Covers approximately 20% of the Earths land. Extremely cold climate Simple vegetation structure Limitation of drainage Short season of growth and reproduction Large population oscillations
The ground is permanently frozen 10 inches to 3 feet (25 to 100 cm) down so that trees can't grow there. The bare and sometimes rocky ground can only support low growing plants like moss.
In the winter it is cold and dark and in the summer, when the snow and the top layer of permafrost melt, it is very soggy and the tundra is covered with marshes, lakes, bogs and streams that breed thousands of insects and attract many migrating birds.
The average annual temperature is -18° F (-28° C). The sun barely rises during some months in the winter, and the temperature can drop to -94° F (-70° C).
During the summer the sun shines almost 24 hours a day. Temperatures can get up to 54° F (12° C), but it can get as cold as 37° F (3° C). Average summer temperatures range from 37° to 60°F (3° to 16°C).