Novel plant assemblages are a long-recognized feature of late-glacial North America, but identifying their causes has been hampered by inaccurate radiocarbon chronologies and the multiplicity of ecological and climatic events during the late Pleistocene. Recently we reported that the formation of no-analog vegetation may have been linked to declines in Pleistocene megafaunal communities, based on pollen and spores from the coprophilous fungus Sporormiella at sites in Indiana and New York. We present a new, multi-proxy analysis from Silver Lake, OH, which 1) updates the radiocarbon chronology of a classic pollen record with a well-established zone of no-analog vegetation, 2) combines a new sub-centennial pollen record with charcoal, Sporormiella, and x-ray fluorescence (XRF) spectroscopy analyses for an integrated record of landscape change before, during, and after the period of no-analog vegetation, and 3) replicates both the absolute and relative temporal patterns of landscape change at Appleman Lake, IN. At Silver Lake, the decline in Sporormiella at 13.9kaBP was immediately followed by the formation of novel plant assemblages, as well as the highest-magnitude charcoal peak in the record. Increased Ca and Sr concentrations during the no-analog interval indicate either increased moisture, increased input of nutrients from deciduous litter, or both. The duration of the no-analog assemblages (13.9-11.8kaBP) roughly corresponds to the period of peak insolation dissimilarity, but is more temporally constrained than previously reported in subcontinental-scale syntheses (17-11kaBP). We propose a hierarchy of controls on late-glacial plant communities, where biotic interactions such as megaherbivory mediate climate-driven vegetation change.
Bibliographical noteFunding Information:
We are deeply grateful for the detailed comments of two anonymous reviewers, which greatly improved this manuscript. This work was supported by NSF Grants DEB-0716471 and DEB-0716951 , a graduate student research grant from the Geological Society of America, and the Climate, People, and Environment Program at the University of Wisconsin-Madison . Initial core description and imaging were done at LacCore (the National Lacustrine Core Facility), a NSF-supported facility at the University of Minnesota-Twin Cities; remaining core material is archived at the LacCore core repository. We would like to thank YMCA Camp Willson for providing access and logistical support to core Silver Lake. Jeremiah Marsicek, Jenna Bonavia, Michael Urban, Lucy Xue, and Luke Straka provided field and lab assistance. Jessica Blois provided assistance with R code and the Bayesian change-point analysis; Jenn Marlon assisted with CharAnalysis and charcoal interpretations. Sara Hotchkiss provided assistance with charcoal morphotype identifications. The Williams Lab group provided valuable comments on this manuscript. Fig. 1 was created by Fei Du of the UW-Madison Cartography Lab. Guy Robinson provided helpful modern Sporormiella reference slides. Thanks to Maarten Blaauw and Andres Christen for assistance with Bacon. We also thank Amy Myrbo, Anders Noren, and Kristina Brady at the LRC, Eric Grimm for advice and assistance, and Karen Jackson Medaris for her hospitality and accommodations during the fieldwork.
Copyright 2012 Elsevier B.V., All rights reserved.
- No-analog communities
- Pleistocene extinctions
- X-ray fluorescent spectroscopy