CHAPTER 5: SPATIAL DISTRIBUTION OF TROPICAL RAINFORESTS AND MANGROVES

Question 1

What is natural vegetation? Give examples.

Answer 1

Natural vegetation refers to plant life which covers particular parts of the world’s land area, without human interference. Tropical Rainforests, Mangroves, Desert.

Question 2

What is climate?

Answer 2

Refers to the average weather conditions of a place over a long period of time(more than 30 years).

Question 3

What is the tropical climate?

Answer 3

The part of the world located between the tropic of cancer and the tropic of capricorn.

Question 4

Where are mangroves found?

Answer 4

Along the shores/coastal areas

Question 5

Where are tropical rainforests found?

Answer 5

In the tropical climate very close to the equator.

Question 6

What do plants in the tropical climate need to survive?

Answer 6

They get a high amount of rainfall and a lot of sunlight.

Question 7

Why are tropical rainforest plants different from temperate deciduous forests?

Answer 7

They do not shed all of their leaves at a particular time of the year, instead they continue to grow and replace old leaves that die and fall off, thus maintaining a constantly green appearance. However, temperate deciduous forests shed their leaves before each winter season to conserve water for the dry season.

Question 8

Do tropical rainforests have a variety of plant species?

Answer 8

Yes. They have a very large variety of plant species, ore that any other type of ecosystem in the world and no plants in a rainforest are more significantly represented than others.

Question 9

What are the 3 main layers in the vertical forest structure?

Answer 9

Emergent, canopy, undergrowth

Question 10

what does the Emergent layer consist of?

Answer 10

The crowns of the tallest trees in the rainforest growing up to 30 metres and more form the emergent layer.

Question 11

What does the canopy layer consist of?

Answer 11

Most trees grow up to 20-30 metres. Since they grow very close together, their crowns interlock to form a thick and near continuous mass of branches and leaves to form the emergent layer.

Question 12

What does the undergrowth layer consist of? how is the amount of vegetation in this layer?

Answer 12

Below the canopy layer where little sunlight is able to reach this layer due to the leaves in the canopy layer blocking 97-98% of the sunlight, not many plants grow here, except plants that are able to grow in shade and the seeds of the leaf. The amount of vegetation growing here is relatively sparse except when there are gaps in the canopy such as when a canopy tree falls down and near riverbanks. Certian species of undergrowth plants take advantage of this and grow upwards very quickly and filling th egaps.

Question 13

What are the special features of rainforest plants

Answer 13

buttress roots, drip tips, waxy leaves, broad leaves

Question 14

Why do they have broad leaves?

Answer 14

Broad leaves means more surface area. This enables the plant to capture as much sunlight as possible to make more food for it’s own survival and growth.

Question 15

Why do they have drip tips and what are they?

Answer 15

Drip tips are leaves with small narrow tips that point downwards. Drip tips together with waxy leaves allow rainwater that falls on the leaves to flow off easily, which prevents the leaves from fungi and bacteria growing on them as it dries quicker, given the frequent heavy rainfall that occurs. This also prevents the leaves from having too much water and dropping off.

Question 16

Why do they have waxy leaves?

Answer 16

These give the surface of leaves a glossy look and helps them reduce the amount of water vapour that it loses to the atmosphere through transpiration, since rainforests have high temperatures.

Question 17

Why do they have buttress roots?

Answer 17

Buttress roots can grow up to 5 metres above ground space and they keep rainforest trees which can grow to great heights upright and prevent them from toppling over.
Tropical rainforest trees require the support provided by the buttress roots as the rest of their roots do not extend deep beneath the ground surface as nutrients are concentrated in the topmost layer of rainforest soils(released when fallen leaves and branches decompose). This alows them to absorb the nutrients more quickly.

Question 18

Do Mangroves have a variety of species?

Answer 18

No. There is only a total of 60-70 mangrove species worldwide as not many plant species hav evolved to survive the waters of higher salinity.

Question 19

what are the plants in Lower lying parts of the coast why are they found there?

Answer 19

Close to the low tide level, thus flooded for a longer period of time compared to areas further inland, closer to the high tide level. Mangrove species which are able to tolerate higher salinity levels and longer period of flooding are found closest to the low tide level. (Avicennia, Sonneratia)

Question 20

what is the Density of mangrove forest compared to tropical forest and why?

Answer 20

The density in a mangrove forest tends to be significantly lower than in a tropical rainforest, resulting in less competition for sunlight as the coastal environment is difficult to survive in and coastal plants need to obtain as much energy from the sun as possible. But tropical rainforests recieve a lot of sunlight so they are very dense

Question 21

Why does a mangrove have a horizontal zonation?

Answer 21

Because only some mangrove plants can survive the high salinity and withstand longer periods of flooding by the tide compared to others.

Question 22

what are the plants in higher inland parts of the coast why are they found there?

Answer 22

Rhizophora and bruguiera are found closer to the high tide level instead where the during of flooding by the tide is shorter as they cannot tolerate long periods of flooding and high levels of salinity like the Avicennia and sonneratia.

Question 23

what are the special features of Mangroves?

Answer 23

salt-secreting leaves, salt-excluding roots, aerial roots

Question 24

Which group has salt secreting leaves? What do they do?

Answer 24

Avicennia

Question 25

Which groups does not have salt secreting leaves? what do they have?

Answer 25

Sonneratia. They deposit excess salt in older leaves which they eventually shed. The removal of salt in this manner helps to prevent salt from building up within the plant.

Question 26

What are the functions of aerial roots and their characteristics? Why?

Answer 26

They all grow partially above the soil surface, enabling them to take in oxygen directly from the air when they are exposed during low tide as the soil is waterlogged as it is flooded for several hours, poor in oxygen, soft and unstable. This helps them survive oxygen poor soil. The roots also help to anchor the mangrove plant to the soft soil, preventing them from being uprooted and washed away by the strong waves.

Question 27

What are the different types of aerial roots?

Answer 27

Cone roots, prop roots, knee-bend roots, pencil roots

Question 28

What are the roots of a bruguiera?

Answer 28

Have knee-bend roots, bend upwards to emerge from soil bending down towards the soil at regular intervals.

Question 29

What are the roots of a Rhizophoria?

Answer 29

curved prop roots, grow from trunk and lower branches towards the ground. (broader base around it)

Question 30

What are the roots of a Avicennia?

Answer 30

have pencil roots(known as that due to slender appearance) can grow up to 20 cm tall

Question 31

What are the roots of Sonneratia?

Answer 31

have cone roots which are thicker (known as cone because of it’s cone appearance) can grow up to 1.5m tall.