Chapter 12 Natural Vegetation


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Chapter 12 Natural Vegetation

  2. 2. You will learn: about the relationship between climate and vegetation the global distribution of the different types of forests the characteristics of the different types of forests the benefits of natural vegetation to people the case study of tropical rainforest in Singapore
  3. 3. Today’s lesson, You will learn: what is natural vegetation what are primary and secondary vegetation what are the three major types and seven different sub-types of natural vegetation in the world how do climate affect the types of natural vegetation in the world
  4. 4. What is Natural Vegetation? Natural vegetation refers toplants which have grownnaturally and not plantedby people.
  5. 5. Primary and Secondary Vegetation Primary Vegetationrefers to untouched, unspoiled forest thatexists in its original condition Secondary VegetationRefers to forest that has been disturbed insome way, naturally or unnaturallyAreas with secondary vegetation have fewervarieties of plants
  6. 6. Primary and Secondary Vegetation
  7. 7. Types of Natural Vegetation There are many types of natural vegetation and they can be grouped into three main major types  Forests  Grasslands  Deserts Each major type of natural vegetation can be subdivided into various sub -types
  8. 8. Types of natural vegetation Forests Deserts Vegetation Grasslands*Tropical rainforests*Temperate deciduous forests *Tropical savannahs *Hot Desert vegetation*Temperate coniferous forests *Temperate grasslands *Cold tundra vegetation
  9. 9. Distribution of Major Climatic types in the World
  10. 10. Distribution of Natural Vegetation in the World
  11. 11. Forests As you can see from the map:  Tropical rain forests are found mainly along the equator between 23.5°N and 23.5°S of the equator).  Temperate forests can be found mainly farther away from the equator mainly 23.5oN and 66.5oN, and between 23.5oS and 66.5oS.  Coniferous forests can be found mainly far from the equator in the northern hemisphere (between 60°N and 70°N of the equator).
  12. 12. Tropical rainforest
  13. 13. Temperate deciduous and coniferous forest
  14. 14. Why different types of natural vegetation exist in different parts of the Earth? Temperature affects vegetation because if it is too cold (less than 6°C), few plants can grow. On the other hand, warm temperatures (above 20°C) allow abundant plant growth
  15. 15. Why different types of naturalvegetation exist in different parts of the Earth? Precipitation (rainfall) also affect vegetation because all plants require water to grow. Most trees require more water to grow than grass.
  16. 16. Why different types of natural vegetation exist in different parts of the Earth? Hence, most forests grow in areas with high rainfall (above 1000 mm a year). In areas with moderate precipitation of between 200 mm and 1000 mm, grasslands are more common. In areas with less than 200 mm of rain, deserts are found.
  17. 17. Climate – Vegetation RelationshipIn summary:Natural vegetation is influenced mainly by climate A climate-vegetation relationship exists because rainfall and temperature determine the type of natural vegetation found in a place High rainfall - forests Moderate rainfall - grasslands Low rainfall - desert vegetation
  18. 18. Climate – Vegetation RelationshipIn summary: Climate is a major factor that influences the distribution of natural vegetation. Other factors like the type of soil and altitude can also affect its distribution.
  19. 19. Forests Forests refer to large areas of land that consist mainly of trees and a variety of other plants They are usually found: Distribution Climate Temperature Rainfall (mm) o CBetween latitudes of -12 to 30 300 mm to 2000 mm o o66.5 S and 66.5 N
  20. 20. Tropical RainforestsYou will learn: where are tropical rainforests found what are the characteristics of a tropical rainforesta) The different layers of a tropical rainforestb) The different types of plants found in the different layersc) At least one of the adaptations of the tropical rainforest
  21. 21. Location of Tropical Rainforests Distribution Climate Location Temperature Rainfall o C (mm)Between High High • Amazon Basin inlatitudes of Between 1000 South America, o23.5 N and 20 to 30 mm to • Malaysia and o23.5. S of the 2000 Indonesia inEquator which mm Southeast Asia,has a tropical • the Congo Basinclimate in Africa
  22. 22. Tropical Rainforests
  23. 23. Characteristics of Tropical Rainforests1. Trees grow very close to each other, making the forest very dense.2. Plants grow in 3 distinct layers. • Emergent • Canopy • Undergrowth
  24. 24. The THREE LAYERS Undergrowth
  25. 25. Characteristics of Tropical Rainforests EMERGENT LAYER • Reach heights of 40 to 50 metres • Grow to receive more sunlight. • Often have buttress roots to support the tall and heavy trunks. CANOPY LAYER • Reach about 15 to 30 metres • Crowns of trees interlock to form continuous leaf cover (canopy) • Cool and moist interior – blocks out 70% of sunlight • Lianas are common – woody climbing plants that hang down. • Epiphytes are common – plants that grow on other trees to get more sunlight
  26. 26. Characteristics of Tropical Rainforests EMERGENT LAYER CANOPY LAYER } UNDERGROWTH • Made up of shrubs, grasses, ferns, mosses and fungi. • Plant growth is sparse because of the lack of sunlight
  27. 27. Characteristics of Tropical Rainforests• Some plants, called epiphytes overcome the shortage of sunlight by growing high up on tree branches to get sunlight (examples: ferns, orchids).• Other plants, known as lianas, grow upwards to get more sunlight by winding around tree trunks.
  28. 28. Adaptation??
  29. 29. Tropical rainforests: Leaves Tropical forest trees are evergreens as the leaves remain green throughout the year. This is unlike deciduous trees, which shed their leaves in the autumn or in the dry seasons. The leaves are also broad to absorb as much as much sunlight as possible. They are also waxy and have drip tips to allow water to drain off.
  30. 30. Tropical rainforests: Leaves The bark of trees in the tropical rainforest is thin because they are not required to protect the trees from dry or cold conditions. Branches are also located in the top one- third portion of the trunks and they are shaped like umbrellas to capture as much sunlight as possible.
  31. 31. Tropical rainforests: Roots Roots of tropical forest trees are shallow because they do not need to reach deep into the soil for water. This also allows the roots to tap the abundant nutrients found in the layer of leaf litter of on the ground. Tree roots near the Some of the tallest trees have buttress surface, Malaysia roots to support their great weight and prevent them from falling over.
  32. 32. The Shrinking Rainforests The world loses about 100 000 sq km of rainforests each year Forests are cleared for growing crops and building houses and roads, and logged every day We must do our part to save the remaining rainforests
  33. 33. The Shrinking RainforestsImpacts of deforestation: Flooding Landslide due to soil erosion Loss of biodiversity of plants and animals Decrease in oxygen and increase in carbon dioxide
  34. 34. Temperate Coniferous ForestsCLIMATE AND DISTRIBUTIONDistribution Climate Location Temperature Rainfall o C (mm)Only -12 to 10 300mm to • Japanbetween 750mm • Chinalatitudes of • Europe o23.5 N and • North o66.5. N of Americathe Equator
  35. 35. Temperate Coniferous ForestsCHARACTERISITICS1. Cone Shaped tree (think Christmas Tree!) • Allows snow to slide off the tree branches easily. • Prevents increase weight of the snow on the branches which can cause them to break.
  36. 36. Temperate Coniferous ForestsCHARACTERISITICS2. Trees are evergreen • They adapt to extreme conditions instead of shedding their leaves.3. Forests have only one variety of tree in each area. Example: Pine, Fir, Spruce4. Only have one layer of vegetation5. Very little undergrowth except for moss,lichen and leaf litter on the forest floor.
  37. 37. Features and Adaptation - Trees• Coniferous trees are cone-shaped and have sloping and supple (easily bendable) branches to allow snow to slide down without snapping branches
  38. 38. Features and Adaptation - Leaves • The leaves are small, needle- shaped, waxy & leathery to: • Minimise water loss • Prevent the accumulation of snow
  39. 39. Features and Adaptation – Barks • Barks are rough, tough & contains resin (thick, sticky liquid) to protect against cold and to conserve moisture
  40. 40. Features and Adaptation – Roots
  41. 41. Features and Adaptation – Roots• Coniferous trees have shallow spreading roots which enable them to absorb water from the surface during the short warm months.• Roots do not go deep as the ground there may be permanently frozen, even during the summer.
  42. 42. Features and Adaptation – Roots• Coniferous trees have shallow spreading roots which enable them to absorb water from the surface during the short warm months.• Roots do not go deep as the ground there may be permanently frozen, even during the summer.
  43. 43. Quiz Time:• State one difference and one similarity in the characteristics of the natural vegetation found in a Tropical Rainforest and a Temperate Coniferous forest.• Explain how these characteristics help the plants to adapt to the living conditions in which they are found.
  44. 44. BENEFITS OF FORESTSYou will learn: what are some of the benefits of the natural vegetation to the Earth and humans.
  45. 45. BENEFITS OF FORESTSOxygen in the atmosphere:• Plants play an important role in maintaining the amount of oxygen in the airFormation of rain:• Plants add to the amount of water vapour in the air through transpiration and hence rainfall is usually high in places populated by many plants
  46. 46. BENEFITS OF FORESTSNatural resource:• The hardwood trees in rainforests provide wood required to make things like furniture and houses Medicinal value: • Many plants that grow in tropical rainforests have medicinal properties
  47. 47. BENEFITS OF FORESTSRecreation:A place where nature lovers can relax
  48. 48. BENEFITS OF FORESTSNatural habitats:• Loss of natural vegetation will result in the loss of food and habitat for animalsPrevents erosion of soil• Plants can prevent soil erosion
  49. 49. Case Study: Bukit Timah Nature ReserveIn Singapore, only a few small areas ofrainforests are left.The government has set aside areas coveredby rainforests as Nature Reserves are part ofconservation efforts.• Bukit Timah Nature Reserve is 164hectares in size.• Believed to be only 0.2% of the rainforestoriginally in Singapore.• Last 1% of primary rainforest in Singapore.
  50. 50. Case Study: Bukit Timah Nature ReserveCHARACTERISTICS OF BUKIT TIMAH NATURE RESERVE1. Tall trees (+30m) due to hot and wet climate2. Trees have buttress roots to support themselves3. Trees are evergreen and grow closely together.4. Crowns interlock to form canopy that prevents sunlight from reaching the forest floor.5. Dark and damp forest floor.6. Wide variety of trees and other plants. • Different hardwood trees: seraya, meranti and nemusi • Species of climbing palms: rattan
  51. 51. Case Study: Bukit Timah Nature ReserveVALUE OF TROPICAL RAINFORESTS1.Medicinal Properties2.Water Catchment areas • When rain falls, the rainwater is trapped by the leaves and falls to the ground. The water will drain slowly into the ground and eventually into nearby reservoirs.
  52. 52. Case Study: Bukit Timah Nature ReserveVALUE OF TROPICAL RAINFORESTS3. Recreational Activities • Such as trekking and jogging4. National Heritage • Part of our history and our national heritage. • Singapore is on of the only two cities to have a sizeable amount of rainforest in a built up area.