Late Quaternary dynamics of tundra and forest vegetation in the southern Niagara Escarpment, Canada

Summary• Here, paleoecological studies from southern Ontario, Canada, are detailed to reconstruct vegetation history of the last 13 000 14 C year, with emphasis on late‐glacial treeless vegetation. • Two sites (Crawford Lake and Twiss Marl Pond) were investigated using combined pollen and plant–macrofossil stratigraphic data. Comparison of multivariate analysis of pollen data with climate variations inferred independently from oxygen isotopes at the same site facilitated systematic evaluations of climate–vegetation interactions during different stages of vegetation development. • Pollen results show a distinctive successional change from Alnus–Dryas–Cyperaceae sparse tundra or periglacial desert toSalix–Juniperus–Cyperaceae dense tundra, with abundant arctic/alpine plant macrofossils, during the first few centuries after ice retreat. The area around the two sites was then dominated byPicea(c.12 000–10 00014C BP). Vegetation shifts, summarized by log‐contrast principal component analysis of the pollen record, indicated a lagged response of forests to deglacial climate warming. The major vegetation shift atc.750014C BP from coniferousPinus‐dominated to mixed forests probably corresponded to a major shift from deglacial to full postglacial climates. Vegetation during the mid‐ and late Holocene responded more directly to natural (drought‐triggered pathogen‐inducedTsuga decline) and human disturbances (aboriginal and EuroCanadian settlements). • This study demonstrates that bedrock basins most faithfully recorded the earliest vegetation change because they usually experienced a short delay in lake formation after ice retreat.