Effects of forest harvesting on reptiles and amphibians of the southeastern United States
Todd, Brian D.
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Reptiles and amphibians are currently experiencing population declines that are attributed to several causes. Habitat loss, including conversion, degradation, and alteration, is the single greatest factor threatening reptile and amphibian populations. Forest harvesting represents one prominent form of land-use that may result in habitat loss for reptiles and amphibians and contribute to ongoing declines. There are few studies of the effects of forest harvesting on reptiles and results are often conflicting, suggesting a strong need for more detailed studies of reptile responses to forest harvesting. In contrast, amphibians generally exhibit declines in abundance and richness following forest harvesting, particularly after clearcutting. Therefore, there is an increased need to understand which mechanisms underlie observed changes in amphibian abundance in richness in response to forest harvesting. I conducted studies on the responses of reptiles and amphibians to forest harvesting on the Savannah River Site, Aiken, SC by creating 4 experimental treatments representing a range of forest harvesting intensities: (1) unharvested control (> 30 years old); (2) partially thinned stand in which the canopy was thinned to approximately 85% of that in the control (thinned forest); (3) clearcut with coarse woody debris retained; and (4) clearcut with coarse woody debris removed. I found that the relative abundance of small-bodied snakes was lower after clearcutting compared with unharvested controls of second-growth planted pines. I also found that the relative abundance of small-bodied snakes was greater in partially thinned forest stands compared with unharvested controls. In a second study I found that forest clearcutting can lead to decreased growth and survival of southern toads (Bufo terrestris) in field enclosures despite having no effect on their relative abundance between clearcuts and unharvested forests. In a third study, I found that survival of juvenile marbled salamanders (Ambystoma opacum) in field enclosures was greatly reduced in all harvested treatments compared with unharvested controls but adults only exhibited reduced survival in clearcut treatments. In a final study, I found that fewer amphibians migrated through clearcut treatments than forested treatments, particularly when emigrating from reproductive wetlands. Also, salamanders had a greater affinity for migrating through forests than did frogs.