Amphibian Biomass Export from Geographically Isolated Wetlands: Temporal Variability, Species Composition, and Potential Implications for Terrestrial Ecosystems

Abstract

Recently metamorphosed amphibians transport substantial biomass and nutrients from wetlands to terrestrial ecosystems. Previous estimates (except 1) were limited to either a subset of the community or a single year. Our goal was to examine temporal variability in biomass export of all amphibians within breeding ponds and the composition of that export. We completely encircled ponds with drift fences to capture, count, and weigh emerging recently metamorphosed individuals in Maine (four wetlands, six years) and Missouri (eight wetlands, 2–4 years). We estimated total amphibian biomass export, export scaled by pond surface area, species diversity, and percentage of biomass from anurans. Biomass export and export composition varied greatly among ponds and years. Our estimates were of similar magnitude to previous studies. Amphibian biomass export was higher when species diversity was low and the proportion of anurans was higher. Biomass estimates tended to be highest for juvenile cohorts dominated by a single ranid species: green frogs (Missouri) or wood frogs (Maine). Ranid frogs made up a substantial proportion of amphibian biomass export, suggesting that terrestrial impacts will likely occur in the leaf litter of forests. Future studies should examine the impacts of ranid juveniles on terrestrial ecosystem dynamics.

Keywords

• spatial subsidy
• aquatic-terrestrial linkages
• species diversity
• Ranidae
• Ambystomatidae
• recently metamorphosed