EEB 337H - Families of Vascular Plants 

The Hudson Bay Lowlands

Across the northern portion of Ontario, draining north and east into Hudson Bay and James Bay, lies one of the largest wetlands in the world. The weight of the most recent continental ice sheet depressed the land here so that, when the glacier melted, seawater flooded in to create the Tyrell Sea. Since that time the land has been slowly rising, so as to produce the modern shoreline of Hudson Bay. Even now isostatic rebound is continuing, as can be seen by the succession of beach ridges that parallels the coastline.

Only five tree species predominate across this vast expanse: balsam poplar and trembling aspen (Populus balsamifera and P. tremuloides), tamarack (Larix laricina), and black and white spruce (Picea mariana and P. glauca). Dominant shrubs include Salix spp., Ribes spp., Betula pumila, Myrica gale, Alnus crispa and A. rugosa, Ledum groenlandicum, Kalmia polifolia, and others.

Fens on the Manitoba-Ontario border.
John Riley, photographer; NRC 2003.
Tamarack (Larix laricina) fen in the Moose River basin of the southern lowlands. Richer black spruce (Picea mariana) swamps occur along streams.
John Riley, photographer; NRC 2003.
As the land rises new beach ridges are formed by storms. Landward (to the left in the photo), vegetation succession creates a patchwork of tundra heath, lichen spruce woodland, and dune communities (Riley 2003).
John Riley, photographer; NRC 2003.
In the southernmost part of the lowland southern species like white elm (Ulmus americana) persist along the banks of rivers like the Kenogami, seen here.
John Riley, photographer; NRC 2003.

The photographs on this page appear in Flora of the Hudson Bay Lowland and its postglacial origin (2003) and are used with permission here. They were taken by John L. Riley and are © the National Research Council of Canada 2003.

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