Tropical Rainforests

Tropical Rainforests • Climate • Distribution of Rainforest • Structure of the Forest • Plant adaptations • Threats to the forest • Useful products

Distribution of Rainforests

Climate • The temperature averages 28-30°C all year but gets warmer in March and September when the sun is not directly overhead and there is less cloud. • There is a convectional storm almost every afternoon except in March and September when, because there is less sunshine, there is less evaporation so the atmosphere is not so full of moisture and there are fewer clouds. • The climate is described as humid

Structure of the Forest Emergents Canopy Under canopy Shrub layer Groundlayer There are 5 layers in the forest

Structure of the Rainforest EMERGENT TREE CANOPY UNDER CANOPY SHRUB LAYER GROUND LAYER

Plant adaptations 1. Emergents and 2. the Canopy • Many plants have waxy leaves and ‘drip tips’ to allow heavy rainfall to run off. • The canopy and the emergents have buttress roots, to anchor the tree. • Large leaves and dark green foliage to maximise photosynthesis. • These emergent trees grow to over 40m as they try to gather the maximum amount of sunlight. • The canopy forms a closed layer which allows little light through. • There is a huge amount of growth in all layers every year. • The increase in the Biomass is balanced by the amount of decay. This is Nutrient cycling. This can be shown in a Gersmehl Diagram. (see slide 15)

3. The under canopy • In this layer plants have to be shade tolerant; they have very big and very dark green leaves. • There are often few branches on the tall, straight trunks. • Flowers are very bright to attract insects; the air is too still for wind pollination. • There are sometimes parasitic plants living on the trunks of trees: they get their food from the host tree. • Many of the plants have valuable fruits such as Brazil nuts, bananas, mangoes, rubber

4. The shrub Layer • In this layer the shrubs are bushy and have many stems • Shrubs have dark green leaves at the top of the plant • The plants are shade tolerant • They often have bright flowers which are strongly scented • Tea, coffee and cocoa are crops that grow naturally in this layer

5. Ground Layer • It is very dark on the forest floor • Ferns and orchids are common plants at this level. Some of the plants are parasitic. • There are many gaps between plants but it is very difficult to get around due to the tangle of vines and dead, fallen branches. The Litter layer is quite thick but • Plant and animal material decays quickly in the hot, humid conditions. This is the Litter layer.

Threats to the Forest • An area of forest the size of Belgium is clear felled for timber every year • Local people have growing populations and need farmland • Timber from the tall, straight trees is much sought after for building and for furniture • Big business wants to extract resources from under the forest • Hydro-electric schemes flood the forest • Accidental fires burn out of control Satellite image of deforestation in theAmazon region, taken from the Brazilian state of Para on July 15, 1986. The dark areas are forest, the white is deforested areas, and the gray is regrowth. The pattern of deforestation spreading along roads is obvious in the lower half of the image. Scattered larger clearings can be seen near the center of the image.

Glossary Biomass: Living and dead matter produced, including plants and animals. (Kg/m2/annum) Canopy: The highest layer of the rainforest, made up of the tops of trees. Animals such as howler monkeys, red-eyed tree frogs, sloths and parrots live here. Equator: An imaginary circle around the earth, equally distant at all points from the North and South poles. It divides the earth into two halves - the Northern and Southern Hemispheres. Emergent: The tops of the tallest trees in a rainforest. Evaporate: When moisture changes from liquid to gas in the air. Extraction: To remove something (for example, to take out Brazil nuts from the Amazon rainforest). Forest Floor: The ground layer, made up of tree roots, soil and decaying matter. Mushrooms, earthworms, and elephants all make their homes here. Greenhouse Effect: The warming of the planet caused by chemicals which trap heat in the air. This process is being sped up by humans who put too many heat-trapping chemicals into the air. Some causes include car exhaust, factory smoke, and burning rainforests. Interdependence: The concept that everything in nature is connected to each other, and cannot survive without the help of other plants, animals and abiotic factors (such as sun, soil, water and air) around it. Nutrients: Food needed for growth by living things. Species: A distinct kind of plant or animal that has many common characteristics or qualities. Sustainable: Using products of the forest in a way that does not permanently destroy them, so that people in the future can also use them. Tropic of Cancer: A circle around the earth, parallel and to the north of the equator. Tropic of Capricorn: Similar to the Tropic of Cancer, but to the south of the equator. Understorey: The second layer of rainforests, made up mostly of young trees and shrubs. Animals that live here include jaguars, tapirs, snakes, and woodpeckers.

Additional Glossary • Buttress roots– wide spreading roots like scaffolding that support the very tall emergent and canopy trees. • Climogram- a graph that shows temperature and rainfall on double axes. This is useful for describing climate and comparing the climate of two or more places. • Convectional storm- rain that is the result of early evening cooling of moist air so that the vapour condenses and a short heavy storm happens • Humid- the air is almost saturated with moisture and cooling a small amount will result in rainfall • Nutrient Cycling– the process of material dropping to the forest floor, decaying and the nutrients being added to the soil then being taken up by plants to make new growth. • Parasitic- a plant or animal that lives on and gets its food from another species • Photosynthesis- the biological process that uses sunlight, water and carbon dioxide to produce food for the plant and oxygen. The plants need to have Chlorophyll in their leaves for this to happen

Useful Products It is difficult to know how many useful products come from the rainforest; many species of plant and animal have yet to be studied. However we do know of many food crops such as coffee, cocoa, tea, Brazil nuts, Oil palms, coconuts etc. that are found in tropical forests and can be farmed and harvested. Raw materials such as Copra, Sisal, Hemp, Mahogony, Teak, Rubber are all rainforest crops There are huge deposits of useful minerals under the forest e.g. Iron ore, Bauxite, Gold, Silver, Tin and Diamonds The high rainfall and fast flowing rivers make Hydro Electricity cheap once the dams and generators have been installed. Many medicines such as quinine for Malaria, Aspirin and several anti-cancer drugs have been extracted from Rainforest plants.

Gersmehl Diagram for the Rainforest Sunlight Animal waste + Decay Harvest Biomass Leaf fall Back to Emergents slide Each circle represents a store of nutrients. Each arrow represents a flow of nutrients. The size of the circle is proportional to the volume of nutrients stored. The width of the arrow is proportional to the volume of nutrients flowing along that route. Litter Nutrient Take up Decay Water Soil Weathered Rock Erosion

Tropical Rainforests