Tundra is a low, dense vegetation type consisting of small shrubs, perennial herbs, lichens, and bryophytes that can be found in cold, humid climates in polar or alpine zones. The tundra region has long and cold winters, short and cool summers, little precipitation and strong winds. Permafrost is common under the soil. The surface only melts in the summer, and the surface is poorly drained and often saturated. Tundra can be divided into polar tundra and high mountain tundra. The former is located in the border regions of Eurasia and North America, and the latter is located in temperate cold and humid alpine areas.