Page 21 - The World About Us

Malaysia forest
2.1.5
1.1.1

How are nutrients cycled through the rainforest biome?

All ecosystems require both energy decaying and decomposing leaves. fig.54 Gersmehl diagram showing nutrient
and nutrients in order to func on. In the rainforest the forest floor is cycling in a tropical rainforest.
Energy is transferred through food damp and warm. These are ideal
chains and webs from primary condi ons for ro ng, so leaves here Biomass
producers to primary consumers, break down rapidly. As a result few Precipita on
through secondary consumers and nutrients are found in the li er Fallout
upwards to the apex predators. compared to the biomass.
Nutrients, which are the elements As organic ma er breaks down, the
needed to turn simple molecules like nutrients are taken up rapidly by the Uptake
glucose into more complex fats and tree roots. The trees o en have Li er
proteins, are also passed through the symbio c rela onships with fungi
ecosystem. They pass from one which increase the breakdown and Decomposi on Soil
element of the ecosystem to another. uptake from li er to biomass. Most
Some mes the same elements are rainforest trees have dense mats of
used over and over again; nutrients surface roots to absorb nutrients Leaching
cycle through the ecosystem. before they are washed away, or Runoff
Weathering
The Gersmehl diagram in figure 54 leached, by the very heavy rainfall.
shows how nutrients cycle through the When rainforests are cut down the A Gersmehl diagram shows the rela ve
three stores in the rainforest: biomass, loss of trees and their associated fungi scale of each of the stores of nutrients in an
ecosystem, through the compara ve size of
li er and soil. Most nutrients are stored reduces nutrient cycling. This results in the circles. The respec ve importance of
in the living material, mostly trees. The increased run-off and leaching. This the inputs, transfers and losses is shown by
li er refers to the organic ma er no loss of nutrients results in the rapid the thickness of the arrows.
longer part of the living plants and decline in the nutrient stock of the
animals, so this is mostly dead, ecosystem.

Water cycling in the rainforest

Water is also cycled through the evapo-transpira on.
rainforests. In some rainforests up to 50% Around one quarter of water is lost to
of the rainfall has reached the air a er the forest as run-off. This lost water is
being transpired by the plants as a result replaced by rain brought in on global
of photosynthesis. Another 25% is winds from the oceans. Deforesta on
evaporated by the sun off the leaves of disrupts the water balance of the forest
plants a er a previous rainfall. Collec vely ecosystem. It can result in drought where
these two processes are referred to as previously there was rainforest. fig.55 Tree roots & fungi recycle nutrients.

fig.56 Deforesta on, shown here on the borders of Amazonia risks, not just KEY TERMS
losing the trees, but changing the weather and climate as well.
Gersmehl Diagram: created in 1976 by P.F.
Gersmehl to show the differences in stores
and nutrient flows in different biomes.
Nutrient cycling: this describes the
movement of nutrients needed for life
throughout the different elements of an
ecosystem.
Outputs: these are losses from a system,
such as nutrients washed away by rivers.
Stores: these are where the nutrients are
held within an ecosystem - the biomass,
litter and soil.
Transfers: this describes the path by which
nutrients move from one store to another
via a variety of physical and biological
processes

21

Biodiverse ecosystems are under threat from human activity.