IB Environmental Systems and Societies/Biomes

2.4 Biomes


2.4.1 Define the term biome.

  • A collection of ecosystems sharing similar climatic conditions; for example, tundra, tropical rainforest, desert.
  • Int: Biomes usually cross national boundaries (biomes do not stop at a border; for example, the Sahara, tundra, tropical rainforests).

2.4.2 Explain the distribution, structure and relative productivity of tropical rainforests, deserts, tundra and any other biome.

- Tropical Rainforests:

  • High productivity
  • High precipitation (2500 mm yr¹) throughout the year
  • High insolation
  • High temperature (26 ʻC)
  • Good nutrient cycling = High rate of decomposure
  • Highest NPP

- Temperate Forests:

  • Medium productivity
  • 4 seasons (Insolation and temperature varies)
  • Good growing season in the summer but limited in the winter
  • High temperatures and insolation in the summer = Greater productivity
  • Rainfall between 500 and 1500 mm yr¹
  • Second highest NPP

- Tundra:

  • Low productivity
  • Lowest of precipitation (50 mm yr¹)
  • Low insolation (Days are shorter)
  • Low Temperature
  • Poor nutrient cycling because itʼs locked in the permafrost therefore low rate of decomposure
  • For 1-2 months the productivity is very high because the sun is up for almost the whole day

- Deserts:

  • Very low productivity
  • Low precipitation (Under 250 mm yr¹)
  • High insolation, but all water is evaporated or absorbed by the ground
  • Hot days & Cold nights
  • Low nutrient cycle
  • Species adapted to survive

- Grassland:

  • Wide diversity, but low levels of productivity
  • Enough precipitation to prevent deserts forming, but not enough to support forests
  • Nutrient cycle is sufficient
  • Insolation, precipitation and evaporation rates are balanced
  • Grass can grow under the surface even in cold periods, waiting to emerge until the ground warms