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Effects on long-toed salamanders (Ambystoma macrodactylum) of removing canopy cover adjacent to breeding sites and in terrestrial habitats Ferguson, Christine May

Abstract

Knowledge of the effects of logging on amphibians in British Columbia is limited. The long-toed salamander, Ambystoma macrodactylum, is a pond-breeding species with a relatively widespread distribution in the province. I examined the effects of removing canopy cover on long-toed salamanders in both aquatic and terrestrial habitats. The study was conducted at the Opax Mountain Silvicultural Systems Research Area, near Kamloops, B.C. I compared the relative abundance of breeding salamanders in ponds with canopy cover conditions ranging from completely open to natural levels of canopy cover. Similar comparisons were made for juvenile salamanders emerging from breeding ponds. Capture rates of breeding salamanders were positively related to canopy cover index, and were higher in more permanent ponds. The same pattern was observed for emerging juvenile salamanders at one of the two replicate sites, Mud Lake. The relationship was different at the second site, Opax, where capture rates were negatively related to canopy cover index. Emergence of juveniles tended to start earlier at ponds at the Mud Lake site compared to those at Opax. Juvenile salamanders emerged earlier from more open ponds at the Opax site, but not at the Mud Lake site. Differences in effects between sites may result from the shorter growing season at the higher elevation Opax site, which would place constraints on the number of larvae that obtain a large enough size to reach metamorphosis. Higher temperatures in ponds that receive more sunlight would allow faster larval growth, thus increasing the number of emerging juvenile salamanders. The effect of reduced canopy cover on long-toed salamanders in terrestrial habitats was examined by comparing their relative abundance in 1.7- ha patch cut areas with that in uncut forested controls. The experiment was set up in a split-plot design, with volume of downed wood (high or low) as the split-plot factor. Very low capture rates at one of the two replicate sites limited my ability to detect differences between treatments. The pattern observed at the Mud Lake site suggests that activity of long-toed salamanders may be restricted in patch cuts during the summer.

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