Tropical Rain Forests

Tropical rainforests and man’s impact on this biome

What is biome? • A biome is a large geographical area of distinctive plant and animal groups, which are adapted to that particular environment. The climate and geography of a region determines what type of biome can exist in that region. Major biomes include deserts, forests, grasslands and tundra. Each biome consists of many ecosystems whose communities have adapted to the small differences in climate and the environment inside the biome.

World distribution of TRF • Tropical rainforest are found between 10 ° N and 10 ° S latitude. They can be found in three major geographical areas around the world:

• Central America in the Amazon river basin. • Africa - Zaire basin, with a small area in West Africa • Indo-Malaysia - west coast of India, Assam, Southeast Asia, New Guinea and Queensland, Australia.

Distribution

Climate in TRF • Temperature • High and constant throughout the year • (because the rainforests are located near the tropics where the angle of the sun is always high) • Mean annual temperature is high, around 27℃ • Annual temperature range is under 3℃ --no seasonality • Daily range of temperature is also small—about 7℃ (because of dense cloud cover) • high humidity • At daytime the humidity measures about 80%. At night the humidity is even higher at 95%.

• Precipitation • Heavy rainfall • Annual rainfall > 2000mm (convergence of trade winds at the ITCZ, unstable air) • Evenly distributed throughout the year • Max rainfall: In April and October ( Spring +Autumn equinoxes) • Least rainfall: in June and December ( summer+ winter solstices) • Mainly convectional rain • Thunderstorms are common.

Example Iquitos, Peru's climograph displays the distinguishing characteristics of the rain forest climate: high annual temperatures and ample rainfall. 

Figure CS.4 Convective thunderstorms over Brazil (July 2002) (Source: Copyright 2002 EUMETSAT) •

Humidity in the rain forest can be oppressive with dew point temperatures ranging from 15oC - 20oC (59oF- 68oF). • early morning radiation fogs form heavy dew drips from the rain forest vegetation. These condensation products evaporate into the air as the Sun rises, thus increasing the air's humidity.

• Winds • the winds are light, allowing land and see breezes to develop in coastal areas • The combination of constant warmth and abundant moisture makes the tropical rainforest a suitable environment for many plants and animals. Tropical rainforests contain the greatest biodiversity in the world. Over 15 million species of plants and animals live within this biome

soil • • • • • •

• •

Mainly oxisols Poor, acidic and infertile. Highly weathered,often down to 10 meters or more contains less organic matter because the warm humid conditions encourage faster decay and recycling of nutrients back into living forest high rainfall tends to leach out soluble nutrients The high concentration of iron and aluminium oxides by the laterization process gives the oxisols a reddish brown color and sometimes produces minable deposits e.g. bauxite Hard pan may exist Only about 20% of the humid tropics has soils that can support agriculture

Vegetation (Flora) CHARACTERISTICS  Dense, luxuriant -hot and wet all year -long growing season -enough moisture and sunlight  Great species diversity (up to 100,000) -favourable growing conditions e.g.: In Amazon, >300 species in 1km² palm, rubber, ebony( 烏木 )  Complex structure - great number of different species  Dominant community is trees -Mainly hardwood -slow growing -live to great age e.g.: greenheart( 綠心硬木樹 )

Vegetation (Flora)  Evergreen - no seasonal variation -no seasonal pattern in flowering, fruiting and leaf fall • Extensive shallow roots -mean of support -absorb nutrient on the surface of the soil -absorb water and oxygen e.g.: Buttress roots (3.9m), aerial root ( 氣根 ), stilt roots  Large, green leaves with smooth surface, drip tips -to absorb sunlight -to drain excess water off the leaf • Continuous cover by canopy -absorb >70% of light -intercept >80% of rainfall -provide habitat for animals, insects, birds

Buttress roots

stilt roots

Vegetation (Flora) Forest Structure b.





Synusia - a group of plants of similar life form and play a similar role in the community Autotrophic Plants (with chlorophyll) - Mechanically independent plants e.g.: trees, shrubs, herbs - Mechanically dependent plants e.g.: climbers (e.g.: lianas), stranglers and epiphytes (mosses, liverworts 葉苔 , lichens) Heterotrophic plants (without chlorophyll) e.g.: saprophytes (fungi), parasites (getting food from host, harmful to the hosts)

Epiphytes

Fungi

Lichens Lianas

Stranglers

Vertical Stratification There are five storeys: ☻ A-layer (Emergent layer) - tall emergent (>30m) - broad crowns - straight trunks supported by buttress roots e.g.: palm species, light-demanding species ☻ B-layer (Canopy layer) - mainly canopy (about 30m) - forms continuous cover - high branches ☻ C-layer ( young tree layer) - about 10-15m - consist of young trees - shorter and more slender( 纖細） - oval- shaped crowns ☻ D-layer (shrub layer) - about 1-5m - sparse with many ferns ☻ E-layer (undergrowth/ground layer) - mainly mosses, lichens and saprophytes - the density is depending on the degree on openness of the forest

Animals (Fauna) Great variety of animal life -mammals, birds, insects, micro-organisms -because of the suitable living environment > rich section of plant species for food >constant environment conditions throughout the year Different kinds of fauna: • canopy-dwelling birds • Mammals (living in trees) - sloth, monkeys, anteaters • Ground-living animals -deer and rodents ( 齧齒目動物 ) -they depend on seed and fruit falling from canopy layer • Amphibia ( 兩棲類 ) e.g.: frog • Reptiles e.g.: snakes

Golden frog

Squirrel Monkey

Primates

Cuckoos

Nutrient Cycling in Tropical Rain Forest

BIOMASS Uptake by plants

Fallout atmosphere

SOIL Decomposed Leaching

Weathered

rock

Litter

Runoff

Why is biomass the largest store of nutrient? Densely populated, tall, evergreen trees Temperature

Precipitation

Storage and Transfer of nutrients within selected biomes Stored in biomass

Stored in Stored Soil to Biomass litter in soil biomass to litter

Litter to soil

Equatorial rainforest

11081

178

352

2028

1540

4480

Coniferous forest

3350

2100

142

178

145

86

Tropical savanna

978

300

502

319

312

266

Temperate Steppe

540

370

5000

422

426

290

Why there is so few nutrient in soil and litter? •

Decaying matter (dead wood and leaf litter) is processed so efficiently because of the abundance of decomposers including bacteria, fungi, and termites. These organisms take up nutrients, which are released as wastes when organisms die. Virtually all organic matter is rapidly processed, even fecal matter and perspiration.

termite

fungi

• It is onl y a mat ter of min utes @ O@!! , in many rainforests, before dung is discovered and utilized by various insects. • covered with brightly colored butterflies, beetles, and flies, while du ng bee tles fever is hly r oll por ti ons of th e wa ste in to b all s f or use l ater a s l ar va l f ood . • Insects are not only attracted to dung for the energy value, but often for the presence of nutrients like cal ciu m s alt s

Beetle

•

Uptake of nutrients by plant roots is facilitated by a unique relationship between the roots and a fungi, mycorrhizae( 菌 根 ). • The mycorrhizae attach to plant roots and are specialized to increase the efficiency of nutrient uptake nutrient from the soil. In return, plants provide the fungi with sugars and shelter among their roots. • Studies have also shown that mycorrhizae can help a tree resist drought and disease.

Dung-mimics • The attractiveness of dung to small rainforest insects has led to the development of dungmimics both among predators and prey. These animals, generally insects and spiders, sit motionless for hours at a time trying to look as dung-like as possible to avoid detection.

Energy Flow in Rain forest •

Though there is a large quantity of vegetation, • as much of the vegetation is above the reach of forest animals, tropical rainforests support only a small biomass of large herbivores, • Much of their sustenance comes from the consumption of fallen fruits, seeds, and flowers.

Pomelo 柚 (Jerunga) fruit

Green cacao pods still on the tree. Cacao is cauliflorous, meaning the fruit grow directly out of the tree trunk and branches.

FALLEN FRUIT AND SEED COLLECTORS • Whole niches have opened for species that feed exclusively on fallen matter. • This niche is filled in Asia by the mouse deer; in Africa by the duikers; and in South and Central America by the agouti.

• However, small mammals are the rule and larger mammals are far less common than in temperate forests and the African savannas. • The scarcity of large mammals is in part due to the lack of leaves at ground level on which to feed. • Only a few large mammal species exist in tropical rainforests: the okapi, the elephant, the pygmy hippo, the bongo, and the gorilla of Africa; the tapir, the rhinoceros, the forest deer, and the elephant of Asia; and the tapir of South America.

The Okapi is a primitive giraffe, about the size of a horse, found in a small region of rainforest in the Congo.

Tapirs are large mammals found in the rainforests of Central and South America and also Malaysia. The tapir is a bizarre-looking animal with a body shaped like a pig but short elephant-like trunk. Tapirs feed on plants.

•

PREDATORS Due to the scarcity of large prey, larger predators are relatively rare in the rainforest. Many of these carnivores have adapted to cope with the shortage of large grounddwelling prey by hunting in the canopy and supplementing their diet with smaller animals like fish, rodents, birds, and reptiles. The largest group of mammalian predators on the forest floor are the cats. Jaguar in Belize.

• Besides the great cats, the rainforest also has several smaller species like the leopard cat (Asia), margay (New World), and ocelot (New World). These generally range from the size of a housecat to a dog. Most are nocturnal and hunt both on the forest floor and in the canopy. • They eat a broad range of animals: frogs, fish, rodents, turtles, deer, and caiman.

OTHER CARNIVOROUS MAMMALS Wild boar in Malaysia

Coati 浣熊 rock

OMNIVORES

The Red River Hog is found in forests of western and central Africa south of the Sahara. The Red River Hog is omnivorous feeding on grass, water plants, roots, bulbs, fruit, and carrion

Man’s activities in the TRF Here, we are going to find out how man’s activities results changes in the TRF. In short, there are mainly four types of man’s activities in TRF.

Man’s activities in the TRF • Logging for timber (deforestation) • Shifting cultivation • Mining • Settlement expanding

Logging for timber • In TRF, there are large numbers of timber. TRF is the largest producer of timber in the world. Large scale of deforestation for timber damage large area of land. • Example 1 :280,000m³ of land in TRF are destroyed for timber in the south-west Australia. • Example 2 :The annual cut has been increased to over 1,500,000m³ . • People having deforestation of timber for building and woodchips.

Logging for timber • Effects:

SOIL EROSION When large numbers of trees are removed, the soil structure is affected. Soil easily to be washed away when heavy rainfall comes ,as there are no plant roots to hold the soil. Soil erosion occurred.

Logging for timber SALINISATION OF STREAMS Salts accumulate in the laterite soil and can be moved relatively easily by an increase in groundwater. Removal of trees cause the groundwater level to rise and eventually the saline water enters the drainage system.

Logging for timber Certainly, this will cause a loss of native flora and fauna. The habitat of animals living in the TRF will also be affected. For examples, birds such as the whipbird are disappearing with the destruction of habitat.

Shifting cultivation • In the TRF, there many natives living in. They burn trees for land to plant crops. In case, the soil in TRF is not suitable for crops growing. When they found the soil is less fertile and cannot grow crops, they will leave the land and find another site by burning trees. This method they are using called shifting cultivation.

Shifting cultivation • Effects: • Damaged in soil structure Unsuitable ways in using the land in TRF cause damage in soil structure, Land in TRF is not suitable for farming. Because there is strong leaching washed the nutrients and minerals away. It is not fertile for crops growing.

Shifting cultivation • Land may loss the productivity. Over-cultivation may found in TRF, when the pressure on land is greater than the carrying capacity, the land may loss the productivity. ． It affects the number of flora and fauna , 26 species of plants and animals in jarrah forest lost. Their habitat are affected.

Mining • Besides timber, TRF also have another precious resource---minerals. For examples, gold and tin. However, mining in TRF lead to 800ha forest lost each year in south-western Australia. Little rehabilitation in TRF results in great damage to TRF.

Settlement expanding • The native are continuing to expand their family. Population is increasing in these years. Small towns in TRF are expanding. Infrastructure damages forest. It produces more pollution in TRF.

The effects of damaging the TRF • The change of climate • Cutting down the trees causes less evapotranspiration, the amount of clouds and rainfall decrease, the climate becomes dry, thus the micro-climate changes. • Because of the lack of the vegetation cover, the sunlight reaches the ground directly, the temperature increases greatly. At night, the heat on the ground loses rapidly, the temperature drops rapidly as well, that forms a larger diurnal range of temperature. • As there are less vegetation doing photosynthesis, the oxygen they emit and the carbon dioxide they absorb decrease. The carbon dioxide in air increases, that causes greenhouse effects and global warming.

The effects of damaging the TRF • Destroy the nutrients cycling • Most of the nutrients of rainforest is stored in the biomass. The fertility of the soil relies on the decomposition. After the trees are cut, many nutrients will run off, and the amount of humus produced by decomposition will decrease. Lack of humus and the roots of vegetation, water and nutrients cannot be stored in the soil.

The effects of damaging the TRF • Cause soil erosion • Since the vegetation decreases, the amount of infiltration decreases and the amount of surface run-off increases. Also, the lack of vegetation cover, the sunlight may cause the soil becomes hard and dry.

• Flooding of streams • As the soil erosion is serious, the surface run-off will wash the soil to the steams and rivers, forms deposition. During a rainstorm, most of the rainfall form surface runoff, flow to the rivers rapidly, cause flooding.

The effects of damaging the TRF • Destroy the habitat of wild animals • Local wild animals will die because of the lack of food and habitat. After cutting trees, the species diversity in rainforest will drops greatly • Most of the oxygen which is needed for survival of organism • is released by photosynthesis But people cutting down trees, turn the forest to farm because of the economical benefits. And the industrialization and the urbanization harm the tropical rainforest. Lead the rainforest which has high species diversity, lost its function of breeding the different species.

The effects of damaging the TRF

• Desertification If the ground loses its vegetation cover, soil erosion may be easily occurred. The lost of forest will lead high temperature. And the loose soil will become desert at last. Many places in the world are in the process of desertification.

Things can do to redeem the harm to the tropical rainforest • To foster a rainforest • Once the rainforest is destroyed, it is hard to revert it. Besides we need to solve the increasing population density and the problem of impoverished, we need to enhance the management to the rainforest. Let the residents turn to forestry, and find out the substitutes of shifting cultivation, that they can use the resources of the forest efficiently.

Things can do to redeem the harm to the tropical rainforest • The international action • There are many international organizations which participate in the protection of rainforest, such as the BBC World Service. Through these organizations, countries agree to enhance their cooperation, promote the protection to the forest and to exploit the forest systematically. In order to keep the species diversity of the forest, countries will mark out national parks and nature reserves.