Diagram of Tundra Food Web

      Only a few species live in this difficult environment. The food chains are short, and vulnerable to stresses. Permafrost under the temporarily thawed ground makes water drainage impossible, so there are many small lakes and puddles, and much of the ground is soggy. When all the water freezes it becomes unavailable to life forms, and so creates a sort of cold drought in which animals and plants may die of thirst. The detritus eaters, bacteria, fungi, and tiny soil organisms, work very slowly because the cold temperatures slow down chemical reactions. Available nutrients in the soil are therefore scarce, even though undigested material lies on the surface of the ground.

     Plants in this biome are small, perhaps four inches high. They form little cushions or mats that lie closely on the ground. The albedo of the plants is less than that of the surrounding soil, which lets them absorb a little more of the solar heat. The ground is a little warmer than the air, so the plants stay as close to the ground as possible. Some of them have little hairs on their stems to hold warmer air as the cold winds blow. The vegetation consists of grasses, wild flowers, sedges, mosses, dwarf willows, and lichens. Many of the plants are perennials so that they can store food from season to season. Most can reproduce vegetatively from underground shoots, as sudden freezing storms can occur at any time, and make seed production a gamble.

    The musk oxen eat the plants, but their predators do not live in this biome. The musk oxen reproduce slowly, and the availability of vegetation limits the size of their herds. They are driven toward the predators when food becomes scarce.

     The lemmings and the foxes are linked: more lemmings lead to more foxes, and more foxes lead to fewer lemmings. Their numbers fluctuate, but stay within the carrying capacity of the vegetation. When there are too few lemmings, the foxes starve.

    The snowy owl also hunts the lemmings. Snowy owls will leave the area when lemmings become scarce, and many do not return, but are killed by predators outside the tundra.

     Some parts of the tundra have additional animals: seasonally migrating birds, arctic mice, snowshoe hares, voles, and ptarmigans. Some areas even have migrating reindeer or caribou. The population dynamics remain carefully balanced, however. The plant communities are fragile, and the availability of light, warmth, and nutrients places absolute limits on the growth possible.
 The Tundra Biome

 An Energy Pyramid in the Tundra Biome

            
© Elizabeth Anne Viau, 1999. This material may be used freely for instructional purposes but not sold for a price beyond the cost of reproduction. Please inform the author if you use it at eviau@earthlink.net