| Summary: | There are large climatic differences among the boreal regions of the world. The extreme continental climates of central Siberia, with a mean annual temperature of –11°C or colder and precipitation of only 150 mm, for example, contrasts strikingly with the semicoastal climate of Newfoundland, with a mean annual temperature of +5°C and precipitation of 1400 mm. Yet both are considered boreal. This wide range in mean annual temperatures translates into large variation in the soil thermal conditions. Although much of the northern region of the boreal forest is underlain by continuous and discontinuous permafrost, southern regions are entirely permafrost-free. Boreal Canada has been classified into four major ecoclimatic provinces (Ecoregions Working Group 1989). The Subarctic Ecoclimatic Province extends from treeline in northern Canada south to the border with continuous stands of closed spruce. It ranges from the highly continental areas of northern Yukon Territory to the wetter and somewhat warmer regions of the Labrador Peninsula. The Boreal Ecoclimatic Province includes the main body of the boreal forests of Canada from the Mackenzie River east to Newfoundland. It is a complicated province that has been divided into High, Mid-, and Low Boreal, with a wide range of climate conditions. The Subarctic Cordilleran Ecoclimatic Province occurs only at higher elevations in western Canada. Forested areas in this region are usually restricted to valley bottoms or low, south-facing slopes. The Cordilleran Ecoclimatic Province includes the mountain ranges along the west coast and the continental divide from Montana to Alaska and from the Yukon River south to the boundary with the coastal forests. The boreal portion of this province has climates similar to that of the eastern section of the Interior Highland Ecoregion of Alaska (Fig. 2.3, Gallant et al. 1995). Alaska does not fit well into these Canadian ecoclimatic provinces because of differences in elevation, the effects of the two east-west-oriented mountain ranges (the ...
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