echoesof.science · Ages 10–11
Rainforests: layers, soil and water
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Tropical rainforests grow between the Tropic of Cancer and the Tropic of Capricorn: mainly in South and Central America, West and Central Africa, Indonesia and South-East Asia. They have from about 2,000 mm to as much as 10,000 mm of rain a year and stay warm all year.
Rainforests cover only about 2–6% of Earth's surface, but more than half of the world's plant and animal species live in them. The Amazon alone has around 40,000 plant species and nearly 1,300 bird species.
There are four layers. Emergent trees stick out above the rest and face strong sun and wind; they have small, waxy leaves that lose less water. The canopy, 30–50 m up, cuts off most of the light and wind. The shady understory has small trees, vines and ferns with large leaves to catch the little light. The forest floor is the darkest layer.
Experiment: Do leaves give off more water in the sun? A fair test
- Choose two plants (or branches) of about the same size. Put one in the sun and one in the shade.
- Weigh each empty bag (or write down that it is dry).
- Put a bag over the same number of leaves on each plant and close it gently around the stem.
- As a control, close an empty bag in the sun and one in the shade.
- The next day, carefully remove the bags and compare the water inside. Weigh each bag again, or tip the water into a measuring spoon.
- Which plant transpired more? Did the empty bags collect any water?
| Bag | Water collected (g or spoonfuls) |
|---|---|
| Plant in the sun | Prediction |
| Plant in the shade | Prediction |
| Empty bag in the sun | Prediction |
| Empty bag in the shade | Prediction |
Questions
Name the four layers of a rainforest from top to bottom and give one fact about each.
Explain why rainforest soil is not very fertile even though so much grows there.
In your fair test, what did you change, what did you measure and what did you keep the same? Why did you use empty bags?
How do trees help to make rain in the Amazon?
Sources for every fact on this sheet: echoesof.science/school/rainforests/sources/