Volume 4, 1951 - The Arctic Circle - Home

face of exposed banks than into level ground. This point
is at about the same latitude as Fort Severn, where permafrost
was also reported by Richardson. Small areas of
frozen ground probably occur under insulating layers of
peat at more southern localities in Manitoba, but, congruous
with the general upsweep of isotherms from eastto west,
W.A. Johnston states that frozen ground in British Columbia
occurs only locally, and then only at high altitudes.
It might be noted here that further knowledge of
the Manitoba flora is of particular value in the study of
plant distribution. Many plants reach in this province the
limit of their range, whether this be to the east, west,
north, or south of their main area. The range of climate
is very great between the forty-ninth and the sixtieth
parallels, the yearly average of daily mean temperature in
southern Manitoba being 35 to 37 degrees Fahrenheit, and
at Churchill 18 degrees. A small corner of southeastern
Manitoba lies within the Great Lakes-St. Lawrence forest
region, characterized by white and red pine, white cedar,
red and sugar maple, and yellow birch. The southwestern
portion includes a region of true prairie, north of which
is an aspen-poplar parkland area of transition to the
northern conifer forest, v1hich is itself replaced in the
northvfest by subarctic tundra. The Hayes route to the Bay
lies entirely within the conifer forest region. The trees
characteristic of this forest extend north to Swampy Lake,
where bals am fir drops out. Jack pine occurs on dry, sandy
sites as far as the mouth of the Shamattawa, fifty miles
above York Factory, while aspen drops out a short distance
beyond this. Paper birch ranges to within 30 miles of the
Bay, and white and black spruce, tamarack, and balsam poplar
are the only forest trees of this transition section to
reach the Hayes estuary. A remarkable relict station of
the boreal conifer forest occurs in the Spruce Vfoods Forest
Reserve south of Brandon, where isolated clumps of white
spruce, associated with creeping juniper, are scattered
throughout an area of typical prairie vegetation.
The geology, physiography, and glacial and postglacial
history of the province have also played an importan"
part in determining the present vegetation pattern. BorderiJ
the Bay is the Hudson Bay Lowland, a belt of former marine
submergenoe 100 to 150 miles wide, of which the part south
of Churchill is underlain by Ordovician and Silurian limestones.
North of Churchill, the acid granites of the
Precambrian Shield reach the Bay, the western boundary of
the Shield in Manitoba being a line drawn up the middle of
Lake Winnipeg to the vicinity of Reindeer Lake on the