Natural+Vegetation

Vegetation Regions
 media type="file" key="Natural Vegetation 1.mp3" width="240" height="20"

Natural vegetation refers to those plants that grow without any human interference. Natural vegetation is usually quite different from plants that people cultivate for food and use in industry. Different types of natural vegetation grow in response to different climatic and soil conditions.

Geographers have identified seven natural vegetation regions across Canada. These regions are composed of three types of natural vegetation: tundra, forest, and grassland. Of these, forest vegetation covers most of Canada.

Tundra
The tundra is the most northerly vegetation region of Canada. It is located above the tree line, which marks the northern boundary of tree growth. Trees do not grow in the tundra because the climate is too cold and dry. Most of the tundra has permafrost, or permanently frozen ground. Only the top metre or so of permafrost, known as the active layer, thaws during the short summer. Water cannot drain downward, so the surface remains water-logged. This thawing permits a very short growing season. Small shrubs, mosses, and lichens grow close to the ground where they soak up as much heat as possible from the earth. Lichens are slow-growing plants that cling to rocks. Tundra plants bloom and mature very quickly to produce their seeds before the cold weather returns. There is very little humus in the tundra's thin layer of soil because of the small amount of vegetation, the water-logged nature of the soil, and the cold climate. The lack of vegetation limits the variety of wildlife as well as the population of each species.

1. Describe permafrost, in your own words. 2 Marks

Boreal and Taiga Forest
To the south of the tundra is the boreal and taiga forest, the largest vegetation region in Canada. It is separated from the tundra by the tree line. North of this line, it is too cold for trees to grow. Coniferous trees grow south of this tree line because there is a longer growing season and more precipitation than in the tundra. Coniferous trees, or evergreens, lose some needles throughout the year but are never bare. Since they don't drop many needles, the humus layer beneath them is very shallow. This gives the topsoil a grey colour. The needles are acidic, so they make the soil acidic. Rainfall and snow melt wash away many soluble minerals.

2. Why is the humus layer here so shallow? 2 Marks

Mixed Forest
South of the boreal forest in eastern Canada is a mixed forest of coniferous and deciduous trees. Spruce, fir, pine, cedar, and hemlock are found in the same forest with maple, beech, ash, oak, and birch. This variety of trees bas provided an excellent resource for the lumbering industry. Today, less than half of the forest remains in the southern part of the region because of farming, lumbering, urban development, and transportation routes. Along the exposed coastlines of the Maritime provinces where the cold winds create a harsher climate, the forest may give way to small shrubs, such as junipers, that grow close to the ground for protection.

The mixed forest is a transition zone between the boreal forest to the north and the deciduous forest to the south. Both coniferous and deciduous trees can survive in the warm summers and cool winters. The regular, abundant precipitation in this region is suitable for both deciduous and coniferous trees. The humus created from the leaves of such a wide variety of trees creates a deep grey-brown topsoil rich in minerals. Because humus holds water, fewer soluble minerals are removed from the topsoil in mixed forest than in boreal forest. Soils in mixed forest regions are suitable for farming.

3. Why would you get better soil for farming in mixed forests than you would in Boreal forest? 2 Marks

Deciduous Forest
The only deciduous forest in Canada is found in southwestern Ontario. It is the northern portion of the large deciduous forest regions of the northeastern United States. Only small remnants of this forest remain since most of it has been cleared for farming and urban development.

The summers in southwestern Ontario are long and hot, the winters relatively mild, and the precipitation plentiful. These conditions are ideal for hardwood trees such as maple, beech, hickory, ash, and black walnut. These trees need at least five months of warm weather to store up energy in the form of sap in their roots and trunk to survive the winter.

The soils of this region are similar to those of the mixed forest but contain more humus and are less acidic because of the greater number of deciduous trees. The humus-rich topsoil is dark brown in colour. Some of the soluble nutrients are removed from the topsoil by the abundant rain. Still they are the most fertile soils of eastern Canada.

4. What is missing in this vegetation zone that would have made the soil acidic if it were present?

Grasslands
The grasslands, or the prairies, are located in the southern part of Manitoba, Saskatchewan, and Alberta. The climate here is too dry for most species of trees to survive. Some, such as trembling aspen, willow, and spruce, grow in river valleys where more moisture is available. Grass, however, is suited to this dry climate. The deep intertwined root system of the grass forms a sod mat. This sod mat absorbs and stores moisture, and holds the soil in place. The grass dies off on the surface if it doesn't find enough water, but its roots remain alive. When moisture returns, the grass sprouts again.

The grasslands consist of three sub-regions. The driest areas of southern Saskatchewan and Alberta make up the short-grass prairie. Drought-resistant short grasses, sagebrush, and cactus are the only types of vegetation which can survive here. The warm, dry climate limits the growth of vegetation which, in turn, limits the amount of humus produced in the soil. The limited rainfall and high evaporation have created calcified soils that are unsuitable for crops. The land can be used for grazing animals, particularly cattle.

Surrounding the short-grass prairie is a region where increased precipitation encourage the growth of taller grasses.This long-grass prairie is ideal for growing grains and oil seeds. Year after year as the tall grasses die in the fall, they produce large amounts of humus which results in a rich, black soil. The rainfall is just enough to keep the minerals within easy reach of the grass roots. This is the richest soil in Canada and produces some of the best grains in the world. Between the warm dry grasslands and the cooler, wetter boreal forest is the third grassland sub-region called parkland. This is a transition zone of long-grass prairie dotted with clumps of trees. Coniferous trees are more common in the northern part of the parkland, while deciduous trees dominate in the southern part.

5. What factor limits the amount of humus produced in short grassland soil? 1 Mark 6. Why does long grass prairie have more humus? 2 Marks 7. What is the third type of grassland called? Why do you think it has this name? 2 Marks

Cordilleran Vegetation
In the Cordillera, temperatures are warmer in the valleys than high in the mountains.The rainfall on the west side of a mountain is more likely to be heavier than on the east side. As a result, Cordilleran vegetation varies greatly. Grasses and cactuses grow in dry, hot valleys on the east side. Here the sons are similar to that found in the prairie grasslands. Irrigation is often required for agriculture.

Vegetation also changes as altitude increases. Forests of coniferous trees grow on louver slopes where precipitation is heavier. These forests are important to the logging industry of British Columbia. The vegetation on the higher slopes of the Cordilleran mountain ranges is similar to that of the tundra. Above the tree line there are only meadows of flowers and shrubs. On the very highest slopes, no vegetation can survive. Here, there is only bare rock, snow, and ice.

Soils of all types are found on the mountains of the Western Cordillera. The distribution of each soil type depends on the particular elevation, slope, rainfall, and vegetation cover of each area within the mountain range. Soil characteristics can change completely in a short distance.

8. Is there one type of soil in the Western Cordillera? Why or why not? 2 Marks

West Coast Forest
Along the West Coast of Canada grow lush forests of Douglas fir, Sitka spruce, red cedar, and western hemlock. The heavy rainfall plus the mild climate of the coastal region provide excellent growing conditions for the trees of this temperate rainforest. Trees more than 1 m in diameter and over 50 m high are common. These splendid trees have played a crucial role in British Columbia's forest industry. Some of the old-growth forests have become the focus of environmental groups who wish to protect these ancient trees. The lush vegetation provides a lot of plant material to make humus but the high rainfall leaches minerals deep into the soil.

9. If the high rainfall pushes the minerals deep into the soil, could small plants still use these minerals? What about the trees? Why? 3 Marks

IN CLOSING...
In southern Canada, there is little natural vegetation left because most of the land bas been taken over for farming, lumbering, or the building of cities. In many areas, the large trees of the old-growth forests have been replaced with younger smaller trees. In many other places they have not been replaced at all.

The different vegetation regions in Canada provide us with many products. The coniferous trees of the boreal forest are the raw materials for pulp, paper, and lumber. Deciduous trees provide wood for eastern Canada's furniture industry. The huge trees of the West Coast forest provide lumber for use in Canada and for export. Beef for your next barbecue may come from cattle raised on the short grasses of the western prairies and may be cooked using charcoal from the hardwood trees of eastern Canada. Wheat for your bread might be grown in the long-grass prairies.

10. What do you think the danger(s) might be in not replacing the trees that we chop down? 2 Marks

Pair Up Activity
1. Summarize your section(s). Highlight the most important points, like we've done previously.

2. Provide a picture that shows your natural vegetation region(s)

3. Give the name of one major city in your region (or largest population centre)

4. Give the name of the closest body of water to your region (or in your region)

5. Give the names of what provinces/territories that lie within your region(s)