Collaborative Research: Megaherbivore and climatic controls on fire and vegetation dynamics during the last deglaciation

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Ecologists have long sought to understand how species reshuffle into novel ecological communities during periods of major environmental change, and the consequences of this reshuffling for the services that those ecological communities provide for human society. This project capitalizes on a major historical event - massive changes in plant communities roughly 17,000 years ago - to determine the relative roles that climate change, species interactions, and fire played in the creation of novel communities. Results from this research will inform contemporary debates about the potential for climate change to create 'no analog' communities that differ fundamentally in their structure, function, and the services they provide to society. They will also guide management practices intended to restore communities to prior states and improve our understanding of the consequences of widespread extinctions.This project builds on prior evidence that plant communities changed dramatically during the last deglaciation because the extinction of large grazers released plants from herbivore suppression. New research will test the novel Megafaunal Release Hypothesis by assessing the relative importance of climate and species interactions on vegetation and fire dynamics. The investigators will collect and analyze a series of lake-sediment cores in the eastern US, and quantify relationships among independent climatic and ecological proxies within and across sites in order to test the Megafaunal Release Hypothesis. Eight new lake sites will be analyzed for indicators of past vegetation composition (fossil pollen), fire regime (sedimentary charcoal), megafaunal abundance (spores from fungi found in dung), and temperature (organic geochemistry). Broader impacts include the mentoring and training of a postdoctoral research scientist, a graduate student, and several undergraduates, and the expansion of collaborations among paleontologists, geographers, and ecologists to understand future environmental change. All data will be made publicly available through standard community data repositories.