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 land areas.

     The 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.

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 trophic level.

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 and recyclers)

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.