Chapter 5

What is natural vegetation?

It refers to plant life which covers particular parts of the world’s land areas and develops without human interference.

What types of natural vegetation are there?

Temperate grassland

Temperate deciduous forest

Mediterranean forest

tropical rainforest

Tundra

Temperate coniferous forest

desert

tropical grassland

Temperate grassland (describe the area)

Open grassy plains that are sparsely populated with trees

Temperate deciduous forest (like oak/elm) (describe the area)

Has trees which drop their leaves in the fall (4 seasons)

Mediterranean forest (e.g. eucalyptus forest), what are the conditions.

Condition: dry summers and rainy winters

Tropical rainforests (e.g. amazon) (describe area)

Evergreen trees in areas of high temperatures and rainfall

Tundra (Like in Alaska, iceland) (describe the growth of trees)

Tree growth is hindered by low temperatures and short growing seasons

Temperate coniferous forest (e.g. pine, cedar) what are the conditions of it?

Warm summers, cool winters

Desert (e.g. sahara desert). Describe the land

Barren area of landscape where little precipitation occurs

Tropical grassland (Savannah). Describe the land

Comprised of a mixture of trees and grasses

What is climate?

Refers to the average weather conditions of a place over a long period of time, usually more than 30 years

The type of climate can?

affect the type of vegetation growing in the area

Tropical climates are experienced by?

The part of the world located between the Tropic of Cancer and Tropic of Capricorn

Tropical climates are characterised by?

High annual rainfall (around 2000mm) and high temperatures throughout the year

How do we make inference of a climograph?

Temperature, precipitation

Average temperature:

The average temperature of 26. Temperature range diff of 1 degree celcius

Rainfall (heavy, total annual rainfall/mm) n frequency

Heavy rainfall of 1804 mm

Total annual rainfall → 1000 mm, a max of 2400mm

rainfall throughout the year, no month where there is low/absent rainfall

Spatial distribution of the tropical rainforest

Amazon rainforest

Congo Basin

South East asian rainforest

Describe the distribution of the tropical rainforest (3m)

They are located in the tropical zone, from 23.5°N (the Tropic of Cancer) to 23.5°N (the Tropic of Capricorn)

Tropical rainforests are generally concentrated along the Equator and in places with a hot (over 27°C) and wet (over 2000 mm) equatorial climate

Specifically Central South America, Central Africa and South East Asia

Distribution of the Tropical Rainforest

Today, less than 5 per cent of Earth’s land is covered with these forests (about 2.41 million square miles or 6.2 million km²)

Over half of these forests lie in Brazil, which holds about one-third of the world’s remaining tropical rainforests. Another 20 per cent of the world’s remaining rainforests exists in Indonesia and Congo Basin, while the balance of the world’s rainforests are scattered around the globe in tropical regions.

Why is a rainforest, a rainforest?

Rain - because it thrives in a climate with heavy rainfall of >2000mm (total annual rainfall)

Forest - because it consists mainly of trees. Numerous species of trees, together with a wide variety of plants.

This makes the forest very dense (with foliage)

Why is a rainforest, a rainforest and not a grassland?

Rainforests have:

High mean annual temperatures (27°C)

High temperatures (>20°C) all year round

Coupled with regular and high total annual rainfall (2000mm)

Hot & Humid climate makes it very favourable for plant and tree growth

As a result, a wide variety of plants and trees are able to not only survive but thrive.

What is unique about the Tropical Rainforest?

The tropical rainforest biome is one of the most diverse and productive biomes on Earth

Tropical rainforests provide 40, per cent of the oxygen on Earth even though they only cover about 6 per cent of the Earth’s surface

Define a biome

A large naturally occurring community of flora and fauna

What is so unique about the Tropical Rainforest (prt 2)

The biome is characterised by its rainfall and evergreen species

Approximately 25 per cent of the medications in use today have come from tropical rainforests

Structure of the rainforest

3 layers:

Emergent

Canopy

Undergrowth

The tropical rainforest is evergreen. This meant they do not shed their leaves at a particular time of the year

An adaptational feature of the evergreen

Areas that experience the tropical climate receive abundant sunlight and high rainfall throughout the year

This makes them suitable for plant growth throughout the year, as they can carry out photosynthesis.

Species diversity in the tropical rainforest

The favourable conditions for plant growth support a large variety of plant species

An estimated 3 to 50 million species

Biodiversity

Every living thing, including plants, bacteria, animals and humans

Natural vegetation found

tropical rainforests

1. Amazon rainforests (South America)

2. Congo rainforest (Africa)

3. Valdivian Temperate rainforest (South America)

4. Daintree rainforest

5. Southeast Asian rainforest (Asia)

6. Tongass National Forest (North America)

7. Kinabalu National Park (Malaysia)\

8. Santa Elena Cloud Forest Reserve (Costa Rica)

Mangroves (along the *coastal areas)

• 70% of the coastlines in the tropics are covered by mangroves

3 layered vertical structure of tropical rainforests

Undergrowth layer

Canopy Layer (20m -30m)

Emergent Layer (>30m)

The emergent layer consists of?

Consists of the tallest and usually oldest trees, which are about 40m-50m high and spread out over the tops of other trees. These trees take the brunt of climatic changes (e.g. they receive the highest sunlight, hottest temperatures, wind and rain.)

Shorea Curtisii Seraya characteristics

Small leaves (7 cm- 10 cm)

Winged seeds

40m in height

Buttress roots

Shallow root system

Tall and straight trunks

Thin barks

Branches out at the top, Small white fragrant flowers

Small crowns

The canopy layer

Beneath the Emergent layer, there are smaller trees 25-35 m high

These trees form a living umbrella sheltering the flora and fauna below from extremes of heat, wind and rain

They grow very close to one another

Their crowns form a dense, unbroken mass of branches and leaves as a canopy cover

The cover is like an umbrella, blocking up to 90% of the sunlight from reaching the forest floor.

Lianas and epiphytes live and grow in?

The canopy

What are lianas? + example

A thick, woody vine that grow on the ground and twine up a tree to reach sunlight

An example: Monkey Ladder Vine

The forest floor/undergrowth conditions n characteristics!

At the forest floor, humidity remains high (95% R H) and the temperature is fairly stable (20-30°C). Less than 10% of sunlight reaches the ground.

• The undergrowth layer is dark because most of the sunlight is blocked by the canopy layer

• Plants are small, thin and widely spaced due to a lack of sunlight

• Plants have much larger leaves compared to plants in the emergent and canopy layers to receive as much sunlight as possible.

Adaptie features of the plants and trees of the tropical Rainforest

Parts of plants/trees

• Crowns

• Branching

• Leaves

• Flowers

• Seeds

• Trunks

• Bark

• Roots (above ground)

• Roots system (below ground)

Attributes/characteristics

• Size

• height

• colour

• scent

• methods

• thin/thick

• special physical features

• shallow/deep

Location of tropical rainforests

In central and south America, west and central africa, and southeast asia

What do the plants in tropical rainforests have (adaptational features), and why?

Broad leaves → leaves

Waxy leaves → leaves

Drip tips → Leaves

Buttress roots → roots

To cope with the intense competition for sunlight and high rainfall, individual competition for sunlight and high rainfall, individual tropical rainforest plants have adapted to these conditions.

Adaptational features for bark and branches, reasons.

Adaptation:

• Tall, straight trunks

• Branches spread out near the top (increase surface area)

Reason

• to help the trees obtain the maximum amount of sunlight

Adaptation:

• Smooth bark

  Reason

• To allow rainwater to flow down the trunk easily.

Adaptational features: evergreen (what is it? and elaborate on it.)

Plants are evergreen (appear constantly green)

• They do not shed their leaves as is no seasonal changes.

Adaptational feature: broad leaves (why)

Broad leaves = large surface area

Enables plants to capture and absorb as much sunlight as possible for photosynthesis (usually in the undergrowth layer when sunlight is blocked by the canopy layer)

Adaptational feature: waxy leaves (describe and why)

Leaves have thick, waxy, leathery or hairy surfaces

The waxy surfaces give a glossy appearance

These leaves minimise the loss of moisture through transpiration due to the high temperatures in tropical rainforests

Adaptational feature: drip tips (describe, also why)

Some leaves have small, narrow tips that point downwards

Together with the waxy surface, this allows water to flow off the leaves. This helps the leaves to dry quickly, preventing fungi and bacteria from growing on the leaves.

How many features are combined in leaves in the rainforest?

The leaves have a combination of 3 features

• leaves are broad with a waxy surface and have drip tips

Adaptational feature: fruits and flowers

Air is still in tropical rainforests. The lack of wind makes it hard for seed dispersal and pollination to occur by wind.

Fruit and flowers are colourful and strongly smelling to attract insects and other animals for dispersal or pollination

Adaptational feature: Buttress roots

Supports the heavy weight of the tall trees in tropical rainforests

Keep plants upright and prevent them from toppling over. This helps the plant to grow to great heights to reach as much sunlight as possible

Buttress roots can grow 5m above the ground surface

Why is the roots shallow?

The roots that anchor underground are shallow as water is available throughout the year (high rainfall), hence there is no need to develop deep roots to tap into underground water.

What are mangroves?

Mangroves are natural vegetation found along or very close to the coastline.

Where do mangroves grow?

Mangroves grow in brackish conditions. This means that the water where mangroves grow has a mixture of saline and fresh water

What is the special feature of mangroves?

They are the only trees in the world that can tolerate saltwater, in which water with higher salinity compared to fresh water, excreting the excess salt through their leaves.

What is the growth pattern of roots for mangroves?

Numerous long roots which form nest-like structures

What is a mangrove forest?

Collection of mangrove plants that form a habitat

Where can they be found?

On every continent except for Europe and Antarctica

What do these forests help to form?

Unique habitats which can shelter an immense diversity of wildlife, including numerous endemic species.

What are the climatic conditions that support mangrove forests? (3m)

Temperature

• Mangrove forests are found in areas with tropical temperatures of an average 27 ⁰C, with no seasonal changes

• There is only a range of 2-3 °C in terms of temperature changes.

Precipitation

• Even distribution throughout the year

• Total annual rainfall of more than 2000mm

Describe and explain the global distribution of mangrove forests

• Mangrove plants can be found along or very close to the coastline in the tropics, between the Tropic of Cancer (23 1/3⁰N) and the Tropic of Capricorn (23 1/3⁰S)

• They can be found on every continent except Europe and Antarctica. These plants cannot withstand cold conditions and thrive where the average air and water temperatures do not go below 20⁰C.

• The largest percentage of mangroves is found between the 5⁰ N and 5⁰ S latitudes

Characteristics of Mangrove forests

Physical Growth Conditions

• Mangrove trees need calm, sheltered and shallow coastal areas to grow. The calm, sheltered water conditions encourage the accumulation of nutrient-rich sediments

• Found in areas near river mouths

• Can grow in saline conditions

What are some examples of the common mangrove species found in Southeast Asia?

Avicennia, Sonneratia, Bruguiera and Rhizophora

Compared to TRFs, what is the growth density of mangroves around the world?

Less dense than TRFs

What are the three HORIZONTAL ZONATIONS of mangrove forests?

Coastal zone

Middle zone

Inland zone

What is the vertical growth patterns of mangroves?

No vertical layers

More or less uniform in height at 10-15m tall

How are mangroves distributed for horizontal zonations?

Each mangrove species tends to be distributed in particular areas according to certain conditions, with each area characterised by a dominant species

What are the diversity characteristics of mangrove forests?

• Less diverse than TRFs

• About 60-70 mangrove tree species worldwide because not many land species have evolved to survive in waters of higher salinity

What grows in these zonations?

These 3 types of zontations each contain

• different types of trees and roots

• Adapt to the saline and muddy environment

• Saltwater mangrove trees grow near the coast, but freshwater mangrove trees, which are less tolerant of land, grow inland.

Characteristics of coastal zone

Flooded for longer periods of time

nearest to the sea, flooded with salt water at high tides

Plant species here can tolerate higher salinity levels and longer periods of flooding

Trees have tube-like breathing roots, which are pencil roots

What is characteristics of pencil roots?

Just above the water during high tide to absorb oxygen

Characteristics of middle zone for trees

They have prop/stilt roots growing from trunks for anchoring plants firmly to muddy soil

Characteristics of prop roots and functions

Prop roots are roots that arise from the trunk and lower branches

They are aerial roots

Long and branch out from the middle of the trees

Prop roots help to hold trees firmly to the ground and absorb oxygen

When will roots become stilt roots?

When they take the function of flying buttresses when tree is older

Inland zone characteristics

Trees have knee-like roots to provide support on soft soil and absorb oxygen

Furthest away from the sea

Trees here are the least resistant to salty water, as the duration of flooding by the tide is shorter

EXAMPLE:

The Bruguiera(oriental mangrove) species that are the least salt-tolerant reside here.

What mangrove species have wide-spreading roots?

Avicennia and Sonneratia.

Hard to differentiate where one plant’s roots start and where another plant’s roots end

How do mangroves deal with the high salinity in water?

Roots of mangroves are able to exclude salt and only take in water. These roots are called salt-excluding roots (e.g. Bruguriera)

What are the adaptational features for mangrove leaves?

Broad leaves with a leathery texture to help prevent loss of moisture through transpiration

Drip tips enable rainwater to flow off quickly and easily

Adaptational features of mangroves (depositing excess salt on old leaves)

The Sonneratia (e.g.) is not able to secrete salt through its leaves

Instead, they deposit salt in older leaves, which they will eventually shed

The removal of salt in this way helps to prevent salt from building up within the plant

Adaptational feature: fruits (water dispersal)

Fruits of some species are buoyant, that is, able to float on water

This allows some of them to be carried away by water to other coastal areas

The little seedlings, called propagules, then fall off the tree and can be swept away by the ocean current

Adaptational feature: fruits (germination in mud)

These fruits are spear-shaped so that when fruits fall off, they are able to lodge themselves into the mud and germinate

This way, it is harder for the plant to be washed away by the time it lodges itself into the mud and germinates.

Adaptational feature: fruits (germination in tree)

Fruits of some species pre-germinate on trees, as the fruit may not be able to find a suitable spot to anchor and grow after the fruit falls off.

The fruit may fall during the high tide when the mud is not exposed. Pre-germination gives the fruit the best chance of success.

Adaptational feature: trunks

Mangrove branches start from the base of the tree above the waterline

as the tree leaves cannot survive submerged in water

The bark of mangroves is thin

The trunks of mangroves are thin and straight

Mangroves contribute to the environment in what way?

Part of the climate resilience toolkit, acting as natural barriers to protect shorelines from erosion. They can reduce wave height by up to 66%, which is becoming increasingly important as the frequency of severe storms has risen by 40%.