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Earth: Our Home Geography Elective
Chapter 3 Types of Natural Vegetation
You will learn: to describe the global distribution of different types of forests to describe the characteristics of different types of forests to compare the ways in which different types of forests adapt to the environment
What is Natural Vegetation? Natural vegetation refers to plants that grow naturally in a place with little or no human interference. It plays an important role in a forest ecosystem by providing food and shelter for the animals and native people that live in the forest.
Major types of natural vegetationForest biome The vegetation in a forest biome consists of mainly trees. It generally has many varieties of plants. Tropical rainforest Temperate deciduous forest Coniferous forest
Grassland biome Grasses constitute the main plants in a grassland biome. It has few varieties of plants. Tropical grassland Temperate grassland
Desert biome The vegetation in a desert biome consists of mainly sparse vegetation, such as scrubs and tough grasses in the hot desert, and mosses and lichens in the cold desert. It has very few varieties of plants. Hot desert vegetation Cold desert vegetation (tundra)
Distribution of Natural Vegetation Climate is a major factor in influencing the distribution of natural vegetation. There are 3 climatic types.. Polar region Very low temperatures, often below 0C. Very low annual precipitation, below 250 mm Low to modern temperatures, ranging from 0C to 34C, Temperate region depending on the season. Moderate annual precipitation, 300 mm to 1 000mm High temperatures throughout the year, 20C to 30C. High Tropical region precipitation, above 1 000 mm Tropical region Temperate region Polar region
Distribution of Natural Vegetation Temperature and precipitation can influence plant growth. Plant growth is more abundant in areas where temperatures are consistently above 20C than in areas where temperatures fall below 6C.
Distribution of Natural Vegetation Water is required by plants to make food. Thus, different types of natural vegetation forests are found in different parts of the world. - forests --- high precipitation at above 1 000mm per year. - grasslands --- moderate precipitation between 200mm to 1 000mm per year. - hot desert vegetation or tundra --- no or little precipitation at less than 250 mm per year.7
Distribution of Natural Vegetation
Tropical forests are a cradle of biodiversity. It has been estimated that half of the plant and animal life forms that live on this planet are found in this environment, even though tropical forests cover only six percent of the earths surface.Source: The Tropical Rainforest by Francesco Petretti, Journey Editions, 1998, Italy.
Tropical Rainforest Tropical rainforests - found in places that experience tropical equatorial climate - high temperatures, about 27C - high amount of rainfall, above 1 500mm throughout the year - examples of tropical rainforests are Amazon Basin in South America, Congo Basin in Africa and parts of Southeast Asia10
Tropical Rainforest Structure of the forest - 5 layers:- Emergent layer, 30m to 50m - Canopy layer, 15m to 30m - Understorey layer, 6m to 15m - Shrub layer, grow up to 6m - Undergrowth layer, grow up to 5m11
Tropical RainforestEmergent layer 50 m Tall trees, called emergents, reach a height of 30 m to 50 m. Their crowns appear above the canopy layer. These trees have tall, thick and straight trunks. 30 m Canopy layer The trees in this layer reach a height of 15 m to 30 m. Their wide, shallow and umbrella-shaped crowns form a continuous leaf cover, called a canopy, as they prevent sunlight from penetrating into the lower layers of the forest. 15 m Understorey layer The trees here have narrower, oval-shaped crowns because most of the sunlight is blocked by the canopy. These trees grow where gaps in the canopy allow sunlight to pass through. Their heights range from 6 m to 15 m. Young trees of the emergent and canopy layers are also found in this layer. 6m Shrub layer Tree saplings and woody plants are found in this layer. They may grow up to 6 m high. 5m Undergrowth layer The undergrowth or forest floor is made up of grasses, ferns, mosses and fungi. Plant growth is sparse because very little sunlight reaches this layer. Plants in this layer reach a maximum height of 5 m. 0m
Characteristics of the 5 layers
Emergent layer - trees have tall, thick and straight trunks Canopy layer - tree crowns inter-lock - presence of epiphytes & lianas, and parasitic plants Understorey layer - trees with narrower crowns - presence of parasitic plants Shrub layer - tree saplings & woody plants found Undergrowth layer - sparse due to lack of sunlight that reaches the forest floor13
Tropical Rainforest Characteristics - a wide diversity of plant species - 750 species of trees and 1 500 species of other plants in 1 hectare - the high temperature and rainfall throughout the year enables it to support a large variety of plants Density - extremely dense - density is due to high temperature and rainfall that encourage abundant vegetation growth
Tropical Rainforest Characteristics & Adaptations Leaves - are evergreens - due to high rainfall throughout the year, trees do not shed leaves at the same time - are waxy with drip tips - to allow rainwater to drain off easily
Tropical Rainforest Characteristics & Adaptations Flowers & fruits - are colourful & sweet-smelling - to attract insects for pollination and animals for seed dispersal
Quick Quiz Can you identify the flower?
Quick Quiz It is a type of Rafflesia, a spectacular plant found in the tropical rainforest. There are 15 to 19 species of Rafflesia. Rafflesia is known to produce the largest individual flower on earth.
Tropical rainforest Characteristics & Adaptations Bark & branches - thin and smooth branches - does not need protection against cold or dry conditions - branches are found at the uppermost one-third of the trunks to get as much sunlight as possible Roots - shallow and spreading - nutrients are found at topsoil due to high decomposition - buttress roots (of some tall trees) - support weight of trees.19
Tropical Monsoon Forest Tropical monsoon forest - found in the tropics - high temperatures, about 26C - high amount of rainfall, above 1 500mm throughout the year, but with distinct wet and dry seasons - located in South Asia, Southeast Asia,southern China and northern Australia20
Tropical Monsoon Forest Distribution
Tropical Monsoon Forest Structure of the forest - 3 layers: - Canopy layer, 25m to 30m - Understorey layer, about 15m - Undergrowth layer
Tropical Monsoon Forest30 m Canopy layer Trees can grow to 25 to 30 m in height. They are more spread out than those in a tropical rainforests, plants such as creepers, vines, epiphytes and parasitic plants are found within this layer. 15 m Understorey layer The trees in the understorey are about 15 m in height. 6m Undergrowth Bamboo thickets and grasses grow densely here during the wet season. They are dense during the dry season. 0m
Tropical Monsoon Forest Characteristics of the 3 layersCanopy layer - more spread out than those in tropical rainforest - presence of epiphytes & lianas, and parasitic plants Understorey layer - consists of shorter trees about 15m in height Undergrowth - bamboo thickets and grasses grow densely here during the wet season but are less dense during dry season24
Tropical Monsoon Forest Characteristics Diversity of plant species - about 200 species in 1 hectare - less species compared to tropical rainforest due to inconsistent rainfall Density - plant growth is abundant but less dense than tropical rainforest
Tropical Monsoon Forest Characteristics & Adaptations Leaves - are deciduous - shed leaves during the dry season to minimise loss of water through transpiration - waxy with drip tips to allow rainwater to drain off easily
Tropical Monsoon Forest Characteristics & Adaptations Bark & branches - thick & coarse - protects the trunk from heat and dryness during the dry season - withstand extreme heat from natural - forest fires - branches found around middle of trunks as trees grow less dense than tropical rainforest
Tropical Monsoon Forest Characteristics & Adaptations Roots - deep tap roots - to tap water sources deep under the ground as rainfall is irregular throughout the year
Tropical forests in a glance What are the similarities between the tropical rainforest and the tropical monsoon forest? What are the differences?
Tropical forests in a glance Similarities - both forests are dense - leaves are waxy with drip-tips
Tropical forests in a glance Differences diversity density leaves bark & branches roots31
AnswersTropical rainforest Differences in terms of more denser evergreenSmooth, thin bark Branches at top onethird
diversity density leaves bark & branches roots
Tropical monsoon forest less less dense deciduousThick bark Branches around middle of tree
deep tap roots32
What do you think the feature with the shape of a heart is?33
Quick Quiz Its actually a picture of the mangrove forest in New Caledonia, an island near Australia in the southern Pacific Ocean. The sand is clearly seen because the saltiness of the soil has discouraged plant growth. Source: The Earth from the Air for Children by Yann Arthus-Bertrand, 2002, Thames & Hudson, UK.
Mangrove forests Found mainly in areas experiencing tropical climate, along sheltered coastal regions and places where rivers constantly deposit clay and silt.
Mangrove Forests Structure - grows to a height of 2m to 40m - horizontal zones of mangrove speciesHigh tide Low tide
Coastal area Avicennia and Sonneratia trees are common in this zone, which is the nearest to the coast. They have adapted to growing in salt water, as the coastal zone is flooded with seawater during high tide. The trees have breathing roots or aerial roots.
Middle zone Rhizophora trees are common in this zone. They have prop roots or stilt roots.
Inland zone Bruguiera trees grow further inland, as they are the least tolerant of salt water. They have knee-like roots.
Mangrove Forests Characteristics & Adaptations - four main species which are known as halophytes - Avicennia, Sonneratia, Rhizophora, Bruguiera - dense & luxuriant Leaves - evergreen - salt secretors - ultrafiltrators37
Mangrove Forests Characteristics & Adaptations Flowers- generally colourful to attract insects to pollinate Fruits - buoyant so that waves and currents can carry them away - elongated with sharp tips to anchor in soft muddy soil
Mangrove Forests Characteristics & Adaptations Roots - aerial roots that are exposed - allow them to take in oxygen - prop roots - anchor the trees firmly in the muddy soil
Coniferous Forests Coniferous forest - found in places that experience a cool continental climate - experiences seasons - temperatures range from -40C to 21C - low amount of precipitation, usually in the form of snow, 300mm to 635mm in a year - located in Alaska, northern Canada, northern USA, northern Scandinavia & Russia40
Coniferous Forests Distribution
Coniferous Forest Structure - no distinct layers - generally uniform in height, about 20m to 30m - trees grow close together - little undergrowth
Coniferous forests Characteristics & AdaptationsDiversity - few species as not many trees can adapt to the climate - the trees grow in pure stands Density - forest are not dense as the climate does not support dense vegetation growth
Coniferous Forest Characteristics Leaves - evergreen - retain leaves so that photosynthesis can take place whenever temperature rises above 6 C - needle-like with small surface area to reduce water loss due to transpiration - store water for use in winter
Coniferous Forest Characteristics & Adaptations Flowers & Fruits - trees bear female and male cones - female cones produce seeds - male cones produce pollen - cones can be dispersed by wind or animals after pollination
Coniferous forest Characteristics & Adaptations Bark and branches - thick bark - to protect from long, cold winters - flexible branches that slope downwards - to enable snow to slide off easily Roots - shallow, spreading roots - enable trees to absorb water easily from soil surface when snow melts46
Importance of Forests Support diversity of plants and animals. Natural habitats for animals. Provide us with resources. Home to some natives. Part of our natural heritage.
Learning OutcomesGlobal distribution of tropical rainforests, tropical monsoon forests, mangroves and coniferous forests. Characteristics and adaptations of tropical rainforests, tropical monsoon forests, mangroves and coniferous forests. Skills - Compare and contrast the characteristics of different forests.48