Stream Salamander Species Richness and Abundance in Relation to Environmental Factors in Shenandoah National Park, Virginia

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ABSTRACT.-

Stream salamanders are sensitive to acid mine drainage and may be sensitive to acidification and low acid neutralizing capacity (ANC) of a watershed. Streams in Shenandoah National Park, Virginia, are subject to episodic acidification from precipitation events. We surveyed 25 m by 2 m transects located on the stream bank adjacent to the water channel in Shenandoah National Park for salamanders using a stratified random sampling design based on elevation, aspect and bedrock geology. We investigated the relationships of four species (Eurycea bislineata, Desmognathus fuscus, D. monticola and Grinophilus porphyriticus) to habitat and water quality variables. We did not find overwhelming evidence that stream salamanders are affected by the acid-base status of streams in Shenandoah National Park. Desmognathus fuscus and D. monticola abundance was greater both in streams that had a higher potential to neutralize acidification, and in higher elevation (>700 m) streams. Neither abundance of E. bislineata nor species richness were related to any of the habitat variables. Our sampling method preferentially detected the adult age class of the study species and did not allow us to estimate population sizes. We suggest that continued monitoring of stream salamander populations in SNP will determine the effects of stream acidification on these taxa.

INTRODUCTION

Stream salamanders in the eastern United States, such as Eurycea, Desmognathus and Gyrinophilus species, are potential indicators of stream health (Rocco and Brooks, 2000; Ohio EPA, 2001; Barr and Babbitt, 2002). They can constitute significant biomass in eastern deciduous forests and are important in community ecology (e.g., predator-prey interactions) and ecosystem energy flow and nutrient cycling (Spight, 1967; Burton and Likens, 1975; Petranka and Murray, 2001). In headwater streams, salamanders often replace fish as the dominant predator (Ohio EPA, 2001). These species lay their eggs in cryptic sites in streams or seeps. After metamorphosis, juveniles and adults forage in leaf litter and rocky substrates adjacent to and within streams. Compared to many anurans, salamanders are relatively longlived, take longer to reach maturity and lay fewer eggs (Petranka, 1998). Some species, such as the northern spring salamander ( Gyrinophilus porphyriticus), remain as larvae as long as 4 y (Petranka, 1998).

Stream salamanders are sensitive to acidification, drought, contaminants and habitat destruction or alteration such as urbanization, logging and road construction (Orser and Shure, 1972; Welsh and Ollivier, 1998; Corn and Bury, 1989; Rocco and Brooks, 2000). In Shenandoah National Park (SNP), located in the Blue Ridge Physiographic Province of Virginia, primary threats include habitat alteration (e.g., past land use, including logging, agriculture, road and trail construction, tree defoliation and mortality caused by gypsy and balsam woolly adelgid moths) and acidification of soils and water (Mitchell, 1998). Gypsy moth canopy defoliation from 1990-1992 affected the water chemistry of several SNP watersheds, causing increased levels of dissolved nitrogen (as NO^sub 3^^sup -^) and a subsequent decrease in stream acid-neutralizing capacity (ANC), the ability of a watershed to neutralize acid inputs (Webb et al., 1995; Eshleman et al., 2000). When gypsy moth defoliation ceased, nitrogen export declined (Eshleman et al., 2000), yet the ability of the watershed to neutralize acidic inputs was likely compromised (Webb et al., 1995). The composition of bedrock strongly affects the susceptibility of streams to acid deposition, and stream acidity can be predicted by ANC (Bricker and Rice, 1989). In SNP, water in stream catchments underlain primarily by siliciclastic bedrock exhibit low ANC and pH values (as low as 5.0; Bulger et al., 1999).

Stream salamanders are negatively affected by low soil and water pH (Roudebush, 1988; Wyman, 1988; Kucken et al. …