Tundra is a biome characterized by extremely cold temperatures and poor drainage, typically limited by the presence of permafrost—a layer of permanently frozen subsoil. Due to the shallow active layer that thaws in the short summer, nutrient cycling is slow, and the growing season is extremely brief. Vegetation in this biome is adapted to harsh conditions, often consisting of low-growing plants such as mosses, lichens, sedges, and dwarf shrubs, which survive by adhering close to the ground to minimize wind exposure and cold stress. The ecological structure supports specialized fauna that are adapted to seasonal changes, often exhibiting migration patterns or having thick insulating layers to survive prolonged periods of cold.