Background/Question/Methods
Discovering and understanding factors which structure and organize communities continues to remain a central goal of ecology.  In forests, the diversity and heterogeneous distribution of leaf litter is known to be one such factor, as it significantly affects detritivorous food webs in stream systems.  Furthermore, recent work suggests that leaf litter may serve a substantial role in this regard for temperate, forested ponds and wetlands by altering community composition and the performance of individuals within those communities. However, we have little idea how different species of tree litter, many of which range widely in physical and chemical attributes, specifically contribute to pond and wetland community organization and composition, although it is predicted that increased nutritional quality and nutrient accessibility will promote growth and diversity within the community. To investigate this question, we ran a replicated, outdoor mesocosm experiment in which identical, diverse communities of 2 generalist snail species, 5 tadpole species, a shredding amphipod, a shredding isopod, periphyton, phytoplankton, fungi, and bacteria were supplied with one of 10 different tree litter species, a mixture of all 10 species, or no leaves.  Leaf species used for this experiment were all local and common to wetland areas around the study site (northwest PA).  Variables including pH, temperature, light attenuation, dissolved oxygen were measured to track the abiotic environment generated by the litter species and biotic measurements tracked changes among most elements of the community.
Results/Conclusions:
Over the 5 month duration of the experiment, we saw substantial differences among all communities through changes in amphibian survival and time to metamorphosis, zooplankton density and diversity, snail productivity and density, periphyton and chlorophyll mass, and detritivore demographics.  Of these results, we observed 60-80% mortality of amphibians in tulip poplar (Liriodendrum tulipfera) and red maple (Acer rubrum) treatments, high snail productivity in chestnut (Castanea dentata) replicates, and synergistic effects of the mixture treatment.  These results are highly linked to the chemistry of the litter treatments, and the bottom-up effects which that chemistry exerts upon aquatic food webs.  We conclude that the species of leaf litter provided to forested pond or wetland habitat may play a significant role in determining the productivity, development, and composition of wetland and pond food webs.  This work further suggests that changing diversity and composition of our forests may dramatically impact the composition and structure of embedded aquatic communities.