Between the tundra and the closed-canopied boreal forest is a vast region of largely undisturbed, open-canopied conifers with a ground cover of lichens (Figure 26.1). This region has been called various names in the North American literature: subarctic forest, lichen woodland, hemiarctic, and spruce woodland. Refer to Löve (1970) and Blüthgen (1970) for the semantics of these terms.
The subarctic woodlands are primarily climatic in origin, occupying the transitional areas between the summer location of Arctic airstreams and more southern airstreams. As in all transition zones, small variation in the primary forcing variable changes the vegetation composition and structure. This change in airstream position interacts with the available plants, landforms, elevations, substrates, and fire regime to create a vegetation mosaic reflecting past and present interactions.
The North American subarctic woodland is one of the last remaining extensive and continuous ecosystems (Figure 26.2a). It covers approximately 2 million square kilometers, most of which is without roads or permanent settlements. Hunting, trapping, and some mineral extraction are the primary land uses. The subarctic has a population of indigenous people whose way of life is still strongly related to the land. Furthermore, during part of the year it is the home of caribou (Rangifer tarandus), the last large migratory ungulate herd in North America.
The subarctic woodland in North America (Figure 26.2a) occurs from the northern interior of Alaska, cutting through the Richardson Mountains and north of the Mackenzie Mountains, to the south end of Hudson Bay.