2012 Annual Report
Total amphibian species richness in the 48 wetlands selected for this study was 18, of which 14 were frogs and four were salamanders. Total species richness in all restored sites was identical to that in natural sites, whereas only about half of these species occurred in the prior converted sites that held water. Jaccard’s coefficient of community similarity revealed that amphibian assemblages in the Northern region (Delmarva) are only 50% similar to those in the Southern region (Virginia and northeastern North Carolina). The ranges of several species include Delmarva, whereas those of other species include southeastern Virginia and northeastern North Carolina. In the Northern region, species richness in restored sites (10) was equal to that in natural sites (10), and both were twice as high as in Prior Converted sites (5). In the Southern region, total species richness in restored sites (10) was higher than in natural (5) and prior converted sites (3). Rank order of total amphibian species richness for combined samples was restored>natural>>prior converted.
The presence of amphibian larvae (frog tadpoles and salamander larvae) indicates which species actually use a wetland for reproduction. Mean number of amphibian species based solely on larval samples in all restored sites was similar to the mean for natural sites, and both were higher than the mean for prior converted sites; however, the difference is not significant. The wide range of variation in this metric in all of the wetlands contributed to the lack of significance. Rank order of amphibian larval species richness for combined samples was restored>natural>prior converted.
Canopy cover has been shown to be a key factor in breeding site selection by some amphibians. Number of species in restored wetlands with open or partial canopies were similar to numbers in natural wetlands. None of the relationships were significant; however, natural wetlands with full canopies that shaded the wetland throughout the day tended to support the fewest species.
The abundance of emergent aquatic vegetation was highly variable and had little effect on species richness in Conservation Effects Assessment Project (CEAP) wetlands. Several wetlands with abundant emergent aquatic vegetation supported similar numbers to those with little to no vegetation.
The relative abundance of the amphibian larvae was highly variable among the three types of wetlands and between regions, years, and habitat characteristics (canopy cover and aquatic vegetation). In general, restored wetlands supported higher numbers of larvae than natural and prior converted wetlands. The extreme variation among sites and between years, however, hindered revelation of any significant differences.
The primary conclusion of this study is that the Cooperative Resolution Program (CRP) and Wetland Reserve Program (WRP) restored wetlands were functionally similar or superior to natural wetlands in their ability to support diverse amphibian assemblages. Some restored wetlands exceeded natural wetlands in the number of species they supported. Restored wetlands with shallow to deep basins with several terraces that have open canopies, no fish, support aquatic vegetation, and dry by mid-summer are optimal habitats for amphibians in the mid-Atlantic region. Longer hydrologies would allow establishment of fish, all of which are predators of amphibians. Natural Resources Conservation Service wetland restoration projects should take amphibian habitat requirements into consideration to ensure that such wetlands are suitable for most of the species in the landscape. CRP and WRP programs in the mid-Atlantic have successfully created the conditions needed by amphibians to provide their own unique ecosystem services in this region.