Publication Date

1998

Comments

Published in the Journal of Herpetology. 32:399-404.

Abstract

Effects of two types of timbering on populations of the Peaks of Otter salamander (Plethodon hubrichti) were determined using average numbers found during multiple night collections. Sampling was done prior to, and for two years after, timbering on four sites in each of three treatments (clearcut, shelterwood cuts, and reference). The average numbers of P. hubrichti at the reference and shelterwood cut sites were stable over time while those at the clearcut sites showed a significant decrease post-timbering. Two years after timbering, 30% of the pre-timbering populations remained at the clearcut sites. Jolly-Seber population estimates on one clearcut site decreased from 43 to eight animals after cutting. In contrast, one reference site had a population estimate that oscillated around a mean of 71. Of the animals marked before timbering, significantly fewer were recaptured after timbering at the clearcut site (17.5%) relative to the reference site (39.0%). Juveniles appeared to be the size class affected to the greatest degree. Adults and juveniles on clearcuts most likely emigrated and/or died after treatment.

While most investigators believe that timbering is harmful to salamanders, it is difficult to document the effects. Most studies use population censuses in timbered areas and compare these numbers to adjacent untimbered areas. Salamander populations in timbered areas are usually lower, and sometimes absent, when compared to untimbered areas (Blymer and McGinnes, 1977; Bury, 1983; Enge and Marion, 1986; Pough et al., 1987; Ash, 1988; Bury and Corn, 1988; Stiven and Bruce, 1988; Welsh, 1990; Raymond and Hardy, 1991; Petranka et al., 1993; Dupuis et al., 1995). It is thought that opening the forest canopy increases exposure of the forest floor to sun and wind. This dessicates the habitat, thus reducing habitat quality for salamanders. Plethodontid salamanders may be particularly sensitive to habitat changes due to timbering since they are lungless, requiring moist skin for gas exchange, and are fully terrestrial, requiring moist microhabitats for egg development (Pough et al., 1987).

Salamander populations are not the only part of the forest ecosystem affected by timbering. Duffy and Meier (1992) reported that the herbaceous community may not recover to the same pre-timbering species diversity in 40-150 year logging cycles. Forest floor organic matter decreased exponentially to about 50% of the initial levels within 15 yr following timbering, then recovered over the next 50 yr to within 5% of pre-timbering levels (Covington, 1981). Seastedlt and Crossley (1981) reported that microarthropod decomposers were significantly less abundant two years after timbering. Many changes can occur with loss of the forest canopy, some of which would directly affect food availability to salamanders (Mitchell et al., 1996).

There are drawbacks to most earlier assessments of the effects of timbering on salamander populations. Foremost is most earlier studies assume that the pre-timbering population levels in the treatment and reference (control) sites were similar. Since salamander populations may have clumped dispersion patterns (Kramer et al., 1993) this assumption may not be justified. In this study both pre and post-timbering population levels were assessed for an endemic species, Plethodon hubrichti.