woolly leaves to preserve moisture like desert plants, and many are 

 prostrate to avoid the winds and seek the protection of the snow 

 from the extreme cold. Grass is abundant, and in many ways the 

 meadows of the Arctic are similar to the savanna and steppe-lands. 

 Mosses and lichens are especially numerous in the ancient shield 

 areas. There are some 250 species of mosses. 



These plants develop high osmotic pressure and, therefore, can 

 stand low temperatures. Over 330 species of lichens have been 

 found. Lichens are less dependent than most other plants on the 

 type of rock or soil on which they grow because they are symbiotic, 

 one part living on another. In the bogs and water-logged areas the 

 sphagnum moss, peat, and sedges are the chief plants. Thus, the 

 tundra is an area of grasses, flowering plants, heath with berry- 

 bearing plants, mosses, and lichens, with a few stands of trees on 

 the better soils, and patches of dwarfed prostrate willows, junipers 



and aspen. 



PERMAFROST 



\z''\e' 



Fisure 2-3. — Trees with shallow roots grow in permafrost areas. 



All the plants in the tundra region have a very slow rate of 

 growth. The size of the plants is not an indication of age, and 

 many very small plants are 10 to 20 years old. It takes mosses 

 9 to 10 years to regrovv after they have been grazed by migrating 

 reindeer, because they grow only about V^ inch a year. 



The treeline which roughly follows the July isotherm of 50° F. 

 (lO'' C.) marks the northern edge of the vast coniferous forests. 

 In North America the treeline lies along the foothills of the Brooks 



26 



