A. Physical Patterns in a Changing World · Physical Patterns in a Changing World

Natural Vegetation Regions and How They Change

A3.9 A3.10About 50 minutes

Learning goals

I can describe the patterns and characteristics of major natural vegetation regions, such as tundra, boreal forest, grassland and tropical rainforest.
I can explain how climate, soil and landforms shape natural vegetation.
I can describe natural processes and human activities that change vegetation, such as climate change, deforestation and invasive species.

Words to know

natural vegetation
The plants that would grow in a place if people had not changed it.

vegetation region
A large area with similar natural plants, shaped mainly by climate and soil.

coniferous
Trees with needles and cones, such as spruce, pine and fir. Most stay green all year.

deciduous
Trees that lose their leaves in the fall, such as maple, oak and birch.

treeline
The edge beyond which it is too cold (or too high) for trees to grow.

deforestation
Clearing forests and not replacing them, for farming, logging, mining or building.

invasive species
A plant, animal or other living thing brought from somewhere else that spreads quickly and harms the local environment.

monoculture
Growing only one kind of crop or tree over a large area.

Why maples here and cactuses there?

In the fall, Ontario's maple trees turn red and orange. In the Sonoran Desert in the southwestern United States, giant cactuses stand on dry, rocky ground. In the Amazon, trees grow so tall and close that the forest floor is shady even at noon. Plants grow where the climate and soil suit them, so vegetation regions follow climate regions closely.

Tall saguaro cactuses with upturned arms stand among small shrubs on rocky ground below desert mountains. — Desert vegetation in the Sonoran Desert. Saguaros store water in their thick stems, an adaptation to a hot climate with very little rain. AI-generated image

Remember from Grade 4

You learned that Canada's regions have different natural vegetation, like tundra in the North, boreal forest on the Canadian Shield, prairie grassland in the Interior Plains, and temperate rainforest on the B.C. coast. Now let's look at these regions around the world.

Vegetation region	Climate	Plants	Where (examples)
Tundra	Polar: very cold, short summers, permafrost	No trees; mosses, lichens, grasses, low shrubs, small flowers	Northern Canada, Alaska, northern Russia, Greenland's coasts
Boreal forest	Continental/subarctic: long cold winters, short summers	Mostly coniferous (spruce, fir, jack pine, tamarack), with some birch and aspen	Across northern Canada, Alaska, Scandinavia, Russia
Temperate deciduous and mixed forest	Continental or temperate, with four seasons	Maple, oak, beech, birch, mixed with pine and hemlock	Southern Ontario and Quebec, eastern United States, western Europe, eastern China
Temperate rainforest	Mild, very wet	Huge trees: western red cedar, Sitka spruce, Douglas fir; ferns and mosses	Coast of British Columbia, southern Chile, New Zealand
Grassland	Semi-arid to moderate rain, often dry summers	Grasses and wildflowers; few trees except near rivers	Canadian Prairies, Eurasian steppes, Argentine pampas
Tropical savanna	Hot, with a wet and a dry season	Tall grasses with scattered trees	Much of central and eastern Africa, northern Australia
Desert	Dry (hot or cold)	Sparse plants with ways to save water: cactuses, succulents, deep or wide roots	Sahara, Sonoran Desert, central Australia
Tropical rainforest	Hot and wet all year	Tall trees in layers, vines; more kinds of plants and animals than any other land region	Amazon basin, Congo basin, Southeast Asia

Major natural vegetation regions.

What shapes vegetation?

Temperature and growing season: trees need a long enough warm season. North of the treeline, it is too cold for trees, so tundra plants grow low to the ground, out of the wind.
Precipitation: forests need more water than grasslands; deserts have the least.
Soil: rich, deep soil (like the Prairies') supports grasses and crops; thin, rocky soil (like much of the Canadian Shield) supports hardy conifers.
Landforms and elevation: on a mountain, vegetation changes as you climb, like travelling toward the poles. The forest gives way to alpine meadows, then bare rock and snow.

Vegetation zones on a high mountain: forest at the bottom, coniferous forest higher up, then alpine meadow, then rock and snow at the top, where it is coldest. Not to scale.

How vegetation changes

Natural processes:

Wildfire is a natural part of the boreal forest. Jack pine cones are sealed shut with resin and open in the heat of a fire to release their seeds, so the forest regrows.
Climate change is shifting regions: in parts of the Arctic, shrubs are spreading on the tundra as summers warm.
Floods, droughts, storms and insects also change vegetation.

Human activities:

Deforestation: large areas of the Amazon rainforest have been cleared for cattle ranching, soybean farms and logging.
Monoculture: in parts of Southeast Asia, rainforest has been replaced by plantations of a single crop, such as oil palm.
Overgrazing: too many animals eat the plants faster than they can regrow, leaving bare soil that erodes.
Soil erosion after land is cleared makes it harder for plants to grow back.
Invasive species: the emerald ash borer, a beetle from Asia, was found in Ontario in 2002 and has killed huge numbers of ash trees. An invasive reed called phragmites crowds out native plants in Ontario wetlands.
Protection and restoration: people also plant trees, restore wetlands and protect land. First Nations, Métis and Inuit communities lead many conservation projects. For example, in 2019 the Łutsël K'é Dene First Nation and its partners established Thaidene Nëné, a large protected area in the Northwest Territories.

Worked example

Let's explain a vegetation pattern

Travelling north from Toronto to the Arctic coast, the vegetation changes from maple and oak forest to spruce forest to treeless tundra. Explain why.

Identify the pattern: deciduous and mixed forest → boreal (coniferous) forest → tundra.
Link to climate: going north, the latitude increases, so it gets colder and the growing season gets shorter.
Explain each change: deciduous trees need longer, warmer summers. Conifers can survive long, cold winters and thin soils, so they take over in the boreal forest. Past the treeline, summers are too short and cold for trees, and permafrost stops deep roots, so only low tundra plants grow.
Conclude: the vegetation pattern follows the climate pattern.

Vegetation changes because the climate gets colder with a shorter growing season as you go north, and different plants are adapted to each set of conditions.

Travelling north from Toronto: broad-leaved forest gives way to boreal conifers, and past the treeline only low tundra plants grow. Not to scale.

Hands-on activity

Neighbourhood vegetation survey

You need: a notebook, a pencil, and a plant or tree identification app or field guide (optional). Go with a grown-up.

Walk around your block, a park or a schoolyard.
Make a tally of trees: coniferous (needles and cones) and deciduous (broad leaves).
Look for native plants (for example sugar maple, white pine, milkweed) and possible invasive ones (for example phragmites along ditches, or ash trees with D-shaped holes and peeling bark, a sign of emerald ash borer).
Note anything people have changed: lawns, planted gardens, paved areas.
Write two sentences: Is your area's vegetation mostly natural or changed by people? What vegetation region are you in?

What to look for: correct sorting of conifers and deciduous trees, and the idea that most city vegetation is planted, not natural. Don't touch or pick plants you can't identify, and wash hands afterwards.

Just for fun

Funny but true: many jack pine cones stay sealed shut with resin until a fire heats them up. They're the only pine cones that need to be "baked" before they're ready.

Your turn

What is natural vegetation?

Why are there no trees in the tundra?

Name two coniferous trees of the boreal forest.

Which vegetation region has more kinds of plants and animals than any other on land?

How do desert plants survive with so little water? Give one way.

Describe one human activity that changes vegetation, with an example.

How is climbing a mountain like travelling toward the poles?

More practice: warm-up

Do deciduous trees lose their leaves in the fall?

What vegetation region covers much of the Canadian Prairies?

Name a tree of B.C.'s temperate rainforest.

What insect from Asia has killed many ash trees in Ontario?

What is the line beyond which trees cannot grow called?

More practice: on your own

Explain why wildfire is not always bad for the boreal forest.

What is the difference between a savanna and a temperate grassland?

Why can replacing a rainforest with an oil palm plantation harm the environment, even though it is still full of trees?

How can overgrazing lead to soil erosion?

Name one way people are protecting or restoring vegetation.

Challenge

Predict how the treeline in northern Canada might change as the climate warms, and explain one effect on people or animals.

An invasive species spreads quickly where it is introduced, but it is not a problem in its home region. Suggest why.

Explain how climate, soil and vegetation interact on the Canadian Prairies.

Check your understanding

Quiz

Which vegetation region has no trees, with mosses, lichens and low shrubs?

Most trees in the boreal forest are...

Tall grasses with scattered trees in a hot climate with a wet and dry season describes a...

The emerald ash borer is an example of...

The main thing that shapes where vegetation regions are is...

Large areas of the Amazon rainforest have been cleared mainly for...

For parents and teachers

Big idea: Expectations A3.9 and A3.10 ask students to describe patterns and characteristics of major natural vegetation regions (for example grasslands, boreal forests, tropical rainforests, tundra) and the natural processes and human activities that change them (for example climate change, soil erosion, deforestation, monoculture, grazing, invasive species). This builds on the regions of Canada from Grade 4.

How to help: Do the vegetation survey together. Compare a vegetation map and a climate map in an atlas: they look alike. Check Ontario's government or conservation authority websites for local invasive species.

Common difficulties:

Thinking natural vegetation is whatever grows now: in cities and farms, most plants were planted by people.
Thinking all forest fires are bad: fire is natural in the boreal forest, though climate change is making fire seasons more severe.
Confusing coniferous and deciduous: tamarack is a conifer that does lose its needles in fall, a fun exception.

Safety: don't touch unknown plants (some, like giant hogweed, can burn skin); wash hands after outdoor surveys.