AUTHORS: Thilina D. Surasinghe*, Bridgewater State University; Robert F. Baldwin, Clemson University; Matt Johnson, National Audubon Society; Nathan Weaver, Georgia Department of Natural Resources
ABSTRACT: Impacts of land uses at variable spatial-scale on aquatic amphibians have been extensively researched in North America. In this study, we documented variation in the species composition of stream salamanders in response to three forest management practices— old-growth, shelterwood, and pine plantations— in low-order streams of Southern Appalachian Mountains. During our survey, at each sampling site (N=15), we surveyed five, 5-m stream segments (consecutive segments separated by a 10-m gap), and repeated the survey on three different occasions. We also measured multiple habitat variables at each site. No larval diversity indices (species richness, Shannon, and Simpson) differed significantly across forest management practices. In contrast, the same indices showed a greater adult diversity in both old-growth and shelterwood forests than in pine plantations. An NMDS ordination showed that adult salamanders associated more with both old-growth and shelterwood forests than pine plantations with the exception of mud and seepage salamanders. Habitat associations among larvae differed markedly from that of adults; two-lined, common dusky, ocoee, mud, and red salamanders mostly associated shelterwood forests while black-bellied and seal salamanders associated both pine plantations and old-growth forests. Multivariate generalized linear models suggested relationships between adult species composition and conductivity, stream pH, water temperature, basal area of riparian hemlock, canopy cover, stream width, and fine sediments in the channel. In comparison, predictors of larval species composition included conductivity, the extent of riffles, undercut banks, and large woody debris. AIC-based model comparisons indicated that water quality variables and riparian habitat structure were critical predictors of adult species composition while stream substrate composition and channel geomorphology were the most important for larval species composition. Our study showed that species responses to differential forest management can vary depending on life stages. Such life-history structured niche divergence warrants consideration when implementing sustainable silvicultural practices.
