The tree line is the edge of a habitat at which trees are capable of growing and beyond which they are not. It is found at high elevations and high latitudes . Beyond the tree line, trees cannot tolerate the environmental conditions (usually low temperatures, extreme snowpack, or associated lack of available moisture). The tree line is sometimes distinguished from a lower timberline , which is the line below which trees form a forest with a closed canopy .
32-411: Timberline is an alternate term for the tree line . It may also refer to: Tree line At the tree line, tree growth is often sparse, stunted, and deformed by wind and cold. This is sometimes known as krummholz (German for "crooked wood"). The tree line often appears well-defined, but it can be a more gradual transition. Trees grow shorter and often at lower densities as they approach
64-583: A mountain range spanning the northern portion of the Idaho Panhandle , eastern Washington , and southeastern British Columbia which are part of a larger grouping of mountains, the Columbia Mountains . They begin at Mica Peak and Krell Hill near Spokane and extend approximately 320 km north (200 miles) from the border to Kinbasket Lake , at the now-deserted location of the onetime fur company post, Boat Encampment . The range
96-639: A carpet of Cladonia spp. lichens . The proportion of trees to lichen mat increases southwards towards the "forest line", where trees cover 50 percent or more of the landscape. A southern treeline exists in the New Zealand Subantarctic Islands and the Australian Macquarie Island , with places where mean annual temperatures above 5 °C (41 °F) support trees and woody plants, and those below 5 °C (41 °F) do not. Another treeline exists in
128-579: A few mosses, lichens, and species of grass do so. In addition, no trees survive on any of the subantarctic islands near the peninsula. Southern Rata forests exist on Enderby Island and Auckland Islands (both 50°S) and these grow up to an elevation of 370 metres (1,200 ft) in sheltered valleys. These trees seldom grow above 3 m (9.8 ft) in height and they get smaller as one gains altitude, so that by 180 m (600 ft) they are waist-high. These islands have only between 600 and 800 hours of sun annually. Campbell Island (52°S) further south
160-487: A major impact on the ability of trees to place roots into the ground. When roots are too shallow, trees are susceptible to windthrow and erosion. Trees can often grow in river valleys at latitudes where they could not grow on a more exposed site. Maritime influences such as ocean currents also play a major role in determining how far from the equator trees can grow as well as the warm summers experienced in extreme continental climates. In northern inland Scandinavia there
192-545: 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 tree line to be 400 metres (1,300 ft) lower than on exposed intervening shoulders. 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
224-492: A too-cold summer climate (tundra) that none have any indigenous tree species. The Falkland Islands (51°S) summer temperature is near the limit, but the islands are also treeless, although some planted trees exist. Antarctic Peninsula is the northernmost point in Antarctica (63°S) and has the mildest weather—it is located 1,080 kilometres (670 mi) from Cape Horn on Tierra del Fuego —yet no trees survive there; only
256-799: Is bounded on its west, northeast and at its northern extremity by the Columbia River , or the reservoir lakes now filling most of that river's course. From the Columbia's confluence with the Beaver River , they are bounded on their east by the Purcell Trench , which contains the Beaver River, Duncan River , Duncan Lake , Kootenay Lake and the Kootenay River . The Selkirks are distinct from, and geologically older than,
288-524: Is often 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 trees can grow; farther north, it
320-537: Is substantial maritime influence on high parallels that keep winters relatively mild, but enough inland effect to have summers well above the threshold for the tree line. Here are some typical polar treelines: Trees exist on Tierra del Fuego (55°S) at the southern end of South America, but generally not on subantarctic islands and not in Antarctica. Therefore, there is no explicit Antarctic tree line. Kerguelen Island (49°S), South Georgia (54°S), and other subantarctic islands are all so heavily wind-exposed and with
352-556: Is taken over all days whose mean temperature is above 0.9 °C (33.6 °F). A growing season of 94 days above that temperature is required for tree growth. Because of climate change , which leads to earlier snow melt and favorable conditions for tree establishment, the tree line in North Cascades National Park has risen more than 400 feet (120 m) in 50 years. Several types of tree lines are defined in ecology and geography : An alpine tree line
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#1732782402987384-433: Is the highest elevation that sustains trees; higher up it is too cold, or the snow cover lasts for too much of the year, to sustain trees. The climate above the tree line of mountains is called an alpine climate , and the habitat can be described as the alpine zone . 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
416-547: Is too cold all year round to sustain trees. Extremely low temperatures, especially when prolonged, can freeze the internal sap of trees, killing them. In addition, permafrost in the soil can prevent trees from getting their roots deep enough for the necessary structural support. Unlike alpine tree lines, the northern tree line occurs at low elevations. The arctic forest–tundra transition zone in northwestern Canada varies in width, perhaps averaging 145 kilometres (90 mi) and widening markedly from west to east, in contrast with
448-489: Is treeless, except for one stunted Spruce, probably planted in 1907. The climate on these islands is not severe, but tree growth is limited by almost continual rain and wind. Summers are very cold with an average January temperature of 9 °C (48 °F). Winters are mild 5 °C (41 °F) but wet. Macquarie Island (Australia) is located at 54°S and has no vegetation beyond snow grass and alpine grasses and mosses. Selkirk Mountains The Selkirk Mountains are
480-636: The Rocky Mountains . The neighboring Monashee and Purcell Mountains , and sometimes including the Cariboo Mountains to the northwest, are also part of the larger grouping of mountains known as the Columbia Mountains . A scenic highway loop, the International Selkirk Loop , encircles the southern portions of the mountain range. The Selkirks were named after Thomas Douglas, 5th Earl of Selkirk . In 1857 gold
512-424: 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 seldom abrupt: it usually forms a transition zone between closed forest below and treeless alpine zone above. This zone of transition occurs "near the top of the tallest peaks in the northeastern United States, high up on
544-536: The Selkirk Mountains was the home of the last naturally occurring caribou herd in the contiguous United States , the South Selkirk mountain caribou. The herd was cross boundary, spending some time in extreme northern Idaho , eastern Washington , and British Columbia , Canada. The South Selkirk mountain caribou is a woodland mountain caribou , an ecotype of the boreal woodland caribou , one of
576-603: The Selkirks. This area, some of it protected in Washington's Salmo-Priest Wilderness , is also home to mule deer and white-tailed deer , elk , black bears , cougars , bobcats , red fox , bald eagles , golden eagles , osprey , great blue heron , porcupine , badgers , coyote , martens , bighorn sheep , mountain goats, gray wolves and moose . Formerly rarely seen, grizzly bears are also known to roam through this region now in abundance. The southern end of
608-456: The desiccation of foliage , especially of shoots that project above the snow cover. The actual tree line is set by the mean temperature, while the realized tree line may be affected by disturbances, such as logging . Most human activities cannot change the actual tree line, unless they affect the climate. The tree line follows the line where the seasonal mean temperature is approximately 6 °C or 43 °F. The seasonal mean temperature
640-514: The dry mountains of the western United States, to 1.4 °F (0.78 °C) per 1,000 feet (300 m) in the moister mountains of the eastern United States. Skin effects and topography can create microclimates that alter the general cooling trend. Compared with arctic tree lines, alpine tree lines may receive fewer than half of the number of degree days (above 10 °C (50 °F)) based on air temperature, but because solar radiation intensities are greater at alpine than at arctic tree lines
672-440: The giant volcanoes in central Mexico, and on mountains in each of the 11 western states and throughout much of Canada and Alaska". Environmentally dwarfed shrubs ( krummholz ) commonly form the upper limit. The decrease in air temperature with increasing elevation creates the alpine climate. The rate of decrease can vary in different mountain chains, from 3.5 °F (1.9 °C) per 1,000 feet (300 m) of elevation gain in
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#1732782402987704-639: The heart of the Selkirks were among the first national parks created in Canada, along with Yoho and Banff National Parks in the Rockies. Until the completion of the Trans-Canada Highway via the Rogers Pass , automotive traffic between most of British Columbia and the rest of Canada necessarily was forced to follow the path of the Columbia River via its Big Bend , around the north end of
736-597: The most critically endangered mammals. In 2009 the herd of 50 animals was declining. Predation from wolves that had been reintroduced to the area negatively effected the herd, and by April 2018, only three remained, and in January 2019, the American Association for the Advancement of Science (AAAS) announced in its scientific journal, Science , that British Columbia's provincial biologists captured
768-437: The number of degree days calculated from leaf temperatures may be very similar. At the alpine tree line, 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, however, may promote tree growth by insulating the trees from extreme cold during the winter, curtailing water loss, and prolonging
800-464: The predominance of conifers ): The alpine tree line at a location is dependent on local variables, such as aspect of slope, rain shadow and proximity to either geographical pole . In addition, in some tropical or island localities, the lack of biogeographical access to species that have evolved in a subalpine environment can result in lower tree lines than one might expect by climate alone. Averaging over many locations and local microclimates ,
832-467: The soil, resulting in a localized arid environment unsuitable for trees. Many south-facing ridges of the mountains of the Western U.S. have a lower treeline than the northern faces because of increased sun exposure and aridity. Hawaii's treeline of about 8,000 ft (2,400 m) is also above the condensation zone and results due to a lack of moisture. On coasts and isolated mountains, the tree line
864-459: The southwesternmost parts of the Magellanic subpolar forests ecoregion, where the forest merges into the subantarctic tundra (termed Magellanic moorland or Magellanic tundra). For example, the northern halves of Hoste and Navarino Islands have Nothofagus antarctica forests but the southern parts consist of moorlands and tundra. Some typical Arctic and alpine tree line tree species (note
896-454: The telescoped alpine timberlines. North of the arctic tree line lies the low-growing tundra , and southwards lies the boreal forest . Two zones can be distinguished in the arctic tree line: a forest–tundra zone of scattered patches of krummholz or stunted trees, with larger trees along rivers and on sheltered sites set in a matrix of tundra; and "open boreal forest" or "lichen woodland", consisting of open groves of erect trees underlain by
928-444: The tree line, above which they are unable to grow at all. Given a certain latitude, the tree line is approximately 300 to 1000 meters below the permanent snow line and roughly parallel to it. Due to their vertical structure, trees are more susceptible to cold than more ground-hugging forms of plants. Summer warmth generally sets the limit to which tree growth can occur: while tree line conifers are very frost-hardy during most of
960-517: The treeline rises 75 metres (245 ft) when moving 1 degree south from 70 to 50°N, and 130 metres (430 ft) per degree from 50 to 30°N. Between 30°N and 20°S, the treeline is roughly constant, between 3,500 and 4,000 metres (11,500 and 13,100 ft). Here is a list of approximate tree lines from locations around the globe: Like the alpine tree lines shown above, polar tree lines are heavily influenced by local variables such as aspect of slope and degree of shelter. In addition, permafrost has
992-469: 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. Wind can mechanically damage tree tissues directly , including blasting with windborne particles, and may also contribute to
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1024-560: Was discovered in the Selkirks. Coal , copper , marble , mercury , silver , and zinc were also found in the mountains. During the development of Western Canada , the Selkirks presented a formidable barrier to the construction of the Canadian Pacific Railway , until A.B. Rogers discovered the mountain pass that bears his name in 1881–1882. As a result of the railway's construction via that route, Mount Revelstoke and Glacier National Parks (Canada) in
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