Stream-Associated Amphibian Response to Forestry Practices in Western Washington

In a BACI landscape-level experiment conducted in western Washington over five years (2006–2010), we compared the responses of stream-associated amphibians (Coastal Tailed Frog [Ascaphus truei], and torrent [Rhyacotriton] and giant [Dicamptodon] salamanders) to clearcut harvest with three treatments and unharvested references. Treatments varied in buffer length: the current Washington State Forest Practices (FP) buffer (~50% of stream length), a full buffer (100%) and no buffer (0%); and had three or four replicates. No amphibian species was extirpated from any treatment. Treatment effects on density varied. Giant salamander density declined 82% (95% CI: 55-93%) pre- to post-harvest in the FP treatment relative to the reference. Pre- to post-harvest, density of Coastal Tailed Frog larvae was 4.1 (1.6-10.0) and 8.2 (3.3-20.1) times greater in the 100% and FP treatments than the reference, and post-metamorphic Coastal Tailed Frog density in the 0% treatment was 5.5 (0.9-36.6) times that of the reference. We also found no clear evidence of a treatment response for torrent salamanders and found no treatment effect on body condition for any species. Overall, we conclude that the Forest Practices buffer, as currently applied, is effective in maintaining stream-associated amphibian populations, at least in the two years immediately post-harvest.