A Tundra is a Bio-me where the tree growth is hindered by low temperatures and short growing seasons. Arctic tundra occurs in the far Northern Hemisphere, north of the taiga belt. The word "tundra" usually refers only to the areas where the subsoil is permafrost, or permanently frozen soil.
Arctic tundra contains areas of stark landscape and is frozen for much of the year. The soil there is frozen from down, and it is impossible for trees to grow.
Temperature changes in polar deserts frequently cross the freezing point of water. Most of the interior of Antarctica is polar desert.