IGCSE Geography / Rural environments

The forest biomes

Edexcel International GCSE Geography (4GE1), chapter 5: Rural environments, specification point 5.1a. Free lesson.

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Forest biomes differ in climate, vegetation and how their plants survive. Comparing tropical rainforest, temperate forest and boreal forest helps you link each biome’s conditions to its tree adaptations.

What a tropical rainforest climate graph shows

A climate graph shows the usual rainfall and temperature through a year. In Manaus, in the Amazon at 3°S, rainfall is high in every month and totals about 2,300 mm. Temperature stays almost level at about 26 to 28 °C, so there is no cold winter or marked summer. August is drier than other months, but it still has rain. Read the rainfall bars from the left axis and the temperature line from the right axis. March is the wettest month, with 314 mm. August is the driest, with 58 mm. A tropical rainforest climate is hot all year and wet all year, with over 2,000 mm of rain.

How tropical rainforest trees grow in layers

Heat and rain support very high biodiversity, meaning many different species. The Amazon holds about 1 in 10 of all known species. Trees grow in layers because light is strongest above the forest and limited below the canopy. Emergents are the tallest trees, above the rest of the forest and in full sunlight. The canopy is an unbroken roof of leaves that catches most of the light. Most forest animals live here. The under canopy contains young trees growing in shade. The forest floor is dark and damp, so only plants that cope with deep shade grow there. Buttress roots…

Why rainforest soil is poor

Nutrients are minerals that plants need to grow. Although rainforest vegetation is rich, most nutrients are stored in living trees rather than in the soil. The forest keeps nutrients moving quickly through a cycle. Evergreen trees drop some leaves throughout the year. Hot, damp conditions make dead leaves decay quickly. Shallow roots take up the released nutrients quickly, so they are stored in the trees. Little stays in the soil. Heavy rain can also wash nutrients out of the soil, a process called leaching. Clearing trees breaks this cycle, so the forest can no longer recycle…

How temperate and boreal forests differ

Further from the Equator, temperate and boreal forests both have to survive winter. Their climates and tree types differ, so each has its own adaptations. Temperate forest grows in eastern USA and western Europe. It has a mild yearly mean temperature of about 10 °C and 750 to 1,500 mm of precipitation. Oak and beech are deciduous, meaning they lose their leaves in autumn. This saves water and energy through winter. Boreal forest, also called taiga, crosses Canada and Siberia between 50°N and 60°N. Winters can reach −40 °C and summers are about 10 °C. Precipitation is 300 to…

How to explain a rainforest plant adaptation

For a two-mark explanation, link a feature of the plant to the rainforest climate, then explain how that feature helps it survive.

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