temperate forests

Deciduous forest

  We’ve learnt that deciduous leaves fall off in autumn in preparation of winter to minimize the amount of water loss when transpiring. It is also known that the leaves turn brown during this period. However, you may asked one question. How do the leaves turn brown?

  It is because during the shorter days and cooler weather of autumn, green chlorophyll in the leaves begins to decompose, revealing orange, yellow, and red.  This is because the plant has limited sunlight and water thus the leaves are unable to continue producing chlorophyll. Actually, these colors were present in the leaves all year long, but had been hidden by the green pigment of the chlorophyll.  

Since there is no more chlorophyll, how do the trees survive without leaves during the winter when they cant make food?  

To prepare for winter, deciduous trees and plants become dormant. They lose their leaves and seal the places where leaves were attached with a protective covering called a leaf scar. If they kept their leaves, the water in the leaves would freeze into ice, damaging the leaves and leaving the plant vulnerable to bacteria or fungi. Plants also make a concentrated sugar solution to stop water from freezing in their stems.

How does the tree know when to start growing leaves? The longer days and warmer weather of spring signal to the trees to grow new leaves and begin photosynthesis again.

Then how does the environment have an effect on such adaptation? The trees get a lot of sunlight in summer and thus are able to get energy to make food for the plant. Some food is stored in the roots for the next spring. However, when the temperature gets lower, the tree cuts off the supply of water to the leaves and seals off the area between the leaf stem and the tree trunk. This is why trees get limited supply of water and sunlight during autumn. Finally, when the temperature get warmer, the leaves then start growing back.

We also learnt examples of tress like the Oak Tree. Leaves are big and broad to increase surface area to get as much sunlight as possible in summer. However, these leaves also losses a lot of water during transpiration making then shed their leaves in the autumn.

Knowing this, I have a question I can’t seem to find the answer to. Why do the trees have such big leaves if they lose a lot of water during the winter? Is it because they need to get a lot of sunlight during the summer? However, small leaves also can capture sunlight and make food for the plant. If this is so, why is it that the plant has big leaves instead of small leaves that will help decrease the amount of water loss during the winter? If they had small leaves, won’t they be able to make food even in the winter and don’t have to stay dormant?

Many of us have seen leaves found in temperate forests and tropical forest. There is a distinct difference in leaves for both climates. Then, what effect does climate have to the edge of the leaf?

Leaves in temperate deciduous forests mostly have toothed edges but the leaves in tropical rainforest have smooth entire edges. This is because climate and leaf margin are closely tied. The leaves of tree species native to colder climates usually have more teeth cut more deeply into the leaf; they are more dissected on their edges so they have a higher perimeter-to-area ratio. The presence of a toothed edge seems to assist in unfolding young leaves from buds so they can maximize photosynthesis when breaking winter dormancy.

The forest floor grows rapidly in summer and spring and disappears during winter. Another question I couldn’t find an answer to is, why the plants on the forest floor disappear when they can get as much sunlight as they want during autumn and winter when the leaves drop and they can get a lot of sunlight? Is it because its too cold? Is it also because of water loss?

Coniferous forest

We learnt that the coniferous forest is evergreen. They have cone shaped structures to allow snow to slide off and needle-like leaves to lessen water loss. They also have supple braches don’t break easily so the tree won’t fall off because of imbalance of weight. The leaves are evergreen because they do not lose much water during transpiration as they have small surface area. Thus the leaves always stays green and does not need to fall off.

We also know that there is only one type of plant in the coniferous forest, but why is that so? Is it because not many plants cant adapt to such a climate thus resulting in low diversity?

The soil in coniferous forests is not fertile unlike the soil in temperate deciduous forest. Why?

In the deciduous forest,it is not evergreen and the leaves drop very autumn thus resulting in very fertile soil. This is also the reason why their leave litter is so thick. Remember the trip to bukit timah? The leaf litter there, a tropical rainforest is already quite thick; but the leave litter in the deciduous forest is thicker because the leaves drop more. However in coniferous forests, it is evergreen and the leaves hardly drop thus not providing any nutrients. Thus, the soil isn’t fertile.

Bukit Timah Nature Reserve(:

Haha, this is some information about the BTNR that we're going tmrw. Yay:D Haha so cool.

 

 

Singapore, lying within the tropical zone, and blessed with high temperature and high rainfall all year round, was once covered with tropical rainforests. It has been estimated that primary rainforest once covered about 82% of the land area of Singapore, approximately 442 km² or 44,200 hectares (ha).

However, ever since people have settled on the island, more and more of the original natural vegetation has been cleared, to make way for settlements and for agriculture and plantations. Today, only 192 ha or 0.43% of the original forest cover remains. Most of the surviving primary forest is restricted to the more pristine areas of the 163ha Bukit Timah Nature Reserve (BTNR), and in scattered patches throughout the 3,043 ha Central Catchment Nature Reserve (CCNR). The remainder of these two nature reserves is occupied mostly by secondary forest.

The Bukit Timah Nature Reserve contains the largest patch of primary rainforest left in Singapore. Bukit Timah Hill, at about 163.63 metres above sea level, is the highest point in Singapore.

Importance of Tropical Rainforests in Singapore
Even though we do not possess very large areas of tropical rainforests, as compared to other countries like Malaysia, Indonesia, Congo and Brazil, our few remaining rainforests are still very important, for various reasons.

• Tropical rainforests have taken hundreds of years to develop and once cleared, they are almost impossible to replace. There are many species of plant and animal in the rainforests, most of which are found nowhere else in the world. And when they are destroyed, some species may become extinct and be lost forever. These include plants with medicinal value which have not even been identified and tested. So, rainforests in Singapore now perform the very important role of providing a place for many species to thrive and grow.
• Rainforests in Singapore also provide us with an idea of what Singapore was like at the beginning of the nineteenth century. Singapore was once covered by tropical rainforests. Hence, by looking at the rainforests now, we get a glimpse of what Singapore might have been like then.
• The rainforests form our water catchment areas. When rain falls, the rainwater is trapped by some of the leaves on the trees. The rainwater then drains slowly into the ground and may be collected in the nearby reservoirs. In this way rainforests help us 'catch' the rain and add to our water supply.
• As Singapore becomes increasingly built up, rainforests act as giant 'lungs' by absorbing large amounts of carbon dioxide and producing oxygen in exhange.
• The rainforests are beautiful and scenic, with fresh air and natural surroundings. They provide us with a peaceful alternative to the busy city, and these last bastions of wilderness are places of peace and quiet where Singaporeans can go to enjoy and appreciate nature at its best. They can also be a tourist attraction.
• The rainforests are a legacy of our natural heritage, and it is important to protect and conserve them, keeping them intact for the country's future generations to learn and appreciate the richness of our country's heritage.