I. Tundra biome Located in the tundra climate zone, mostly in the Northern Hemisphere around the Arctic Circle, and is considered the easiest to define and is the most continuous of all biomes.
Arctic tundra is a formation class which has a brief summer of long days and short or absent nights.
Alpine tundra is another formation class that occurs above the treeline at high elevation, and resembles arctic tundra in appearance. Permafrost , permanently frozen soil, is present, and its upper layer melts in the summer creating marshy conditions over wide areas. Decomposition of dead plants is slow due to cold temperatures, so a thick organic layer of topsoil develops here. Tundra plants are small, and consist of sedges, grasses, mosses, lichens, forbs, and occasionally the dwarf willow, a very low shrub. Also found in higher elevations in some mountain ranges, like the Rocky Mountains.