Nazov Skoly ECOSYSTEMS Project Geography year: 2007/2008 Meno Trieda An ecosystem is a living community of plant and animals sharing an environment with non-living elements such as climate and soil. Ecosystems exist on a variety of scales. An example of a small scale ecosystem (micro) is a pond. A medium scale ecosystem (messo) could be a forest. The tropical rainforest is an example of a very large ecosystem (biome). Sunlight is the main source of energy. This allows the plant to convert the energy by photosynthesis. This allows the plants to provide food for some animals, birds and fish. These are called Herbivores. The other animals eat the animals that have eaten the plants. These are Carnivores. This process is called the FOOD CHAIN. The World has many different ecosystems. Each one has its own climate, soil, plants and animals. Tropical rainforests: Tropical rainforests are rainforests generally found near the equator. They are common in Asia, Africa, South America, Central America, and on many of the Pacific Islands. Rainforests are characterized by high rainfall. This often results in poor soils due to leaching of soluble nutrients. Rainforests are home to two-thirds of all the living animal and plant species on the planet. It has been estimated that many hundreds of millions of new species of plants, insects, and microorganisms are still undiscovered and as yet unnamed by science. Tropical rainforests are also often called the "Earth's lungs", however there is no scientific basis for such a claim as tropical rainforests are known to be essentially oxygen neutral, with little or no net oxygen production. Taiga: Taiga (or Boreal Forests) represent the largest terrestrial biome. Taiga occurs between 50 and 60 degrees north latitudes, boreal forests can be found in the broad belt of Eurasia and North America. It is also found in Siberia, Scandinavia, Alaska, and Canada. Taiga is a belt of coniferous forest found close to Arctic Tundra. Coniferous trees are needle-leaved trees that are usually evergreen and shallow rooted and usually bear cones. Coniferous trees are tolerant to a wide range of soils and climates. It is therefore suited to the thin, nutrient poor and acidic soils common in the extreme northern latitudes. The worst impact on taiga is done by human. Human needs wood for many purposes due to this tree-cutting in taiga is very often. For example in Canada, less than 8% of the Boreal forest is protected from development and more than 50% has been allocated to logging companies for cutting. Savanna: A savanna is a grassland scattered with shrubs and isolated trees, which can be found between a tropical rainforest and desert biome. There is not enough rain falls on a savanna to support forests. Savannas are also known as tropical grasslands. They are found in a wide band on either side of the equator on the edges of tropical rainforests. Savannas have warm temperature all the year round. There are actually two very different seasons in a savanna; a very long dry season (winter), and a very wet season (summer). In the dry season only an average of about 4 inches of rain falls. Between December and February it does not rain at all. Oddly enough, it is actually a little cooler during this dry season. Desert: Deserts take up one-third of the Earth's land surface. They are mainly found around the Tropics of Cancer and Capricorn. A desert is a landscape form or region that receives very little precipitation per year. Deserts are defined as areas that receive an average annual precipitation of less than 250 mm. Deserts has high daytime temperatures (in summer up to 60 °C), and low night-time temperatures (in winter down to 0 °C) due to extremely low humidity. Water acts to trap infrared radiation from both the sun and the ground, and dry desert air is incapable of blocking sunlight during the day or trapping heat during the night. That is why the difference between night and day temperature is so big. Tundra: Tundra is the coldest of all the biomes. Tundra comes from the Finnish word tunturi, meaning treeless plain. It is noted for its frost-molded landscapes, extremely low temperatures, little precipitation, poor nutrients, and short growing seasons. Dead organic material functions as a nutrient pool. Arctic tundra is located in the northern hemisphere, encircling the north pole and extending south to the coniferous forests of the taiga. The arctic is known for its cold, desert-like conditions. The growing season ranges from 50 to 60 days. The average winter temperature is -34° C (-30° F), but the average summer temperature is 3-12° C (37-54° F) which enables this biome to sustain life. Rainfall may vary in different regions of the arctic. Yearly precipitation, including melting snow, is 15 to 25 cm (6 to 10 inches). Soil is formed slowly. A layer of permanently frozen subsoil called permafrost exists, consisting mostly of gravel and finer material. When water saturates the upper surface, bogs and ponds may form, providing moisture for plants. There are no deep root systems in the vegetation of the arctic tundra, however, there are still a wide variety of plants that are able to resist the cold climate. There are about 1,700 kinds of plants in the arctic and subarctic.