| Summary: | Forest harvesting reduces the abundance of terrestrial salamanders although the
mechanism of the response is unknown. Maintaining riparian buffers around headwater
streams has been suggested as one strategy to protect amphibians from the effects of
forest harvesting. To understand better the proximate response of terrestrial salamanders
to forest harvesting and to determine the efficacy of 30 m riparian buffers in mitigating
these effects, I sampled amphibians with increasing distance from streams before and
after harvesting. The three treatments were each replicated twice: control, 30 m buffer
and clearcut.
The relative abundance of aquatic-breeding salamanders (Ambystoma gracile and
Taricha granulosa) changed little one year post-harvest in the buffer and clearcut
treatments indicating harvesting did not immediately impact their numbers. The response
of the terrestrial salamanders to forest harvesting was more variable. The relative
abundance of Ensatina eschscholtzii decreased on the buffer and clearcut sites while the
relative abundance of Plethodon vehiculum increased after harvesting. I suggest the
changes in relative abundance by the terrestrial-breeding salamanders are due to changes
in movement patterns which alter their capture rates rather than an actual increase or
decrease in relative abundance for either salamander.
Movement patterns provided ambiguous results for all four salamanders as to
whether they were showing compensatory behaviour in response to harvesting. The
movement distances and rates of the four species did not appear to be related to habitat
type. The growth rates of Ambystoma gracile, Ensatina eschscholtzii, and Plethodon
vehiculum recaptured in clearcuts were lower than those individuals recaptured in
forested habitat, indicating there was some cost associated with being in clearcut habitat.
Thirty-meter riparian buffers appear to be effective in mitigating the effects of
forest harvesting for three of the four salamanders captured. The proportion of captures
within 30 m increased in the buffer after harvesting for Ambystoma gracile, Taricha
granulosa, and Plethodon vehiculum. Buffer strips may be even more critical to juvenile
survival since over 80% of juvenile Ambystoma gracile were captured within 30 m of the
stream in the buffer treatment and only 40% in the control and clearcut treatments
respectively. Additionally, the proportion of aquatic-breeding salamanders moving
parallel to the stream increased postharvest in the buffer treatments indicating the riparian
buffer may be used as a corridor for movement during their breeding migrations.
Overall, all species were present on treated sites after harvesting indicating direct
mortality from the physical process of logging itself was limited. Shifts in distribution
and increased parallel movement for the aquatic-breeding salamanders in the buffer
treatments indicate these buffers are acting as corridors for movement. === Forestry, Faculty of === Graduate
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