What is a tundra biome?

The tundra is the coldest of the major land biomes, defined by low temperatures, little precipitation, and a very short summer growing season. A defining feature is permafrost, a layer of permanently frozen ground beneath the surface that stops water from draining and prevents deep roots, which is why trees cannot grow there. Instead, the tundra supports low vegetation like mosses, lichens, grasses, and dwarf shrubs that hug the ground for warmth. Arctic tundra rings the top of the Northern Hemisphere, while alpine tundra occurs above the tree line on tall mountains. Despite the harsh conditions, the tundra bursts with insects, migratory birds, and animals such as caribou, arctic foxes, and lemmings in summer.