This project seeks to answer one main question: how resilient are Michigan’s ecosystems to climate change? Specifically, this project focuses on how major climate changes in the Late Holocene, such as the Medieval Climate Anomaly (MCA), impacted vegetation and fire regimes of this area. Inland lakes may have created a microclimate in parts of Michigan in the past that made these ecosystems unusually resilient to past climate changes. A paleoecological analysis of fossil pollen, amoebae, and charcoal from two peat bogs located near two of Michigan’s interior lakes were collected and analyzed. Cores were collected from the peat bogs using a Russian corer. For pollen analysis, samples were taken every centimeter, and 300 pollen grains were counted in each sample. Charcoal samples were also collected every centimeter, and the total area of charcoal in each sample was calculated using Image-J. Samples for testate amoebae were collected every two centimeters, and 150 were counted in each sample. A chronology was based on two radiocarbon dates.
Results/Conclusions
The pollen record indicated major changes in this ecosystem at the time of European settlement, and at ~1550 cal BP (~950 AD). When compared with similar ecosystems through squared-chord dissimilarity distances, all of the ecosystems contained the same vegetation composition, except at ~1200 cal BP. The unusual assemblages represented at that time co-occurred with the MCA, and suggested that even though this warming event changed the other ecosystems, the inland lakes immediately adjacent to this study site may have buffered the ecosystem. This suggests that there could be considerable variability in local resilience to future climate change in Michigan.
Charcoal analysis showed some interesting fire events. The first occurred at ~4100 cal BP, a well-known dry event. Another fire event occurred at ~2800, and the high percentage of Bullinularia indica and Hyalosphenia subflava testate amoebae confirmed that these bogs were experiencing a dry event. These events suggest that while perhaps these inland lakes provided small temperature microclimates, they do not significantly affect moisture levels during climate anomalies. Overall, these records showed that microclimates have played a significant role in shaping human landuse around the lakes, but they may not buffer natural systems from future precipitation-driven changes that decrease fire-return intervals.