Taiga ( London UK Jobs )

Climate and geography ( London UK Jobs )

Taiga ( London UK Jobs ) is the world's largest land biome ( London UK Jobs ), and makes up 27% of the world's forest ( London UK Jobs ) cover; the largest areas are located in Russia and Canada ( London UK Jobs). The taiga ( London UK Jobs ) is the terrestrial biome ( London UK Jobs ) with the lowest annual average temperatures after the tundra and permanent ice caps. However, extreme minimums in the taiga ( London UK Jobs ) are typically lower than those of the tundra ( London UK Jobs ). The lowest reliably recorded temperatures in the Northern Hemisphere were recorded in the taiga ( London UK Jobs ) of northeastern Russia. The taiga ( London UK Jobs ) or boreal forest ( London UK Jobs ) has a subarctic climate with very large temperature range between seasons, but the long and cold winter is the dominant feature ( London UK Jobs ). This climate is classified as Dfc, Dwc, Dsc, Dfd, Dwd and Dsd in the Köppen climate classification scheme, meaning that the short summer (24-hr average 10°C or more) lasts 1–3 months and always less than 4 months. There are also some much smaller areas grading towards the oceanic Cfc climate with milder winters. The mean annual temperature generally varies from -5°C to 5°C, but there are taiga areas in both eastern Siberia and interior Alaska-Yukon where the mean annual reaches down to -10°C. According to some sources, the boreal forest ( London UK Jobs ) grades into a temperate mixed forest ( London UK Jobs ) when mean annual temperature reaches about 3 °C. Permafrost is common in areas with mean annual temperature below 0 °C. The winters last 5 – 7 months, with average temperatures below freezing ( London UK Jobs ). Temperatures vary from −54 °C to 30 °C (-65 °F to 86 °F) throughout the whole year.

The summers, while short, are generally warm and humid. In much of the taiga ( London UK Jobs ), -20 °C would be a typical winter day temperature and 18 °C an average summer day.

The growing season, when the vegetation in the taiga ( London UK Jobs ) comes alive, is usually slightly longer than the climatic definition of summer as the plants of the boreal biome ( London UK Jobs ) have a lower threshold to trigger growth. In Canada, Scandinavia and Finland, the growing season is often estimated by using the period of the year when the 24-hr average temperature is 5 °C or more. For the Taiga Plains in Canada, growing season varies from 80 to 150 days, and in the Taiga ( London UK Jobs ) Shield from 100 to 140 days. Some sources claim 130 days growing season as typical for the taiga ( London UK Jobs ). Other sources mention that 50 - 100 frost-free days are characteristic. Data for locations in southwest Yukon gives 80 - 120 frost-free days ( London UK Jobs ). The closed canopy boreal forest ( London UK Jobs ) in Kenozersky near Plesetsk, Arkhangelsk Province, Russia, on average has 108 frost-free days. The longest growing season is found in the smaller areas with oceanic influences; in coastal areas of Scandinavia and Finland, the growing season of the closed boreal forest ( London UK Jobs ) can be 145 – 180 days. The shortest growing season is found at the northern taiga - tundra ecotone, where the northern taiga forest ( London UK Jobs ) no longer can grow and the tundra dominates the landscape when the growing season is down to 50 – 70 days, and the 24-hr average of the warmest month of the year usually is 10°C or less. 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 ( London UK Jobs ) inside the Arctic circle have midnight sun in mid-summer and polar night in mid-winter.

The taiga ( London UK Jobs ) experiences relatively low precipitation throughout the year (generally 200–750 mm annually, 1,000 mm in some areas), primarily as rain during the summer months, but also as fog and snow (London UK Jobs ). As evaporation is also low for most of the year, precipitation exceeds evaporation, and is sufficient to sustain the dense vegetation growth. Snow may remain on the ground for as long as nine months in the northernmost extensions of the taiga ( London UK Jobs ) ecozone.

In general, taiga ( London UK Jobs ) grows to the south of the 10 °C July isotherm, but occasionally as far north as the 9 °C July isotherm. The southern limit is more variable, depending on rainfall; taiga ( London UK Jobs) may be replaced by forest ( London UK Jobs ) steppe 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 ( London UK Jobs ) 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 ( London UK Jobs ), or more locally (on the Pacific Ocean coasts of North America and Asia) into coniferous temperate rainforests (London UK Jobs ).

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 ( London UK Jobs )

Taiga soil tends to be young and nutrient-poor; it lacks the deep, organically-enriched profile present in temperate deciduous forests ( London UK Jobs ). 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 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. Since the soil is acidic due to the falling pine needles, the forest floor has only lichens and some mosses growing on it. ( forestry jobs in pakistan )

Flora ( London UK Jobs )

Since North America and Asia used to be connected by the Bering land bridge, a number of animal and plant ( London UK Jobs ) species (more animals than plants) were able to colonize both continents and are distributed throughout the taiga ( London UK Jobs ) biome ( London UK Jobs ) (see Circumboreal Region). Others differ regionally, typically with each genus having several distinct species, each occupying different regions of the taiga. Taigas ( London UK Jobs ) also have some small-leaved deciduous trees ( London UK Jobs ) like birch, alder, willow, and poplar; mostly in areas escaping the most extreme winter cold. However, the Dahurian Larch tolerates the coldest winters in the northern hemisphere in eastern Siberia ( London UK Jobs ). The very southernmost parts of the taiga may have trees such as oak, maple, elm, and tilia scattered among the conifers, and there is usually a gradual transition into a temperate mixed forest ( London UK Jobs ), such as the Eastern forest ( London UK Jobs )-boreal  ( London UK Jobs ) transition of eastern Canada. In the interior of the continents with the driest climate, the boreal forests ( London UK Jobs ) might grade into temperate grassland.

There are two major types of taiga ( London UK Jobs ). The southern part is the closed canopy forest ( London UK Jobs ), consisting of many closely-spaced trees with mossy ground cover. In clearings in the forest (London UK Jobs ), shrubs and wildflowers are common, such as the fireweed. The other type is the lichen woodland or sparse taiga ( London UK Jobs ), with trees that are farther-spaced and lichen ground cover; the latter is common in the northernmost taiga ( London UK Jobs ). In the northernmost taiga ( London UK Jobs ) the forest ( London UK Jobs ) cover is not only more sparse, but often stunted in growth form; moreover, ice pruned asymmetric Black Spruce (in North America) are often seen, with diminished foliage on the windward side. In Canada, Scandinavia and Finland, the boreal forest ( London UK Jobs ) is usually divided into three subzones: The high boreal (north boreal) or taiga zone; the middle boreal (closed forest ( London UK Jobs )); and the southern boreal, a closed canopy boreal forest ( London UK Jobs ) with some scattered temperate deciduous trees among the conifers, such as maple, elm and oak. This southern boreal forest ( London UK Jobs ) has the longest and warmest growing season of the biome, and in some regions (including Scandinavia, Finland and western Russia) this subzone is commonly used for agricultural purposes. The boreal forest ( London UK Jobs ) is home to many types of berries; some are confined to the southern and middle closed boreal forest ( London UK Jobs ) (such as raspberry), others grow in most areas of the taiga ( London UK Jobs ) (such as cranberry and cloudberry), and some can grow in both the taiga ( London UK Jobs ) and the low arctic (southern part of) tundra (such as bilberry and lingonberry).

The forests ( London UK Jobs ) of the taiga ( London UK Jobs ) are largely coniferous, dominated by larch, spruce, fir, and pine. The woodland mix varies according to geography and climate so for example the Eastern Canadian forests ( London UK Jobs ) ecoregion of the higher elevations of the Laurentian Mountains and the northern Appalachian Mountains in Canada is dominated by balsam fir Abies balsamea, while further north the Eastern Canadian Shield taiga ( London UK Jobs ) of northern Quebec and Labrador is notably black spruce Picea mariana and tamarack larch Larix laricina.

Evergreen species in the taiga ( London UK Jobs ) (spruce, fir, and pine) have a number of adaptations specifically for survival in harsh taiga ( London UK Jobs ) winters, although larch, the most cold-tolerant of all trees (London UK Jobs ), citation needed] is deciduous. Taiga ( London UK Jobs ) 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". The narrow conical shape of northern conifers, and their downward-drooping limbs, also help them shed snow. ( London UK Jobs )

Because the sun is low in the horizon for most of the year, it is difficult for plants ( London UK Jobs ) to generate energy from photosynthesis. Pine, spruce and fir 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 ( London UK Jobs ) roots are unable to absorb water, so desiccation can be a severe problem in late winter for evergreens.

Although the taiga ( London UK Jobs ) is dominated by coniferous forests ( London UK Jobs ), some broadleaf trees also occur, notably birch, aspen, willow, and rowan. Many smaller herbaceous plants ( London UK Jobs ) grow closer to the ground. Periodic stand-replacing wildfires (with return times of between 20–200 years) clear out the tree ( London UK Jobs ) canopies, allowing sunlight to invigorate new growth on the forest (London UK Jobs ) floor. For some species, wildfires are a necessary part of the life cycle in the taiga ( London UK Jobs ); 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 ( London UK Jobs ), however, the taiga ( London UK Jobs ) has low biological diversity.

Coniferous trees ( London UK Jobs ) are the dominant plants of the taiga ( London UK Jobs ) biome ( London UK Jobs ). A very few species in four main genera are found: the evergreen spruce, fir, and pine, and the deciduous larch. 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 ( London UK Jobs), while taiga ( London UK Jobs ) of the Russian Far East and Mongolia is dominated by larch.

Fauna ( London UK Jobs )

The boreal forest ( London UK Jobs ), or taiga ( London UK Jobs ), supports a large range of animals. Canada's boreal forest ( London UK Jobs ) includes 85 species of mammals, 130 species of fish, and an estimated 32,000 species of insects. Insects play a critical role as pollinators, decomposers and as a part of the food chain; many nesting birds rely on them for food. 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 ( London UK Jobs ). Some hibernate underground in winter.

The taiga ( London UK Jobs ) is home to a number of large herbivorous mammals, such as moose and reindeer/caribou. Some areas of the more southern closed boreal forest ( London UK Jobs ) also have populations of other deer species such as the elk (wapiti) and roe deer. There is also a range of rodent species, including beaver, squirrel, mountain hare, snowshoe hare and vole ( London UK Jobs ). These species have evolved 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.

A number of wildlife species threatened or endangered with extinction can be found in the Canadian boreal forest ( London UK Jobs ), including woodland caribou, American black bear, grizzly bear and wolverine. Habitat loss, mainly due to logging, is the primary 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. 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.

More than 300 species of birds have their nesting grounds in the taiga ( London UK Jobs ). This includes 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, and Raven, or else seed-eating birds, including several species of grouse and crossbills.

Threats ( London UK Jobs )Human activities ( London UK Jobs )

Large areas of Siberia’s taiga ( London UK Jobs ) have been harvested for lumber since the collapse of the Soviet Union. In Canada, less than eight percent of the boreal forest ( London UK Jobs ) is protected from development and more than 50% has been allocated to logging companies for cutting. The main form of forestry ( London UK Jobs ) in the boreal forest ( London UK Jobs ) of Canada is clearcutting, where most if not all trees are removed from an area of forest. Clearcuts upwards of 110 km² have been recorded in the Canadian boreal forest. Some of the products from logged boreal forests ( London UK Jobs ) include toilet paper, copy paper, newsprint and lumber. More than 80% of boreal forest ( London UK Jobs ) products from Canada are exported for consumption and processing in the United States. Some of the larger cities situated in this biome are Murmansk, Arkhangelsk, Yakutsk, Anchorage, Yellowknife, Tromsø, Luleå and Oulu ( London UK Jobs ).

Most companies that harvest in Canadian forests ( London UK Jobs ) are certified by an independent third party agency such as the Forest  ( London UK Jobs ) Stewardship Council (FSC), Sustainable Forests ( London UK Jobs ) Initiative (SFI), or the Canadian Standards Association (CSA). While the certification process differs between these various groups, all of them include forest ( London UK Jobs ) stewardship, respect for aboriginal peoples, compliance with local, provincial and/or national environmental laws, forest ( London UK Jobs ) 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 ( London UK Jobs )

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; the aspen-leaf miner; the larch sawfly; the spruce budworm (Choristoneura fumiferana); the spruce coneworm.

Protection ( London UK Jobs )

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. The taiga ( London UK Jobs ) stores enormous quantities of carbon, possibly more than the temperate and tropical forests combined, much of it in peatland.

Natural disturbance ( London UK Jobs )

One of the biggest areas of research and a topic ( London UK Jobs ) still full of unsolved questions is the recurring disturbance of fire and the role it plays in propagating the lichen woodland . 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 . The significance 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 . The recurrent cycle of large, damaging fire occurs approximately every 70 to 100 years . Understanding the dynamics of this ecosystem is entangled with discovering the successional paths that the vegetation exhibits after a fire. Trees ( London UK Jobs ), shrubs ( London UK Jobs ) and lichens ( London UK Jobs ) all recover from fire induced damage through vegetative reproduction as well as invasion by propagules . Seeds that have fallen and become buried provide little help in re-establishment of a species ( London UK Jobs ). The reappearance of lichens is reasoned to occur because of varying conditions and light/nutrient availability in each different microstate . 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 . Self replacement is simply the re-establishment of the pre-fire ( London UK Jobs ) dominant species. Species-dominance relay is a sequential attempt of tree ( London UK Jobs ) 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 . Fire frequency has a large role in shaping the original inception of the lower forest ( London UK Jobs ) line of the lichen woodland taiga ( London UK Jobs ).

Centuries ago, the southern limits of lichen woodland taiga ( London UK Jobs ) were only being formed . It has been hypothesized and subsequently proved by Serge Payette that the Spruce-Moss forest ( London UK Jobs ) ecosystem was changed into the lichen woodland biome due to the initiation of two compounded strong disturbances . 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 ( London UK Jobs ). 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 ( London UK Jobs ), indicate that they are an alternative stable state to the spruce–moss forests ( London UK Jobs )” .