West American larch
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Western larch ( Larix occidentalis ) |
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The Western Larch ( Larix occidentalis ) is a plant from the genus of the larch ( Larix ) in the family of Pinaceae (Pinaceae). This larch species, native to western North America , is the largest of all larch species; it is an important supplier of wood in its natural habitat.
description
Habit and growth
The West American larch is a deciduous tree ; which in its home country reaches heights of about 60 meters with trunk diameters of up to 1.5 meters. In Central Europe , on the other hand, it is usually only 25 meters high. The crown of the tree is narrowly conical when young and widens with age. In forest plantings, most of the trunk becomes knotless, which increases the value of the timber. While the main branches are horizontal to slightly upward, the side branches are often drooping.
There is no comprehensive knowledge about the root system. However, the taproot can reach depths of more than 2 meters in loose soils. In rather sparse stands, the lateral roots often extend 6 meters and more beyond the crown eaves.
In the first ten years of life, the West American larch is the fastest-growing of all conifer species found in the Northern Rocky Mountains.
Bark and leaves
The purple-gray bark of the trunk forms deep and wide cracks; the remaining stripes have a scaly border. With its very thick bark, the tree protects itself from damage from forest fires; on older trees the bark is up to 15 cm thick. The bark of the thick branches is light orange-brown. The bark of young branches is initially still hairy, but loses the hair almost completely in the course of the first year.
The buds are dark brown. The thin needle-shaped leaves are 3 to 5 cm long and light grass green on both sides. They are about 0.6 to 0.8 mm wide and 15 to 30 are in rosette-shaped clusters. In the fall, the needles turn light yellow before falling off.
Cones and seeds, genetics
The West American larch is single-sexed ( monoecious ), so it has male and female cones on the same tree. The pollen measures 71 to 84 µm in diameter. The female cones are ovate to cylindrical; they are purple in color and 2 to 4 cm long. The individual cones have around 40 to 80 cone scales, which are yellow to orange in color in summer. The cone scales are long protruding with protruding or turned back tips. When they ripen in autumn and early winter, the cones turn brown and release around 75 to 80 seeds, half of which are not fully developed. The dead cones often remain on the tree for years and are then dark gray. Even at the age of only eight years, sperm production begins; From the age of about 25, full masts occur every three to six years .
The red-brown seeds are about 3 mm in size, together with the wing they are almost 1 cm long. The thousand grain mass is about 2.7 g. As with all larches, the winged seeds are spread by the wind ( anemochory ); Widths of up to 250 m can be achieved in this way. Winter cold or stratification increase the germination rate significantly.
The seeds of the West American larch germinate epigeously. In natural locations, germination takes place when the snowmelts (late April to early June), usually 1 to 2 weeks earlier than that of important competing tree species. The seedling reaches a height of about 5 centimeters in the first year.
The number of chromosomes in the West American larch is 2n = 24.
Distribution and location
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The West American larch is native to the west coast of North America in British Columbia, Canada and in the US states of Oregon , Washington , Idaho and Montana . It grows there at altitudes of 500 to 2200 m. The occurrences in the eastern Cascade Mountains in Washington and in the Blue Mountains (Washington and Oregon) are particularly numerous .
It is seldom planted in Central Europe and can only be found in larger collections.
The West American larch is hardy and can withstand cold down to about −50 ° C. It prefers moist, but not waterlogged soils, but also thrives in drier locations. She is extremely in need of light; any competition for light is harmful. For this very reason, natural rejuvenation does not take place in the shade.
Discovery and Taxonomy
From a European perspective, the West American larch was first discovered by Meriwether Lewis and William Clark on their expedition through western North America, the Lewis and Clark Expedition , which lasted from 1803 to 1806 . Lewis and Clark described the larch they discovered in 1806, but did not yet regard them as a species in their own right. It was not until the English botanist Thomas Nuttall classified it as a separate species Larix occidentalis in 1849 and is therefore the author of the first description that is valid today .
use
The wood of the West American larch is hard and weather-resistant. It is relatively straight grain with a straw colored sapwood and a maroon colored core . The wood is only slightly brittle, can be split easily and has an oily surface. The bulk density of fresh wood is about 0.5 g / cm³. In North America it is a sought-after wood for the construction of yachts ; In addition, it is used as construction timber , for railway sleepers and fences , but also as firewood .
The resin of the tree hardens in the air and is sugary; native Indians used it like chewing gum . Today “Venetian turpentine ” is extracted from the tree resin .
Largest specimens
The tallest standing specimen with a height of 58.5 m and a trunk diameter of 1.38 m (as of 2000) is in the Umatilla National Forest in Oregon . The specimen with the largest trunk volume of 83 m³ is the Seeley Lake Giant in the Lolo National Forest (near Paxton Camp) in Montana ; this tree is 49.4 m high with a trunk diameter of 2.21 m.
According to a tree ring count, the oldest specimen is said to have stood on a tree stump near Cranbrook in British Columbia and was 920 years old.
Probably the largest of all the specimens planted in Great Britain is in Kyloe Woods , Northumberland and has so far reached a height of 33 meters.
Diseases and pests
The most damaging tree parasite on the West American larch from a forestry point of view is the parasitic plant Arceuthobium laricis (English "Larch dwarf mistletoe") from the genus dwarf mistletoe ( Arceuthobium ) in the sandalwood family , a relatively close relative of the mistletoe . It can attack young trees as early as 3 to 7 years of age and damage them, among other things, by killing the top of the tree, but also by promoting the occurrence of other tree diseases and insects. The fruits of this tree parasite are ejected at high speed and can land up to 14 meters away from the infested tree. This parasite occurs in approximately 80% of the natural population. The result is, among other things, a significant decline in growth and witch brooms .
Important tree diseases of the West American larch are the premature needle shedding, caused by the fungus Hypodermella laricis and by Fomitopsis officinalis , a member of the tree sponge relatives (Fomitopsidaceae). Another harmful fungus is the pine fire sponge ( Phellinus pini ) from the order of the bristle disks (Hymenochaetales), called “red ring rot” in English. There are other types of fungus, such as Encoeliopsis laricina , that attack the tree, but these cause much less damage to the forest.
From Europe entrained larch leaf miner ( Coleophora laricella ) that eats the young leaves is a problematic pest become. It was first observed in the Northern Rocky Mountains in 1957 and has now spread to practically all larch forests. Native and introduced parasites keep the larch leaf miner somewhat in check; the leaf damage reduces tree growth, but causes only a low mortality rate among the trees. The butterfly species Choristoneura freemani from the family of tortoiseshells (Tortricidae) is also an important pest. It causes a lot of damage, as the main instinct is often severely damaged.
Other insects that damage the West American larch are the Pristiphora erichsonii from the family of sawfly (Tenthredinidae) and Zeiraphera improbana , another species of butterfly from the family of the tortrix (Tortricidae). Both of these types occur sporadically and can then cause great damage. Other, but less dangerous pests include Anoplonyx occidens (English "western larch sawfly"), Anoplonyx laricivorus (English "two-lined larch sawfly") and Semiothisa sexmaculata incolorata , a member of the Spanner family (Geometridae).
Bark beetles are one of the less important pests of the West American larch. Sometimes Dendroctonus pseudotsugae attacks weakened trees. The book printer art Ips plastographus , the sapwood beetle art Scolytus laricis and the butterfly species Nepytia canosaria from the Spanner family also damage the tree.
ecology
The seeds of the West American larch are a sought-after source of food for bird species such as the spruce siskin ( Carduelis pinus ), the birch siskin ( Carduelis flammea ) and the crossbill ( Loxia leucoptera ).
The extremely thick bark offers the mature tree good protection against forest fires. As a fully grown tree, the West American larch is the most fire-resistant species in the Northern Rocky Mountains . The seeds of the West American larch are particularly susceptible to germination after forest fires.
The West American larch sometimes hybridizes with the rocky mountain larch ( Larix lyallii ).
Sources and further information
Individual evidence
- ↑ a b c d e f Ed Wicker; see the literature list.
- ↑ a b c d Schmidt and Shearer; see web links.
- ^ Thomas Nuttall: Larix occidentalis . In: The North American sylva . tape 3 , 1849, p. 143 ( online; plate 120 ).
- ↑ Christopher J. Earle; see web links.
- ↑ R. Stoltmann: Guide to the record trees of British Columbia . Western Canada Wilderness Committee . 1993; 58 pages.
- ↑ See image description on Commons .
- ^ Hypodermella laricis. In: Forest Pests: Insects, Diseases & Other Damage Agents. Bugwood Network, May 18, 2006, accessed November 6, 2011 (English, images).
literature
- Alan Mitchell, translated and edited by Gerd Krüssmann: The forest and park trees of Europe: An identification book for dendrologists and nature lovers . Paul Parey, Hamburg and Berlin 1975, ISBN 3-490-05918-2 .
- Ed F. Wicker: Larix occidentalis . In: Peter Schütt, Horst Weisgerber, Hans J. Schuck, Ulla Lang, Bernd Stimm, Andreas Roloff: Lexicon of Conifers. Distribution - Description - Ecology - Use; the great encyclopedia . Nikol, Hamburg 2004, ISBN 3-933203-80-5 , p. 243-248 .
- William H. Parker: Larix occidentalis . In: Flora of North America Editorial Committee (Ed.): Flora of North America North of Mexico . Volume 2: Pteridophytes and Gymnosperms . Oxford University Press, New York / Oxford a. a. 1993, ISBN 0-19-508242-7 (English).
Web links
- Christopher J. Earle: Larix occidentalis. In: The Gymnosperm Database. May 27, 2011, accessed November 6, 2011 .
- Wyman C. Schmidt, Raymond C. Shearer: Western Larch. USDA Forest Service; Northeastern Area State & Private Forestry, accessed November 6, 2011 .
- Larix occidentalis in the endangered Red List species the IUCN 2006. Posted by: Conifer Specialist Group, 1998. Retrieved on 12 May, 2006.
