Basin‐Scale Surveys of Stream‐Associated Amphibians in Intensively Managed Forests

Abstract

Abstract:Conservation and management of native species on landscapes managed for intensive wood production represents an ongoing challenge to forest managers. Previous research suggests that impacts of forest practices on stream‐associated amphibians (SAA; giant [Dicamptodonspp.], torrent [Rhyacotritonspp.], and plethodontid [Plethodonspp.] salamanders and coastal tailed frogs [Ascaphus truei]) in Oregon and Washington, USA, vary spatially and temporally as a result of biotic and abiotic factors, some of which can be influenced by management treatments. Although individual harvest units can encompass multiple stream reaches and entire second‐order basins, nearly all published research studies used stream reaches of various lengths as sample units. To address this discrepancy between research and operational scales, we sampled first‐, second‐, and third‐order streams in 70 randomly selected third‐order basins in Oregon and Washington in 2007 and 2008 to estimate detection and occupancy parameters for SAA and to develop basin‐level density estimates for different species and genera. We estimated occupancy probabilities of 0.99 (95% CL = 0.96–1.00) for torrent and giant salamanders, 0.93 (95% CL = 0.76–0.92) for Dunn's salamanders (Plethodon dunni), and 0.60 (95% CL = 0.46–0.72) for tailed frogs. Our estimates can be compared with estimates for unmanaged third‐order basins in Oregon and Washington to provide a relative measure of potential impacts of forest management on these taxa. In addition, our estimates provide baseline information with which to assess potential effects of future environmental changes on the 4 genera.