Page 691 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

Chapter 20 Terrestrial Biomes 655
areas of this region protected from fire, broadleaf trees are dominant. Into New England and westward in a narrow belt to the Great Lakes, white and red pines and eastern hemlock are the principal conifers, mixed with broad- leaf deciduous oak, beech, hickory, maple, elm, chestnut, and many others. In Canada, part of this forest biome is known as Carolinian forest and occurs in southern Ontario (Figure 20.10). The region is heavily populated, industrialized, and disturbed by agricultural activity. A nonprofit group called Carolinian Canada (www.carolinian .org/index.htm) works to protect and conserve this threat- ened forest ecosystem.
These mixed stands contain valuable timber, and log- ging has altered their distribution. Native stands of white pine in Michigan and Minnesota were removed before 1910, although reforestation sustains their presence today. In northern China, these forests have almost disappeared as a result of centuries of harvest. The forest species that once flourished in China are similar to species in east- ern North America: oak, ash, walnut, elm, maple, and birch. This biome is quite consistent in appearance from continent to continent and at one time represented the principal vegetation of the humid subtropical (hot sum- mer) regions of North America, Europe, and Asia.
A wide assortment of mammals, birds, reptiles, and amphibians is distributed throughout this biome. Rep- resentative animals (some migratory) include red fox, white-tailed deer, southern flying squirrel, opossum, bear, and a great variety of birds, including Tanager and Cardinal. To the west of this biome in North America are the rich soils and midlatitude climates that favour grass- lands, and to the north is the gradual transition to the poorer soils and colder climates that favour the conifer- ous trees of the northern boreal forests.
Boreal and Montane Forest
Stretching from the east coast of Canada and the Atlantic Provinces westward to the Canadian Rockies and portions of Alaska, and from Siberia across the entire extent of Rus- sia to the European Plain is the boreal forest biome, also known as the northern needleleaf forest (Figure 20.11). The northern, less densely forested part of this biome, transi- tional to the arctic tundra biome, is called the taiga. This biome is characteristic of microthermal climates (having a cold winter season and also some summer warmth); the Southern Hemisphere has no such biome except in a few mountainous locales. The needleleaf forests at high eleva- tions on mountains worldwide are called montane forests.
Boreal forests of pine, spruce, fir, and larch occupy most of the subarctic climates on Earth that are domi- nated by trees. Although these forests have similar veg- etation life forms, individual species vary between North America and Eurasia. The larch (Larix) is one of only a few needleleaf trees that drop needles in the winter months, perhaps as a defense against the extreme cold of its native Siberia (see the Verkhoyansk climograph and photograph in Figure 10.16). Larches also occur in North America.
This biome also occurs at high elevations at lower latitudes, such as in the Sierra Nevada, Rocky Mountains, Alps, and Himalayas. Douglas fir and white fir grow in the western mountains of Canada and the United States.
▲Figure 20.10 Mixed broadleaf forest, Toronto, Ontario. Fall colours in the foliage of the Carolinian Forest in rouge National Urban Park in Toronto. The term Carolinian is used mostly by Canadians to describe the northern extreme of the mixed broadleaf forest. It is an endangered ecosystem, threatened
by urbanisation and development, containing more rare species of plants and animals than any other region in Canada. [Bill Brooks/ Alamy.]
▲Figure 20.11 Boreal forest of Canada (boreal means “northern”). [robert Christopherson.]