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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Although headwater streams constitute a significant portion of stream length within watersheds, their aquatic fauna, contributions to regional biodiversity, and responses to forest management have been understudied. Ma cro in ver te brate communities, physical habitat, and water chemistry were sampled from 40 headwater streams in managed forests in the Oregon Coast Range mountains. We characterized functional and structural attributes of ma cro in ver te brate communities in relation to physical, chemical, and biological gradients. Substrate composition, specific conductance, and riparian forest age showed the strongest correlations with resultant ordination patterns in ma cro in ver te brate community composition. Among individual metrics of community structure and composition, total ma cro in ver te brate density and dominance by three taxa showed the strongest correlations with forest age. No community measures were related to densities of torrent salamanders (Rhyacotriton kezeri) or crayfish (Pacifastacus leniusculus), suggesting these potential predators had little influence on overall ma cro in ver te brate community structure. Rare taxa were sampled from several reaches, including Rhyacophila probably viquaea for which little information is available, and an Eobrachycentrus sp., previously known to occur only in the Cascade mountains. Headwater streams within these managed forests of northwestern Oregon appear to be taxa rich, continue to support taxa limited to headwater streams, and harbor taxa about which little is known.