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