The forest of four seasons
A temperate forest grows in the middle latitudes, between the tropics and the polar regions. It has four distinct seasons: spring, summer, fall and winter. Much of southern Canada, the eastern United States, Europe, eastern China and Japan was once covered in temperate forest.
Climate
| Feature | Temperate forest |
|---|---|
| Temperature | About −30 °C in winter to 30 °C in summer |
| Rainfall | About 750–1500 mm per year, spread through the year |
| Growing season | About 140–200 days |
| Soil | Rich and fertile |
Types of temperate forests
| Type | Trees | Where |
|---|---|---|
| Temperate deciduous forest | Broadleaf trees that drop their leaves: maple, oak, beech, birch | Southern Ontario and Quebec, eastern U.S., Europe |
| Temperate coniferous forest | Evergreen needle-leaf trees: pine, spruce, fir, cedar | Mountains of BC and Alberta |
| Mixed forest | Both deciduous and coniferous trees | Maritimes, central Ontario, Great Lakes–St. Lawrence region |
| Temperate rainforest | Huge conifers in a very wet climate | BC coast, including Haida Gwaii and the Great Bear Rainforest |
Why leaves change colour
Deciduous trees lose their leaves each fall to survive winter.
- As days get shorter and cooler, trees stop making chlorophyll, the green pigment.
- As chlorophyll breaks down, yellow and orange pigments that were hidden underneath show through.
- Some trees, like sugar maples, make new red pigments in fall.
- A layer of cells forms at the base of each leaf stem, and the leaf falls.
Dropping leaves helps trees save water in winter, when the ground is frozen and water is hard to get. It also prevents snow from piling on broad leaves and breaking branches.
The maple leaf on Canada’s flag celebrates these forests, and Canada produces about 70% of the world’s maple syrup, mostly in Quebec.
Forest layers
| Layer | What’s there |
|---|---|
| Canopy | Tall trees like maple, oak and beech |
| Understory | Smaller trees like dogwood and young saplings |
| Shrub layer | Bushes like raspberries and hazelnut |
| Herb layer | Wildflowers, ferns, grasses; many bloom early in spring before the canopy leafs out |
| Forest floor | Leaf litter, mosses, mushrooms |
Animals
Temperate forest animals must survive big seasonal changes.
| Strategy | Examples |
|---|---|
| Hibernation | Black bears enter a deep winter sleep; chipmunks and groundhogs hibernate |
| Migration | Many songbirds fly south for winter |
| Storing food | Squirrels bury nuts; blue jays cache acorns |
| Growing thicker coats | Deer and foxes grow winter fur |
| Staying active | Chickadees fluff feathers; deer browse on twigs |
Common animals: white-tailed deer, black bears, raccoons, red foxes, squirrels, owls, woodpeckers, salamanders and many insects.
The forest floor recycling system
Each fall, millions of leaves fall to the ground. Earthworms, insects, fungi and bacteria break down the leaf litter into rich humus. This returns nutrients to the soil, making temperate forest soils some of the most fertile in the world. That’s also why so much temperate forest was cleared for farms.
The temperate rainforest
Canada’s west coast has one of the world’s largest temperate rainforests. Moist air from the Pacific brings 1500–4000 mm of rain a year. Giant trees like western red cedar, Sitka spruce and Douglas fir can live over 1000 years and grow taller than 70 m. The Great Bear Rainforest is home to the rare white Kermode ("spirit") bear.
Threats
| Threat | Effect |
|---|---|
| Clearing for farms and cities | Most original deciduous forest in southern Ontario is gone |
| Logging | Removes old-growth trees |
| Invasive species | Emerald ash borer has killed millions of ash trees |
| Acid rain | Damaged forests in eastern Canada |
| Climate change | Shifts tree ranges; more pests and wildfires |
Common mistakes
- Thinking leaves turn colour because of frost. Shorter days are the main trigger.
- Thinking all trees in Canada lose their leaves. Conifers keep their needles.
- Thinking rainforests are only tropical.
Try it yourself
- Collect fallen leaves and identify the trees using a field guide.
- Crush a green leaf in rubbing alcohol (with an adult) and use paper chromatography to see the hidden pigments.
- Track a tree near your home through all four seasons with drawings or photos.
Quick recap
- Temperate forests have four seasons and rich soils.
- Deciduous trees drop leaves in fall; coniferous trees stay green.
- Leaves change colour as chlorophyll breaks down.
- Animals survive winter by hibernating, migrating or storing food.
- Canada has deciduous, coniferous, mixed and temperate rainforests.