Date of Award:

5-1-2001

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Biology

Committee Chair(s)

Edmund D. Brodie Jr.

Committee

Edmund D. Brodie Jr.

Committee

James A. MacMahon

Committee

Charles P. Hawkins

Abstract

Because the ranges of stream-breeding amphibians in the Pacific Northwest occur partly on industrial timberlands, it is valuable to study population distributions of these animals in forest environments that rarely reach old growth status and are subject to timber harvest on a regular basis. To determine how short-term changes in forest age affect the density of stream-breeding amphibians, first-order streams located on private industrial timberlands in Skamania County, Washington, were sampled during the summers of 1998 and 1999. Species captured included Dicamptodon tenebrosus, Dicamptodon copei, Rhyacotriton cascadae, and Ascaphus truei. Regression tree analysis showed that relative densities of Rhyacotriton cascadae could be grouped into approximate forest age classes that correspond to forest successional stages seen in regenerating forests in this region. Rhyacotriton cascadae densities were highest in 25- to 60-year-old forests and lower in forests less than 25 years of age and forests greater than 60 years of age. Dicamptodon tenebrosus and Dicamptodon copei were not consistently associated with any particular forest age class. Ascaphus truei was not included in the analysis because of a small number of captures. The results suggest that despite the presence of suitable substrate conditions, populations of Rhyacotriton cascadae are negatively affected for several years following clearcut timber harvest but are capable of reaching high densities soon thereafter.

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