Are ecotonal systems more sensitive to climate change? Past ecotonal
dynamics and rates of vegetation change in Michigan
- Sam Wiles,
- Nora Schlenker,
- David Nelson,
- Bryan Shuman,
- John Williams
David Nelson
University of Maryland Center for Environmental Science
Author ProfileJohn Williams
University of Wisconsin-Madison
Corresponding Author:jww@geography.wisc.edu
Author ProfileAbstract
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Ecotones are expected to be sensitive to climate change, but supporting
evidence is scarce. Dense paleoecological data networks are ideal for
studying past ecotonal dynamics because of their broad spatiotemporal
coverage. Here we test the ecotonal sensitivity hypothesis by
reconstructing movements of a major temperature-governed forest ecotone
over the last 11,000 years in lower Michigan and comparing the
variability of ecotone-proximal and distal vegetation. NMDS ordination
indicates four meaningful axes of variation in Holocene Michigan
vegetation, with axis 2 capturing the latitudinal ecotone and axis 4
differentiating by moisture sensitivity. The ecotone advanced northwards
by 150 km from 11 to 6 ka, during a 3.5⁰CTJuly warming, then retreated.
Ecotone-proximal sites have higher rates of compositional change than
distal sites. These findings support the ecotonal sensitivity
hypothesis, constrain estimates of climate-driven forest ecotonal
movement, and reinforce concerns about the sensitivity of ecotonal
ecosystems to anthropogenic global warming.