We examined relationships between Columbia torrent salamanders (Rhyacotriton kezeri) and biotic and abiotic habitat attributes at landscape and reach (within-stream) scales in managed forests of northwestern Oregon, USA. In 2000, we found 851 torrent salamanders in 58% of 119 headwater (first-order) streams from randomly selected 2.58-km2 sections of the study area. Landscape-level variation in torrent salamander distribution and relative abundance was related to abiotic landform features that included parent geology, elevation, and aspect, but variation was not related to age or composition of adjacent riparian forests. In 2001, we conducted a more detailed study of salamander occurrence and abundance within 179 10-m stream reaches stratified by geology and gradient. The stream reaches were randomly selected from 40 streams known to contain salamanders. We recorded 1,224 salamanders from 92 (51%) of the stream reaches. Akaike's Information Criterion (AIC) model selection indicated that the global model containing all 23 variables best explained salamander occupancy in stream reaches, but a model containing only stream gradient also received empirical support. The stream-gradient model was the best candidate model explaining reach-level salamander abundance. Three other models explaining abundance (an abiotic landform model, the global model, and a physical substrate model) also received empirical support. Overall, our study suggests that variation in physical features of stream habitats may have an important influence on distribution and abundance of Columbia torrent salamanders at multiple spatial scales.
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Vol. 68 • No. 2