Predator-avoidance behavior in anuran tadpoles: a new bioassay for characterization of water-soluble cues |
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Authors: | Teruhiko Takahara Yukihiro Kohmatsu Ryohei Yamaoka |
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Institution: | (1) Department of Natural Resources, Cornell University, Ithaca, NY 14853, USA;(2) Rubenstein School of Environment and Natural Resources, University of Vermont, 343 Aiken Center, Burlington, VT 05405, USA |
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Abstract: | Most surveys of large wood in streams are conducted by counting and measuring every piece of large wood within a reach, a
technique that is effective but time-consuming. In this study we evaluated an alternative method that takes less time and
can be employed in studies in which an estimate of total large wood volume along a stream reach is the primary metric of interest.
In first- through third-order streams we estimated in-stream large wood volume and large wood frequency, comparing large wood
census estimates to those from a modified a line-intercept technique that has been commonly used in terrestrial forest surveys.
Estimates of large wood volume from line transects located in the geographic center of the stream (parallel to stream axis
and equidistant from bankfull margins) were highly correlated with those from the wood census (P < 0.001, r
2 = 0.88, Pearson’s r = 0.935), but produced slightly greater estimates of large wood volume (regression slope = 1.28, SE = 0.16). Line-intercept
estimates of large wood frequency (number per 100 m of stream) were significantly correlated to the wood census counts, but
the line-intercept method underestimated frequency by about 50% (P = 0.016). Differences in the estimated large wood volume between line-intercept and wood census surveys were associated with
variability in the diameter of the large wood, but unrelated to stream bankfull width, for the range of stream sizes evaluated
in this study (≈ 2 to 11 m). Our results suggest that in small constrained streams, line-intercept surveys are an effective
method for estimating in-stream large wood volume and that these estimates better approximate results from whole-stream census
techniques where the diameter of in-stream wood is relatively consistent.
Handling editor: K. Martens |
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Keywords: | Large wood Large woody debris Line-intercept Wood census Wood volume Stream assessment |
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