Page 693 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

Chapter 20 Terrestrial Biomes 657
▲Figure 20.14 A male elk (Cervus canadensis) in the boreal forest. [Steven k. Huhtala.]
3500 years old. The bark is fibrous and a metre thick and lacks resins, so it effectively resists fire. Imagine the lightning strikes and fires that must have passed by the Sherman tree in 35 centuries! Standing among these giant trees is an overwhelming experience and creates a sense of the majesty of the biosphere.
Soils of the boreal forest are characteristically acidic and leached of humus and clays. In certain regions, per- mafrost (discussed in Chapter 17) is coupled with rocky and poorly developed soils so that only trees with shallow root systems are present. The poor drainage conditions associated with summer thaw of the active layer results in the characteristic presence of muskeg (moss-covered) bogs. Global warming is causing increased thawing of
permafrost in forested regions; affected forests are dying in response to the resultant waterlogged soils.
Representative fauna in this biome include wolf, elk, moose (the largest member of the deer family), bear, lynx, beaver, wolverine, marten, small rodents, and migratory birds during the brief summer season (Figure 20.14). Birds include hawks and eagles, several species of grouse, Pine Grosbeak, Clark’s Nutcracker, and several species of owls. About 50 species of insects particularly adapted to the presence of coniferous trees inhabit the biome.
Temperate Rain Forest
The lush forests in wet, humid regions make up the temperate rain forest biome. These forests of broadleaf and needleleaf trees, epiphytes, huge ferns, and thick un- dergrowth correspond generally to the Marine West Coast climates (occurring along middle to high-latitude west coasts), with precipitation approaching 400 cm per year, moderate air temperatures, summer fog, and an overall maritime influence. In North America, this biome occurs only along narrow margins of British Columbia and the U.S. Pacific Northwest. Similar temperate rain forests exist in southern China, small portions of southern Japan, New Zealand, and a few areas of southern Chile.
The biome is home to bear, badger, deer, wild pig, wolf, bobcat, fox, and numerous bird species, including the Northern Spotted Owl (Figure 20.15). In the 1990s, this owl became a symbol for the conflict between species-preservation efforts and the use of resources to fuel local economies. In 1990, the U.S. Fish and Wild- life Service listed the owl as a “threatened” species under the U.S. Endangered Species Act, citing the loss
(a) Old-growth Douglas fir, redwoods, cedars, and a mix of trees, ferns, and mosses. Only a small percentage of these forests remain.
▲Figure 20.15 Temperate rain forest. [(a) Bobbé Christopherson. (b) Woodfall Wild Images/Photoshot.]
deciduous old-growth
(b) The Northern Spotted Owl, here with fledgling, is an “indicator species” representing the health of the temperate rainforest ecosystem in the U.S. Pacific Northwest.