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An Energy Pyramid in the Coniferous Forest

 

Energy Pyramid

    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