The Southern Hudson Bay taiga is contained within the conceptually larger
Nearctic realm and possesses a number of neighbouring
ecoregions including the
Eastern Canadian Shield taiga,
Northern Canadian Shield taiga,
Central Canadian Shield forests, and
Midwestern Canadian Shield forests. Prominent geological features in the region include the Hudson Platform and an underlying layer of
Paleozoic limestone bedrock. Its soils, which are primarily Gelic and Dystric
Histosols and Eutric
Gleysols, are characterized by shallow layers of
permafrost, slightly acidic pH levels, and hydromorphic conditions. The Southern Hudson Bay taiga represents an area where a number of hydrologically significant rivers, such as the
Nelson River and the
Mattagami River, deposit their headwaters from farther inland into the
Arctic Ocean via
Hudson Bay. Alternative geographic classifications also commonly refer to the region as the
Hudson Bay Lowlands. The
Palaeozoic and
Proterozoic sedimentary deposits overlaying the
bedrock with an elevation rarely exceeding 120 m. The relatively flat land slopes gently toward the two bays, which act as a
drainage basin for the region. However, the relatively poor drainage system has spurred the natural development of numerous
wetlands. It is encircled by the
Canadian Shield, with which it overlaps in a few areas to the east and west. To its north is the cold
Arctic Archipelago Marine ecozone, and to the south is the milder
Boreal Shield. Hence, this ecozone is transitional, which is easily evident as it transforms from
barren tundra in the north to open
taiga forests in the south. These forests resemble those of the
boreal zone, with sparser
vegetation. Thousands of depressions carved by retreating
glaciers have become
lakes and wetlands. The Hudson Plains is also noted for
coastal marshes and extensive
tidal flats, with
tidal marshes along the coast of Hudson Bay. Belts of
raised beaches are evident where rebound from glacier retreat is most prominent. ==Climate==