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The taiga is found throughout the high northern latitudes, between the tundra, and the temperate forest, near 50° around the Arctic Circle.
Biomes
Terrestrial biomes
Tundra
Taiga/boreal forests
Montane grasslands and shrublands
Temperate coniferous forests
Tropical and subtropical coniferous forests
Temperate broadleaf and mixed forests
Mediterranean forests, woodlands, and scrub
Tropical and subtropical moist broadleaf forests
Tropical and subtropical dry broadleaf forests
Temperate grasslands, savannas, and shrublands
Tropical and subtropical grasslands, savannas, and shrublands
Deserts and xeric shrublands
Flooded grasslands and savannas
Riparian
Wetland
Aquatic biomes
Pond
Littoral/intertidal zone
Mangrove forests
Kelp forest
Coral reef
Neritic zone
Continental shelf
Pelagic zone
Benthic zone
Hydrothermal vents
Cold seeps
Pack ice
Other biomes
Endolithic zone

Taiga (pronounced [ˈtaɪɡə], Russian: Тайга́; from Turkic[1] or Mongolian) is a biome characterized by coniferous forests. Covering most of the inlands Canada, Alaska, Sweden, Finland, inland Norway, the Scottish Highlands and Russia (especially Siberia), as well as parts of the extreme northern continental United States (northern Minnesota, Michigan's Upper Peninsula, northern Wisconsin, Upstate New York, Vermont, New Hampshire, and Maine), northern Kazakhstan, northern Mongolia, and northern Japan (Hokkaidō), the taiga is the world's largest terrestrial biome.

Although this biome is correctly named Taiga, the term Boreal forest is usually used to refer to the more southerly part of the biome, while the term Taiga is more often used to describe only the more barren northern areas of the Arctic tree line.

Since North America and Asia were formerly connected by the Bering land bridge, a number of animal and plant species (more animals than plants) were able to colonize both continents and are distributed throughout the taiga biome (see Circumboreal Region). Others differ regionally, typically with each genus having several distinct species, each occupying different regions of the taiga. Taigas also have some small-leaved deciduous trees like birch, alder, willow, and aspen; mostly in areas escaping the most extreme winter cold. However, the deciduous larch tolerates the coldest winters on the northern hemisphere in eastern Siberia. The very southernmost parts of the taiga may also have trees like oak, maple, elm and tilia scattered among the conifers.

Contents

Climate and geography

White Spruce taiga, Denali Highway, Alaska Range, Alaska

Taiga, the world's largest land biome, has a harsh continental climate with a very large temperature range between seasons classified as "Cfc" "Dfc" or "Dfb" in the Köppen climate classification scheme. Aside from the tundra and permanent ice caps, it is the coldest biome on Earth. High latitudes mean that for much of the year the sun does not rise far above the horizon. Winters last at least 6-7 months, with average temperatures below freezing. Temperatures vary from −54°C to 27°C (-65°F to 70°F) throughout the whole year, half of the year temperatures averaging below freezing.The summers, while short, are generally warm and humid. In general, taiga grows to the south of the 10 °C July isotherm, but occasionally as far north as the 9 °C July isotherm.[2] The southern limit is more variable, depending on rainfall; taiga may be replaced by open steppe woodland south of the 15 °C July isotherm where rainfall is very low, but more typically extends south to the 18 °C July isotherm, and locally where rainfall is higher (notably in eastern Siberia and adjacent northern Manchuria) south to the 20 °C July isotherm. In these warmer areas, the taiga has higher species diversity with more warmth-loving species such as Korean Pine, Jezo Spruce and Manchurian Fir, and merges gradually into mixed temperate forest, or more locally (on the Pacific Ocean coasts of North America and Asia) into coniferous temperate rainforests.

The taiga experiences relatively low precipitation throughout the year (200–750 mm annually), primarily as rain during the summer months, but also as fog and snow; as evaporation is also low for most of the year, precipitation exceeds evaporation and is sufficient for the dense vegetation growth. Snow may remain on the ground for as long as nine months in the northernmost extensions of the taiga ecozone.[3]

Much of the area currently classified as taiga was recently glaciated. As the glaciers receded, they left depressions in the topography that have since filled with water, creating lakes and bogs (especially muskeg soil), found throughout the Taiga.

Soils

Taiga soil tends to be young and nutrient-poor; it lacks the deep, organically-enriched profile present in temperate deciduous forests.[4] The thinness of the soil is due largely to the cold, which hinders the development of soil and the ease with which plants can use its nutrients.[4] Fallen leaves and moss can remain on the forest floor for a long time in the cool, moist climate, which limits their organic contribution to the soil; acids from evergreen needles further leach the soil, creating spodosol.[5] Since the soil is acidic due to the falling pine needles, the forest floor has only lichens and some mosses growing on it.

Flora

Boreal Forest near Lake Baikal in Russia

There are two major types of taiga, closed forest, consisting of many closely-spaced trees with mossy ground cover, and lichen woodland, with trees that are farther-spaced and lichen ground cover; the latter is more common in the northernmost taiga.[6] In the northernmost taiga the forest cover is not only more sparse, but often stunted in growth form; moreover, ice pruned asymmetric Black Spruce are often seen, with diminished foliage on the windward side.[7]

The forests of the taiga are largely coniferous, dominated by larch, spruce, fir, and pine. Evergreen species in the taiga (spruce, fir, and pine) have a number of adaptations specifically for survival in harsh taiga winters, although larch, the most cold-tolerant of all trees, is deciduous. Taiga trees tend to have shallow roots to take advantage of the thin soils, while many of them seasonally alter their biochemistry to make them more resistant to freezing, called "hardening".[8] The narrow conical shape of northern conifers, and their downward-drooping limbs, also help them shed snow.[8]

Because the sun is low in the horizon for most of the year, it is difficult for plants to generate energy from photosynthesis. Pine and spruce do not lose their leaves seasonally and are able to photosynthesize with their older leaves in late winter and spring when light is good but temperatures are still too low for new growth to commence. The adaptation of evergreen needles limits the water lost due to transpiration and their dark green color increases their absorption of sunlight. Although precipitation is not a limiting factor, the ground freezes during the winter months and plant roots are unable to absorb water, so desiccation can be a severe problem in late winter for evergreens.

Moss (Ptilium crista-castrensis) cover on the floor of taiga

Although the taiga is dominated by coniferous forests, some broadleaf trees also occur, notably birch, aspen, willow, and rowan. Many smaller herbaceous plants grow closer to the ground. Periodic stand-replacing wildfires (with return times of between 20-200 years) clear out the tree canopies, allowing sunlight to invigorate new growth on the forest floor. For some species, wildfires are a necessary part of the life cycle in the taiga; some, e.g. Jack Pine have cones which only open to release their seed after a fire, dispersing their seeds onto the newly cleared ground. Grasses grow wherever they can find a patch of sun, and mosses and lichens thrive on the damp ground and on the sides of tree trunks. In comparison with other biomes, however, the taiga has a low biological diversity.

Coniferous trees are the dominant plants of the taiga biome. A very few species in four main genera are found: the evergreen spruce, fir, and pine, and the deciduous larch or tamarack. In North America, one or two species of fir and one or two species of spruce are dominant. Across Scandinavia and western Russia the Scots pine is a common component of the taiga.

Fauna

The taiga is home to a number of large herbivorous mammals and smaller rodents. These animals have also adapted to survive the harsh climate. Some of the larger mammals, such as bears, eat during the summer in order to gain weight and then go into hibernation during the winter. Other animals have adapted layers of fur or feathers to insulate them from the cold.

A number of wildlife species threatened or endangered with extinction can be found in the Canadian Boreal forest including woodland caribou, American black bear, grizzly bear and wolverine. Habitat loss due to destructive development, mostly in the form of logging, is the main cause of decline for these species.

Due to the climate, carnivorous diets are an inefficient means of obtaining energy; energy is limited, and most energy is lost between trophic levels. However, predatory birds (owls and eagles) and other smaller carnivores, including foxes and weasels, feed on the rodents. Larger carnivores, such as lynx and wolves, prey on the larger animals. Omnivores, such as bears and raccoons are fairly common, sometimes picking through human garbage.

A considerable number of birds such as Siberian Thrush, White-throated Sparrow and Black-throated Green Warbler, migrate to this habitat to take advantage of the long summer days and abundance of insects found around the numerous bogs and lakes. Of the perhaps 300 species of birds that summer in the taiga, only 30 stay for the winter.[9] These are either carrion-feeding or large raptors that can take live mammal prey, including Golden Eagle, Rough-legged Buzzard, and Raven, or else seed-eating birds, including several species of grouse and crossbills.

Plesetsk Cosmodrome is situated in the taiga

Threats

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Human activities

Large areas of Siberia’s taiga have been harvested since the collapse of the Soviet Union.[10] In Canada, less than eight percent of the Boreal forest is protected from development and more than 50% has been allocated to logging companies for cutting.[11] The main form of forestry in the Boreal forest in Canada is clearcutting, where most if not all trees are removed from an area of forest. Clearcut upwards of 110 km² have been recorded in the Canadian Boreal forest. Some of the products from logged Boreal forests include toilet paper, copy paper, newsprint and lumber. More than 80% of Boreal forest products from Canada are exported for consumption and processing in the United States.

Most companies that harvest in Canadian forests are certified by an independent third party agency such as the Forest Stewardship Council (FSC), Sustainable Forests Initiative (SFI), or the Canadian Standards Association (CSA). While the certification process differs between these various groups, all of them include forest stewardship, respect for aboriginal peoples, compliance with local, provincial and/or national environmental laws, forest worker safety, education and training, and other environmental, business and social requirements. The prompt renewal of all harvest sites by planting or natural renewal is also required.

Insects

Recent years have seen outbreaks of insect pests in forest-destroying plagues: the spruce-bark beetle (Dendroctonus rufipennis) in the Yukon Territory, Canada, and Alaska;[12] the aspen-leaf miner; the larch sawfly; the spruce budworm (Choristoneura fumiferana);[13] the spruce coneworm.[14]

Natural Disturbance

One of the biggest areas of research and a topic still full of unsolved questions is the recurring disturbance of fire and the role it plays in propagating the lichen woodland (Kurkowski:1911). The phenomenon of wildfire by lighting strike is the primary determinant of understory vegetation and because of this, it is considered to be predominate driving force behind community and ecosystem properties in the lichen woodland (Nilsson:421). The importance of fire is clearly evident when one considers that understory vegetation influences tree seedling germination in the short term and decomposition of biomass and nutrient availability in the long term (Nilsson:421). The recurrent cycle of large, damaging fire occurs approximately every 70 to 100 years (Johnson:212). Understanding the dynamics of this ecosystem is entangled with discovering the successional paths that the vegetation exhibits after a fire. Trees, shrubs and lichens all recover from fire induced damage through vegetative reproduction as well as invasion by propagules (Johnson:200). Seeds that have fallen and become buried provide little help in re-establishment of a species. The reappearance of lichens is reasoned to occur because of varying conditions and light/nutrient availability in each different microstate (Johnson:200). Several different studies have been done that have led to the formation of the theory that post-fire development can be propagated by any of four pathways: self replacement, species-dominance relay, species replacement, or gap-phase self replacement (Kurkowski:1911). Self replacement is simply the re-establishment of the pre-fire dominant species. Species-dominance relay is a sequential attempt of tree species to establish dominance in the canopy. Species replacement is when fires occur in sufficient frequency to interrupt species dominance relay. Gap-Phase Self-Replacement is the least common and so far has only been documented in Western Canada. It is a self replacement of the surviving species into the canopy gaps after a fire kills another species. The particular pathway taken after a fire disturbance depends on how the landscape is able to support trees as well as fire frequency (Kurkowski:1912). Fire frequency has a large role in shaping the original inception of the lower forest line of the lichen woodland taiga.

Centuries ago, the southern limits of lichen woodland taiga were only being formed (Payette:289). It has been hypothesized and subsequently proved by Serge Payette that the Spruce-Moss forest ecosystem was changed into the lichen woodland biome due to the initiation of two compounded strong disturbances (Payette:289). The two disturbances were large fire and the appearance and attack of the spruce budworm. The spruce budworm is a deadly insect to the spruce populations in the southern regions of the taiga. J.P. Jasinski confirmed this theory five years later stating “Their [lichen woodlands] persistence , along with their previous moss forest histories and current occurrence adjacent to closed moss forests, indicate that they are an alternative stable state to the spruce–moss forests” (Jasinski:561). The implications of proving of this theory have far reaching implications.

1)Nilsson, M.C. "Understory vegetation as a forest ecosystem driver, evidence from the northern Swedish boreal forest." Frontiers in Ecology and the Environment. 3.8 (2005): 421-428.

2)Kurkowski, Thomas. "Relative Importance of Different Secondary Successional Pathways in an Alaskan Boreal Forest." Canadian Journal of Forest Research. 38. (2008): 1911-1923.

3)Payette, Serge. "Origin of the lichen woodland at its southern range limit in eastern Canada: the catastrophic impact of insect defoliators and fire on the spruce-moss forest." Canadian journal of forest research. 30.2 (2000): 288-305.

4) Sayre, A.P. Taiga. 1st. New York: Twenty-First Century Books, 1994. 1-28.

5)Johnson, E.A. "Vegetation Organization and Dynamics of Lichen Woodland Communities in the Northwest Territories." Ecology. 62.1 (1981): 200-215.

6) Jasinski, J.P. "The Creation of Alternative Stable States in Southern Boreal Forest: Quebec, Canada." Ecological Monographs. 75.4 (2005): 561-583.

See also

References

  1. ^ "taiga." Dictionary.com Unabridged (v 1.1). Random House, Inc. 12 Mar. 2008. web link
  2. ^ Arno & Hammerly 1984, Arno et al. 1995
  3. ^ A.P. Sayre, Taiga, (New York: Twenty-First Century Books, 1994) 16.
  4. ^ a b Sayre, 19.
  5. ^ Sayre, 19-20.
  6. ^ Sayre, 12-3.
  7. ^ C. Michael Hogan, Black Spruce: Picea mariana, GlobalTwitcher.com, ed. Nicklas Stromberg, November, 2008
  8. ^ a b Sayre, 23.
  9. ^ Sayre, 28.
  10. ^ Taiga Deforestation
  11. ^ Global Forest Watch Canada 2000. Canada’s Forests At A Crossroads — An Assessment in the Year 2000
  12. ^ http://www.colorado.edu/INSTAAR/AW2004/get_abstr.html?id=88 A New Method to Reconstruct Bark Beetle Outbreaks
  13. ^ Spruce budworm and sustainable management of the boreal forest
  14. ^ http://www.fs.fed.us/pnw/pubs/journals/pnw_2006_chapin001.pdf

Notes

  • Arno, S. F. & Hammerly, R. P. 1984. Timberline. Mountain and Arctic Forest Frontiers. The Mountaineers, Seattle. ISBN 0-89886-085-7
  • Arno, S. F., Worral, J., & Carlson, C. E. (1995). Larix lyallii: Colonist of tree line and talus sites. Pp. 72–78 in Schmidt, W. C. & McDonald, K. J., eds., Ecology and Management of Larix Forests: A Look Ahead. USDA Forest Service General Technical Report GTR-INT-319.
  • Sayre, A. P. (1994). Taiga. New York: Twenty-First Century Books. ISBN 0-8050-2830-7

External links


Wiktionary

Up to date as of January 15, 2010

Definition from Wiktionary, a free dictionary

German

Pronunciation

  • IPA: /ˈtaɪ̯ɡa/

Noun

Taiga f.

  1. taiga (subarctiv zone of coniferous forest)

This German entry was created from the translations listed at taiga. It may be less reliable than other entries, and may be missing parts of speech or additional senses. Please also see Taiga in the German Wiktionary. This notice will be removed when the entry is checked. (more information) November 2009


Simple English

s, just below the tundra, and just above the steppes.]]

taiga, Copper River, Alaska.]]

Taiga (IPA pronunciation: /'taɪgə/ or /taɪ 'ga/, from Mongolian) is characterized by coniferous forests. Taiga covers most of inland Alaska, Canada, Sweden, Finland, inland Norway, northern Kazakhstan and Russia (especially Siberia), as well as parts of the extreme northern continental United States. The taiga is the world's largest region with forests. In Canada, boreal forest is the term used to refer to the southern part of these forests, while "taiga" is used to describe the northern areas south of the Arctic tree line.

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