A Deciduous Forest Energy Pyramid
Deciduous forests are closer
to the equator than the coniferous forests of the tiaga, and
so they have a longer growing season. This gives the plants more
time to produce food, and the forest yields about 6000 Kilocalories
per square meter per year for animals to eat. These primary producers
form the first trophic level.
The trees in the deciduous forest shed their
leaves in winter. This prevents their branches from being broken
by the weight of the snow, but also means that they have to grow
leaves anew each spring. The trees and shrubs produce flowers,
seeds, and fruits, such as wild cherries and persimmons. Many
of the shrubs beneath the trees also produce fruit, such as huckleberries,
blackberries, and thimbleberries. below the shrubs there are
wild flowers, clumps of grasses, and ferns.
Herbivores
eat the leaves and fruits of the forest. Some of the animals
that live in coniferous forests also live here. Squirrels, small
rodents, and deer find food in the deciduous forest, and other
plant eaters, including many birds and insects, are also members
of the community of primary consumers. These animals
are on the second trophic level. These animals can use the 6000 Kilocalories
per square meters per year produced by the plants, but the most
of this energy is used up in the processes of living, such as
breathing, circulating the blood, growth, and reproduction. Only
about one tenth of the energy is stored in the bodies of the
herbivores, so animals eating these herbivores can only get 600
Kilocalories per square meters per year from their bodies.
The small
carnivores, the secondary consumers, form the third
trophic level. Many of these animals, such as woodpeckers
and skunks, eat insects, while others, such as racoons, foxes,
and snakes, eat the small rodents and frogs. The small carnivores
have 600 kilocalories per square kilometer per year to eat, but,
again, nine tenths of these Kilocalories are used up in keeping
the animals alive. The bodies of the secondary consumers contain
only 60 Kilocalories per square meter per year.
This biome can support
a fourth trophic level. Large carnivores, such as bears and cougars,
form a layer of tertiary consumers. These animals
can eat the larger herbivores, such as deer, as well as anything
else in the biome. However, only 60 Kilocalories per square meter
are passed up to them from the lower levels, so they have to
be able to cover a lot of ground to be able to find enough food
to stay alive. Because these animals are at the top of the food
chain, they are called top predators.
No animals
prey on the top predators. This is partly because these animals
are so big, strong, and fierce, and partly because the nourishment
in their flesh represents only one tenth of the 60 Kilocalories
per Kilometer per year that they capture. This is only 6 kilocalories
per square Kilometer per year
Here is a diagram that shows the energy
numbers:
Notice that every time you go
up a trophic level, you divide the number of available Kilocalories
per square meter per year by 10.
This is a general rule for all
ecosystems.
Food Webs in the Deciduous
Forest
The Deciduous Forest
Copyright ® 1999. Elizabeth Anne Viau
and her licensors. All rights reserved. This material
may be used by individuals for instructional purposes but not
sold. Please inform the author if you use it at eviau@earthlink.net
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