The Boreal White and Black Spruce zone
(BWBS) occupies the low-lying topography of northeastern valley bottoms
and plateau regions of British Columbia. This zone is a western extension
of the Great Plains region of Canada. The BWBS is found in valley
bottom to about 1300m (Meidinger and Pojar 1991). It occurs below
the Spruce-Willow-Birch zone in the north and the Engelmann Spruce
Subalpine Fir zone in the southern part of its range.
The climate of the BWBS is very cold with
long winters and a short growing season. Annual precipitation is between
330 and 570mm with a mean annual temperature ranging from –2.9
- 2 C (Meidinger and Pojar 1991). Due to the intense cold and often
shallow snowpack, discontinuous permafrost is common in this zone.
Deep layers of organic material can lead to frost lenses being formed
instead of permafrost in some places.
Three biogeoclimatic subzones are currently
recognized in the BWBS zone (Meidinger and Pojar 1991). The dry, cool
BWBS subzone (BWBSdk) is generally located west of the Rocky Mountains.
The moist, warm BWBS subzone (BWBSmw) is found from the Alberta border
west and north to Yukon and Nunavut. The wet, cool BWBS subzone (BWBSwk)
is found above the BWBSmw along the mid-slopes of the Rocky Mountains
from the Alberta border to Yukon.
Soils generally consist of compact glacial
till with high amounts of clay and moderate to imperfect drainage.
Gray Luvisols are common throughout the region along with moderately
thick Mor humus forms. In some instances, the thick humus forms insolate
the soils late into the growing season resulting in permafrost pockets.
Organic soil development is common on the many wetlands found throughout
the landscape in subdued terrain.
Ecosystems
The following information is summarized
from DeLong, MacKinnon and Jang. (1990), MacKinnon, DeLong and Meidinger
(1990) and Meidinger and Pojar (1991).
Zonal vegetation in BWBSdk is typically
dominated by lodgepole pine and White spruce in the overstory. Soopolalie
(Sheperdia canadensis), highbush cranberry (Vibernum edule), prickly
rose (Rosa acicularis), step moss (Hylocomium splendens) and knight’s
plume moss (Ptilium crista-castrensis) are common in the understory.
Common zonal vegetation in the BWBSmw
subzone is Trembling aspen and White Spruce in the overstory. Understory
vegetation typically consists of highbush cranberry, prickly rose,
tall bluebells (Mertensiana paniculata), palmate colt’s foot
(Petasites frigidus var. palmatus), and step moss.
The BWBSwk is dominated by zonal vegetation
of black spruce, white spruce and subalpine fir in the overstory.
The understory is dominated by Labrador tea (Ledum groenlandicum),
black huckleberry (Vaccimium membranaceum), step moss and red-stemmed
feathermoss (Pleurozium schreberi).
Bog conditions are common throughout the
BWBS zone. On these sites, acidic conditions prevail and black spruce,
tamarack and sphagnum mosses (Sphagnum spp.) are common species in
these situations.
Grasslands occur sporadically in steep
south facing slopes along the Peace and Stikine Rivers.
Resources
Forestry activities are often restricted
to winter conditions when the ground is frozen on the many imperfectly
drained areas. Increased forestry harvesting has occurred due to new
technology, which allows the use of smaller diameter logs for a wide
range of forest products.
This region of British Columbia has been
surveyed extensively for oil and gas exploration and development.
Seismic survey lines are a common feature of the landscape in many
areas.
Agriculture is common use of sites on alluvial
plains and morainal deposits in the southern parts of the BWBS zone.
These sites are some of the most productives sites in British Columbia
for agriculture.
Hunting and fishing are the most common
recreational activities in this zone.
References
DeLong, C., A. MacKinnon, and L. Jang.
1990. A field guide for site identification and interpretation for
the northeast portion of the Prince George Forest Region. B.C. Min.
For., Res. Br., Victoria, B.C., Land Management Handbook. No. 22.
http://www.for.gov.bc.ca/hfd/pubs/docs/lmh/lmh22.htm
MacKinnon, A., C. DeLong, and D. Meidinger.
1990. A field guide for identification and interpretation of ecosystems
of the northwest portion of the Prince George Forest Region. B.C.
Min. For., Res. Br., Victoria, B.C., Land Management Handbook. No.
21
Meidinger, D. and Pojar, J. 1991. Ecosystems
of British Columbia. British Columbia Ministry of Forests.
330 pp. http://www.for.gov.bc.ca/hfd/pubs/Docs/Srs/SRseries.htm
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