Restoration of Breeding Habitat for Rare Amphibians

Although fire is recognized as an important disturbance in longleaf pine uplands of the southeastern United States, less is known about the importance of fire or other disturbances in the wetlands embedded in this system. Reticulated flatwoods salamanders (Ambystoma bishopi), a federally endangered species, breed in the grassy understory of ephemeral pine flatwoods wetlands. These areas contain water in the winter, but are dry by April or May in most years, making it possible for them to burn during the summer lightning season. Years of fire suppression allowed a dense mid-story of shrubs to develop in these wetlands, and the disappearance of a grassy understory not only removed a component of larval salamander habitat, but removed the fine fuels important for carrying a fire through the dry wetland in summer. Prescribed burns applied in winter rarely burn through ponds because of the presence of standing water at this time of year. Flatwoods salamanders and possibly other amphibians (e.g., ornate chorus frogs (Pseudacris ornata)) are less likely to occur in wetlands with high canopy cover and low herbaceous groundcover, conditions that can occur from fire exclusion. We experimentally evaluated mechanical removal of shrubs as a substitute for fire, because these overgrown wetlands were difficult to burn. Our objective was to evaluate whether mechanical treatments could serve as a surrogate for fire and create vegetative conditions that are similar to high-quality breeding sites (sites that have supported flatwoods salamander larvae in recent years). Therefore, we chose a series of wetlands including sites that have recently supported flatwoods salamander breeding (i.e., high-quality) and sites with no recent use by flatwoods salamanders that had a dense-midstory and low herbaceous groundcover (i.e., low-quality). A subset of the low-quality ponds (n = 7) were then assigned to be mechanically treated (i.e., treatment sites). Both before and after the treatment was applied, we measured characteristics of the vegetation and documented use by amphibians through larval dip-netting surveys and night-time call surveys. Pre-treatment, flatwoods salamanders were documented at 4/4 high-quality, 0/7 treatment, and 0/5 low-quality sites. Ornate chorus frogs were documented at 4/4 high-quality, 2/7 treatment, and 1/5 low-quality sites. The first year following treatment, flatwoods salamanders were documented at 4/4 high-quality, 0/4 treatment, and 0/4 low-quality sites. Ornate chorus frogs were documented at 2/4 high-quality, 0/4 treatment, and 1/4 low-quality sites. Mechanical treatments reduced canopy cover (from 57.4% to 44.1%) to similar levels as high-quality sites (41.1%); however, herbaceous groundcover had not recovered (18.1% compared to 48.2% at high-quality sites). Because of drought conditions in the post-treatment year, amphibian use of all the wetlands was reduced, and we were unable to sample some sites because they remained dry. More time will be required to assess the response of herbaceous groundcover and whether mechanical methods can be used as a surrogate for fire to restore amphibian breeding habitat. Identifying surrogates for fire could add an important technique to the management toolbox.

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