The taiga during the short summer season. The taiga, covering a large art of the world, but little understood by most people, is threatened due to climate change.
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An image of the North American taiga (boreal forest) during the short summer period.
The Taiga is a nearly continuous belt of coniferous trees across North America and Eurasia overlying formerly glaciated areas and areas of patchy permafrost. The term “boreal forest” is sometimes used to refer to the more southerly part of the biome, while taiga is used to describe more barren areas of the north approaching the tree line and the tundra biome. The term “boreal” is taken from Boreas, Greek god of the north wind.
The taiga is the world’s largest terrestrial biome accounting for 29% of the world’s forest cover. It stretches over Eurasia and North America. Winters are very cold , summers are warm, rainy, and humid. In North America it covers most of inland Canada and Alaska as well as parts of the extreme northern continental United States (northern Minnesota through the Upper Peninsula of Michigan to Upstate New York and northern New England). It also covers most of Sweden, Finland, much of Norway, lowland/coastal areas of Iceland, much of Russia, northern Kazakhstan, northern Mongolia, and northern Japan. However, the predominant tree species varies. For example, the taiga of North America consists of mainly spruces; Scandinavian and Finnish taiga consists of a mix of spruce, pines and birch; Russian taiga has spruces, pines and larches depending on the region, the Eastern Siberian taiga being a vast larch forest.
The growing season, when the vegetation in the taiga comes alive, is usually slightly longer than the climatic definition of summer as the plants of the boreal biome have a lower threshold to trigger growth. For the Taiga Plains in Canada, growing season varies from 80 to 150 days. Data for locations in southwest Yukon gives 80–120 frost-free days. High latitudes mean that the sun does not rise far above the horizon, and less solar energy is received than further south. But the high latitude also ensures very long summer days, as the sun stays above the horizon nearly 20 hours each day, with only around 6 hours of daylight occurring in the dark winters, depending on latitude. The areas of the taiga inside the Arctic circle have midnight sun in mid-summer and polar night in mid-winter.
The taiga experiences relatively low precipitation throughout the year , primarily as rain during the summer months, but also as fog and snow. Snow may remain on the ground for as long as nine months in the northernmost extensions of the taiga. Muskeg (bogs) occur in poorly drained, glacial depressions. Sphagnum moss forms a spongy mat over ponded water. Growing on this mat are species of the tundra such as cottongrass and shrubs of the heath family. Black spruce and larch ring the edge.
Taiga soil tends to be young and poor in nutrients. It lacks the deep, organically enriched profile present in temperate deciduous forests. 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. Fallen leaves and moss can remain on the forest floor for extended periods in the cool, moist climate. Acids from evergreen needles further leach the soil. Acidic soil often limits flora diversity to little more than lichens and some mosses. Herbs and berries can be found in clearings and areas with a prevalence of deciduous trees. The boreal forest is home to many types of berries such as raspberry, cranberry, cloudberry), bilberry and lingonberry. Diversity of soil organisms in the boreal forest is high, comparable to the tropical rainforest.
Since North America and Asia used to be connected by the Bering land bridge, a number of animal and plant species colonized both continents and are distributed throughout the taiga biome. 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 poplar; mostly in areas escaping the most extreme winter cold. Southernmost regions of the taiga may have trees such as oak, maple, elm, and tilia scattered among the conifers.
Evergreen species in the taiga 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.
- Many species of tree found there seasonally alter their biochemistry to make them more resistant to freezing, called “hardening”.
- The conical or spire-shaped promotes shedding of snow and prevents loss of branches.
- Needleleaf – narrowness reduces surface area through which water may be lost (transpired), especially during winter when the frozen ground prevents plants from replenishing their water supply and dessication could become problematic. The needles of boreal conifers also have thick waxy coatings–a waterproof cuticle–in which stomata are sunken and protected from drying winds.
- Evergreen habit – retention of foliage allows the trees photosynthesize with their older leaves in late winter and spring when light is good but temperatures are still too low for new growth. Larch are dominant in areas underlain by nearly continuous permafrost and having a climate even too dry and cold for the waxy needles of spruce and fir. Dark needles promotes maximum heat absorption allowing for photosynthesis at temperatures lower than would otherwise be the case.
A wide variety of wildlife are found in the taiga. Insects play a critical role as pollinators, decomposers, and as a part of the food web. Many nesting birds rely on them for food especially in the months of February and March. The cold winters and short summers make the taiga a challenging biome for reptiles and amphibians, which depend on environmental conditions to regulate their body temperatures, and there are only a few species in the boreal forest including red-sided garter snake, common European adder, blue-spotted salamander, northern two-lined salamander, Siberian salamander, wood frog, northern leopard frog, boreal chorus frog, American toad, and Canadian toad. Most hibernate underground in winter. Fish of the taiga must be able to withstand cold water conditions and be able to adapt to life under ice covered water. Species in the taiga include Alaska blackfish, northern pike, walleye, longnose sucker, white sucker, various species of cisco, lake whitefish, round whitefish, pygmy whitefish, arctic lamprey, various grayling species, brook trout (including sea-run brook trout in the Hudson bay area), chum salmon, Siberian taimen, lenok and lake chub.
The taiga is home to a number of large herbivorous mammals, such as moose and reindeer/caribou. Some areas have populations of other deer species such as the elk (wapiti) and roe deer.The largest animal in the taiga is the wood bison, found in northern Canada, Alaska and has been newly introduced into the Russian far-east. There is also a range of rodent species including beaver, squirrel, mountain hare, snowshoe hare, North American porcupine and vole. These species have adapted to survive the harsh winters in their native ranges. Some larger mammals, such as bears, eat heartily 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. Predatory mammals of the taiga must be adapted to travel long distances in search of scattered prey or be able to supplement their diet with vegetation or other forms of food (such as raccoons). Mammalian predators of the taiga include Canada lynx, Eurasian lynx, stoat, Siberian weasel, least weasel, sable, American marten, North American river otter, European otter, American mink, wolverine, Asian badger, fisher, gray wolf, coyote, red fox, brown bear, American black bear, Asiatic black bear, polar bear and Siberian tiger.
More than 300 species of birds have their nesting grounds in the taiga. 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 300 species of birds that summer in the taiga only 30 stay for the winter. These are either carrion-feeding or large raptors that can take live mammal prey, including Golden Eagle, Rough-legged Buzzard (also known as the Rough-legged Hawk), and Raven, or else seed-eating birds, including several species of grouse and crossbills.
Large areas of Siberia’s taiga have been harvested for lumber since the collapse of the Soviet Union. In some cases, after clearcutting of trees, topsoil was also removed for shipment to Japan. In Canada, eight percent of the taiga is protected from development. The main forestry practice in the boreal forest of Canada is clearcutting, which involves cutting down most of the trees in a given area, then replanting the forest as a monocrop (one species of tree) the following season. Industry officials claim that this process emulates the natural effects of a forest fire, which they claim clearcutting suppresses, protecting infrastructure, communities and roads. However, from an ecological perspective, this is a falsehood, for several reasons, including: a) Removing most of the trees in a given area is usually done using large machines which disrupt the soil greatly, and the dramatic diminution of ground cover permits large-scale erosion and avalanches, which further damage the habitat and sometimes endangers infrastructure, roads, and communities. b) Clearcutting removes most of the biomass from an area, and the various macro and micro-nutrients it contains. This sudden decrease in nutrients in an area contrasts with a forest fire, which returns most of the nutrients to the soil. c) Forest fires leave standing snags, and leave patches of unburned trees. This helps preserve structure and micro-habitats within the area, whereas clearcutting destroys most of these habitats. In the past, clearcuts upwards of 110 km² have been recorded in the Canadian boreal forest. However, today 80% of clearcuts are less than 260 hectares(2.6 square km). Some of the products from logged boreal forests include toilet paper, copy paper, newsprint, and lumber. More than 90% of boreal forest products from Canada are exported for consumption and processing in the United States. However with the recession and fewer US homes being built, that has changed. Some of the larger cities situated in this biome are Murmansk, Arkhangelsk, Yakutsk, Anchorage, Yellowknife, Tromsø, Luleå, and Oulu.
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 groups, all of them include forest stewardship, respect for aboriginal peoples, compliance with local, provincial 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.
The zone of latitude occupied by the boreal forest has experienced some of the greatest temperature increases on Earth, especially during the last quarter of the twentieth century. Winter temperatures have increased more than summer temperatures. The number of days with extremely cold temperatures (e.g., −20 to −40 °C) has decreased irregularly but systematically in nearly all the boreal region, allowing better survival for tree-damaging insects. In summer, the daily low temperature has increased more than the daily high temperature. In Fairbanks, Alaska, the length of the frost-free season has increased from 60–90 days in the early twentieth century to about 120 days a century later. Summer warming has been shown to increase water stress and reduce tree growth in dry areas of the southern boreal forest in central Alaska, western Canada and portions of far eastern Russia. Precipitation is relatively abundant in Scandinavia, Finland, northwest Russia and eastern Canada, where a longer growth season (i.e. the period when sap flow is not impeded by frozen water) accelerate tree growth. As a consequence of this warming trend, the warmer parts of the boreal forests are susceptible to replacement by grassland, parkland or temperate forest.
In Siberia, the taiga is converting from predominantly needle-shedding larch trees to evergreen conifers in response to a warming climate. This is likely to further accelerate warming, as the evergreen trees will absorb more of the sun’s rays. Given the vast size of the area, such a change has the potential to affect areas well outside of the region. In much of the boreal forest in Alaska, the growth of white spruce trees are stunted by unusually warm summers, while trees on some of the coldest fringes of the forest are experiencing faster growth than previously.
Recent years have seen outbreaks of insect pests in forest-destroying plagues: the spruce-bark beetle (Dendroctonus rufipennis) in Yukon and Alaska; the mountain pine beetle in British Columbia; the aspen-leaf miner; the larch sawfly; the spruce budworm (Choristoneura fumiferana); the spruce coneworm.
Many nations are taking direct steps to protect the ecology of the taiga by prohibiting logging, mining, oil and gas production, and other forms of development. In February 2010 the Canadian government established protection for 13,000 square kilometres of boreal forest by creating a new 10,700 square kilometre park reserve in the Mealy Mountains area of eastern Canada and a 3,000 square kilometre waterway provincial park that follows alongside the Eagle River from headwaters to sea.
Two Canadian provincial governments, Ontario and Quebec, introduced measures in 2008 that would protect at least half of their northern boreal forest. Although both provinces admitted it will take years to plan, work with Aboriginal and local communities and ultimately map out precise boundaries of the areas off-limits to development, the measures are expected to create some of the largest protected areas networks in the world once completed.
The taiga stores enormous quantities of carbon, more than the world’s temperate and tropical forests combined, much of it in wetlands and peatland. In fact, current estimates place boreal forests as storing twice as much carbon per unit area as tropical forests.