Tree line

The tree line is the edge of the habitat at which trees are capable of growing. It is found at high elevations and high latitudes. Beyond the tree line, trees cannot tolerate the environmental conditions (usually cold temperatures or associated lack of available moisture).[1]:51 The tree line is sometimes distinguished from a lower timberline or forest line, which is the line below which trees form a forest with a closed canopy.[2]:151[3]:18

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").[4]:58

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 the tree line, above which they cease to exist.[4]:55

Tree line above St. Moritz
Tree line above St. Moritz, Switzerland. May 2009
Tree line
In this view of an alpine tree line, the distant line looks particularly sharp. The foreground shows the transition from trees to no trees. These trees are stunted in growth and one-sided because of cold and constant wind.

Types

Distribution of Plants in a Perpendicular Direction in the Torrid, the Temperate, and the Rigid Zones 1848 Alexander Keith Johnston
This Map of the "Distribution of Plants in a Perpendicular Direction in the Torrid, the Temperate, and the Rigid Zones" was first published 1848 in "The Physical Atlas". It shows tree lines of the Andes, Himalaya, Alps and Pyrenees.

Several types of tree lines are defined in ecology and geography:

Alpine

Treeline In The Tararuas
An alpine tree line in the Tararua Range

An alpine tree line 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.[2]:151 The climate above the tree line of mountains is called an alpine climate,[5]:21 and the terrain can be described as alpine tundra.[6] 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.[7]:109 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 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, and on mountains in each of the 11 western states and throughout much of Canada and Alaska".[8] Environmentally dwarfed shrubs (krummholz) commonly 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 (1.9 °C) per 1,000 feet (300 m) of elevation gain in the dry mountains of the western United States,[8] to 1.4 °F (0.78 °C) per 1,000 feet (300 m) in the moister mountains of the eastern United States.[9] Skin effects and topography can create microclimates that alter the general cooling trend.[10]

Compared with arctic timberlines, alpine timberlines may receive fewer than half of the number of degree days (>10 °C) 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 very similar.[8]

Summer warmth generally sets the limit to which tree growth can occur, for while timberline conifers are very frost-hardy during most of the year, they become sensitive to just 1 or 2 degrees of frost in mid-summer.[11][12] 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.[13][14] Survival depends on a sufficiency of new growth to support the tree. The windiness of high-elevation sites is also a potent determinant of the distribution of tree growth. Wind can mechanically damage tree tissues directly, including blasting with windborne particles, and may also contribute to the desiccation of foliage, especially 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, however, may promote tree growth by insulating the trees from extreme cold during the winter, curtailing water loss,[15] and 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 (1,300 ft) lower than on exposed intervening shoulders.[16]

Desert

In a desert, the tree line marks the driest places where trees can grow; drier desert areas having insufficient rainfall to sustain them. These tend to be called the "lower" tree line, and occur below about 5,000 ft (1,500 m) elevation in the desert of the southwestern United States.[17] 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 quickly, giving trees a longer growing season and more access to water.

Desert-alpine

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, 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.

Double tree line

Different tree species have different tolerances to drought and 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.[18]:37

Exposure

On coasts and isolated mountains the tree line 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.

Arctic

Treeline on mountain over Firth River in Ivvavik National Park, YT
Treeline on a mountain in the Canadian Arctic

The arctic tree line is the northernmost latitude in the Northern Hemisphere where trees can grow; farther north, it is too cold all year round to sustain trees.[19] Extremely cold 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 timberlines, the northern timberline 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,[20] in contrast with the telescoped alpine timberlines.[8] North of the arctic timberline lies the low-growing tundra, and southwards lies the boreal forest.

Two zones can be distinguished in the arctic timberline:[21][22] 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 a carpet of Cladonia spp. lichens.[21] The proportion of trees to lichen mat increases southwards towards the "forest line", where trees cover 50 percent or more of the landscape.[8][23]

Antarctic

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) don't.[24] Another treeline exists in the southwestern most parts of the Magellanic subpolar forests ecoregion, where the forest merges into the subantarctic tundra (termed Magellanic moorland or Magellanic tundra).[25] For example, the northern halves of Hoste and Navarino Islands have Nothofagus antarctica forests but the southern parts consist of moorlands and tundra.

Other tree lines

Several other reasons may cause the environment to be too extreme for trees to grow. This can include geothermal exposure associated with hot springs or volcanoes, such as at Yellowstone; high soil acidity near bogs; high salinity associated with playas or salt lakes; or ground that is saturated with groundwater that excludes oxygen from the soil, which most tree roots need for growth. The margins of muskegs and bogs are common examples of these types of open area. However, no such line exists for swamps, where trees, such as bald cypress and the many mangrove species, have adapted to growing in permanently waterlogged soil. In some colder parts of the world there are tree lines around swamps, where there are no local tree species that can develop. There are also man-made pollution tree lines in weather-exposed areas, where new tree lines have developed because of the increased stress caused by pollution. Examples are found around Nikel in Russia and previously in the Erzgebirge.

Tree species near tree line

Jojo-Maly Szyszak 2005
Severe winter climate conditions at alpine tree line causes stunted krummholz growth. Karkonosze, Poland.
Larix gmelinii0
Dahurian Larch growing close to the Arctic tree line in the Kolyma region, Arctic northeast Siberia

Some typical Arctic and alpine tree line tree species (note the predominance of conifers):

Eurasia

North America

South America

Valle del Frances
View of a Magellanic Lenga forest close to the tree line in Torres del Paine National Park, Chile

Australia

Worldwide distribution

Alpine tree lines

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, 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).[29]

Here is a list of approximate tree lines from locations around the globe:

Location Approx. latitude Approx. elevation of tree line Notes
(m) (ft)
Finnmarksvidda, Norway 69°N 500 1,600 At 71°N, near the coast, the tree-line is below sea level (Arctic tree line).
Abisko, Sweden 68°N 650 2,100 [29]
Chugach Mountains, Alaska 61°N 700 2,300 Tree line around 1,500 feet (460 m) or lower in coastal areas
Southern Norway 61°N 1,100 3,600 Much lower near the coast, down to 500–600 metres (1,600–2,000 ft).
Scotland 57°N 500 1,600 Strong maritime influence serves to cool summer and restrict tree growth[30]:85
Northern Quebec 56°N 0 0 The cold Labrador Current originating in the arctic makes eastern Canada the sea-level region with the most southern tree-line in the northern hemisphere.
Southern Urals 55°N 1,100 3,600
Canadian Rockies 51°N 2,400 7,900
Tatra Mountains 49°N 1,600 5,200
Olympic Mountains WA, United States 47°N 1,500 4,900 Heavy winter snowpack buries young trees until late summer
Swiss Alps 47°N 2,200 7,200 [31]
Mount Katahdin, Maine, United States 46°N 1,150 3,800
Eastern Alps, Austria, Italy 46°N 1,750 5,700 More exposure to cold Russian winds than Western Alps
Sikhote-Alin, Russia 46°N 1,600 5,200 [32]
Alps of Piedmont, Northwestern Italy 45°N 2,100 6,900
New Hampshire, United States 44°N 1,350 4,400 [33] Some peaks have even lower treelines because of fire and subsequent loss of soil, such as Grand Monadnock and Mount Chocorua.
Wyoming, United States 43°N 3,000 9,800
Rila and Pirin Mountains, Bulgaria 42°N 2,300 7,500 Up to 2,600 m (8,500 ft) on favorable locations. Mountain Pine is the most common tree line species.
Pyrenees Spain, France, Andorra 42°N 2,300 7,500 Mountain Pine is the tree line species
Wasatch Mountains, Utah, United States 40°N 2,900 9,500 Higher (nearly 11,000 feet or 3,400 metres in the Uintas)
Rocky Mountain NP, CO, United States 40°N 3,550 11,600 [29] On warm southwest slopes
3,250 10,700 On northeast slopes
Japanese Alps 36°N 2,900 9,500
Yosemite, CA, United States 38°N 3,200 10,500 [34] West side of Sierra Nevada
3,600 11,800 [34] East side of Sierra Nevada
Sierra Nevada, Spain 37°N 2,400 7,900 Precipitation low in summer
Khumbu, Himalaya 28°N 4,200 13,800 [29]
Yushan, Taiwan 23°N 3,600 11,800 [35] Strong winds and poor soil restrict further grow of trees.
Hawaii, United States 20°N 3,000 9,800 [29] Geographic isolation and no local tree species with high tolerance to cold temperatures.
Pico de Orizaba, Mexico 19°N 4,000 13,100 [31]
Costa Rica 9.5°N 3,400 11,200
Mount Kinabalu, Borneo 6.1°N 3,400 11,200 [36]
Mount Kilimanjaro, Tanzania 3°S 3,100 10,200 [29] Upper limit of forest trees; woody ericaeous scrub grows up to 3900m
New Guinea 6°S 3,850 12,600 [29]
Andes, Peru 11°S 3,900 12,800 East side; on west side tree growth is restricted by dryness
Andes, Bolivia 18°S 5,200 17,100 Western Cordillera; highest treeline in the world on the slopes of Sajama Volcano (Polylepis tarapacana)
4,100 13,500 Eastern Cordillera; treeline is lower because of lower solar radiation (more humid climate)
Sierra de Córdoba, Argentina 31°S 2,000 6,600 Precipitation low above trade winds, also high exposure
Australian Alps, Australia 36°S 2,000 6,600 West side of Australian Alps
1,700 5,600 East side of Australian Alps
Andes, Laguna del Laja, Chile 37°S 1,600 5,200 Temperature rather than precipitation restricts tree growth[37]
Mount Taranaki, North Island, New Zealand 39°S 1,500 4,900 Strong maritime influence serves to cool summer and restrict tree growth
Tasmania, Australia 41°S 1,200 3,900 Cold winters, strong cold winds and cool summers with occasional summer snow restrict tree growth
Fiordland, South Island, New Zealand 45°S 950 3,100 Cold winters, strong cold winds and cool summers with occasional summer snow restrict tree growth
Torres del Paine, Chile 51°S 950 3,100 Strong influence from the Southern Patagonian Ice Field serves to cool summer and restrict tree growth[38]
Navarino Island, Chile 55°S 600 2,000 Strong maritime influence serves to cool summer and restrict tree growth[38]

Arctic tree lines

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 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 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:

Location Approx. longitude Approx. latitude of tree line Notes
Norway 24°E 70°N The North Atlantic current makes Arctic climates in this region warmer than other coastal locations at comparable latitude. In particular the mildness of winters prevents permafrost.
West Siberian Plain 75°E 66°N
Central Siberian Plateau 102°E 72°N Extreme continental climate means the summer is warm enough to allow tree growth at higher latitudes, extending to northernmost forests of the world at 72°28'N at Ary-Mas (102° 15' E) in the Novaya River valley, a tributary of the Khatanga River and the more northern Lukunsky grove at 72°31'N, 105° 03' E east from Khatanga River.
Russian Far East (Kamchatka and Chukotka) 160°E 60°N The Oyashio Current and strong winds affect summer temperatures to prevent tree growth. The Aleutian Islands are almost completely treeless.
Alaska 152°W 68°N Trees grow north to the south-facing slopes of the Brooks Range. The mountains block cold air coming off of the Arctic Ocean.
Northwest Territories, Canada 132°W 69°N Reaches north of the Arctic Circle because of the continental nature of the climate and warmer summer temperatures.
Nunavut 95°W 61°N Influence of the very cold Hudson Bay moves the treeline southwards.
Labrador Peninsula 72°W 56°N Very strong influence of the Labrador Current on summer temperatures as well as altitude effects (much of Labrador is a plateau). In parts of Labrador, the treeline extends as far south as 53°N. Along the coast the northernmost trees are at 58°N in Napartok Bay.
Greenland 50°W 64°N Determined by experimental tree planting in the absence of native trees because of isolation from natural seed sources; a very few trees are surviving, but growing slowly, at Søndre Strømfjord, 67°N. There is one natural forest in the Qinngua Valley.

Antarctic tree lines

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 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 a few mosses, lichens, and species of grass do so. In addition, no trees survive on any of the subantarctic islands near the peninsula.

BeagleChannelGlacier
Trees growing along the north shore of the Beagle Channel, 55°S.

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 is treeless, except for one stunted pine, planted by scientists. 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.

Long-term monitoring of alpine treelines

There are several monitoring protocols developed for long term monitoring of alpine biodiversity. One such network which is developed on the line of Global Observation Research Initiative in Alpine Environments (GLORIA), in India HIMADRI.

See also

References

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  10. ^ Geiger, R. (1950). The Climate near the Ground. Cambridge, MA: Harvard University Press.
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  19. ^ Pienitz, Reinhard; Douglas, Marianne S. V.; Smol, John P. (2004). Long-term environmental change in Arctic and Antarctic lakes. Springer. p. 102. ISBN 978-1402021268.
  20. ^ Timoney, K.P.; La Roi, G.H.; Zoltai, S.C.; Robinson, A.L. (1992). "The high subarctic forest–tundra of northwestern Canada: position, width, and vegetation gradients in relation to climate". Arctic. 45 (1): 1–9. doi:10.14430/arctic1367. JSTOR 40511186.
  21. ^ a b Löve, Dd (1970). "Subarctic and subalpine: where and what?". Arctic and Alpine Research. 2 (1): 63–73. doi:10.2307/1550141. JSTOR 1550141.
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  23. ^ R.A., Black; Bliss, L.C. (1978). "Recovery sequence of Picea mariana–Vaccinium uliginosum forests after burning near Inuvik, Northwest Territories, Canada". Canadian Journal of Botany. 56 (6): 2020–2030. doi:10.1139/b78-243.
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  32. ^ "Physiogeography of the Russian Far East".
  33. ^ "Mount Washington State Park". New Hampshire State Parks. Archived from the original on 2013-04-03. Retrieved 2013-08-22. Tree line, the elevation above which trees do not grow, is about 4,400 feet in the White Mountains, nearly 2,000 feet below the summit of Mt. Washington.
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Further reading

Algonquin Peak

Algonquin Peak is in the MacIntyre Range in the town of North Elba, in Essex County, New York. It is the second highest mountain in New York, and one of the 46 Adirondack High Peaks in Adirondack Park. Its name comes from its reputedly being on the Algonquian side of a nearby informal boundary between the Algonquian and their Iroquois neighbors.

Algonquin is popular with hikers, accessible from the popular Adirondak Loj trailhead near Heart Lake outside Lake Placid for a day trip. While the climb is shorter than that of nearby Mount Marcy, it is steeper, requiring almost as much vertical ascent in a considerably shorter distance.

The usual route is via the blue-blazed Van Hoevenberg Trail 0.9 miles (1.4 km) to its junction with the yellow-blazed MacIntyre Range Trail and following that the remaining 3.1 miles (5 km) to the summit, during which the route gets progressively steeper and rockier, going over many steep rock chutes called "slides".

The mountain's summit is an alpine zone above tree line, and views of the surrounding high peaks are available in all directions. However, the large numbers of hikers on the summit have in the past caused damage to the fragile plant life, and strict regulations have been put in place both at the trailhead and on the summit (all hikers must sign in; no dogs are allowed without a leash) to protect it. On busy days a Summit Steward both reminds hikers of these rules and educates them about the ecosystem.

Less frequently, the mountain is approached from the southeast via the steep, narrow, 2.1-mile (3.4 km) Boundary Trail from Lake Colden. This trail is also dangerous because of the poor markings and steep, slippery slides that streams have formed on.

Alpine climate

Alpine climate is the average weather (climate) for the regions above the tree line. This climate is also referred to as a mountain climate or highland climate.

Alpine lake

Alpine lakes are classified as lakes or reservoirs at high altitudes, usually starting around 5,000 feet (1524 metres) in elevation above sea level or above the tree line.Alpine lakes are usually clearer than lakes at lower elevations due to the colder water which decreases the speed and amount of algae and moss growth in the water. Often these lakes are surrounded by varieties of pine trees, aspens, and other high altitude trees.

Blizzard Warning

A Blizzard Warning (SAME code: BZW) is an advisory issued by the National Weather Service of the United States which means sustained winds or frequent gusts of 35 mph / 15 m/s or greater with heavy snow is forecast for a period of 3 hours or more. A blizzard tends to reduce visibilities to 1/4 of a mile (400 m) or less. A Severe Blizzard Warning is a variation issued in some cases of winds above 45 mph / 20 m/s and temperatures below 10 °F/-12 °C. Most local weather offices will activate and broadcast the SAME alarm tone on relevant NOAA Weather Radio stations for both varieties of warning. When the Wireless Emergency Alerts system went live in 2012, Blizzard Warnings were initially sent as alerts to mobile phones, however, this practice was discontinued in November 2013.

In Canada, comparable warnings are issued by Environment Canada. These are the main two types of Canadian blizzard warnings as of 2010:

National Warning below tree line - when winds are 40 kilometres/hr or greater with widespread reductions in visibility to 400 metres (1/4 mile) or less from blowing snow or blowing snow with falling snow for at least 4 hours.

Northern (Arctic) Warning above tree line - same as National Warning but must last for at least 6 hours.The same warnings are issued by Weatheradio Canada and re-issued by media outlets like The Weather Network.

Chicoma Mountain

Chicoma Mountain (; also spelled Tschicoma or Tchicoma) is the highest point in the Jemez Mountains, a prominent mountain range in the U.S. State of New Mexico. The tree line in this area is exceptionally high, and the mountain is forested almost all the way to its summit which is conspicuous from the towns of Los Alamos, Santa Fe, and Española and other areas in the valley of the Rio Grande in northern New Mexico. Like the rest of the Jemez, it is of volcanic origin; it lies on the northeast rim of the Valles Caldera, one of the best examples of a caldera in the United States.

The mountain is sacred to many of the Puebloan peoples of New Mexico, who traditionally regarded it as the "center of all." Much of it lies within the territory of the Santa Clara Pueblo. Access by hikers, hunters, and others, is correspondingly limited, although the summit can be reached via public lands on the north side. The Puye Cliff Dwellings in Santa Clara Canyon are an archaeological site of some significance; however, the cliff dwellings are not near Chicoma. Puye Cliff Dwellings are accessible via NM 30 to NM 5, about 30 minutes south of Chicoma Mountain. The site is located on the pueblo's land on the east side of the mountain, and are sometimes open to the public for a fee.

Fell

A fell (from Old Norse fell, fjall, "mountain") is a high and barren landscape feature, such as a mountain range or moor-covered hills. The term is most often employed in Fennoscandia, the Isle of Man, parts of Northern England, and Scotland.

Horseranch Range

The Horseranch Range is a 40 km (25 mi) long north-south trending mountain range in northern British Columbia, Canada, located at the head of the Red River to the northwest of Deadwood Lake. Part of the Dease Plateau of the Cassiar Mountains system, it contains no glaciers and lies completely above tree line.

Inglefield Mountains

The Inglefield Mountains are a mountain range in southeastern Ellesmere Island, Nunavut, Canada. The mountain range is mostly covered by ice fields, with granitic nunataks reaching a height of 1,500 m (4,921 ft) above sea level. Rocky cliffs border the coastal areas. Like most other mountain ranges in the Canadian Arctic, the Inglefield Mountains are part of the Arctic Cordillera.

There have been very few sightings of wildlife in the Inglefield Mountains because the mountains are north of the Arctic tree line and because of the harsh cold climate. However, the areas nunataks may support one-third of the nationally vulnerable Canadian ivory gull population. During the 1980s, the rock outcrops supported between 730 and 830 adult ivory gulls.

Montane ecosystems

Montane ecosystems refers to any ecosystem found in mountains. These ecosystems are strongly affected by climate, which gets colder as elevation increases. They are stratified according to elevation. Dense forests are common at moderate elevations. However, as the elevation increases, the climate becomes harsher, and the plant community transitions to grasslands or tundra.

Nights Behind the Tree Line

Nights Behind The Tree Line is an audio book by Henry Rollins.

North American Arctic

The North American Arctic comprises the northern portions of Alaska (USA), Northern Canada and Greenland. Major bodies of water include the Arctic Ocean, Hudson Bay, the Gulf of Alaska and North Atlantic Ocean. The western limit is the Seward Peninsula and the Bering Strait. The southern limit is the Arctic Circle latitude of 66° 33’N, which is the approximate limit of the midnight sun and the polar night.

The Arctic region is defined by environmental limits where the average temperature for the warmest month (July) is below 10 °C (50 °F). The northernmost tree line roughly follows the isotherm at the boundary of this region. The area has tundra and polar vegetation.

Picea engelmannii

Picea engelmannii, with common names Engelmann spruce, white spruce, mountain spruce, or silver spruce, is a species of spruce native to western North America, from central British Columbia and southwest Alberta, southwest to northern California and southeast to Arizona and New Mexico; there are also two isolated populations in northern Mexico. It is mostly a high altitude mountain tree, growing at 900 metres (3,000 ft) – 3,650 metres (11,980 ft) altitude, rarely lower in the northwest of the range; in many areas it reaches the alpine tree line.

Pinetree Line

The Pinetree Line was a series of radar stations located across the northern United States and southern Canada at about the 50th parallel north, along with a number of other stations located on the Atlantic and Pacific coasts. Run by North American Aerospace Defense Command (NORAD) (after its creation), over half were manned by United States Air Force personnel with the balance operated by the Royal Canadian Air Force. The line was the first coordinated system for early detection of a Soviet bomber attack on North America, but before the early 1950s radar technology quickly became outdated and the line was in full operation only for a short time.

Riffelalp

Riffelalp is a hamlet in the municipality of Zermatt in the canton of Valais. It is located at a height of 2,222 metres (7,290 ft) above sea level, just above the tree line, approximately halfway between the town of Zermatt and the Gornergrat mountain. Once the site of the prestigious Riffelalp Grand Hotel, today Riffelalp mainly consists of a large hotel complex, the Riffelalp Resort 2222m, and a chapel.

Riffelalp is connected to Zermatt by the Gornergrat railway, although Riffelalp railway station is located some distance from the resort. The 675 metres (2,215 ft) long Riffelalp tram links the two together.

Rocky Mountains subalpine zone

The Rocky Mountains subalpine zone is the biotic zone immediately below tree line in the Rocky Mountains of North America. In Colorado, the subalpine zone occupies elevations approximately from 9,000 to 12,000 feet (2,700 to 3,700 m); while in northern Alberta, the subalpine zone extends from 1,350 to 2,300 metres (4,400 to 7,500 ft).

Siffleur Wilderness Area

The Siffleur Wilderness Area is a provincially designated wilderness area in the Canadian Rockies of Alberta. It was established in 1961 and it, as one of the three wilderness areas of Alberta, has the strictest form of government protection available in Canada. All development is forbidden and only travel by foot is permitted. Hunting and fishing are not allowed. The other two wilderness areas are White Goat Wilderness Area and Ghost River Wilderness Area and together the three areas total 249,548.80 acres (100,988.82 ha).Siffleur is located near the west end and south side of Canadian Highway 11 and slightly south of the White Goat Wilderness area. It is near the north end of Banff National Park and the south end of Jasper National Park. Mountains rise to 3,300 metres (10,800 ft). The area has rugged mountains, glacier-carved valleys, mountain lakes, and alpine meadows. There are two distinct vegetation zones. Above 2,100 metres (6,900 ft), the tree line, are grasses, sedges and wildflowers. Below that are subalpine forests of spruce, fir, and lodgepole pine. At even lower elevations there are aspen and balsam poplar. Animals in the lower regions include woodland caribou, moose, elk, white-tailed deer, mule deer, grizzly bear, black bear, cougar, coyote, timber wolf, and wolverine. Animals in the upper regions include golden-mantled ground squirrels, bighorn sheep, mountain goat, hoary marmot, pika, white-tailed ptarmigan, grey-crowned rosy finch, water pipit and horned lark. Eagles are seen in both the lower and upper regions.Like Siffleur Mountain and Siffleur River, the French siffleur name was applied by James Hector in 1858 for the shrill whistles of the marmot which inhabit the area.

Thorndike Peaks

The Thorndike Peaks are a mountain range located south of the entrance to Makinson Inlet, on the east coast of Ellesmere Island, Nunavut, Canada. They are part of the Arctic Cordillera and are virtually unexplored. There are no trees or wildlife in the Thorndike Peaks because the mountains are north of the Arctic tree line and because of the harsh cold climate.

Tundra

In physical geography, tundra () is a type of biome where the tree growth is hindered by low temperatures and short growing seasons. The term tundra comes through Russian тундра (tûndra) from the Kildin Sami word тӯндар (tūndâr) meaning "uplands", "treeless mountain tract". Tundra vegetation is composed of dwarf shrubs, sedges and grasses, mosses, and lichens. Scattered trees grow in some tundra regions. The ecotone (or ecological boundary region) between the tundra and the forest is known as the tree line or timberline.

There are three regions and associated types of tundra: Arctic tundra, alpine tundra, and Antarctic tundra.

White Goat Wilderness Area

The White Goat Wilderness Area is a provincially designated wilderness area in the Canadian Rockies of Alberta. It was established in 1961 and it, as one of the three wilderness areas of Alberta, has the strictest form of government protection available in Canada. All development is forbidden and only travel by foot is permitted. Hunting and fishing are not allowed. The other two wilderness areas are Ghost River Wilderness Area and Siffleur Wilderness Area and together the three areas total 249,548.80 acres (100,988.82 ha).White Goat is located near the west end and north side of Canadian Highway 11 and slightly north of the Siffleur Wilderness area. It is near the north end of Banff National Park, the south end of Jasper National Park, and east of the Columbia Icefield. Mountains rise to over 3,300 metres (10,800 ft). The area has rugged mountains, glacier-carved valleys, mountain lakes, waterfalls, and alpine meadows. There are two distinct vegetation zones. Above 2,100 metres (6,900 ft), the tree line, are grasses, sedges and wildflowers. Below that are spruce, fir, and lodgepole pine. Animals in the lower regions include woodland caribou, moose, elk, white-tailed deer, mule deer, grizzly bear, black bear, cougar, coyote, timber wolf, and wolverine. Animals in the upper regions include golden-mantled ground squirrels, bighorn sheep, mountain goat, hoary marmot, pika, white-tailed ptarmigan, grey-crowned rosy finch, water pipit and horned lark. Eagles are seen in both the lower and upper regions.

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