abundant in areas of dense cover. Temporally variable environmental conditions could affect microhabitat quality and influence the fine-scale spatial distributions of salamanders. Spatial and temporal variability in microhabitat use greatly influence individual detectability, which is always a challenge for terrestrial salamanders. We conducted repeated area-constrained surveys to examine variation in salamander microhabitat use of terrestrial salamanders in relation to season, year, and weather conditions. We found that time since rain (TSR) was the best predictor of relative salamander microhabitat use, but the strength of this relationship varied among years. In addition, TSR was also the best predictor of salamander surface activity. We captured most salamanders within leaf litter, but the proportion of leaf litter captures varied with TSR. Our results illustrate the importance of accounting for variable detectability when sampling for terrestrial salamanders. Disturbances which affect leaf litter depth and decomposition rates could influence the availability and quality of microhabitats and potentially increase competition among individuals for natural cover objects.

Comparing Population Patterns to Processes: Abundance and Survival of a Forest Salamander following Habitat Degradation

Habitat degradation resulting from anthropogenic activities poses immediate and prolonged threats to biodiversity, particularly among declining amphibians. Many studies infer amphibian response to habitat degradation by correlating patterns in species occupancy or abundance with environmental effects, often without regard to the demographic processes underlying these patterns. We evaluated how retention of vertical green trees (CANOPY) and coarse woody debris (CWD) influenced terrestrial salamander abundance and apparent survival in recently clearcut forests. Estimated abundance of unmarked salamanders was positively related to CANOPY ( Canopy = 0.21 (0.02–1.19; 95% CI), but not CWD ( CWD = 0.11 (−0.13–0.35) within 3,600 m2 sites, whereas estimated abundance of unmarked salamanders was not related to CANOPY ( Canopy = −0.01 (−0.21–0.18) or CWD ( CWD = −0.02 (−0.23–0.19) for 9 m2 enclosures. In contrast, apparent survival of marked salamanders within our enclosures over 1 month was positively influenced by both CANOPY and CWD retention ( Canopy = 0.73 (0.27–1.19; 95% CI) and CWD = 1.01 (0.53–1.50). Our results indicate that environmental correlates to abundance are scale dependent reflecting habitat selection processes and organism movements after a habitat disturbance event. Our study also provides a cautionary example of how scientific inference is conditional on the response variable(s), and scale(s) of measure chosen by the investigator, which can have important implications for species conservation and management. Our research highlights the need for joint evaluation of population state variables, such as abundance, and population-level process, such as survival, when assessing anthropogenic impacts on forest biodiversity.

Terrestrial salamander abundance on reclaimed mountaintop removal mines

Mountaintop removal mining, a large-scale disturbance affecting vegetation, soil structure, and topography, converts landscapes from mature forests to extensive grassland and shrubland habitats. We sampled salamanders using drift-fence arrays and coverboard transects on and near mountaintop removal mines in southern West Virginia, USA, during 2000–2002. We compared terrestrial salamander relative abundance and species richness of un-mined, intact forest with habitats on reclaimed mountaintop removal mines (reclaimed grassland, reclaimed shrubland, and fragmented forest). Salamanders within forests increased in relative abundance with increasing distance from reclaimed mine edge. Reclaimed grassland and shrubland habitats had lower relative abundance and species richness than forests. Characteristics of reclaimed habitats that likely contributed to lower salamander abundance included poor soils (dry, compacted, little organic matter, high rock content), reduced vertical structure of vegetation and little tree cover, and low litter and woody debris cover. Past research has shown that salamander populations reduced by clearcutting may rebound in 15–24 years. Time since disturbance was 7–28 years in reclaimed habitats on our study areas and salamander populations had not reached levels found in adjacent mature forests. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.

Meta-analysis of the effects of canopy removal on terrestrial salamander populations in North America

Terrestrial salamander abundance in North American forests is closely associated with forest characteristics, and salamander populations typically decline following timber removal. However, salamander responses to timber harvest vary considerably from one study to the next – some studies have shown limited or no effects whereas others have found harvest-related declines of up to 95%. To estimate overall effect sizes of timber harvest on salamander populations and to examine factors that contribute to variation in salamander responses to harvest, we carried out a meta-analysis of published studies of the effects of timber harvesting on terrestrial salamander abundance. Based on 108 salamander species/treatment combinations from 24 studies, we found mean harvest-related declines ranged from 29% (95% CI=−2% to 51%) for long-term responses to partial canopy removal to 62% (95% CI=29% to 80%) for short-term responses to clearcutting. Multivariate mixed models suggested that clearcutting had a modestly greater impact on salamander populations than partial harvest and that decreases following harvest were more pronounced at sites with warmer summer high temperatures. In addition, active sampling of salamanders (e.g., surface counts) led to greater apparent effects of timber harvest than passive sampling (e.g., cover boards or pitfall traps), suggesting that sampling methodology influenced the perceived effects of harvest. In the studies evaluated, salamander numbers almost always declined following timber removal, but salamanders were never extirpated and populations typically increased as forests regenerated.

Substrate preference of eastern red-backed salamanders, Plethodon cinereus: A comparison of deciduous and coniferous substrates

AbstractForest tree composition can affect the distribution and abundance of terrestrial salamanders. We examined the effect of leaf litter type (deciduous or coniferous) and soil type (deciduous and coniferous) on red-backed salamander (Plethodon cinereus) substrate choice using a series of laboratory experiments. Salamanders preferred deciduous leaves over coniferous pine needles and the deciduous soil/deciduous leaf litter combination over all others. In addition, our results suggest that leaf litter type may be more important than soil type in influencing salamander substrate preference in our study. Our results suggest that behavioural avoidance may partially explain differences in P. cinereus abundances in deciduous and coniferous forest habitats.

Long-term effects of experimental forest harvesting on abundance and reproductive demography of terrestrial salamanders

Both observational and experimental studies have documented drastic reductions in salamanders after forest harvesting. Yet, the amount of time until salamander populations rebound and the factors limiting recovery after harvesting are unknown. We compared the effects of six oak regeneration practices to a control, representing a disturbance gradient from no treatment to silvicultural clearcut, on the relative abundance and reproductive demography of terrestrial salamanders through 13-years post-harvest. Following the experimental disturbance, relative abundance of terrestrial salamanders in treatments that opened the canopy were significantly and persistently lower than in either untreated control stands or midstory herbicide treatments. In general, this trend persisted through 9–13 years after treatment. Changes to demography of commonly captured salamanders varied by species, but Plethodon cinereus had a greater proportion of juveniles in unharvested treatments 7–13-years post-harvest, and Desmognathus ochrophaeus had a greater proportion of juveniles and a greater number of eggs/female in unharvested treatments 1–6-years post-harvest. Population modeling of P. cinereus indicated that adult survival had the greatest elasticity of the vital rates. Further, >60 years may be needed before P. cinereus reduced by the observed decline could reach pre-harvest levels of abundance. Of the treatments with canopy disturbance, the group selection harvest had the greatest abundances of salamanders 7–13-years post-harvest, but when coupled with future stand entries, the volume of wood fiber extracted, costs of harvesting, reduced sprouting of oaks, and soil disturbances, this method may not have the best balance of ecological and economic sustainability in central Appalachian hardwood forest.

Initial Effects of Clearcutting and Alternative Silvicultural Practices on Terrestrial Salamander Abundance

Abstract: Several studies have demonstrated the negative effects of clearcutting on terrestrial plethodontid salamander populations. However, none has experimentally compared clearcutting with multiple alternative timber‐harvest methods. Using a randomized, replicated design, we compared the short‐term effects ( 1–4 years after harvest ) of clearcutting to effects of leavetree, group selection, and two shelterwood cuts on terrestrial salamanders in the southern Appalachian Mountains of Virginia and West Virginia ( U.S.A. ). Treatment plots were 2 ha each. We also compared salamander age class ( percent juvenile ), fecundity ( percentage of females carrying eggs and average number of eggs per gravid female ), size of gravid females, and species composition and diversity between treatments with canopy removal ( cut ) and those without canopy removal ( uncut ). All treatments with canopy removal had significantly fewer salamanders than the control treatment, but salamander abundances on alternative treatments with canopy removal did not differ significantly from salamander abundances on the clearcuts. There were no significant differences between cut and uncut treatments in the proportion of females that were gravid or in the average number of eggs in gravid females; however, gravid Plethodon cinereus females weighed more on the cut treatments and gravid Desmognathus ochrophaeus females weighed more on uncut treatments. There were no significant differences between cut and uncut treatments in the proportion of the sample that was juvenile, except in the largest species tested, P. glutinosus, which had a significantly higher proportion of juveniles in the uncut treatments. We conclude that initial declines in terrestrial plethodontid abundance caused by timber harvesting may be minimized across the landscape by concentrating high‐intensity timber harvesting ( clearcutting ) in small areas ( a few hectares in size ).

Salamander diversity and abundance in forests with alternative land use histories in the Southern Blue Ridge Mountains

The diversity and abundance of terrestrial salamanders were compared at 12 forest stands having three different land use histories: (a) successional forests established on abandoned farmland; (b) second/third growth forests that had experienced timber harvest; (c) stands having few to no alterations due to land use. Populations were estimated using pitfall trapping conducted during July 1997–June 1998 in the Southern Blue Ridge Province of the Southern Appalachian Mountains. Salamander diversity did not differ among land use categories; however, abundances were greater in the older, least-altered stands. Abundances were positively correlated with late successional qualities of forest, such as increased domination by mesophytic tree species and increased availability of wood debris. However, we did not find large differences between stands that had experienced previous agricultural uses and those that had not been farmed, only logged. At our sites, enough time had passed since agricultural use that any differences between agricultural and forestry uses had diminished. These results show both the sensitivity of salamanders to past habitat alterations and the resiliency of these populations in their ability to recover in these ecosystems given sufficient time.

Using a GIS model to assess terrestrial salamander response to alternative forest management plans

A GIS model predicting the spatial distribution of terrestrial salamander abundance based on topography and forest age was developed using parameters derived from the literature. The model was tested by sampling salamander abundance across the full range of site conditions used in the model. A regression of the predictions of our GIS model against these sample data showed that the model has a modest but significant ability to predict both salamander abundance and mass per unit area. The model was used to assess the impacts of alternative management plans for the Hoosier National Forest (Indiana, USA) on salamanders. These plans differed in the spatial delineation of management areas where timber harvest was permitted, and the intensity of timber harvest within those management areas. The spatial pattern of forest openings produced by alternative forest management scenarios based on these plans was projected over 150 years using a timber-harvest simulator (HARVEST). We generated a predictive map of salamander abundance for each scenario over time, and summarized each map by calculating mean salamander abundance and the mean colonization distance (average distance from map cells with low predicted abundance to those with relatively high abundance). Projected salamander abundance was affected more by harvest rate (area harvested each decade) than by the management area boundaries. The alternatives had a varying effect on the mean distance salamanders would have to travel to colonize regenerating stands. Our GIS modeling approach is an example of a spatial analytical tool that could help resource management planners to evaluate the potential ecological impact of management alternatives.

Effects of seven silvicultural treatments on terrestrial salamanders

We compared the relative abundance of terrestrial salamanders before and after application of seven regeneration treatments in a low-elevation, southern Appalachian hardwood forest in southwest Virginia. Treatments included understory removal, group selection, two shelterwoods, leave-tree, clearcut, and a control. Salamander relative abundance was significantly lower after harvest on the group selection ( p=0.005), shelterwoods ( p=0.007 and p=0.015), leave-tree ( p=0.001), and clearcut treatments ( p=0.001). There was no significant difference in relative abundance during the same period on the control ( p=0.788) or understory removal ( p=0.862) treatments.

Relation of Terrestrial‐Breeding Amphibian Abundance to Tree‐Stand Age

There is a lack of research on the effects of logging on Canadian amphibians. We compared the abundance of terrestrial salamanders in old‐growth forests with that in young and mature post‐harvest stands. We also measured habitat features of amphibians and contrasted these with old‐growth and harvested stands to assess the effects of forest harvest. Quadrat searches demonstrated that clearcut harvesting reduces terrestrial amphibian populations by up to 70% in coastal old‐growth forests. We suggest that this reduction results from a decrease in availability of moist microhabitats. Salamander densities within 10 meters of streams in managed stands were similar to those near and away from streams in old growth. We recommend that forest managers recognize the needs of terrestrial amphibians and help maintain amphibian populations by preserving cool, moist habitats. This can be accomplished within cutblocks by (1) maintaining an even distribution of logs and snags as stable, moist microhabitats; (2) retaining some understory as sources of shade, and (3) preserving streamside buffers. Managers must also ensure some level of landscape connectivity to enable climate‐sensitive amphibians to disperse and recolonize marginal habitats.