In the north of Siberia, the grounds are permanently frozen, sometimes several hundred meters deep; that's what people call "Permafrost" grounds.
In Siberia, the weather is dominated by a strict Continental Clime with 5-7 months of winter and temperatures as low as -50°C (-58°F) or even below, and a very short summer with hot days.
In the Tundra, the uppermost layer of the grounds is melting for a very short time during summer, so that the roots of plants can penetrate a little further into the ground. There are no trees in the Tundra; but you will find a variety of shrubs, grasses, and other typical plants of high mountain fauna.
Due to the frost, the timber-line is about the same as the Arctic Circle, where the Tundra is giving way to the Taiga, a boreal zone; the transition area between those two zones is called Forest Tundra. This coniferous forest ist the single largest woodland worldwide; its size is an estimated 800 mio hectare. The most prevalent trees are spruces and larchs, as well as pines in the south.