Taiga known as boreal forest or snow forest, is a biome characterized by coniferous forests consisting of pines and larches. The taiga is the world's largest land biome. In North America, it covers most of inland Canada and parts of the northern contiguous United States. In Eurasia, it covers most of Sweden, much of Norway, some of the Scottish Highlands, some lowland/coastal areas of Iceland, much of Russia from Karelia in the west to the Pacific Ocean, areas of northern Kazakhstan, northern Mongolia, northern Japan. However, the main tree species, the length of the growing season and summer temperatures vary. For example, the taiga of North America consists of spruces. A different use of the term taiga is encountered in the English language, with "boreal forest" used in the United States and Canada to refer to only the more southerly part of the biome, while "taiga" is used to describe the more barren areas of the northernmost part of the biome approaching the tree line and the tundra biome.
Hoffman discusses the origin of this differential use in North America and why it is an inappropriate differentiation of the Russian term. Although at high elevations taiga grades into alpine tundra through Krummholz, it is not an alpine biome. Taiga is the world's second-largest land biome, after deserts and xeric shrublands, covering 17 million square kilometers or 11.5% of the Earth's land area. The largest areas are located in Canada; the taiga is the terrestrial biome with the lowest annual average temperatures after the tundra and permanent ice caps. Extreme winter minimums in the northern taiga are lower than those of the tundra; the lowest reliably recorded temperatures in the Northern Hemisphere were recorded in the taiga of northeastern Russia. The taiga or boreal forest has a subarctic climate with large temperature range between seasons, but the long and cold winter is the dominant feature; this climate is classified as Dfc, Dsc and Dwd in the Köppen climate classification scheme, meaning that the short summer lasts 1–3 months and always less than 4 months.
In Siberian taiga the average temperature of the coldest month is between −6 °C and −50 °C. There are some much smaller areas grading towards the oceanic Cfc climate with milder winters, whilst the extreme south and west of the taiga reaches into humid continental climates with longer summers; the mean annual temperature varies from −5 °C to 5 °C, but there are taiga areas in eastern Siberia and interior Alaska-Yukon where the mean annual reaches down to −10 °C. According to some sources, the boreal forest grades into a temperate mixed forest when mean annual temperature reaches about 3 °C. Discontinuous permafrost is found in areas with mean annual temperature below 0 °C, whilst in the Dfd and Dwd climate zones continuous permafrost occurs and restricts growth to shallow-rooted trees like Siberian larch; the winters, with average temperatures below freezing, last five to seven months. Temperatures vary from −54 °C to 30 °C throughout the whole year; the summers, while short, are warm and humid.
In much of the taiga, −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 comes alive, is slightly longer than the climatic definition of summer as the plants of the boreal biome have a lower threshold to trigger growth. In Canada and Finland, the growing season is estimated by using the period of the year when the 24-hour average temperature is +5 °C or more. For the Taiga Plains in Canada, growing season varies from 80 to 150 days, in the Taiga Shield from 100 to 140 days; some sources claim 130 days growing season as typical for the taiga. Other sources mention. Data for locations in southwest Yukon gives 80–120 frost-free days; the closed canopy boreal forest in Kenozersky National Park 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; the shortest growing season is found at the northern taiga–tundra ecotone, where the northern taiga forest no longer can grow and the tundra dominates the landscape when the growing season is down to 50–70 days, the 24-hr average of the warmest month of the year is 10 °C or less.
High latitudes mean that the sun does not rise far above the horizon, less solar energy is received than further south. But the high latitude ensures 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 low precipitation throughout the year as rain during the summer months, but as fog and snow; this fog predominant in low-lying areas during and after the thawing of frozen Arctic seas
Eagle Cap Wilderness
Eagle Cap Wilderness is a wilderness area located in the Wallowa Mountains of northeastern Oregon, within the Wallowa–Whitman National Forest. The wilderness was established in 1940. In 1964, it was included in the National Wilderness Preservation System. A boundary revision in 1972 added 73,000 acres and the Wilderness Act of 1984 added 66,100 acres resulting in a current total of 361,446 acres, making Eagle Cap by far Oregon's largest wilderness area. Eagle Cap Wilderness is named after a peak in the Wallowa Mountains, which were once called the Eagle Mountains. At 9,572 feet Eagle Cap was incorrectly thought to be the highest peak in the range, hence the name; the Eagle Cap Wilderness is characterized by high alpine lakes and meadows, bare granite peaks and ridges, U-shaped glacial valleys. Thick timber is found in the lower valleys and scattered alpine timber on the upper slopes. Elevations in the wilderness range from 3,000 feet in lower valleys to 9,838 feet at the summit of Sacajawea Peak with 30 other summits exceeding 8,000 feet.
The wilderness is home to Legore Lake, the highest lake above sea level in Oregon at 8,950 feet, as well as 60 alpine lakes, more than 37 miles of streams. The Eagle Cap Wilderness and surrounding country in the Wallowa–Whitman National Forest was first occupied by the ancestors of the Nez Perce Indian tribe around 1400 AD, by the Cayuse, the Shoshone, Bannocks; the wilderness was used as hunting grounds for bighorn sheep and deer. It was the summer home to the Joseph Band of the Nez Perce tribe. 1860 marked the year. In 1930, the Eagle Cap was established as a primitive area and in 1940 earned wilderness designation. Eagle Cap Wilderness is home to a variety of wildlife, including black bears, Rocky Mountain bighorn sheep, mountain goats. In the summer white-tailed deer, mule deer, Rocky Mountain elk roam the wilderness. Smaller mammals that inhabit the area year-round include the pika, pine martens, badgers and marmots. Birds include peregrine falcons, bald eagles, golden eagles, ferruginous hawks, gray-crowned rosy finch.
Trout streams in the wilderness. The Oregon State record golden trout was caught by Douglas White; the lake where it was caught was not named. Moose have returned to the wilderness. There is possible evidence that grizzly wolverines are returning as well. Plant communities in the Eagle Cap Wilderness range from low elevation grasslands and ponderosa pine forest to alpine meadows. Engelmann spruce, mountain hemlock, sub-alpine fir, whitebark pine can be found in the higher elevations. Varieties of Indian paintbrush, sego lilies, larkspur, shooting star, bluebells are abundant in the meadows; the wilderness does contain some small groves of old growth forest. As Oregon's largest wilderness area, Eagle Cap offers many recreational activities, including hiking, horseback riding, fishing and wildlife watching. Winter brings backcountry snowshoeing opportunities. There are 47 trailheads and 534 miles of trails in Eagle Cap, accessible from Wallowa and Baker Counties, leading to all areas of the wilderness.
Four designated Wild and Scenic Rivers originate in Eagle Cap Wilderness—the Lostine, Eagle Creek and Imnaha. 16 miles of the Lostine from its headwaters in the wilderness to the Wallowa–Whitman National Forest boundary are designated Wild and Scenic. Established in 1988, 5 miles of the river are designated "wild" and 11 miles are designated "recreational." A small portion of the river is on private property. 27 miles of Eagle Creek from its output at Eagle Lake in the wilderness to the Wallowa–Whitman National Forest boundary at Skull Creek are designated Wild and Scenic. In 1988, 4 miles of the river were designated "wild," 6 miles are designated "scenic," and 17 miles are designated "recreational." 39 miles of the Minam River from its headwaters at the south end of Minam Lake to the wilderness boundary, one-half mile downstream from Cougar Creek, are designated Wild and Scenic. In 1988, all 39 miles were designated "wild." 77 miles of the Imnaha River from its headwaters are designated Scenic.
The designation comprises the main stem from the confluence of the North and South Forks of the Imnaha River to its mouth, the South Fork from its headwaters to the confluence with the main stem. In 1988, 15 miles were designated "wild," 4 miles were designated "scenic," and 58 miles were designated "recreational," though only a portion of the Wild and Scenic Imnaha is located within Eagle Cap Wilderness. List of Oregon Wildernesses List of U. S. Wilderness Areas List of old growth forests Eagle Cap Wilderness - Wallowa–Whitman National Forest Eagle Cap Wilderness - Wilderness.net EagleCapWilderness.com Eagle Cap Wilderness - JosephOregon.com
Tsuga heterophylla, the western hemlock or western hemlock-spruce, is a species of hemlock native to the west coast of North America, with its northwestern limit on the Kenai Peninsula and its southeastern limit in northern Sonoma County, California. Tsuga heterophylla is an integral component of Pacific Northwest forests west of the Coast Ranges, where it is a climax species, it is an important timber tree throughout the region, along with many of its large coniferous associates. Western hemlock is a large evergreen coniferous tree growing to 165–230 ft tall, exceptionally 273.42 ft, with a trunk diameter of up to 9 ft. It is the largest species of hemlock, with the next largest reaching a maximum of 194 ft; the bark is brown and furrowed. The crown is a neat broad conic shape in young trees with a drooping lead shoot, becoming cylindric in older trees. At all ages, it is distinguished by the pendulous branchlet tips; the shoots are pale buff-brown white, with pale pubescence about 1 mm long.
The leaves are needle-like, 5–23 mm long and 1.5–2 mm broad flattened in cross-section, with a finely serrated margin and a bluntly acute apex. They are mid to dark green above, they are arranged spirally on the shoots but are twisted at the base to lie in two ranks on either side of the shoot. The cones are small, slender cylindrical, 14–30 mm long and 7–8 mm broad when closed, opening to 18–25 mm broad, they have 15 -- 25 flexible scales 7 -- 13 mm long. The immature cones are green; the seeds are brown, 2–3 mm long, with a slender, 7–9 mm long pale brown wing. Western hemlock is associated with temperate rain forests, most of its range is less than 100 km from the Pacific Ocean. There is however an inland population in the Columbia Mountains in southeast British Columbia, northern Idaho and western Montana, it grows at low altitudes, from sea level to 600 m, but up to 1,800 m in the interior part of its range in Idaho. It is a shade-tolerant tree. Young plants grow up under the canopy of other conifers such as Sitka spruce or Douglas-fir, where they can persist for decades waiting to exploit a gap in the canopy.
They replace these conifers, which are shade-intolerant, in climax forest. However and wildfires will create larger openings in the forest where these other species can regenerate. Initial growth is slow. Once established, saplings in full light may have an average growth rate of 50–120 cm annually until they are 20–30 m tall, in good conditions still 30–40 cm annually when 40–50 m tall; the tallest specimen, 82.83 m tall, is in California. It is long-lived, with trees over 1200 years old known. Western hemlock forms ectomycorrhizal associations with some well-known edible fungi such as chanterelles, it is capable of associating with wood-decay fungi in addition to soil fungi. Western hemlock is the state tree of Washington. Western hemlock is cultivated as an ornamental tree in gardens in its native habitats and along the U. S. Pacific Coast, where its best reliability is seen in wetter regions. In dry areas, as at Victoria, British Columbia, it is exacting about soil conditions, it needs a high level of organic matter, in a acidic soil.
It is cultivated in temperate regions worldwide. It has gained the Royal Horticultural Society's Award of Garden Merit; when planted well upon the banks along a river, western hemlock can help to reduce erosion. Outside of its native range, western hemlock is of importance in forestry, for timber and paper production, it is used for making doors and furniture, it can be an ornamental tree in large gardens, in northwest Europe and southern New Zealand. It has naturalised in some parts of Great Britain and New Zealand, not so extensively as to be considered an invasive species, but an introduced species tree; the edible cambium can be collected by scraping slabs of removed bark. The resulting shavings can be eaten or can be dried and pressed into cakes for preservation; the bark serves as a source of tannin for tanning. Tender new growth needles can be chewed directly or made into a bitter tea, rich in vitamin C. Western hemlock boughs are used to collect herring eggs during the spring spawn in southeast Alaska.
The boughs provide an collectible surface for the eggs to attach to as well as providing a distinctive taste. This practice originates from traditional gathering methods used by Native Alaskans from southeast Alaska the Tlingit people
Tsuga mertensiana, known as mountain hemlock, is a species of hemlock native to the west coast of North America, with its northwestern limit on the Kenai Peninsula and its southeastern limit in northern Tulare County, California. Mertensiana refers to Karl Heinrich Mertens, a German botanist who collected the first specimens as a member of a Russian expedition in 1826-1829. Tsuga mertensiana is a large evergreen coniferous tree growing to 20 to 40 m tall, with exceptional specimens as tall as 59 m tall, they have a trunk diameter of up to 2 m. The bark is thin and square-cracked or furrowed, gray in color; the crown is a neat, conic shape in young trees with a tilted or drooping lead shoot, becoming cylindric in older trees. At all ages, it is distinguished by the pendulous branchlet tips; the shoots are orange–brown, with dense pubescence about 1 mm long. The leaves are needle-like, 7 to 25 mm long and 1 to 1.5 mm broad, blunt-tipped, only flattened in cross-section, pale glaucous blue-green above, with two broad bands of bluish-white stomata below with only a narrow green midrib between the bands.
The cones are small, cylindrical, 30 to 80 mm long and 8 to 10 mm broad when closed, opening to 12 to 35 mm broad, superficially somewhat like a small spruce cone. They have flexible scales 8 to 18 mm long; the immature cones are maturing red -- brown 5 to 7 months after pollination. The seeds are red -- brown, 2 to 3 mm long, with 7 to 12 mm - long pale pink -- brown wing; the geographic range of Tsuga mertensiana closely matches that of Tsuga heterophylla mostly less than 100 km from the Pacific Ocean apart from a similar inland population in the Rocky Mountains in southeast British Columbia, northern Idaho and western Montana. The inland populations most established after deglaciation by remarkable long-distance dispersal of more than 200 km from the coast populations, their ranges, differ in California, where western hemlock is restricted to the Coast Ranges and mountain hemlock is found in the Klamath Mountains and Sierra Nevada. Unlike western hemlock, mountain hemlock grows at high altitudes except in the far north, from sea level to 1,000 m in Alaska, 1,600 to 2,300 m in the Cascades in Oregon, 2,500 to 3,050 m in the Sierra Nevada.
There are two subspecies and a minor variety: Tsuga mertensiana subsp.. Mertensiana. Northern mountain hemlock. Central Oregon northwards. Cones smaller, 30 to 60 mm long, 12 to 25 mm broad when open, with 50 to 80 scales. Tsuga mertensiana subsp. Mertensiana var. mertensiana. Northern mountain hemlock. Leaves gray-green on both sides. Tsuga mertensiana subsp. Mertensiana var. jeffreyi Schneider. Jeffrey's mountain hemlock. Mixed with var. mertensiana. Leaves greener, less glaucous above, paler below. At one time it was thought to be a hybrid with western hemlock, but there is no verified evidence for this. Tsuga mertensiana subsp. Grandicona Farjon. California mountain hemlock. T. hookeriana Carrière, T. crassifolia Flous. Central Oregon southwards. Leaves strongly glaucous. Cones larger, 45 to 80 mm long, 20 to 35 mm broad when open, with 40 to 60 scales. Mountain hemlock is found on cold, snowy subalpine sites where it grows sometimes attaining more than 800 years in age. Arborescent individuals that have narrowly conical crowns until old age and shrubby krummholz on cold, windy sites near timberline add beauty to mountain landscapes.
Areas occupied by mountain hemlock have a cool to cold maritime climate that includes mild to cold winters, a short, warm-to-cool growing season and moderate to high precipitation. Best development of mountain hemlock is on loose, coarse-textured, well-drained soils with adequate moisture, in British Columbia, on thick and acidic organic matter and decayed wood. Adequate soil moisture appears to be important in California and Montana, where summer drought is most pronounced. Mountain hemlock will grow on most landforms, but individuals develop best in mixed stands of forest on sheltered slopes or in draws. From southern British Columbia south, the tree grows better on northerly exposures; the preference for moist, cool sites evidently becomes a necessity as the climate becomes more continental in western Montana and more mediterranean in the central Sierra Nevada at these extremes of its range. In these locations, mountain hemlock grows in isolated populations in north-facing glens and cirque basins where snow collects and may remain well into summer.
Mountain hemlock is adapted to sites with long-lasting snowpacks. In the spring, mountain hemlocks emerging through 2 to 4 m of snow were transpiring, whereas nearby whitebark pines did not transpire until the soil beneath them was free of snow. Mountain hemlock is well adapted to cope with heavy snow and ice loads, with tough branches and the drooping branchlets shedding snow readily. Mountain hemlock is other forms of competition, it is more tolerant than all its associates except Pacific silver fir, western hemlock, Alaska cedar. Mountain hemlock is considered a minor climax species on
A glacier is a persistent body of dense ice, moving under its own weight. Glaciers deform and flow due to stresses induced by their weight, creating crevasses and other distinguishing features, they abrade rock and debris from their substrate to create landforms such as cirques and moraines. Glaciers form only on land and are distinct from the much thinner sea ice and lake ice that form on the surface of bodies of water. On Earth, 99% of glacial ice is contained within vast ice sheets in the polar regions, but glaciers may be found in mountain ranges on every continent including Oceania's high-latitude oceanic island countries such as New Zealand and Papua New Guinea. Between 35°N and 35°S, glaciers occur only in the Himalayas, Rocky Mountains, a few high mountains in East Africa, New Guinea and on Zard Kuh in Iran. Glaciers cover about 10 percent of Earth's land surface. Continental glaciers cover nearly 13 million km2 or about 98 percent of Antarctica's 13.2 million km2, with an average thickness of 2,100 m.
Greenland and Patagonia have huge expanses of continental glaciers. Glacial ice is the largest reservoir of fresh water on Earth. Many glaciers from temperate and seasonal polar climates store water as ice during the colder seasons and release it in the form of meltwater as warmer summer temperatures cause the glacier to melt, creating a water source, important for plants and human uses when other sources may be scant. Within high-altitude and Antarctic environments, the seasonal temperature difference is not sufficient to release meltwater. Since glacial mass is affected by long-term climatic changes, e.g. precipitation, mean temperature, cloud cover, glacial mass changes are considered among the most sensitive indicators of climate change and are a major source of variations in sea level. A large piece of compressed ice, or a glacier, appears blue, as large quantities of water appear blue; this is. The other reason for the blue color of glaciers is the lack of air bubbles. Air bubbles, which give a white color to ice, are squeezed out by pressure increasing the density of the created ice.
The word glacier is a loanword from French and goes back, via Franco-Provençal, to the Vulgar Latin glaciārium, derived from the Late Latin glacia, Latin glaciēs, meaning "ice". The processes and features caused by or related to glaciers are referred to as glacial; the process of glacier establishment and flow is called glaciation. The corresponding area of study is called glaciology. Glaciers are important components of the global cryosphere. Glaciers are categorized by their morphology, thermal characteristics, behavior. Cirque glaciers form on the slopes of mountains. A glacier that fills a valley is called a valley glacier, or alternatively an alpine glacier or mountain glacier. A large body of glacial ice astride a mountain, mountain range, or volcano is termed an ice cap or ice field. Ice caps have an area less than 50,000 km2 by definition. Glacial bodies larger than 50,000 km2 are called continental glaciers. Several kilometers deep, they obscure the underlying topography. Only nunataks protrude from their surfaces.
The only extant ice sheets are the two that cover most of Greenland. They contain vast quantities of fresh water, enough that if both melted, global sea levels would rise by over 70 m. Portions of an ice sheet or cap that extend into water are called ice shelves. Narrow, fast-moving sections of an ice sheet are called ice streams. In Antarctica, many ice streams drain into large ice shelves; some drain directly into the sea with an ice tongue, like Mertz Glacier. Tidewater glaciers are glaciers that terminate in the sea, including most glaciers flowing from Greenland, Antarctica and Ellesmere Islands in Canada, Southeast Alaska, the Northern and Southern Patagonian Ice Fields; as the ice reaches the sea, pieces break off, or calve. Most tidewater glaciers calve above sea level, which results in a tremendous impact as the iceberg strikes the water. Tidewater glaciers undergo centuries-long cycles of advance and retreat that are much less affected by the climate change than those of other glaciers.
Thermally, a temperate glacier is at melting point throughout the year, from its surface to its base. The ice of a polar glacier is always below the freezing point from the surface to its base, although the surface snowpack may experience seasonal melting. A sub-polar glacier includes both temperate and polar ice, depending on depth beneath the surface and position along the length of the glacier. In a similar way, the thermal regime of a glacier is described by its basal temperature. A cold-based glacier is below freezing at the ice-ground interface, is thus frozen to the underlying substrate. A warm-based glacier is above or at freezing at the interface, is able to slide at this contact; this contrast is thought to a large extent to govern the ability of a glacier to erode its bed, as sliding ice promotes plucking at rock from the surface below. Glaciers which are cold-based and warm-based are known as polythermal. Glaciers form where the accumulation of ice exceeds ablation. A glacier originates from a landform called'cirque' – a armchair-shaped geological feature (such as a depressio
The tree line is the edge of the habitat at which trees are capable of growing. It is found at high latitudes. Beyond the tree line, trees cannot tolerate the environmental conditions; the tree line is sometimes distinguished from a lower timberline or forest line, the line below which trees form a forest with a closed canopy. At the tree line, tree growth is sparse and deformed by wind and cold; this is sometimes known as krummholz. The tree line appears well-defined, but it can be a more gradual transition. Trees grow shorter and at lower densities as they approach the tree line, above which they cease to exist. Several types of tree lines are defined in ecology and geography: An alpine tree line is the highest elevation that sustains trees; the climate above the tree line of mountains is called an alpine climate, the terrain can be described as alpine tundra. Treelines on north-facing slopes in the northern hemisphere are lower than on south-facing slopes, because the increased shade on north-facing slopes means the snowpack takes longer to melt.
This shortens the growing season for trees. In the southern hemisphere, the south-facing slopes have the shorter growing season; the alpine tree line boundary is abrupt: it forms a transition zone between closed forest below and treeless alpine tundra above. This zone of transition occurs "near the top of the tallest peaks in the northeastern United States, high up on the giant volcanoes in central Mexico, on mountains in each of the 11 western states and throughout much of Canada and Alaska". Environmentally dwarfed shrubs form the upper limit; the decrease in air temperature due to increasing elevation causes the alpine climate. The rate of decrease can vary in different mountain chains, from 3.5 °F per 1,000 feet of elevation gain in the dry mountains of the western United States, to 1.4 °F per 1,000 feet in the moister mountains of the eastern United States. Skin effects and topography can create microclimates. Compared with arctic timberlines, alpine timberlines may receive fewer than half of the number of degree days based on air temperature, but because solar radiation intensities are greater at alpine than at arctic timberlines the number of degree days calculated from leaf temperatures may be similar.
Summer warmth sets the limit to which tree growth can occur, for while timberline conifers are frost-hardy during most of the year, they become sensitive to just 1 or 2 degrees of frost in mid-summer. A series of warm summers in the 1940s seems to have permitted the establishment of "significant numbers" of spruce seedlings above the previous treeline in the hills near Fairbanks, Alaska. Survival depends on a sufficiency of new growth to support the tree; the windiness of high-elevation sites is a potent determinant of the distribution of tree growth. Wind can mechanically damage tree tissues directly, including blasting with windborne particles, may contribute to the desiccation of foliage of shoots that project above snow cover. At the alpine timberline, tree growth is inhibited when excessive snow lingers and shortens the growing season to the point where new growth would not have time to harden before the onset of fall frost. Moderate snowpack, may promote tree growth by insulating the trees from extreme cold during the winter, curtailing water loss, prolonging a supply of moisture through the early part of the growing season.
However, snow accumulation in sheltered gullies in the Selkirk Mountains of southeastern British Columbia causes the timberline to be 400 metres lower than on exposed intervening shoulders. In a desert, the tree line marks; these tend to be called the "lower" tree line, occur below about 5,000 ft elevation in the desert of the southwestern United States. The desert tree line tends to be lower on pole-facing slopes than equator-facing slopes, because the increased shade on the former keeps them cooler and prevents moisture from evaporating as giving trees a longer growing season and more access to water. In some mountainous areas, higher elevations above the condensation line, or on equator-facing and leeward slopes, can result in low rainfall and increased exposure to solar radiation; this dries out the soil. Many south-facing ridges of the mountains of the Western U. S. have a lower treeline than the northern faces because of aridity. Different tree species have different tolerances to cold. Mountain ranges isolated by oceans or deserts may have restricted repertoires of tree species with gaps that are above the alpine tree line for some species yet below the desert tree line for others.
For example, several mountain ranges in the Great Basin of North America have lower belts of Pinyon Pines and Junipers separated by intermediate brushy but treeless zones from upper belts of Limber and Bristlecone Pines. On coasts and isolated mountains the tree line is much lower than in corresponding altitudes inland and in larger, more complex mountain systems, because strong winds reduce tree growth. In addition the lack of suitable soil, such as along talus slopes or exposed rock formations, prevents trees from gaining an adequate foothold and exposes them to drought and sun; the arctic tree line is the northernmost latitude in the Northern Hemisphere where tr
United States Congress
The United States Congress is the bicameral legislature of the Federal Government of the United States. The legislature consists of two chambers: the House of the Senate; the Congress meets in the United States Capitol in Washington, D. C.. Both senators and representatives are chosen through direct election, though vacancies in the Senate may be filled by a gubernatorial appointment. Congress has 535 voting members: 100 senators; the House of Representatives has six non-voting members representing Puerto Rico, American Samoa, the Northern Mariana Islands, the U. S. Virgin Islands, the District of Columbia in addition to its 435 voting members. Although they cannot vote in the full house, these members can address the house and vote in congressional committees, introduce legislation; the members of the House of Representatives serve two-year terms representing the people of a single constituency, known as a "district". Congressional districts are apportioned to states by population using the United States Census results, provided that each state has at least one congressional representative.
Each state, regardless of population or size, has two senators. There are 100 senators representing the 50 states; each senator is elected at-large in their state for a six-year term, with terms staggered, so every two years one-third of the Senate is up for election. To be eligible for election, a candidate must be aged at least 25 or 30, have been a citizen of the United States for seven or nine years, be an inhabitant of the state which they represent; the Congress was created by the Constitution of the United States and first met in 1789, replacing in its legislative function the Congress of the Confederation. Although not mandated, in practice since the 19th century, Congress members are affiliated with the Republican Party or with the Democratic Party and only with a third party or independents. Article One of the United States Constitution states, "All legislative Powers herein granted shall be vested in a Congress of the United States, which shall consist of a Senate and House of Representatives."
The House and Senate are equal partners in the legislative process—legislation cannot be enacted without the consent of both chambers. However, the Constitution grants each chamber some unique powers; the Senate ratifies treaties and approves presidential appointments while the House initiates revenue-raising bills. The House initiates impeachment cases. A two-thirds vote of the Senate is required before an impeached person can be forcibly removed from office; the term Congress can refer to a particular meeting of the legislature. A Congress covers two years; the Congress ends on the third day of January of every odd-numbered year. Members of the Senate are referred to as senators. Scholar and representative Lee H. Hamilton asserted that the "historic mission of Congress has been to maintain freedom" and insisted it was a "driving force in American government" and a "remarkably resilient institution". Congress is the "heart and soul of our democracy", according to this view though legislators achieve the prestige or name recognition of presidents or Supreme Court justices.
One analyst argues that it is not a reactive institution but has played an active role in shaping government policy and is extraordinarily sensitive to public pressure. Several academics described Congress: Congress reflects us in all our strengths and all our weaknesses, it reflects our regional idiosyncrasies, our ethnic and racial diversity, our multitude of professions, our shadings of opinion on everything from the value of war to the war over values. Congress is the government's most representative body... Congress is charged with reconciling our many points of view on the great public policy issues of the day. Congress is changing and is in flux. In recent times, the American south and west have gained House seats according to demographic changes recorded by the census and includes more minorities and women although both groups are still underrepresented. While power balances among the different parts of government continue to change, the internal structure of Congress is important to understand along with its interactions with so-called intermediary institutions such as political parties, civic associations, interest groups, the mass media.
The Congress of the United States serves two distinct purposes that overlap: local representation to the federal government of a congressional district by representatives and a state's at-large representation to the federal government by senators. Most incumbents seek re-election, their historical likelihood of winning subsequent elections exceeds 90 percent; the historical records of the House of Representatives and the Senate are maintained by the Center for Legislative Archives, a part of the National Archives and Records Administration. Congress is directly responsible for the governing of the District of Columbia, the current seat of the federal government; the First Continental Congress was a gathering of representatives from twelve of the thirteen British Colonies in North America. On July 4, 1776, the Second Continental Congress adopted the Declaration of Independence, referring to the new nation as the "United States of America"; the Articles of Confederation in 1781 created the Congress of the Confederation, a