Geog (chap 5) Flashcards
What is climate?
Climate refers to the average weather conditions of a place over a long period of time, usually more than 30 years.
Where is tropical climate experienced?
The tropical climate is experienced by many countries located between the Tropic of Cancer and the Tropic of Capricorn.
Characteristics of tropical climates
A tropical climate is the climate experienced by areas found within the tropics. It includes a high annual rainfall of about 2,000 mm but it can go up to 4,500 mm. Moreover, there is rainfall throughout the year and there is no month in which rainfall is very low or absent. Moreover, temperatures are high ( 20°C-30°C) throughout the year. Tropical climate is where natural vegetation such as tropical rainforests and mangroves are found.
Describe the global distribution of tropical rainforests.
Tropical rainforests are generally found in places close to the equator, between the Tropic of Cancer (23.5°N), and the Tropic of Capricorn (23,5°S). Some of the main rainforests are found in places such as Southeast Asia, and the Congo Rainforest in Africa. The largest rainforest is the Amazon rainforest, located in South America.
State the characteristics of tropical rainforests.
Firstly, due to the abundant sunlight and high rainfall throughout the year, the vast majority of the rainforest is evergreen. They do not shed all their leaves at particular times of the year, and grow new leaves continuously to replace ones that die and fall off, maintaining a constant green appearance.
The intense contest for sunlight causes plants to grow as tall as possible. However, as not all plants grow to the same height, the rainforest comprises of a 3-layered vertical forest structure; emergent, canopy, and undergrowth.
The emergent layer contains the tallest trees in the tropical rainforest They can be 30m and above in height. The trees receive high amounts of sunlight compared to other layers of the rainforest. This layer prevents 97-98% of the sunlight of the sunlight from passing through to reach the forest floor. Low vegetation is present in this layer.
The canopy layer is very dense with trees, containing the most trees in the rainforest. They are between 20m-30m in height. The trees receive high amounts of sunlight.
The undergrowth layer contains vegetation that grows up to 10m in height. The amount of vegetation found in this layer is sparse as very low amounts of sunlight is able to reach this layer. However, when gaps in the canopy appear, a lot of sunlight is able to reach the undergrowth layer, and plants start growing upwards very quickly and fill up the gaps.
Rainforest plants’ adaptations.
features: Broad leaves, drip tips, waxy leaves, buttress roots
REMEMBER Identify, Describe, Eplain.
Conditions for growth of mangrove forests.
- mangrove plants are unable to withstand freezing temperatures and grow best where average air and water temperatures do not fall below 20°C.
- They require calm water conditions, as the water conditions will encourage the accumulation of fine sediments containing nutrients, and will allow seedlings to take root and grow without getting washed away by strong waves. Hence, mangrove forests are usually found in sheltered environments along or very close to the coast, such as shallow river mouths or behind islands.
- They grow better in places with high water salinity, as not many other plants are able to survive in high water salinity levels, hence reducing the competition for resources for survival.
What are the characteristics of mangroves?
Mangrove plants are evergreen.
As mangroves cannot tolerate shaded conditions and need to obtain as much sunlight as possible. Hence, mangrove plants are uniform in height. The mangrove forests exhibit a horizontal zonation (from coast, moving inland) and comprise 3 zones. They include 4 groups of trees; Sonneratia, Avicennia, Rhizophora, and Bruguiera.
Zone one comprises plant species that are able to tolerate higher salinity levels and longer periods of flooding; Sonneratia and Avicennia. Zone one is close to the low tide level, and is flooded for longer periods of time by the tide compared to areas that are further inland and closer to the high tide level.
Zone three and four comprise Rhizophora and Bruguiera species respectively. These species are not as tolerant of these conditions and are found closer to the high tide level where the duration of flooding is much shorter.
How many different mangrove species are there globally?
about 60-70
Name each type of mangrove tree from low tide to high tide.
Sonneratia, Avicennia, Rhizophora, Bruguiera.
Adaptations of mangroves: Salt-secreting leaves.
Salt-secreting leaves, salt-excluding roots, aerial roots
Mangrove species such as Avicennia have salt-secreting leaves that enable them to remove salt from the saline water that their roots have absorbed. The excess salt crystals are left behind on the leaf surface and are subsequently removed by rain or wind. This helps to prevent salt from building up within the plant.
Adaptations of mangroves: Depositing salt.
Salt-secreting leaves, salt-excluding roots, aerial roots
Mangrove species such as Sonneratia deposit excess salt in older leaves which they eventually shed. This also helps to** prevent salt from building up within the plant.**
Adaptations of mangroves: Salt-excluding roots.
Salt-secreting leaves, salt-excluding roots, aerial roots
Other species including Bruguiera deny the intake of salt using their roots. They have roots which prevent salt from entering. This also helps to prevent salt from building up within the plant.
Adaptations of mangroves: Aerial roots.
(general)
Salt-secreting leaves, salt-excluding roots, aerial roots
There are four types of aerial roots: Cone roots, pencil roots, prop roots, and knee-bend roots.
Aerial roots are roots that partially grow above the soil surface, allowing them to take in oxygen directly from the air when they are exposed during low tide, allowing them to survive in the oxygen-poor soil. (** - explanation)
The roots help to anchor the mangrove plants to the soft soil, preventing them from being uprooted and washed away by strong waves. (** - explanation)
Avicennia has pencil roots
Sonneratia has cone roots
Rhizophora has prop roots
Bruguiera has knee-bend roots
Identify the 2 continents, the region C where the tropical rainforests are distributed globally, and name the 2 largest tropical rainforests.
Continents: Africa, Asia
Region: Southeast Asia
TRF: Amazon (located in South America), Congo (Central Africa)
