4.1.1 Biomes (Cambridge International AS Environmental Management)
Exam board Cambridge International · ASUpdated 2024-03-11
Terrestrial Biomes
Spec point —
4.1.1
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Biomes are large-scale ecological communities or ecosystem types that are characterised by their dominant vegetation, climate and other abiotic factors that shape their biotic communities
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Biomes cover large geographic areas (different ecosystems can be found within a single biome):
- These larger zones have similar climatic and ecosystem characteristics
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Terrestrial biomes (i.e. non-aquatic biomes) are classified into four major classes:
- Forest
- Grassland
- Desert
- Tundra
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These major classes can be divided into further categories, for example:
- Forest biomes are dominated by trees and are categorised into tropical rainforests, temperate deciduous forests and boreal forests
- Grassland biomes are characterised by grasses and herbaceous plants and are categorised into savanna and temperate grasslands
- Desert biomes are characterised by low rainfall and are dominated by cacti and other drought-resistant plants - they can be further divided into subcategories such as hot deserts, cold deserts, coastal deserts and semi-arid deserts
- Tundra biomes are found in high latitudes and are characterised by low temperatures and permafrost - they can be further divided into subcategories such as arctic tundra and alpine tundra
Terrestrial biomes of the world
Forest
Forest Biomes
| Characteristics | Tropical rainforest | Temperate forest | Boreal forest |
|---|---|---|---|
| Location | - Low latitudes - Within Tropics: 23.5° north and south of equator - E.g. Amazon in South America, New Guinea, Southeast Asia, Zaire Basin | - Between 40°–60° north and south of equator - E.g. Western Europe, northeast USA, Eastern Asia | - Between 50°–60° north and south of equator - E.g. Canada, Russia, Scandinavia |
| Annual precipitation | - Over 2000 mm | - 750–1500 mm (all year round) | 300–900 mm (all year round) |
| Temperature range | - 26 to 28°C | - Over 0° C in winter - 20 to 25°C in summer | - -30°C in winter - Up to 20°C in summer |
| Seasons | - No seasons: hot and wet all year round | - Four seasons of equal length | - Two main seasons: winter and summer |
| Growing season | - All year round | - 6–8 months | 2–3 months |
| Soils | - Relatively infertile due to leaching and rapid uptake of nutrients by plants | - Relatively fertile and nutrient rich due to decomposition of organic matter over autumn and winter | - Not very fertile: often acidic, with permafrost - Shallow soil with a thick litter layer due to slow decomposition |
| Biodiversity | - Approx. 50% of world's plant and animal species live within the rainforest biome - Example flora: mahogany, teak trees, lianas, orchids - Example fauna: Toucans, jaguars, frogs, snakes | - Wide range of animals and plants with higher biodiversity than boreal forests - Example flora: deciduous trees e.g. beech, oak, birch - Example fauna: deer, rabbits, squirrels, bears | - Less biodiverse than temperate forests - Example flora: coniferous trees - Example fauna: squirrels, bears, reindeer, wolves |
Grassland
Grassland Biomes
| Characteristics | Savanna | Temperate grasslands |
|---|---|---|
| Location | - 5°–30° north and south of equator - North and south of tropical and monsoon forest biomes - E.g. central Africa: Tanzania, Kenya | - 40°–60° north and south of equator - E.g." veldts" of South Africa, "pampas" of Argentina, "steppes" of Russia, "plains" of USA |
| Annual precipitation | - 800–900 mm | - 250–750 mm |
| Temperature range | - 15–35°C | - -40 to 40°C |
| Seasons | - Wet and dry season | - Four seasons |
| Growing season | - During wet season (4–5 months) | - During summer (dependent on temperature) |
| Soils | - Free draining with thin layer of humus - Not very fertile: most nutrients near surface | - Fertile soil |
| Biodiversity | - Wide range of plant and animal species - Greatest diversity of hoofed animals - Grasses, baobab and acacia trees - Zebras, elephants, giraffes | - Large numbers of plant and animal species - Grasses, sunflowers - Bison, antelopes, rabbits |
Desert
Desert Biomes
| Characteristics | Hot desert |
|---|---|
| Location | - 15°–30° north and south of equator - North Africa e.g. Sahara, Southern Africa e.g. Kalahari and Namib, Australia, Middle East |
| Annual precipitation | - Below 250 mm |
| Temperature range | - Daytime temperatures can reach 50°C but average around 25°C - Night time temperatures below 0°C |
| Seasons | - Summer and winter |
| Growing season | - All year round |
| Soils | - Infertile, dry |
| Biodiversity | - Low biodiversity - Cacti, yucca - Spiders, scorpions, camels, meerkats |
Tundra
Tundra Biomes
| Characteristics | Tundra |
|---|---|
| Location | - North of the Arctic Circle and Antarctica |
| Annual precipitation | - Less than 250 mm |
| Temperature range | - Below 0°C for 6–10 months |
| Seasons | - Winter and summer |
| Growing season | - 6–10 weeks |
| Soils | - Thin infertile soil - Permafrost |
| Biodiversity | - Low biodiversity - Small grasses, mosses, lichen - Snowy owls, snow bunting, tundra swan - Arctic foxes, hares and wolves - Polar bears, musk ox and caribou |
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