geog chapter 5 trf and mangroves

What is natural vegetation?

Natural vegetation refers to plant life which covers particular parts of the world's land areas and develops without human interference. Certain types of natural vegetation exist in specific parts of the world because of the climate of a given location which determines the type of natural vegetation found there.

Where is the tropical climate?

Located between the Tropics of Cancer and the Tropics of Capricorn.

Describe the tropical climate

It has a high annual rainfall (average rainfall of 2000 mm, and can go up to as high as 4500 mm). There is also rainfall throughout the year and there are high mean annual temperatures throughout the year.

What are the four factors when describing climate?

Mean annual temp. (High >20 low

What are the three characteristics of TRF?

Evergreen, meaning that they don't shed their leaves at particular times of the year, large variety of plant species, meaning that no particular rainforest plant species is more significantly represented than others, and distinct vertical forest structure, as they grow as tall as possible due to the intense competition for sunlight. The structure layers are undergrowth, canopy, and emergent.

How have plants in the tropical rainforest adapted to their environment? (Leaves)

In a tropical climate, there is high mean annual temperature and high total annual rainfall. The trees have broad leaves to trap more sunlight and photosynthesise more. The leaves also have a waxy coating to reduce the amount of water lost through transpiration. The leaves also have drip tips to allow rainwater on the leaves to flow off easily, helping the leaves to dry quickly and preventing the growth of fungi and bacteria.

How have plants in the tropical rainforest adapted to their environment? (Roots)

Tropical rainforest trees that grow tall to reach for sunlight usually have buttress roots to keep them upright and prevent them from toppling over. They also have shallow roots to absorb nutrients from the rapid decomposition of dead matter quickly from the topmost layer of the soil.

Where are mangroves found?

Mangrove plants require calm water conditions. Hence, they are found in sheltered environments along or very close to the coast, as they grow better in water with higher salinity levels due to the lack of competition.

What are the characteristics of mangroves?

They are evergreen, meaning that they don't shed their leaves at particular times of the year. They also have a lower diversity of plant species compared to TRF as they are dominated by only 60-70 mangrove plant species worldwide compared to 1000 tree species in a small TRF. The density of trees in a mangrove forest is also significantly lower than in a TRF, resulting in less competition for sunlight. Due to the harsh environment, mangrove plants need as much energy from the sun as possible. They cannot tolerate shaded conditions, hence they are relatively uniform in height.

Which species are more tolerant to more flooding and higher salinity?

Sonneratia and Avicennia

Which species are less tolerant to more flooding and higher salinity?

Rhizophora and Bruguiera

Describe salt-secreting leaves in a mangrove plant

Mangrove species like Avicennia have salt-secreting leaves that enable them to remove excess salt from the saline water that their roots have absorbed by leaving behind salt crystals on the leaf surfaces which are removed by rain or wind. The Sonneratia species deposits their excess salt in older leaves which they eventually shed and prevent salt from building up within the plant.

Describe salt-excluding roots in a mangrove plant

Some mangrove species such as the Bruguiera plant have salt-excluding roots which prevent salt from entering.

Describe aerial roots in a mangrove plant.

Mangrove plants have developed special types of aerial roots that help them adapt to their environment, like cone roots, pencil roots, prop roots, and knee bend roots. The aerial roots of the mangrove plant species all grow partially above the soil surface which enable them to take in oxygen directly from the air when they are exposed during low tide, which helps them to survive in the waterlogged and oxygen-poor soil. The roots also anchor the plants to the soft and unstable soil, preventing them from being uprooted and washed away by strong waves.