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4. Socio-Economic Issues
The Vegetation Ecosystem
Tundra is a Lapp word that denotes a polar plain (Strub, 1996). Tundra is the dominant
vegetation region of northern Canada. Vegetation cover is sparse, next to zero toward the
pole but nearly continuous at the southern limit. The number of species in the high
latitudes (from 60 to 90 degrees) is smaller than that in lower latitudes. Many of the
species have relatives at mid-latitudes (from 30 to 60 degrees).
• The growing season of one to three months is short, and shadows are long, because of
the low angle of the sunlight.
• In the “polar desert,” as described by Strub (1996), precipitation is scarce and
averages about 100 mm (4 in.) annually.
• There is poor precipitation distribution due to snow drifting and poor drainage due to
the imperviousness of the permafrost table, which prevents deep root penetration and
keeps the shallow active layer cold enough to retard absorption of water by the roots.
• The fine-grained soil in the active layer is unstable due to soil heaving by freeze–thaw
cycling.
• There is a high plant mortality rate due to low winter temperatures and the drying
caused by the wind. Low temperatures prevent polar flora from contributing oxygen
to the atmosphere and absorbing carbon dioxide in significant amounts.
• Long nutrient cycles and high soil acidity, because of the low temperatures, inhibit
the decay of plants and animal remains.
• A short supply of the nutrients, particularly nitrogen and phosphorous, in the soil
retard the growth of vegetation.
• The ecosystem is very fragile; a decline in one species affects the other species.
Vegetation Adaptation
• Most polar plants hug the ground. Stems and leaves form a canopy that deflects the
wind and absorbs sunlight efficiently. Temperatures below the canopy are several
degrees higher than the ambient air.
• Dryad flowers, shaped to concentrate sunlight, turn to follow the path of the sun,
thereby raising the temperature of their critical parts by several degrees.
• Some plants grow hair as insulation. Others have frost-resistant structures.
PERD-079: Task 2 - <strong>Literature</strong> <strong>Review</strong> 87