Treatments resulted in a roughly three-fold gradient (P = 0.0001) of photosynthetically active radiation at stream surfaces. We used the results of mixed models analyses on effect sizes (treatment minus reference, α = 0.1) as well as the relative magnitude of effect size (ES) changes (percentage change that exceeded 90% confidence limit ) from pre- to post-treatment periods, respectively, to infer important treatment effects and highlight large but statistically non-significant changes implying potential treatment effects. Quantification of biofilm and drift reflected measurement of basal food resources for higher trophic levels (amphibians). Using a replicated BACI design, we documented pre- versus post-treatment changes in light levels, water temperature, biofilm, drift of detritus and macroinvertebrates, and the abundance, body condition, and growth rates of six stream-associated amphibian species (one anuran and five salamanders).
Each treated reach was paired to an upstream reference reach where cover averaged 92‒97%. Vegetation removal began directly over the stream and moved outward until 0%, 30%, and 70% overhead cover was attained (hereafter no-, low-, and intermediate-shade treatments). variegatus, but demonstrate several new prey items for the family and some differences in frequencies of prey consumed.Įxecutive Summary: We reduced vegetation cover along a 50-m reach on each of 25 headwater streams in northwest Oregon and western Washington. Our results for post-metamorphs were generally consistent with the diet of a post-metamorphic congener, R. Copepoda and Diptera were particularly common in the diet of larvae, whereas Arachnida, Diptera, Collembola, and Coleoptera were more common in the diet of post-metamorphs. A wide range of aquatic and terrestrial prey was documented, supporting both aquatic and terrestrial prey bases for this highly aquatic salamander. We studied the diet of both larval and post-metamorphic Columbia Torrent Salamanders in the Willapa Hills, Washington. There have been no studies of its diet, which may be a significant barrier to its conservation and management. This information lack is acute for the Columbia Torrent Salamander, Rhyacotriton kezeri, a species that is of conservation concern throughout its range. The basic ecology of torrent salamanders, family Rhyacotritonidae, is poorly known.
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