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

 Return to Introduction to Biomes
Home  Science Notes
 Lesson 8 Lesson 5  


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