This project explores the role of centennial to millennial-scale climate variability, particularly wet and dry extremes, in governing the tempo, rate, and spatial pattern of invasion and expansion of three economically and ecologically important tree species (yellow birch, hemlock, beech) near their northwestern range limits in the western Great Lakes region. Geographic ranges and population sizes of these species have expanded episodically in the last 5000 years, and preliminary evidence indicates that these expansions were paced by climate variability. We will use paleoecological methods (analysis of pollen, macrofossils, and stomates from lake and peatland sediments) to delineate the spatial and temporal patterns of these expansions, and paleoclimatological methods (analyses of paleontological and geochemical indicators from peatland sediments) to develop detailed, independent records of spatial and temporal patterns of climate variability. Comparison of the paleoecological and paleoclimatological data will link the ecological responses to climate variations across a range of timescales. Understanding ecological and climatic dynamics of the past will contribute to our ability to predict ecological responses to ongoing and future climatic change.
Climate Extremes and Episodic Invasions: a Late Holocene Case Study From the Western Great Lakes Region