Populus tremula

Populus tremula, commonly called aspen, common aspen, Eurasian aspen, European aspen, or quaking aspen,[2] is a species of poplar native to cool temperate regions of Europe and Asia, from Iceland[3] and the British Isles[4] east to Kamchatka, north to inside the Arctic Circle in Scandinavia and northern Russia, and south to central Spain, Turkey, the Tian Shan, North Korea, and northern Japan. It also occurs at one site in northwest Africa in Algeria. In the south of its range, it occurs at high altitudes in mountains.[5][6]

Not to be confused with Populus tremuloides, the American aspen, also called trembling aspen and quaking aspen.

Populus tremula
Scientific classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Rosids
Order: Malpighiales
Family: Salicaceae
Genus: Populus
Section: Populus sect. Populus
Species:
P. tremula
Binomial name
Populus tremula
Distribution map

Description
Adult leaves (left); juvenile and sucker leaves (right)

It is a substantial deciduous tree growing to 40 metres (130 ft) tall by 10 m (33 ft) broad, with a trunk attaining over 1 metre (3 ft 3 in) in diameter.[7] The bark is pale greenish-grey and smooth on young trees with dark grey diamond-shaped lenticels, becoming dark grey and fissured on older trees.

The adult leaves, produced on branches of mature trees, are nearly round, slightly wider than long, 2–8 cm (1–3 in) diameter, with a coarsely toothed margin and a laterally flattened petiole 4–8 cm (2–3 in) long. The flat petiole allows them to tremble in even slight breezes, and is the source of its scientific name,[7] as well as one of its vernacular names "langues de femmes" attributed to Gerard's 17th-century Herball. The leaves on seedlings and fast-growing stems of suckers (root sprouts) are of a different shape, heart-shaped to nearly triangular.[8] They are also often much larger, up to 20 centimetres (7.9 in) long; their petiole is also less flattened.

The flowers are wind-pollinated catkins produced in early spring before the new leaves appear; they are dioecious, with male and female catkins on different trees. The male catkins are patterned green and brown, 5–10 centimetres (2.0–3.9 in) long when shedding pollen; the female catkins are green, 2–6 centimetres (0.79–2.36 in) long at pollination, maturing in early summer to bear 10–20 (50–80) capsules each containing numerous tiny seeds embedded in downy fluff. The fluff assists wind dispersal of the seeds when the capsules split open at maturity.[9][5][7]

It can be distinguished from the closely related North American Populus tremuloides by the leaves being more coarsely toothed.[5]

Like other aspens, it spreads extensively by suckers (root sprouts), which may be produced up to 40 m from the parent tree, forming extensive clonal colonies.[9][5] This often makes the job of clearing unwanted trees from an area especially difficult, as new suckers will continue to sprout from the extensive root system for up to several years after all surface growth has been eliminated.

Ecology
Populus tremula growing well north of the Arctic Circle in Norway; April 2008.

Eurasian aspen is a water and light demanding species that is able to vigorously colonize an open area after fire, clear cutting or other kind of damages. After an individual has been damaged or destroyed, root suckers are produced abundantly on the shallow lateral roots. Fast growth continues until the age of about 20 years when crown competition increases. After that, growth speed decreases and culminates at about 30 years of age. Aspen can reach an age of 200 years.[7]

It is a very hardy species and tolerates long, cold winters and short summers.

Aspen is resistant to browsing pressure by fallow deer due to its unpleasant taste.[10]

This species is important for the hornet moth, which uses it as a host during the larval stage.

Fossil record

Fossils of Populus tremula have been described from the fossil flora of Kızılcahamam district in Turkey which is of early Pliocene age.[11]

Cultivation

The aspen is found in cultivation in parks and large gardens.[12] The fastigiate cultivar ‘Erecta’, with bright yellow autumn colouring, has gained the Royal Horticultural Society’s Award of Garden Merit.[13][14] The cultivar is colloquially known as "Swedish Culumnar" in Canada.[15]

The hybrid with Populus alba (white poplar), known as grey poplar, Populus × canescens, is widely found in Europe and central Asia. Hybrids with several other aspens have also been bred at forestry research institutes in order to find trees with greater timber production and disease resistance (e.g. P. tremula × P. tremuloides, bred in Denmark[16]).

Use

The wood of aspen is light soft and has very little shrinkage. It is used for lumber and matches but is also valued in the pulp and paper industry, being particularly useful for writing paper. In addition, it is used for plywood and different types of flake and particle boards. Given its hardiness and capacity for rapid growth and regeneration, it plays an important role in the production of wood for renewable energy. Ecologically, the species is important as many insect and fungi species benefit from it. The tree further provides habitat for several mammals and birds that require young forests.[7]

References
  1. Barstow, M.; Rivers, M.C. & Beech, E. (2017). "Populus tremula". IUCN Red List of Threatened Species. 2017: e.T61959941A61959943. Retrieved 9 May 2020.
  2. Benkeblia, Noureddine, ed. (2015). Omics Technologies and Crop Improvement. CRC Press. p. 50. ISBN 978-1-4665-8669-7.
  3. "Blæösp (Populus tremula) Vísindavefurinn".
  4. James Kilkelly Irish native Aspen tree
  5. Rushforth, K. (1999). Trees of Britain and Europe. Collins ISBN 0-00-220013-9.
  6. Den Virtuella Floran: Populus tremula (in Swedish; with maps)
  7. Wühlisch, G. (2009), Eurasian aspen - Populus tremula: Technical guidelines for genetic conservation and use (PDF), European Forest Genetic Resources Programme, p. 6 p
  8. Stace, Clive (2010). New Flora of the British Isles (3rd ed.). Cambridge, UK: Cambridge University Press. p. 314. ISBN 978-0-521-70772-5.
  9. Trees for Life Species Profile: Aspen Archived 2014-02-26 at the Wayback Machine
  10. Rackham, Oliver (1994). The Illustrated History of the Countryside. London : BCA. CN 2922.p. 64.
  11. Kasaplıgil, B.-(1975): Pliocene Flora of Güvem village near Ankara, Turkey, Abstracts of the Papers Presented at the XII International Botanical Congress, Akademika Nauk SSSR, 1: 115, Leningrad
  12. "RHS Plant Selector - Populus tremula". Archived from the original on 23 April 2013. Retrieved 24 April 2019.
  13. "RHS Plantfinder - Populus tremula 'Erecta'". Retrieved 24 April 2019.
  14. "AGM Plants - Ornamental" (PDF). Royal Horticultural Society. July 2017. p. 81.
  15. "Aspen - Swedish Columnar". Retrieved 24 September 2020.
  16. Jensen, N. (1994). Guide til Arboretet i Hørsholm (in Danish).
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