Biogeographical processes
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2A.Boardwalk through
warm temperate rainforest |
Rainforests are an amazing system of recycling and sustainable use that
creates this unique ecosystem. It is unique because the factors
that must come together in just the right amounts to result in a
rainforest are too numerous to count and this is why the rainforests
we have need protecting.
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2B. Subtropia l rainforest:
epiphyte |
Within a rainforest the most important organisms are the trees. The trees are responsible for maintaining the balance of light and evaporation that lead to the other features of a rainforest.
The trees in an area with sufficient rainfall will grow very
tall, cutting off sunlight to the forest floor and creating a
shady moist environment that supports plants like ferns. The higher
than normal rainfall, together with the shade which cuts down
evaporation, makes the soil moist but still warm enough to make
the rotting of any organic matter on the forest floor a relatively
quick process. This is aided by the bacteria and insects that
make the forest floor their home.
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| 2C.The Big Fig: buttress roots |
As the organic matter breaks down it becomes leachate. When it rains, the leachate
soaks through the shallow soil, in the process of
leaching. This moves the nutrients that are contained in the
rotting material down into the soil profile,
where the trees and plants can use it. Because of the large number
and the size of the lush rainforest vegetation, the organic matter
is used very quickly near the top of the soil profile. This means
that the process that keeps the rainforest alive is a relatively
rapid cycle of the breaking down of plant matter and its reuse by
other plants. As an additional part of this cycle, the rainforest
plants help to maintain their own climate. The large rainforest
trees are capable of absorbing most of the water that falls as rainfall
in the rainforest and they then return it to their own area through
evapo-transpiration (unlike other areas where rain falls and much
of it runs off to the sea). This means that condensation occurs
over the rainforest, continuing the higher than normal rainfall.
Overall this makes the rainforest an amazing recycler and an efficient,
sustainable system. As long as it remains undisturbed, the trees
will continue to grow and break down and be fed by old trees and
supported by the climate they need.
This whole process gives rise to the distinct layers
of the rainforest. The canopy forms as the large trees
all strive to get the sunlight they need to grow; this makes them
spread out, filling in the gaps that might otherwise let sunlight
through. Under this is the middle layer or sub-canopy,
which consists of smaller trees that require less sunlight and
the vines and epiphytes that grow on the trunks of the largest
trees. Below this is the forest floor, which is a shady
area where shade loving plants like ferns grow, along with mosses
and fungi in the cooler moist conditions.
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| 2D. Forest floor:leaf litter and ferns |
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| 2E.Boardwalk to Big Fig: forest
floor |
To live in these conditions, plants of the rainforest have specially adapted and
continue to adapt their characteristics. For instance, to be able
to stand up in the shallow soil and to tap into the leached nutrients,
the trees and plants have developed shallow root systems. Buttress
roots in larger trees help them to stand up and obtain more oxygen.
The Big Fig (photo 2C) displays these buttress roots.
Rainforest plants also tend to have soft, wide, horizontal leaves
that can gather more sunlight and have drip tips which speed up
the movement of rainwater off the leaves, to stop it affecting
photosynthesis or causing fungal growths.
Some trees live a parasitic life, or at the very least, have
a relationship of dependency on other trees in the forest. Strangler
figs have fruit that attracts birds, such as figbirds, which upon
eating the figs drop the seed in their faeces. If this falls in
the fork of a tree, the juvenile fig can take root on the other
tree, growing and strangling its host until it reaches the forest
floor and its aerial roots are able to take root in the ground.
This kills the host tree and allows the Strangler Fig to occupy
its place in the competition for sunlight and resources.
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| 2F. Birds nest fern |
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| 2G.Liana vine |
Epiphytes are plants which grow on the sides of taller trees, where they can have
better access to sunlight than they would on the forest floor. They
get access to organic matter that falls from the host tree in the
form of leaves, rotting fruit etc. These plants do not harm the
tree but simply live with it.
Together all these plants and the processes and adaptations that support them make up the basic biological processes of the rainforest that give rise to the biogeographical processes (the study of the processes of the distribution of living things) of the rainforest.
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