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Reverted edits by Raffi (Talk) to last revision by Envoy
#REDIRECT [[Populus tremula]]
{{otheruses}}
{{Taxobox
| color = lightgreen
| name = Aspen
| image = Aspen_grove-750px.jpg
| image_width = 240px
| image_caption = A Quaking Aspen grove
| regnum = [[Plant]]ae
| divisio = [[Flowering plant|Magnoliophyta]]
| classis = [[Dicotyledon|Magnoliopsida]]
| ordo = [[Malpighiales]]
| familia = [[Salicaceae]]
| genus = ''[[Poplar|Populus]]''
| sectio = '''''Populus'''''
| subdivision_ranks = Species
| subdivision =
''[[Populus adenopoda]]''<br/>
''[[Populus alba]]''<br/>
''[[Populus grandidentata]]''<br/>
''[[Populus sieboldii]]''<br/>
''[[Populus tremula]]''<br/>
''[[Populus tremuloides]]''
}}
'''Aspens''' are [[tree]]s of the [[Salicaceae|willow]] family and comprise a section of the [[poplar]] genus, ''Populus'' sect. ''Populus''. There are six species in the section, one of them atypical, and one hybrid:
*''[[Populus adenopoda]]'': Chinese Aspen (China, south of ''P. tremula'')
*''[[Populus sieboldii]]'': Japanese Aspen (Japan)
*''[[White Poplar|Populus alba]]'': White Poplar (northwest Africa, southern Europe, east to central Asia)
*''[[White Poplar|Populus × canescens]]'': Grey Poplar (hybrid ''P. alba'' × ''P. tremula'')
*''[[Populus tremula]]'': Common, Swedish, Trembling or Eurasian Aspen (northern Europe & Asia)
*''[[Populus tremuloides]]'': Quaking, Trembling or American Aspen (northern & western North America)
*''[[Populus grandidentata]]'': Bigtooth Aspen (eastern North America, south of ''P. tremuloides'')
The five typical aspens are all native to cold regions with cool summers, in the far north of the [[Northern Hemisphere]], extending south only at high altitudes in [[mountain]]s. The White Poplar by contrast is native to much warmer regions, with hot, dry summers. They are all medium-sized [[deciduous]] [[tree]]s reaching 15–25 m tall, exceptionally to 30 m.
Aspens (apart from the aberrant White Poplar) are distinguished by their nearly round [[leaf|leaves]] on mature trees, 9–16 cm diameter with irregular rounded teeth. They are carried on strongly flattened leaf stems, which enable the leaves to twist and flutter in the slightest of breezes. The juvenile leaves on young seedlings and root sprouts differ markedly from the adult leaves, nearly triangular, showing here the typical leaf shape of most other [[poplar]]s; they are also often much larger, 13–26 cm long. The five typical aspens are distinguished from each other by leaf size and the size and spacing of the teeth on the adult leaves. White Poplar leaves differ in being deeply five-lobed, covered in thick white down, and having only a slightly flattened leaf stem.
All the aspens (including White Poplar) typically grow in large [[clonal colony|colonies]] derived from a single seedling, and spreading by means of [[root]] suckers; new stems in the colony may appear at up to 30–40 m from the parent tree. Each tree only lives for 40–150 years above ground, but the root system of the colony is long-lived, in some cases for many thousands of years, sending up new trunks as the older trunks die off above ground. For this reason it is considered to be an indicator of ancient woodlands. One such colony in [[Utah]], given the [[nickname]] of [[Pando (Quaking Aspen)|"Pando"]], is claimed to be 80,000 years old, making it possibly the [[list of long-living organisms|oldest living colony]]. Some aspen colonies become very large with time, spreading about a metre per year, eventually covering many hectares. They are able to survive intense [[wildfire|forest fires]] as the roots are below the heat of the fire, with new sprouts growing after the fire is out. However, aspens do not thrive very well in the shade, and it is difficult for aspen seedlings to grow in an already mature aspen stand. Fire indirectly benefits aspen trees, as it allows the saplings to flourish in open sunlight on account of the burned landscape. Lately aspen has increased its popularity in forestry, mostly because of its fast growth rate and ability to regenerate from sprouts, which makes the regeneration of the forest after harvesting much cheaper, as no planting or sowing is required.
In contrast with many trees, aspen bark is base-rich, meaning that aspens are important hosts for bryophytes<ref>[http://www.cairngorms.co.uk/resource/docs/publications/05042007/CNPA.Paper.440.Aspen%20Report.txt The Biodiversity and Management of Aspen woodlands: Proceedings of a one-day conference held in Kingussie, Scotland, on 25th May 2001]</ref> and act as food plants for the [[larva]]e of [[Lepidoptera]] species—see [[List of Lepidoptera that feed on Poplars]].
==Why do the leaves quake?==
The unusual ability of the leaves of ''Populus'' to twist and bend due to the flattened petioles may not be fully understood. It is thought to help protect the trees from severe winds, perhaps by helping dissipate energy more uniformly throughout the canopy. <ref>[http://www.fnr.purdue.edu/inwood/past%20issues/windaffe.htm William R. Chaney, Purdue University: How Wind Affects Trees]</ref> It is also thought to improve the rate of photosynthesis throughout the tree by reducing the exposure of the outer leaves to extreme sunlight (thus reducing [[photoinhibition]]) by presenting the leaves at an oblique angle to the sun throughout the day, while at the same time allowing more light through to the lower leaves which are generally overshaded. This would enable leaves throughout the tree to photosynthesize more efficiently. <ref>[http://academics.hamilton.edu/biology/ewilliam/umarshfieldtrips.html Ernest Williams: Field Trip Guide for Utica Marsh: ''Quaking Aspen'']</ref>
==Cultural aspects and uses==
The aspen tree's quivering leaves are, in Christian lore, said to be the result of arrogance at the [[Crucifixion]] because the aspen did not tremble like other trees. A German version claims that the aspen was the only tree to refuse to acknowledge the divinity of [[Jesus]]. The cross that Christ was crucified on is sometimes said to have been aspen wood. As aspens do not occur in [[Palestine]], this legend is improbable{{Fact|date=February 2007}}. Another old saying was that aspen leaves are made from female tongues, and their quivering is due to women's inability to stop talking{{Fact|date=February 2007}}.
Emigrant [[Basque people|Basque]] shepherds in the 19th and 20th century [[graffiti|carved texts and figures]] on aspens of the [[Basque people#The Basque diaspora|American Southwest]] to express their loneliness.
The [[wood]] is white, and soft, but fairly strong, and with very low flammability. It has a number of uses, notably for making [[match]]es, where its low flammability makes it safer to use (easy to blow out) than most other woods. Shredded aspen wood is also a popular animal bedding, as it lacks the [[phenol]]s associated with pine and juniper, which are thought to cause respiratory ailments in some animals. Heat treated aspen is a popular material for the interiors of a [[sauna]].
== Gallery ==
<gallery>
Image:EurasAspen.jpg|''P. tremula'' (Eurasian Aspen) leaves; adult leaves and shoot left, juvenile leaf right
Image:Aspens autumn yellow.jpg|''P. tremuloides'' (Quaking Aspen) in [[New Mexico]] with fall foliage
Image:Aspen-PopulusTremuloides-2001-09-27.jpg|''P. tremuloides'' (Quaking Aspen) with fall foliage, [[Jasper National Park]], [[Alberta]], [[Canada]]
Image:Fall Aspen Trees in the La Salle Mountains.jpg|''P. tremuloides'' (Quaking Aspen), [[Manti-La Sal National Forest|La Sal Mountains]]
Image:QuakiesSEP2005.JPG|''P. tremuloides'' (Quaking Aspen), [[Little Cottonwood Canyon]], [[Salt Lake County]], [[Utah]]
Image:Populus_tremuloides_8163.jpg|''P. tremuloides'' (Quaking Aspen), [[Klamath Basin National Wildlife Refuges Complex]]
Image:Populus_tremuloides_8165.jpg|''P. tremuloides'' (Quaking Aspen), [[Klamath Basin National Wildlife Refuges Complex]]
Image:Populus_grandidentata.JPG|''P. grandidentata'' (Bigtooth Aspen) in [[Massachusetts]]
</gallery>
{{Multi-video start}}
{{Multi-video item | filename = Quaking aspen in light breeze.ogg | title = Quaking aspen in light breeze | description = Video of a Quaking Aspen in a light breeze (estimated at 5mph) demonstrating the extreme leaf flutter that gives the species its name. (1 [[Megabyte|MB]], [[ogg]]/[[Theora]] format). | format = [[Theora]] }}
{{Multi-video end}}
==References and external links==
<references/>
*[http://www.treesforlife.org.uk/tfl.aspen_info_resource.html Aspen Information Resource, U.K.]
*[http://www.cpluhna.nau.edu/Biota/aspen_forest.htm Quaking Aspen Forests of the Colorado Plateau]
[[Category:Trees]]
[[Category:Salicaceae]]
