Effects of a floodplain restoration on amphibians in an agricultural landscape

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David R. Bowne, Department of Biological and Environmental Sciences, Elizabethtown College, Elizabethtown, PA and Ryan M. Conway, Department of Biology, University of California, Riverside, Riverside, CA

Background/Question/Methods
We evaluated the effects of a novel floodplain restoration technique on amphibians in an agricultural landscape. The restoration technique involved removing legacy sediment that had accumulated in the floodplain behind 18th and 19th century dams. As this restoration altered the ecosystem from single channel stream with highly erodible banks to a broad floodplain wetland, we asked how amphibians responded to this restoration. We hypothesized the wholesale ecosystem conversion would negatively affect the resident populations of streamside amphibian species present immediately before the restoration. We also hypothesized that amphibian species not present at the site immediately prior to the restoration would colonize the restored wetland, thus increasing amphibian species richness over time. We collected one season of pre-restoration data and five seasons of post-restoration data from Big Spring Run, Lancaster County, Pennsylvania, USA. We sampled for salamanders using litter bags, dip nets, and kick nets along three segments in each of two restored branches and three segments in each of two unrestored branches. We documented anurans using an automated recorder and visual surveys.
Results/Conclusions
We detected Eurycea bislineata (northern two-lined salamander) and Pseudotriton ruber (eastern red salamander) pre and post-restoration. Eurycea bislineata was by far the most common salamander species. Best fit occupancy models for this species showed no difference in occupancy between restored and unrestored segments. Mean number of E. bislineata captures per unit effort did not differ between years nor restoration status. No anurans were detected pre-restoration, but we did have visual evidence of adult, tadpoles, and eggs of Lithobates clamitans (green frog) in post-restoration surveys. Our results allow us to reject our hypothesis that the restoration would negatively affect streamside salamanders such as E. bislineata. This species is thriving in the restored wetland. While numbers of anurans are low, we do have evidence that the restoration increased amphibian species richness. Our work demonstrates that floodplain restoration via removal of legacy sediment is a net benefit for amphibians in this agricultural landscape. While the novel restoration was motivated for water quality issue (i.e., reducing downstream sediment and nutrient loads), it has a positive side effect for amphibian diversity.