Tree line above St. Moritz, Switzerland. May 2009

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 and one-sided because of cold and constant wind.

The tree line is the edge of the habitat at which trees are capable of growing. Beyond the tree line, they are unable to grow because of inappropriate environmental conditions (usually cold temperatures or lack of moisture).^[1]:51 Some distinguish additionally a deeper timberline or forest line, where trees form a forest with a closed canopy.^[2]:151

At the tree line, tree growth is often very stunted, with the last trees forming low, densely matted bushes. If it is caused by wind, it is known as krummholz formation, from the German for 'twisted wood'.^[3]:58

The tree line, like many other natural lines (lake boundaries, for example), appears well-defined from a distance, but upon sufficiently close inspection, it is a gradual transition in most places. Trees grow shorter towards the inhospitable climate until they simply stop growing.^[3]:55

Types[link]

There are several types of tree lines defined in ecology and geology:

Alpine[link]

The highest elevation that sustains trees; higher up, it is too cold or snow cover persists for too much of the year, to sustain trees.^[2]:151 Usually associated with mountains, the climate above the tree line is called an alpine climate,^[4]:21 and the terrain can be described as alpine tundra.^[5] In the northern hemisphere treelines on north-facing slopes are lower than on than south-facing slopes because increased shade means the snowpack takes longer to melt which shortens the growing season for trees.^[6]:109 This is reversed in the southern hemisphere.

Desert[link]

The driest places that trees can grow; drier desert areas having insufficient rainfall to sustain trees. These tend to be called the "lower" tree line and occur below about 5,000 ft (1,500 m) elevation in the Desert Southwestern United States.^[7] The desert treeline tends to be lower on pole-facing slopes than equator-facing slopes, because the increased shade on a pole-facing slope keeps those slopes cooler and prevents moisture from evaporating as quickly, giving trees a longer growing season and more access to water.

Desert-alpine[link]

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[link]

Different tree species have different tolerances to drought and cold. Mountain ranges isolated by oceans or deserts may have restricted reportoires 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.^[8]:37

Exposure[link]

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[link]

The northernmost latitude in the Northern Hemisphere where trees can grow; farther north, it is too cold all year round to sustain trees.^[9] Extremely cold temperatures, especially when prolonged, can result in freezing of 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.

Antarctic[link]

The southernmost latitude in the Southern Hemisphere where trees can grow; further south, it is too cold to sustain trees. It is a theoretical concept that does not have any defined location. No trees grow in Antarctica or the subantarctic islands. This tree line would be the southernmost point in the environment at which trees can no longer grow, except there are no landmasses that have a true treeline analogous to the arctic treeline.

Other[link]

The immediate environment is too extreme for trees to grow. This can be caused by 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 areas. 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 of pollution. Example are around Nikel in Russia and previously in the Erzgebirge.

Typical vegetation[link]

Severe winter climate conditions at alpine tree line causes stunted krummholz growth. Karkonosze, Poland.

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[link]

• Dahurian Larch (Larix gmelinii)
• Macedonian Pine (Pinus peuce)
• Swiss Pine (Pinus cembra)
• Mountain Pine (Pinus mugo)
• Arctic White Birch (Betula pubescens subsp. tortuosa)

North America[link]

• Subalpine fir (Abies lasiocarpa)^[6]:106
• Subalpine Larch (Larix lyallii)^[10]
• Engelmann Spruce (Picea engelmannii)^[6]:106
• Whitebark Pine (Pinus albicaulis)^[10]
• Great Basin Bristlecone Pine (Pinus longaeva)
• Rocky Mountains Bristlecone Pine (Pinus aristata)
• Foxtail Pine (Pinus balfouriana)
• Limber Pine (Pinus flexilis)
• Potosi Pinyon (Pinus culminicola)
• Black spruce (Picea mariana)^[1]:53
• Hartweg's Pine (Pinus hartwegii)

South America[link]

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

• Antarctic Beech (Nothofagus antarctica)
• Lenga Beech (Nothofagus pumilio)^[11]
• Polylepis (Polylepis tarapacana)

Australia[link]

• Snow Gum (Eucalyptus pauciflora)

Worldwide distribution[link]

Alpine tree lines[link]

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 (246 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 13,000 ft).^[12]

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

Arctic tree lines[link]

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. Here are some typical polar treelines:

Antarctic tree lines[link]

Kerguelen Island, Île Saint-Paul, South Georgia, South Orkney, and other subantarctic islands are all so heavily wind exposed and with a far too cold summer climate (tundra) that none have any indigenous tree species. The Falkland Islands 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 and has the mildest weather. It is located 1,080 kilometres (670 mi) from Cape Horn on Tierra del Fuego. But no trees live on Antarctica. In fact, only a few species of grass, mosses, and lichens survive on the peninsula. In addition, no trees survive on any of the subantarctic islands near the peninsula. Tierra del Fuego however contains trees.

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

Southern Rata forests exist on Enderby Island and Auckland Islands 50°42′S 166°06′E / 50.7°S 166.1°E / -50.7; 166.1 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 600 - 800 hours of sun annually. Campbell Island further south is almost treeless, except for one stunted pine tree near the weather station 52°33′S 169°09′E / 52.55°S 169.15°E / -52.55; 169.15 and it was 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°37′S 158°51′E / 54.62°S 158.85°E / -54.62; 158.85 and has no vegetation beyond snow grass and alpine grasses and mosses.^{[citation needed]}

See also[link]

• Ecotone: a transition between two adjacent ecological communities
• Edge effect: the effect of contrasting environments on an ecosystem
• Massenerhebung effect
• Tundra: an area where tree growth is inhibited by low temperatures and short growing seasons

References[link]

Trees portal

Further reading[link]

• Arno, S.F.; Hammerly, R.P. (1984). Timberline. Mountain and Arctic Forest Frontiers. Seattle: The Mountaineers. ISBN 0-89886-085-7. 
• Beringer, J.; Tapper, N.J.; McHugh, I.; Lynch, A.H.; Serreze, M.C.; Slater, Andrew (2001). "Impact of Arctic treeline on synoptic climate". Geophysical Research Letters 28 (22): 4247–4250. DOI:10.1029/2001GL012914. 
• Ødum, S (1979). "Actual and potential tree line in the North Atlantic region, especially in Greenland and the Faroes". Holarctic Ecology 2 (4): 222–227. DOI:10.1111/j.1600-0587.1979.tb01293.x. 
• Ødum, S (1991). "Choice of species and origins for arboriculture in Greenland and the Faroe Islands". Dansk Dendrologisk Årsskrift 9: 3–78. 
• Singh, C.P.; Panigrahy, S.; Thapliyal, A.; Kimothi, M.M.; Soni, P.; Parihar, J.S. (2012). "Monitoring the alpine treeline shift in parts of the Indian Himalayas using remote sensing". Current Science 102(4): 559–562. http://cs-test.ias.ac.in/cs/Volumes/102/04/0559.pdf. 
• Panigrahy, S.; Singh, C.P.; Kimothi, M.M.; Soni, P.; Parihar, J.S. (2010). "The Upward migration of alpine vegetation as an indicator of climate change: observations for Indian Himalayan region using remote sensing data". Nnrms(B) 35: 73–80. http://www.isro.org/newsletters/contents/nnrms/NNRMS-Bulletin-2010.pdf. 
• Singh, C.P. (2008). "Alpine ecosystems in relation to climate change". ISG Newsletter 14: 54–57. http://www.scribd.com/doc/13724806/Alpine-Climate. 

Trees on a mountain in northern Utah during early autumn

Trunk base of a Coast Redwood tree in Jedediah Smith Redwoods State Park: Simpson Reed Discovery Trail, near Crescent City, California

A tree is a perennial woody plant. It most often has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance.^[1] A minimum height specification at maturity is cited by some authors, varying from 3 m^[2] to 6 m;^[3] some authors set a minimum of 10 cm trunk diameter (30 cm girth).^[4] Woody plants that do not meet these definitions by having multiple stems and/or small size are usually called shrubs, although many trees such as Mallee do not meet such definitions. Compared with most other plants, trees are long-lived, some reaching several thousand years old and growing to up to 115 m (379 ft) high.^[5]

Trees are an important component of the natural landscape because of their prevention of erosion and the provision of a weather-sheltered ecosystem in and under their foliage. They also play an important role in producing oxygen and reducing carbon dioxide in the atmosphere, as well as moderating ground temperatures. They are also elements in landscaping and agriculture, both for their aesthetic appeal and their orchard crops (such as apples). Wood from trees is a building material, as well as a primary energy source in many developing countries. Trees also play a role in many of the world's mythologies (see trees in mythology).^[6]

Classification[link]

A tree is a plant form that occurs in many different orders and families of plants. Most species of trees today are flowering plants (angiosperms) and conifers. Trees show a variety of growth forms, leaf type and shape, bark characteristics and reproductive organs. For the listing of examples of well-known trees and how they are classified, see List of tree genera.

The tree form has evolved separately in unrelated classes of plants, in response to similar environmental challenges, making it a classic example of parallel evolution. With an estimate of 100,000 tree species, the number of tree species worldwide might total 25 percent of all living plant species.^[7] The majority of tree species grow in tropical regions of the world and many of these areas have not been surveyed yet by botanists, making species diversity and ranges poorly understood.^[8] The earliest tree-like organisms were tree ferns, horsetails and lycophytes, which grew in forests in the Carboniferous period, however these plants were not trees^{[citation needed]}, since they lacked woody tissue. Trees evolved in the Triassic period, with conifers, ginkgos, cycads and other gymnosperms appeared producing woody tissue, and were subsequently followed by tree-form flowering plants in the Cretaceous period.

A small group of trees growing together is called a grove or copse, and a landscape covered by a dense growth of trees is called a forest. Several biotopes are defined largely by the trees that inhabit them; examples are rainforest and taiga (see ecozones). A landscape of trees scattered or spaced across grassland (usually grazed or burned over periodically) is called a savanna. A forest of great age is called old growth forest or ancient woodland (in the UK). A young tree is called a sapling.

Morphology[link]

Tree roots anchor the structure and provide water and nutrients. The ground has eroded away around the roots of this young red pine tree.

Many trees show strong apical dominance.

The parts of a tree are the roots, trunk(s), branches, twigs and leaves. Tree stems consist mainly of support and transport tissues (xylem and phloem). Wood consists of xylem cells, and bark is made of phloem and other tissues external to the vascular cambium. Trees may be grouped into exogenous and endogenous trees according to the way in which their stem diameter increases. Exogenous trees, which comprise the great majority of trees (all conifers, and almost all broadleaf trees), grow by the addition of new wood outwards, immediately under the bark. Endogenous trees, mainly in the monocotyledons (e.g., aloes and dragon trees), grow by addition of new material as discrete bundles within the existing trunk tissue.

Trees can be identified to genus or species by a combination of the tree's shape, and the characteristics of its bark, leaves, flowers, and fruit. The leaves may be either deciduous or evergreen.^[2][3]

As an exogenous tree grows, it creates growth rings as new wood is laid down concentrically over the old wood. In species growing in areas with seasonal climate changes, wood growth produced at different times of the year may be visible as alternating light and dark, or soft and hard, rings of wood.^[3] In temperate climates, and tropical climates with a single wet-dry season alternation, the growth rings are annual, each pair of light and dark rings being one year of growth; these are known as annual rings. In areas with two wet and dry seasons each year, there may be two pairs of light and dark rings each year; and in some (mainly semi-desert regions with irregular rainfall), there may be a new growth ring with each rainfall.^[9] In tropical rainforest regions, with constant year-round climate, growth is continuous and the growth rings are not visible nor is there a change in the wood texture. In species with annual rings, these rings can be counted to determine the age of the tree, and used to date cores or even wood taken from trees in the past, a practice known as the science of dendrochronology. Very few tropical trees can be accurately dated in this manner. Age determination in this manner is also impossible in endogenous trees.

The roots of a tree are generally embedded in earth, providing anchorage for the above-ground biomass and absorbing water and nutrients from the soil. However, while ground nutrients are essential to a tree's growth the majority of its biomass – over 90 percent – comes from carbon dioxide absorbed from the atmosphere (see photosynthesis).^[10] Above ground, the trunk gives height to the leaf-bearing branches, aiding in competition with other plant species for sunlight. In many trees, the arrangement of the branches optimizes exposure of the leaves to sunlight.

Not all trees have all the plant organs or parts mentioned above. For example, the saguaro cactus of North America has no functional leaves. A plant form that is similar to a tree, but generally having smaller, multiple trunks and/or branches that arise near the ground, is called a shrub. However, no precise differentiation between shrubs and trees is possible. Given their small size, bonsai plants would not technically be "trees", but one should not confuse reference to the form of a species with the size or shape of individual specimens. A spruce seedling does not fit the definition of a tree, but all spruces are trees.

Record breaking trees[link]

The world's champion trees can be rated on height, trunk diameter or girth, total size, and age.

Tallest trees[link]

The coniferous Coast Redwood is the tallest tree species on earth.

The heights of the tallest trees in the world have been the subject of considerable dispute and much exaggeration. Modern verified measurements with laser rangefinders, or with tape drop measurements made by tree climbers (such as those carried out by canopy researchers or members of groups like the Native Tree Society), have shown that some older measuring methods and measurements are often unreliable, sometimes producing exaggerations of 5% to 15% or more above the real height. Historical claims of trees growing to 130 m (430 ft), and even 150 m (490 ft), are now largely disregarded as unreliable, and attributed to human error. Historical records of fallen trees measured prostrate on the ground are considered to be somewhat more reliable. The following are now accepted as the top nine tallest reliably measured species (taken only currently standing specimens):

1. Coast Redwood (Sequoia sempervirens): 115.66 m (379.46 ft), Hyperion, Redwood National Park, California, United States^[11]
2. Coast Douglas-fir (Pseudotsuga menziesii): 99.76 m (327.3 ft), Brummit Creek, Coos County, Oregon, United States^[12]
3. Australian Mountain Ash (Eucalyptus regnans): 99.6 m (327 ft), south of Hobart, Tasmania, Australia^[13]
4. Sitka Spruce (Picea sitchensis): 96.7 m (317 ft), Prairie Creek Redwoods State Park, California, United States^[14]
5. Giant Sequoia (Sequoiadendron giganteum): 95.8 m (314 ft), Sequoia National Forest, California, United States^[15]
6. Tasmanian Blue Gum (Eucalyptus globulus): 90.7 m (298 ft), Tasmania, Australia^[16]
7. Manna Gum (Eucalyptus viminalis): 89 m (292 ft), Evercreech Forest Reserve, Tasmania, Australia^[16]
8. Shorea faguetiana: 88.3 m (290 ft) Tawau Hills National Park, in Sabah on the island of Borneo^[17]
9. Alpine Ash (Eucalyptus delegatensis): 87.9 m (288 ft), Tasmania, Australia^[16]

A view of a tree from below; this may exaggerate apparent height

Stoutest trees[link]

The girth of a tree is usually much easier to measure than the height, as it is a simple matter of stretching a tape round the trunk, and pulling it taut to find the circumference. Despite this, UK tree author Alan Mitchell made the following comment about measurements of yew trees:

The aberrations of past measurements of yews are beyond belief. For example, the tree at Tisbury has a well-defined, clean, if irregular bole at least 1.5 m long. It has been found to have a girth that dilated and shrunk in the following way: 11.28 m (1834 Loudon), 9.3 m (1892 Lowe), 10.67 m (1903 Elwes and Henry), 9.0 m (1924 E. Swanton), 9.45 m (1959 Mitchell) ... Earlier measurements have therefore been omitted.

As a general standard, tree girth is taken at "breast height". This is cited as dbh (diameter at breast height) in tree and forestry literature.^[3][18] Breast height is defined differently in different situations, with most forestry measurements taking girth at 1.3 m above ground,^[18] while those who measure ornamental trees usually measure at 1.5 m above ground;^[3] in most cases this makes little difference to the measured girth. On sloping ground, the "above ground" reference point is usually taken as the highest point on the ground touching the trunk^[3][18], but in North America a point, that is the average of the highest point and the lowest point the tree trunk appears to contact the soil, is usually used.^[19] Some of the inflated old measurements may have been taken at ground level. Some past exaggerated measurements also result from measuring the complete next-to-bark measurement, pushing the tape in and out over every crevice and buttress.^[20]

Modern trends are to cite the tree's diameter rather than the circumference. Diameter of the tree is calculated by finding the medium diameter of the trunk, in most cases obtained by dividing the measured circumference by π; this assumes the trunk is mostly circular in cross-section (an oval or irregular cross-section would result in a mean diameter slightly greater than the assumed circle). Accurately measuring circumference or diameter is difficult in species with the large buttresses that are especially characteristic in many species of rainforest trees. Simple measurement of circumference of such trees can be misleading when the circumference includes much empty space between buttresses.

One further problem with measuring baobabs Adansonia is that these trees store large amounts of water in the very soft wood in their trunks. This leads to marked variation in their girth over the year (though not more than about 2.5%^[21]), swelling to a maximum at the end of the rainy season, minimum at the end of the dry season.

The stoutest living single-trunk species in diameter are:

1. Montezuma Cypress Taxodium mucronatum: 11.62 m (38.1 ft), Árbol del Tule, Santa Maria del Tule, Oaxaca, Mexico.^[22] Note though that this diameter includes buttressing; the actual idealised diameter of the area of its wood is 9.38 m (30.8 ft).^[22]
2. Giant Sequoia Sequoiadendron giganteum: 8.85 m (29.0 ft), General Grant tree, General Grant Grove, California, United States^[23]
3. Coast Redwood Sequoia sempervirens: 7.9 m (26 ft), Lost Monarch Jedediah Smith Redwoods State Park, California, United States.
4. Australian Oak Eucalyptus obliqua: 6.72 m (22.0 ft)
5. Australian Mountain Ash Eucalyptus regnans: 6.52 m (21.4 ft), Big Foot
6. Western Redcedar Thuja plicata: 5.99 m (19.7 ft), Kalaloch Cedar, Olympic National Park
7. Sitka Spruce Picea sitchensis: 5.39 m (17.7 ft), Quinalt Lake Spruce, Olympic National Park
8. Kauri Agathis australis (Te Matua Ngahere): 5.33 m (17.5 ft).^[24]
9. Alerce Fitzroya cupressoides: 5.0 m (16.4 ft)

An additional problem lies in instances where multiple trunks (whether from an individual tree or multiple trees) grow together. The Sacred Fig is a notable example of this, forming additional "trunks" by growing adventitious roots down from the branches, which then thicken up when the root reaches the ground to form new trunks; a single Sacred Fig tree can have hundreds of such trunks.^[1] The multi-stemmed Hundred Horse Chestnut was known to have a circumference of 57.9 m (190 ft) when it was measured in 1780.

Largest trees[link]

General Sherman is the largest tree on Earth

The largest trees in total volume are both tall and large in diameter and, in particular, hold a large diameter high up the trunk. Measurement is very complex, particularly if branch volume is to be included as well as the trunk volume, so measurements have only been made for a small number of trees, and generally only for the trunk. No attempt has ever been made to include root volume. Measuring standards vary.

The top ten species measured so far are*:

1. Giant Sequoia Sequoiadendron giganteum: 1,487 m³ (52,508 cu ft), General Sherman^[25]
2. Coast Redwood Sequoia sempervirens: 1,203 m³ (42,500 cu ft), Lost Monarch^[26]
3. Montezuma Cypress Taxodium mucronatum: 750 m³ (25,000 cu ft), Árbol del Tule^[27]
4. Kauri Agathis australis (Tāne Mahuta): 516 m³ ^[28]
5. Western Redcedar Thuja plicata: 500 m³ (17,650 cu ft ), Quinault Lake Redcedar^[25]
6. Tasmanian Blue Gum Eucalyptus globulus: 368 m³ (13,000 cu ft), Rullah Longatyle (Strong Girl, also Grieving Giant) ^[16]
7. Australian Mountain Ash Eucalyptus regnans: 360 m³ (12,714 cu ft), Arve Big Tree^[16]
8. Coast Douglas-fir Pseudotsuga menziesii 349 m³ (12,320 cu ft) Red Creek Tree
9. Sitka Spruce Picea sitchensis 337 m³ (11,920 cu ft) Queets Spruce^[29]
10. Australian Oak Eucalyptus obliqua: 337 m³ (11,920 cu ft) Gothmog^[16]
11. Alpine Ash Eucalyptus delegatensis: 286 m³ (10,100 cu ft), located in Styx River Valley^[16]

(*)This list does not take into account now dead specimens.

Oldest trees[link]

The oldest trees are determined by growth rings, which can be seen if the tree is cut down, or in cores taken from the bark to the center of the tree. Accurate determination is only possible for trees that produce growth rings, generally those in seasonal climates. Trees in uniform non-seasonal tropical climates grow continuously and do not have distinct growth rings. It is also only possible for trees that are solid to the center. Many very old trees become hollow as the dead heartwood decays. For some of these species, age estimates have been made on the basis of extrapolating current growth rates, but the results are usually largely speculation. White (1998)^[30] proposes a method of estimating the age of large and veteran trees in the United Kingdom through the correlation between a tree's stem diameter, growth character and age.

The verified oldest measured ages are:

1. Great Basin Bristlecone Pine (Methuselah) Pinus longaeva: 4,844 years^[31]
2. Alerce Fitzroya cupressoides: 3,622 years^[31]
3. Giant Sequoia Sequoiadendron giganteum: 3,266 years^[31]
4. Sugi Cryptomeria japonica: 3,000 years^[32]
5. Huon-pine Lagarostrobos franklinii: 2,500 years^[31]

Other species suspected of reaching exceptional age include European Yew Taxus baccata (probably over 2,000 years^[33][34]) and Western Redcedar Thuja plicata. The oldest known European Yew is the Llangernyw Yew in the Churchyard of Llangernyw village in North Wales, which is estimated to be between 4,000 and 5,000 years old.

Damage[link]

El Grande, about 85 m (279 ft) high, the most massive (though not the tallest) Eucalyptus regnans was accidentally killed by loggers burning-off the remains of legally loggable trees (less than 85 m) that had been felled all around it.

Callus growth on beech branch following fire (heat) damage.

The two sources of tree damage are either biotic (from living sources) or abiotic (from non-living sources). Biotic sources include insects that bore into the tree, deer that rub bark off, and fungi.^[35]

Abiotic sources include lightning, vehicles impacts, and construction activities. Construction activities can involve a number of damage sources, including grade changes that prevent aeration to roots, spills involving toxic chemicals such as cement or petroleum products, or severing of branches or roots.

Both damage sources can result in trees becoming dangerous, and the term "hazard trees" is commonly used by arborists, and industry groups such as power line operators. Hazard trees are trees that, due to disease or other factors, are more susceptible to falling in windstorms, or having parts of the tree fall.

Evaluating the danger a tree presents is based on a process called the Quantified Tree Risk Assessment.^[36]

Assessment as to labeling a tree a hazard tree can be based on a field examination. Assessment as a result of construction activities that will damage a tree is based on three factors: severity, extent and duration. Severity relates usually to the degree of intrusion into the TPZ and resultant root loss. Extent is frequently a percentage of a factor such as canopy, roots or bark, and duration is normally based on time. Root severing is considered permanent in time.

Trees are similar to people. Both can withstand massive amounts of some types of damage and survive, but even small amounts of certain types of trauma can result in death. Arborists are very aware that established trees will not tolerate any appreciable disturbance of the root system.^[37] However, lay people and construction professionals seldom recognise how easily a tree can be killed.

One reason for confusion about tree damage from construction involves the dormancy of trees during winter. Another factor is that trees may not show symptoms of damage until two years or longer after damage has occurred. For that reason, persons uneducated in arboricultural science may not correlate the actual cause and resultant effect.

Various organisations, such as the International Society of Arboriculture, the British Standards Institute and the Tree Industry Association (formerly the National Arborist Association), have long recognised the importance of construction activities that impact tree health. The impacts are important because they can result in monetary losses due to tree damage and resultant remediation or replacement costs, as well as violation of government ordinances or community or subdivision restrictions.

As a result, protocols for tree management prior to, during and after construction activities are well established, tested and refined. These basic steps are involved:

• Review of the construction plans
• Development of the related tree inventory
• Application of standard construction tree management protocols
• Assessment of potential for expected tree damages
• Development of a tree protection plan (providing for pre-, concurrent, and post construction damage prevention and remediation steps)
• Development of a tree protection plan
• Development of a remediation plan
• Implementation of tree protection zones (TPZ)
• Assessment of construction tree damage, post-construction
• Implementation of the remediation plan

The shield of Currier House (Harvard College).

Trees in culture[link]

The tree has always been a cultural symbol. Common icons are the World tree, for instance Yggdrasil,^[38] and the tree of life. The tree is often used to represent nature or the environment itself.

The tree is also a symbol and mascot for Stanford University and Currier House (Harvard College).

Tree value approximation (USA)[link]

Studies have shown that trees contribute as much as 27% of the appraised land value in certain markets and cite the following^[39] which can be extrapolated with care.

These most likely use diameter measured at breast height, 4.5 feet (140 cm) above ground, not the larger base diameter. A general model for any year and diameter is Value = 17.27939*(diameter^2)*1.022^(year-1985) assuming 2.2% inflation per year.^[41] The right side of this equation is written to paste into Excel or Google to perform the calculation. Extrapolations from any model can vary widely, so value estimates for diameters larger than 30 inches (760 mm) may have to be capped so trees do not exceed 27% of total appraised land value.

See also[link]

References[link]

Notes[link]

Bibliography[link]

• Pakenham, T. (2002). Remarkable Trees of the World. ISBN 0-297-84300-1
• Pakenham, T. (1996). Meetings with Remarkable Trees. ISBN 0-297-83255-7
• Tudge, C. (2005). The Secret Life of Trees. How They Live and Why They Matter. Allen Lane. London. ISBN 0-7139-9698-6

External links[link]

Trees portal

Wikimedia Commons has media related to: Trees

Look up tree in Wiktionary, the free dictionary.

• Gymnosperm database
• Silvics of North America
• University of Florida's Landscape Plants website
• Global Trees Campaign (campaigning to save the world's most threatened trees)
• International Society of Arboriculture
• Eastern Native Tree Society
• Western Native Tree Society
• Trees The Arbor Day Foundation
• Tree Encyclopedia Extensive collection of diagnostic photos, Morton Arboretum Specimens
• Wondermondo - Trees Largest and most unusual trees of the world
• Venerable Trees Venerable trees of the planet

lez:Ттарvep:Pu

Look up Line, line, or lines in Wiktionary, the free dictionary.

Line or lines may refer to:

Science and technology[link]

• Line (electrical engineering), a circuit or loop.
  • A power line for electric power transmission
  • line power or lines power, domestic mains electricity.
  • telephone line
  • RF transmission line
  • Line level, a common standard for audio signals.
• Line (video), a measure of video display resolution or image resolution
• line, former name of the unit of magnetic flux, the Maxwell
• Line (unit), an obsolete unit of length equal to one-twelfth or one-tenth of an inch.
• Line (geometry), an infinitely-extending one-dimensional figure that has no curvature.
• line: a medical catheter, particularly one used for intravenous treatment.
  • CVP line
  • PICC line
  • umbilical line
• Line (text file), a row of characters as a unit of organization within text files.
• A "line of longitude" or "line of latitude" in geography. "The Line" may refer to the equator.
• Relationships in genetics and genealogy, such as Lineage and kinship and descent.

Transport[link]

• Railway line
• Shipping line, a company engaged in sea transport.
• The International Load Line or Plimsoll line (Waterline), indicates the maximum safe draft for the vessel
• Airline
• A bus line, see List of bus operating companies

Business[link]

• Line function, a business activity.
• Product lining, in marketing.

Military[link]

• Line (formation), a standard tactical formation of forces.
  • Line infantry, a line formation of infantrymen who were part of the "Line Regiments".
• Line of battle, in naval warfare, a line of warships, hence "Ship of the line".

Sports[link]

• In water sports: small rope
• The point spread in spread betting
• In cricket, the direction of a delivery, see line and length.
• Offensive line or defensive line in American football.
• Racing line, in auto racing, a path taken through a corner.
• In kiting: kite line
• In fishing: fishing line

Arts[link]

• Line (play), a 1967 long-running play written by Israel Horovitz.
• Line (singer), a Danish singer and finalist in the Danish X Factor
• Lines (Emily Brontë poem), written in December 1837.
• Lines Review, a Scottish literary periodical published between 1952 and 1998.
• "Lines", abbreviation for "Lines Composed a Few Miles above Tintern Abbey, on Revisiting the Banks of the Wye during a Tour. July 13, 1798", a poem by William Wordsworth
• A line of text in writing or typography.
• Line (poetry), the fundamental unit of poetic composition.
• Line, or the melody in a musical composition.
• The dialogue to be spoken in a script or screenplay.

Sewing and fashion[link]

• To insert a Lining
• Fashion line
• Style line
• Empire line or Empire silhouette

The abbreviation LINE[link]

• LINE (combat system), a martial arts system
• Long interspersed nuclear element (LINE), a type of retrotransposon in genomics.

Other[link]

• Line (given name), a Danish and Norwegian female given name
• A length of rope, cable, or chain when put to use (such as a clothesline, anchor line)
• A line or queue of people waiting in a queue area
• A thin continuous length of ink or other marking in a drawing
• A geographical or political border that is clearly defined and demarcated
• A name given to some roads in Ontario, usually running perpendicular to concession roads
• Lines (punishment), punishment by forced writing of text
• Party line (politics), an idiom for a political party or social movement's canon agenda
• Lines of cocaine
• Lines (video game)
• A one-, two- or three-line whip, a notice issued by a Chief Whip in the UK parliament
• A "straight line" is used to set up a joke, while the punch line completes it
• Line Islands, an island group in the central Pacific
• Line, a drug in the video game Togainu no Chi

See also[link]

• Division of Lyne, Australian electoral district
• Lyne (surname)
• Lyne, Denmark (town)
• Liner (disambiguation)
• Lining (disambiguation)

This disambiguation page lists articles associated with the same title. If an internal link led you here, you may wish to change the link to point directly to the intended article.