A tundra is an area without high vegetation bordering a polar region. The vegetation consists of grasses, mosses, lichens and dwarf shrubs. The general climate on a tundra is very unfavorable for the growth of higher plants. The bottom has been frozen or snow-covered for at least six months. The growing season is very short and the average temperature in the hottest month is below 10 ° C. During the summer only the top layer of the soil thaws over a depth of 30 to 60 cm above the permafrost. Although the amount of rainfall is quite low, most soils on a tundra are swampy. This is because the water cannot sink into the frozen bottom layer and because the evaporation is also very low. Tundras are found in Russia, Iceland, Canada and Alaska, among others.
