Ecosystems

1. Ecosystems

2. Global distribution of ecosystems • Distribution of tropical rainforest, savanna grasslands and coniferous forests • Tropical rainforests- vegetation type, soil and how they adapt • Coniferous forests- vegetation type, soil and how they adapt • Savanna grasslands- vegetation type, soil and how they adapt • The human uses of tropical rainforest • The social, political and environmental issues involved • The human uses of savanna grasslands

3. An ecosystem is a living community of plants and animals within a natural environment. The distribution of ecosystems across the world is dependent on the climate and soil they rely on in order to grow.

4. Tropical rainforests are found in places with a hot (over 30°C) and wet (over 2000 mm) equatorial climate. Rainforestsgrow in the tropics, close to the equator and the plants have a twelve month growing season. As a resultant, the rainforest is the most luxuriant vegetation system in the world. Savanna Grasslands are located next to the tropical rainforests. The savanna climate has a distinct hot, wet season and a hot, dry season. The savanna changes as you move north or south from a mix of trees and grass to just grasses. Eventually, it gradually merges into the desert ecosystem. Coniferous Forests These grow in the northern parts of North America, Europe and Asia in places a long way north of the equator. It is very cold in the winter and the growing season is very short. Soils are often thin and poor.

5. TROPICAL RAINFORESTS Vegetation The tropicalrainforest is different from all other ecosystems because of its biodiversity. Over 50 species of tree may be found in only 1 hectare of soil in the rainforest. The forests appear to be evergreen but the trees are deciduous and take it in turns to lose their leaves. The rainforest is organised into five layers. From the top they are as follows; emergents, canopy, under canopy, shrubs, forest floor. Soil The profile of the soil in the rainforest is called a LATOSOL. Latosols are reddish brown and the red colour comes from the oxides of iron and aluminium in the soil. They are very deep soils. The heavy rain in the rainforest leads to leaching (minerals washed out) and this is why the top layer of soil is often light in colour. Adaptations As there is great competition for sunlight and water in the rainforest the trees try to grow very tall. They have a shallow spreading root system to collect as much nutrients as they can. The wide buttress roots at the base of the tall trees help to prevent them falling over. Many other plants have to devise methods of competing for light. Ferns on the forest floor are able to cope in low-light conditions. Lianas are creeping plants that grow up the tree trunks and use them to get to the sunlight. Parasitic plants such as orchids grow in cracks in the branches high up in the canopy.

6. Coniferous Forests • Vegetation • The forests are evergreen. The coniferous trees (fir, pine, spruce) are similar in height, shape and size. There are often only two or three species of tree in one area. Very few other types of vegetation grow in the forest. • Soil • The soil profile of a coniferous forest is called a PODSOL. The soil has a humus layer just below the surface. The A horizon is grey in colour as it has lost its minerals through leaching (washing out of minerals). The B horizon is a reddish-brown colour as the minerals lost from the layers above are deposited here. The C horizon consists of stones and rocks. • Adaptation • The vegetation in the forest make many adaptations due to the harsh, cold climate. Tree characteristics are as follows; • Conical shape- they are flexible and bend in strong winds • Downward sloping branches- snow slides off them more quickly • Evergreen- so that trees can grow as quick as possible in warm periods • Needle leaves- to reduce the loss of water • Thick bark- To protect the tree from severe cold

7. Savanna Grasslands Vegetation There are only two layers of vegetation in the grasslands- the grasses and the trees. Grasses are tall and form a continuous cover, whereas trees are dotted around and there can be wide spaces between them. A denser covering of trees shows places where more water is available. Soil During the dry season, minerals in the soil, such as calcium are drawn up to the surface by the high temperatures and high evaporation rates. Heavy rains in the wet season cause leaching, which washes the minerals deep into the soil. Adaptation The main problem for the vegetation is survival during the dry season. Most plants are xerophtytic (drought resistant). Grasses turn brown and die back in the dry season. Trees adapt to the drought by losing their leaves to reduce water loss or the leaves are small and waxy to reduce transpiration. The roots are usually long to reach underground supplies of water. Some trees have very thick bark to store water during the dry season e.g. baobab tree.

8. The Human Uses of the Tropical Rainforest • Humans use the rainforest in the following ways; • Logging- chopping down of trees • Ranching- large areas of trees chopped down for cattle farming • Mining – valuable minerals such as iron ore, bauxite and even gold. • Rubber tapping – some trees provide natural rubber from the sap • Tourism – increasing numbers of tourists want to visit the rainforest • Farming – farms vary from tiny subsistence farms to huge plantations growing a single crop such as palm oil

9. Impact on the rainforest • Social Issues • indigenous people e.g. Amerindians are left with out homes and many have been killed, either deliberately or by diseases introduced by people coming to the rainforest. • Too many tourists and tourist facilities can damage an area • Environmental Issues • Chopping down of large areas of woodland can influence global warming • Animals habitats are destroyed • Political Issues • Lots of groups do not agree about what should be done with the rainforest and this leads to great conflict

10. Human uses of Savannah Grasslands Local people are often nomadic and keep herds of sheep, cattle or goats.Some live in permanent villages and grow crops . One huge problem is desertification which mean the good land is turned in desert. This has been caused by overgrazing (too many animals) and overcultivation (growing crops every year and not letting the soil recover its fertility). Soil is either blown away in the dry season (dust storms) or washed away in the heavy rains in the wet season. Many tourists also visit the African savannas on wildlife safaris e.g. in Kenya. The wildlife is often disturbed and the people and vehicles damage the landscape.

11. Summary • An ecosystem is a living community of plants and animals within a natural environment. • The distribution of ecosystems across the world is dependent on the climate and soil they rely on in order to grow. • Tropical rainforests are found in places with a hot and wet equatorial climate. • Savanna Grasslands are found in areas with two different seasons (wet and dry). • Coniferous Forests These grow in the northern parts of North America, Europe and Asia where the climate is very cold and the growing season is very short.