In the Arctic, where glacial and Arctic deserts predominate, the processes of soil building occur only in rudimentary form. The soils are skeletal and low in humus. The subarctic north of Asia is occupied by a timberless zone of tundra vegetation. The subarctic climate and tundra vegetation give rise to specifically tundra-type soils, which are characterized by poor drainage (due to permafrost) and only a short period in which it is possible for organic substances to decompose. Those conditions result in the accumulation of undecomposed organic residues in the form of particles of peat. The poor drainage creates an oxygen-free ...(100 of 38030 words)