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