Everything about Aspen totally explained
Aspens are
trees of the
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:
Leaves
Aspens (apart from the aberrant White Poplar) are distinguished by their nearly round
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
poplars; they're 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.
Habitat and Longevity
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
mountains. The White Poplar by contrast is native to much warmer regions, with hot, dry summers. They are all medium-sized
deciduous trees reaching 15–25 m tall, exceptionally to 30 m.
All the aspens (including White Poplar) typically grow in large
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's considered to be an indicator of ancient woodlands. One such colony in
Utah, given the
nickname of
"Pando", is claimed to be 80,000 years old, making it possibly the
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
forest fires as the roots are below the heat of the fire, with new sprouts growing after the fire is out.
However, aspens don't thrive very well in the shade, and it's 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 and act as food plants for the
larvae 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. 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.
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 didn't 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 don't occur in
Palestine, this legend is improbable. Another old saying was that aspen leaves are made from female tongues, and their quivering is due to women's inability to stop talking.
Emigrant
Basque shepherds in the 19th and 20th century
carved texts and figures on aspens of the
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
matches, 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
phenols 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.
Aspen stakes often figure in Slavic folklore, where they're held to be able to vanquish witches.
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-apsens-La-sal.jpg|P. tremuloides (Quaking Aspen), 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
References and external links
Aspen Information Resource, U.K.
Quaking Aspen Forests of the Colorado Plateau
Further Information
Get more info on 'Aspen'.
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