Tundra is a treeless region with frozen sub soil. These are the coldest regions found in the Arctic Circle and mountains tops where temperature is very low. Those occurring at the tops of mountains are alpine tundra and those occurring in the arctic region are arctic tundra. Both have similar kind of climate.
Very few plants and animals survive the harsh climate. A Cover of snow exists till start of summer. Summer season exists only for about 50 to 60 days when sun shines for the most of the day.
Most of the arctic tundra is low-lying. The arctic tundra covers a blanket for 5 million square miles (one tenth of the earth’s land surface north of the tree line). Freezing cold winds, dark winter days and drought are the main reasons that prohibit the growth of trees in the tundra regions. The roots of the trees cannot get through the frozen layer under the soil. This permanently frozen layer of soil is called permafrost.
With the return of summer, millions of birds flock to the tundra region. Arctic tundra bursts into life when the surface of the frozen ground starts to melt. Insects, seeds and berries are plentiful. Unbroken day light allows continuous feeding. While ptarmigans and snowy owl stay around throughout the year, shorebirds and waterfowl are the summer visitors. Lichen, bearberries, reindeer moss and cotton grass are some of the most common plants that grow low to the ground.