An Energy Pyramid in the
The tundra biome covers many
hundreds of square miles, and conditions vary from place to place.
Some areas are richer in plant life than our example here, others
are even more desolate. The part of the tundra that is being
described is covered with shallow pools of water and low-growing
plants. It ix populated mainly by lemmings, snowy owls, and arctic
foxes. The square meter that we are basing our calculations on
is all above water. When figuring out population densities, one
would have to allow for perhaps 20% to 35% water in calculating
tundra is a challenging environment, and the short growing season
limits plant growth. The tundra produces only 600 Kilocalories
per square meter per year for the herbivores to eat. Here is
a diagram of the energy available at teach trophic level.
can see how much energy per square meter is available at each
Primary Producers: (Plants)
The work of the plants is called the
first trophic level. The total amount of plant tissue produced
represents about 600 Kilocalories per square meter per year.
However, some of this material, such as woody stems, may be indigestible.
Edible material includes shoots, small leaves, small flowers,
and starchy tubers in which energy is stored for the next season.
Primary Consumers: (Herbivores)
These are the lemmings. The lemmings
consume the 600 Kilocalories, most of which are burned up in
metabolism. The body has many necessary functions, breathing,
circulating the blood, maintaining the heat of the body, digestion,
repair and growth, eliminating wastes, running around, and reproduction.
This burns up most of the Kilocalories that the animals eat.
Of the food that they eat, about10% is stored as an animal body.
This would be somewhere between (600 * .10 = 60) Kilocalories
that another animal could eat. Of course, the lemming is not
totally digestible -- bones, hair, and teeth may or may not be
digested. The lemmings and other prey animals are the second
Secondary Consumers (Carnivores)
Snowy owls and arctic foxes eat the
lemmings. A snowy owl eats 12 lemmings a day, bones, teeth, fur
and all. Again, most of the calories go to keeping the owl alive
and fueling its metabolism. If some mythical predator were to
eat owls it would get only six Kilocalories per square meter
per year. Snowy owls and foxes can survive on the third trophic level,
but there are no tertiary consumers that eat them.
The food chain here supports only three
trophic levels because carnivores have to cover a lot of ground
to find enough to eat.
Detritus Eaters (waste eaters
There are bacteria and other tiny life
forms that recycle organic waste material. The low temperatures
of the tundra mean that they process wastes slowly, but they
do help to keep the system going.
Another way to illustrate an energy pyramid is by using the
pictures of the animals, like this.
A Food Web in the Tundra
The Tundra Biome
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Photograph from a Corel CD-ROM : for viewing only,
not for downloading.
1999. Elizabeth Anne Viau and her licensors. All
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