Tropical rainforest


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Tropical rainforest

  1. 1. Course: BiogeographyDate: March 5, 2013
  2. 2.  A rainforest is a thick forest in moderately warm to very hot areas which have heavy rainfall and high humidity .
  3. 3.  Tropical Rainforests are found between 5-10 degrees north and south of the equator. Some countries /areas that Tropical forest biomes are found: Brazil Indonesia Malaysia Madagascar Parts of Australia Thailand Amazon Basin Congo
  4. 4.  High annual temperature (27- 30 degree) Temperature is uniform High humidity and cloud cover. no dry season. Mostly convectional rainfall. Average rainfall is between 1,200mm to 3000mm per year.
  5. 5.  Latosols or ferralitic soils Extensive chemical weathering resulting from the high rainfall and temperature leads to the development of deep soils, often 20m to 30m deep The soils have a loose structure and are rapidly eroded once the protective layer of vegetation is removed Except for the top few inches, soil fertility is poor
  6. 6. Thick litter layerThin dark humuslayer Many soil organisms A typical latosol mix soil well  profile Oxides of iron and A and B aluminium stain soil red horizons  Hydrated oxides produces red/yellow colouration Clays produced by intense chemical weathering  C horizon Bedrock
  7. 7.  Emergent Layer – a few tree species grow very tall and emerge up through the canopy. These may be 150 feet tall. The emergent layer is made up of the tallest trees that grow larger than any of the other trees.
  8. 8. It is good to have your leaves inthe emergent layer becausethere is lots of sunlight.
  9. 9.  Canopy Layer – tall trees for this dense layer that absorbs most of the light energy. 80 to 100 feet tall. The canopy layer is where most of the leaves in a tropical rainforest are found. Very dense vegetation
  10. 10.  The canopy is very dense, so it blocks out a lot of the light.The interlocking canopy
  11. 11.  Understory or Subcanopy Layer – made of seedlings that will grow to canopy if light is available and a few shade specialists. Shorter plants living in the understory of the emergent and canopy layers do not get as much light so they have to be able to grow in the shade.
  12. 12. Only about 1% of the sunlight reaches the understory level.- Trees are smaller– Their crowns are not thick– Most have heights of between5m and 15m
  13. 13.  Consists mainly of ferns, shrubs and small young trees. Covered by a carpet of leaves.
  14. 14. •The forest floor is covered with dead leaves.•These dead leaves will decompose (rot) and return thenutrients that they contain to the soil.
  15. 15. The dominant vegetation in Tropical Rainforests is tall, broadleaf, evergreen trees.Broadleaf = leaves have flat, wide blades instead of needles.Evergreen = trees maintain foliage (leaves) all year. Deciduoustrees, those that drop their leaves seasonally, do so as anadaptation to cold conditions. In the tropics, there is no coldseason, therefore there is no need for trees to drop their leaves.
  16. 16.  Leaves • Drip tips on the leaves allow excess water to drip off after a downpour • Leaves are large and smooth with a thin cuticle to facilitate transpiration • Leaves, especially in the upper canopy have a strong petiole so that the large raindrops do not cause them to break off
  17. 17.  Lianas – are vines that grow up trees to their crown then between the branches of neighboring trees. They “lace” the trees together adding support so they won’t fall over since their roots grow in very shallow soil.
  18. 18.  Epiphytes – (epi = outer and phyte = plants) – are plants that grow on other plants. By growing up off the forest floor epiphytes have access to higher quality light (red and blue). A diversity of plants have adapted to an epiphytic life. There are epiphytic flowering plants, mosses, cacti, ferns, and liverworts.
  19. 19.  Many of the trees are covered with epiphytes. The trunks are cloaked in mosses. The large epiphyte in the center is a bromeliad. Large bromeliads like this one are called “tank bromeliads” because their cup of leaves holds a lot of water. That water is the drinking source for arboreal animals. Several species of frogs lay their eggs in it and the tadpoles develop in the treetops.
  20. 20. Buttress roots are common on Tropical Rainforest Trees. They grow across thesurface of the thin rainforest soil. They work like kick stands to keep the tree fromtipping over. Also, because the soil is so nutrient poor, deep roots have no need togrow deep. They’re more effective at the surface where they can absorb nutrientsfrom fallen leaves as they decompose.
  21. 21.  Slash and burn Fire Illegal Logging Agriculture- cash crop and ranching
  22. 22.  One of the most widely used methods to destroy rainforests is using slash and burn agriculture.� With this type of agriculture, all of the trees and plants in the selected area are uprooted or cut down.� The downed trees and flora are then burnt, so that all of the nutrients in the plants are turned into ash, which is mixed with soil.� After all of the vegetation has been burnt and the ashes have been incorporated into the soil, people plant crops.� The area of land that has been cleared in this manner is only viable for a few years.� Once all of the nutrients have been leached from the soil, the area is abandoned and a new area of rainforest is selected to undergo the same process.
  23. 23. This type of agriculture is problematic because�� �The hugenumber of farmers who have descended upon the rainforests haveplaced too much pressure on the land.� Not enough time is beinggiven to cleared patches for the forest to regenerate.� This �slash-and-burn� farming has replaced traditional, sustainable�cultivation in most tropical forests� (Lewis,1990, pg 60).� This isvery unfortunate because �slash-and-burn� agriculture isresponsible for the ruin of fifty acres of rainforest every hour�(Gallant,1991, pg 4)
  24. 24.  During 1997 several fires broke out worldwide and as a result, �More fires were recorded in that year than at any time in history- millions of hectares of forest were destroyed�� (Gay,2001, pg 32). In addition to fires that occur naturally, farmers and native peoples use fire as a tool to clear land for agriculture.� Cattle ranchers also use fire to clear the land for their cattle,��The conversion of the rainforest into grazing for cattle is a genuine ecological catastrophe.� The replacement of the rainforest�s intricate structure by the much simpler structure of pastureland is an intrinsically negative process of biological simplification� (Camarasa,2000, pg 292).
  25. 25.  Many government agencies are fighting illegal logging to protect the forests. However, any type of logging legal or illegal leads to deforestation. Trees are cut down indiscriminately by logging companies, to fulfill the demands of the wood market. This does not give a chance to the local wildlife and trees to regenerate and sustain themselves. Thus, leading to loss of wildlife forever. Read more at Buzzle: effects-of-deforestation.html
  26. 26.  Undisturbed and logged rainforest areas are being totally cleared to provide land for food crops, tree plantations or for grazing cattle (Colchester & Lohmann). Much of this produce is exported to rich industrialised countries and in many cases, crops are grown for export while the local populace goes hungry. Due to the delicate nature of rainforest soil and the destructive nature of present day agricultural practices, the productivity of cash crops grown on rainforest soils declines rapidly after a few years.
  27. 27. Monoculture plantations - those that produce only one species of tree or onetype of food - on rainforest soil are examples of non-sustainable agriculture.They are referred to as cash crops because the main reason for their planting isto make money quickly, with little concern about the environmental damagethat they are causing.
  28. 28.  Cattle ranching has multiple negative effects to both the environment and the people living in it.� For example, cattle ranching �intensifies deforestation by forcing peasant farmers into the rainforest to seek new land to farm when they are evicted by ranchers who want to convert their farmland to pasture�(Lewis,1990, pg 42). Cattle ranching is also negative because it� �causes the land to decline in quality as the soil becomes depleted of nutrients.� In fact, land cleared from rainforests generally supports cattle for only three to seven years before it deteriorates beyond recovery� (Lewis, 1990, pg 42).� Just as the farmers do, the ranchers use the land until all the nutrients are gone.� This makes it difficult for new flora to grow back.
  29. 29.  One of the factors that allows cattle ranching to destroy rainforests is that �rainforest ranchers have relied on government subsidies and international loans, which make cattle ranching artificially profitable�Rainforest governments have also supported cattle ranching with land giveaways, tax breaks, and free technical assistance. Without this support, rainforest ranching would lose much of its appeal� (Lewis,1990, pg 43)
  30. 30. What is Deforestation? Deforestation is clearing Earths forests on a massive scale, often resulting in damage to the quality of the land.
  31. 31. �����Colchester and Lohmann (Ed), The struggle for Land and the Fate of the Forest, 1993, Zed Books, London. Gallant, R. A. (1991). Earths Vanishing Forests. New York: Macmillan� Publishing Company. Gay, K. (2001). Rainforests of the World (2 ed.). Santa Barbara: ABC-CLIO, Inc. Josep M. Camarasa, R. F. (2000). Encyclopedia of the Biosphere (Vol. 2). Michigan: The Gale Group. Lewis, S. (1990). The Rainforest Book. Los Angeles: Living Planet Press.