Date of Completion

Spring 5-4-2018

Thesis Advisor(s)

Tracy Rittenhouse

Honors Major

Ecology and Evolutionary Biology

Disciplines

Animal Experimentation and Research | Biodiversity | Ecology and Evolutionary Biology | Forest Biology | Forest Management | Terrestrial and Aquatic Ecology

Abstract

The composition of tree species within New England forests has changed significantly in recent decades, with an increase in maple (Acer spp.) abundance and a decrease in oak (Quercus spp.) abundance. Changing forest structure results in changing leaf litter composition of the forest floor, which influences the ground-dwelling amphibians that live in the litter. To better understand how changes to forest composition alters amphibian habitat quality, we recorded the growth and survival of 27 juvenile wood frogs (Lithobates sylvaticus or Rana sylvatica) and 27 juvenile American toads (Anaxyrus americanus) in response to leaf litter type. Between early August and late October 2017, half of the individuals of each species were raised in terrestrial enclosures with maple litter, and the other half were raised in terrestrial enclosures with oak litter. We used Kaplan-Meier survival estimates to find that frogs and toads raised in maple leaf litter had higher survival rates than those raised in oak leaf litter. Additionally, we created a mixed-effects model with individual as the random effect to quantify the effect of leaf litter type on growth. In both amphibian species, mass of individuals raised in maple litter was greater than mass of individuals raised in oak litter. Increased survival and enhanced growth in maple litter suggests that juvenile amphibians benefit from the changing forest composition. Our results are in contrast with research in aquatic systems research, which found negative effects of maple litter decomposition on amphibian larvae. Future research should take our results and larval results to model population level effects of forest change on amphibian growth and survival. Furthermore, our research can help inform future soil quality and leaf litter community studies by accounting for a potential increase in amphibian populations as maple forest expands.

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