An Energy Pyramid in the Coniferous
Forest
The evergreen forest has a short growing
season. It produces about 3500 Kilocalories (food calories that
we count in diets) of plant material that animals can eat per
square meter per year. This vegetable material is produced during
the growing season, leaving dried grass under the snow and berries
on the bushes. Winter is hard for animals in this biome, and
some choose to hibernate or migrate to a warmer area in the winter.
Here we see a diagram of an
energy pyramid for the coniferous forest. At the broad green
bottom of the pyramid we see that for every square meter of forest,
the plants produce about 3500 Kilocalories each year. These calories
are in the form of leaves, grasses, twigs and branches. The plants
are called the primary producers, because they
make all the food from sunlight, carbon dioxide in the air, water,
and minerals. These plants form the base of the food chain, and
all the animals are dependent on them.
We move up a trophic
level to the animals who eat
the plants directly. They are called the primary consumers.
When they eat the plants, most of the energy in the plants goes
to respiration, which includes breathing and other processes
of the body. When energy goes to the next trophic level, nine
out of every ten Kilocalories get used up just making the animals'
bodies work. Only 10%, (one Kilocalorie in ten) of the energy
is actually stored in the animals' bodies. For each square meter
of ground, only 350 kilocalories of animal flesh and bone are
turned into animals.
The next
trophic level is the level of the secondary consumers.
These animals eat the bodies of other animals. Again, nine Kilocalories
out of ten get used up making the bodies of these predators work.
Out of every 350 Kilocalories that these predators eat, only
35 Kilocalories become the bodies of these animals. Note that
some of these predators are small, eating insects. frogs, and
small rodents.
This ecosystem
has another trophic level of predators which are called tertiary
consumers. These predators are larger because they have
to cover a lot of territory to find enough to eat. They eat whatever
they can catch: herbivores of all sized and small predators.
Again, nine out of ten of the calories that they eat are used
up making their bodies work. Only 10% of the calories get turned
into predator bodies. This means that out of every 35 Kilocalories
that the predators eat, only 3.5 Kilocalories are used to build
bone and muscle in their bodies.
This graph shows just the Kilocalories,
and how only 10% of these kilocalories move up to the next trophic
level as consumable biological material. The rest of the energy
gets burned up just making the animals' bodies work.
Even small prey animals need
an impressive area of land to provide enough food for their needs
for a year. If you have read the page on Carrying
Capacity you know that land which is overused is
destroyed, so that we can assume that more land is actually needed
than the minimum required.
The land in this biome is shared
by the animals listed above and by many other animals that are
not mentioned, such as bear, deer, raccoons, skunks, insects,
birds, and rodents. The squirrel has to compete with the jay
for nuts, so must search for food over a larger area than the
one calculated.
Although we can calculate consumption
and food utilization for some of the animals that we see, many
measurements, such as how much of the plant material is eaten
by insects, is difficult to measure. Some of the organic material
is used by detritovores, who eat dead material.
Here are some food requirements and
the necessary areas needed to support some animals.
These are really just guesses, and
do not take account of feeding babies or sharing territories
or rocks in the territorial space or replacing animals that die.
However, even working with these numbers, you can see that it
takes a lot of land to support even a small animal!
|
Animal Requirements in KiloCalories |
|
Animal |
Weight |
KCal needed per day |
Ground area
needed per day (at a yield of about 10 KCal per day) |
Ground area
* 365 days = area per year |
KCal yield if eaten
at 800 KCal per pound |
|
| mouse |
1 oz |
10 |
1 meter squared per day |
|
50 |
|
| squirrel |
1 pound |
45 |
4.5 Meters squared per day |
|
800 |
|
| deer |
100 pounds |
100 * 15 = 1500 |
150 Meters squared per day |
|
80,000 |
|
|
Predators |
| owl |
4 pounds |
4 * 45 = 180 KiloCal per day |
4 mice = 4
meters squared |
It takes (4 mice a day
need 4 meters squared a day) 4 * 365 days a year to support this
owl = 1460 meters squared per year |
| Cougar |
130 pounds |
130* 15 = about 2000 KCal per day |
1 deer could
last 40 days = 9 deer a year |
9 deer * 150 Meters squared
each per day = 9 * 150 * 365 days = 492,750 meters squared |
Sumary of Information for the Coniferous Forest
Biome
Growing Season - may be less than 120 days per year
on earth
annual rainfall -- 12 -33 inches
The Evergreen Forest produces 3500 Kilocalories of
food for herbivores per square meter per year
This is about 10 Kilocalories per square meter per
day.
A Food Web in
the Coniferous Forest
The Coniferous Forest
Return to Introduction
to Biomes
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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