Biomes

Factors determining the distribution of major life-zones Differential heating of the Earth’s surface by the sun The shape of the Earth Tilted axis and rotation of the Earth (seasonality) Distribution of water and land and the differences in their physical properties

Belts of different biomes parallel with the Equator Water movement disrupt this pattern

Tundra Between taiga and permanently frozen polar regions. Annual precipitation less than 250mm. Water not available all the time Summer: soil thaws, but half a meter down it remains frozen: permafrost No trees, bogs ponds and herbaceous plants. Woody plants (few) are dwarfs.

Taiga Coniferous forest Short cool summers Long dry cold winters Precipitation is 300-500mm annually in the form of snow. Stream and rivers. Firs, spruces, birches. Soil: shallow hummus layer poor in nutrients and acidic.

Grasslands Between forest and desert biomes. 250-600mm rainfall during mostly summer months Winter cold and dry. Huge amount of hummus (over 1 meter thick) America: Prairie; Eurasia: Steppe; South America: Pampa Large number of herbivores live there

Deserts Less than 250mm annual precipitation. Precipitation is unpredictable with long periods of drought Mild winters in warm deserts (Sahara) with few freezing days Cold winters with extended periods below freezing (Gobi desert) in cold deserts. Sparse plant cover A lot of reptiles and rodents. Most animals are nocturnal. Soil very poor in nutrients.

Savanna Biome between desert and tropical forest 900-1500mm rain with a wet season and a dry season. Temperature high all year long. Tree are drought tolerant (baobab, acacia) Soils are poor because thy are washed out during rainy season. Trees widely spaced, various species of grasses. Plant species is fire tolerant.

Rain forest Close to Equator. Temperature very even all year long. Annual rainfall is 2000-5000mm (up to 17 feet) per year. Humidity is very high Excess rainfall and rapid decomposition the soils are devoid of nutrients. Organic matter is in the form of decaying animals and organisms Many layers of canopy that support a lot of wild life

Aquatic Biomes (www.mbgnet.mobot.org) Largest part of the biosphere (75% covering the Earth surface). The most important biomes are there. Freshwater regions: low salt concentration (<1%) Ponds and lakes Streams and rivers Wetlands (marshes, swamps and bogs) Marine regions: ¾ of Earth’s surface Oceans (tropical and temperate) Coral reefs Estuaries. Shorelines.

Temperate Deciduous Forest Eastern North America and Europe Summers hot and humid, winters are cold Rainfall is between 750mm and 1500 mm per year Oak, maple, hickory, beech, chestnut, birch, fern, mosses and grasses. Foxes, wolves, deer, raccoons, squirrels.

Maintenance and change in ecosystems. Rules for maintenance: Constant energy (sun) Presence of producers Cycle of materials Changes in ecosystems: Some organisms are replaced by other kinds: ecological succession Stable community is a Climax community.

Succession Primary succession: new communities develop on land that is almost lifeless. Secondary succession: an existing community has been partially or totally destroyed and is replaced by others.

The human factor Growth of human population (7 billions individuals) Limiting factors can be food availability Carrying capacity: the size of a population supported by the environment.

Disruption of ecosystems Urbanization. Poor farming practices

Water Pollution Eutrophication (reduce size of lakes) Biological magnification Thermal pollution Oil spills

Air Pollution Aerosols Acids (causing acids rains) Chlorofluorocarbons (CFC’s) destroy the ozone layer.

How can we help? Controlling pollution Conserving natural resources: recycling Conserving soils cover crops Conserving forests: reforestation Conserving wildlife Controlling pests biologically