- •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 to Salix – 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 by Picea ( c. 12 000–10 000 14 C 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 at c. 7500 14 C BP from coniferous Pinus -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-induced Tsuga 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.