a natural zone of the subarctic region of the northern hemisphere, transitional between the forest zones of the temperate region on the south and the tundra zone on the north. Dense and sparse forests occupy 10–20 percent of the zone in the north and 40–50 percent in the south.
The forest-tundra zone, a band 30–50 to 300–400 km wide located some distance from the Arctic Ocean, extends across northern Europe, Asia, and North America. The warm season lasts about four months. The surface of this zone receives less than 335 kilojoules/cm2 (about 80 kilocalories/cm2) of solar radiation per year, 90 percent of it during the warm season. The average July and August temperatures range from 10° to 14°C, and the average January temperature, from −10° to − 40°C. Nighttime frosts and snowfalls may occur at any time of the year. The annual precipitation is 200–400 mm, and the snow cover is 1 m deep. Perennially frozen rocks and insufficient evaporation cause waterlogging in many regions, as well as the formation of sphagnum and hummock peat bogs and cryogenic forms of terrain, such as thermokarsts. Most of the soils (gley-podzolic and peaty-gley, as well as peaty bog soils in some places) are shallow and contain little organic matter. The landscapes are a complex of sparse forests, tundras, bogs, and meadows. Most of the sparsely wooded areas and meadows are found near the river valleys, whereas the tundras are most often found in water divides. Low-growing forms and krummholz are found in sparse forests, which consist of spruce, birch, pine, larch, and alder. Lichen-moss, bush or scrub communities, including perennial grasses, grow between islands of forest. The average gross weight of the ground plants in the sparse forests is more than 1,000 centners per hectare (ha), and on the treeless tundras, about 300 centners per ha. The annual increment is 50–60 centners per ha in the sparse forests and 20–25 centners per ha on the tundras. From an economic standpoint, the reindeer is the most important mammal. Wolves, ermine, wolverines, blue hares, and voles are common. There are many types of birds (willow grouse and various species of geese, ducks, and woodcocks). Approximately 85–90 percent of the land is used as reindeer pasture. The valley meadows produce high yields of cereal grasses and cereal-weed grasses. They are often used as hayfields.
REFERENCESBerg, L. S. Geograficheskie zony Sovetskogo Soiuza, 3rd ed., vol. 1. Moscow, 1947.
Gorodkov, B. N. Rastitel’nost’ tundrovoi zony SSSR. Moscow-Leningrad, 1935.
Grigor’ev, A. A. Subarktika, 2nd ed. Moscow, 1956.
Rastitel’nost’ Krainego Severa SSSR i ee osvoenie, fasc. 1. Edited by B. A. Tikhomirov. Moscow-Leningrad, 1956.
Mil’kov, F. N. Prirodnye zony SSSR. Moscow, 1964.
Ignat’ev, G. M. Severnaia Amerika. Moscow, 1965.
G. M. IGNAT’EV