Notes on Late Wisconsin and Early Holocene History of Vegetation in Canada^∗

Abstract

Nearly all of Canada was covered by the Wisconsin glaciation and most of the country was deglaciated during the time from about 12,000 to 7,000 years ago. The biota generally survived the glaciation south of the ice sheets in North America, in addition to survival in probable refugia along the coasts and in Yukon and the Arctic Islands.

The ice sheets (Laurentide and Cordilleran) completely disturbed the vegetation in Canada. As deglaciation occurred in response to a significant change in climate at the end of the Pleistocene (about 10,000 years ago), recolonization of Canada by vegetation proceeded from the refugia and a northward migration of biota from the southern peripheral region of glaciation. The late glacial episode differed from any subsequent Holocene time episode in terms of the availability of large areas of “raw” soils, the very large volume of meltwater runoff, and the presence of numerous large glacial lakes that at least locally affected the climate.

The main sources of information about late Wisconsin and Holocene vegetation are records of plant macrofossils and fossil pollen and spore assemblages preserved in lake sediments, peat bogs, and alluvial deposits.

Genetic mixing occurred during recolonization when the populations from different refugia met after having been isolated for several thousand years.

The studies of the fossil record are seriously hindered by the lack of basic palynological data (pollen deposition and dispersal in relation to the modern vegetation) and the ecology, phytogeography, and genetics of Canadian vegetation and flora, as well as the relationships between vegetation and climate in particular.

It has been demonstrated clearly that the palynological and paleobotanical studies can provide the necessary information required for construction of paleoclimatological models that can be beneficially used in the study of environmental changes.