American quivering aspen
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American quivering poplar ( Populus tremuloides ) |
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The American quivering aspen ( Populus tremuloides ) or American aspen is a species of poplar ( Populus ) within the willow family (Salicaceae). It occurs in North America (English called Quaking aspen and Queen leef ). Its main distribution center is in southern Alaska and western Canada, but it also occurs in Mexico. It grows in many soils , especially on sandy or gravelly slopes and is a fast-settling pioneer plant on disturbed soils. As a single-stemmed tree or multi-stemmed growth of the same individual ( genetes (clones) through vegetative propagation) it is a tree species with a particularly large distribution area. Populus tremuloides is fast growing, but short-lived and in pure stands it is successively displaced by other species. The light and soft wood does not shrink much and some types are used as lumber , for pulp production or chipboard production. But Populus tremuloides is also an important species in their native ecosystems .
Habit and age
Populus tremuloides is a small to medium-sized, fast-growing tree . The young trees have the greatest increase in height during their first 20 years. Under the best conditions, they can reach a trunk diameter of 137 cm and a stature height of 26 meters, for example the largest specimen in Oregon. Record heights of up to 27 meters can be found in Alaska and the Rocky Mountains. Most old trees do not grow taller than 20 to 25 meters and reach an average diameter of 30 cm. A few trees reach an age of 200 years (a specimen in Alaska is 226 years old). While the individual shoots of a clone are short-lived due to vegetative reproduction, the original individual may already be several thousand years old and thus older than the oldest giant sequoia trees ( Sequoiadendron giganteum ). One particularly old and large clone colony in Utah is known as Pando .
Populus tremuloides has a loose, round crown and a slender, trunk that is lighter than that of the quaking aspen P. tremula . Its leaves are a good distinguishing feature: They are ovoid, pointed and finely serrated.
root
The young plants initially have a short taproot, which quickly develops into a heart-root system on deep soils with good water flow . If the root penetration depth is limited, the roots seek their place in a shallow and spacious manner.
Flat and extensive side branches have cord-like twig roots which, close to the surface, meander over large distances without sinker roots and thereby produce the mass of the root spawn .
Life cycle
Reproduction and youth
Flower and fruit heads
Populus tremuloides is usually dioecious, separate sexes ( dioecious ), so there are male and female specimens. Although the flowers are typically unisexual, 10 to 20 percent of the predominantly female trees and 4 to 5 percent of the predominantly male trees are androdioecan . The shoots (clones) of a single tree are either male or female. Usually both sexes are equally represented, with local deviations in the ratio being observed.
The pendulous catkins are 4 to 6 cm long and appear in temperate coastal regions in April to May and in the central Rockies in May to June before the leaves shoot; an air temperature of at least 12 ° C, which lasts for six days, triggers flowering. Local clones form variations that differ in their flowering dates. Populus tremuloides is a wind pollinator .
The fertilized catkins are ripe four to five weeks after anthesis and then about 10 cm long. Each kitten then consists of several dozen unicellular, light green capsule fruits that are almost 6 mm long. Each of these capsule fruits contains ten small brown seeds surrounded by tufts of long, silky hair.
Seeds and sowing
In a cycle of four to five years, seeds are produced very abundantly, while the fruits are less vigorous in the years in between. Some clones produce seeds annually from the age of two to three years. Large, multi-seeded fruits do not appear until they are 10 to 20 years old, and the optimum is reached between 50 and 70 years of age. At the age of 23, a Populus tremuloides produced 1.6 million seeds. When cleaned, one gram contains 5500 to 8000 individual seeds.
The seeds of a tree ripen in a period of three to five weeks and are distributed a few days after they have reached maturity. With their long, silky tufts of hair, they can be transported several kilometers by wind and water. Fresh seed viability is high (over 95%) but short-lived. Under ideal natural conditions, the seeds remain fertile for two to four weeks and they can be preserved for over a year. The seedlings thrive best at a germination temperature between 5 ° C and 29 ° C. Germination occurs without a dormancy a few days after spreading when a sufficient seedbed has been achieved. Humidity is a critical factor: the seeds germinate when completely submerged in water or in complete darkness, but not when there is too little water in the substrate.
Development of the seedlings
The seeds germinate epigeously (above ground). During the first critical days, when the primary root of a seedling initially grows very slowly, the fine hairs of the seeds take on the functions of anchoring and absorption . Bare mineral soils offer the best conditions and raw humus the worst.
Although the seeds are scattered in great abundance and germinate easily, the survival rate is low. The reasons for this are the short life of the seeds. The right water supply, too high soil temperatures and at the same time large temperature fluctuations in the course of the day shortly after germination, fungal attack, and unsuitable chemistry of the substrate limit the success.
In the first year, the seedlings reach a height of 15 to 30 cm above the ground. At the same time, the plant forms a taproot that extends up to 25 cm deep and has side roots up to 40 cm long. In the next two years, young poplars of this species develop a root system, the individual side roots of which can be 2 m long or longer. In the process, root symbioses ( ectomycorrhizae ) are formed, provided that suitable trunks are present in the soil ( inoculation ).
During the first few years, seedlings grow faster in nature than planted seedlings; with root shoots growing the fastest, of course.
Distribution area and habitat
climate
The climatic conditions in their area of distribution vary greatly. Populus tremuloides avoids very dry climates and only thrives in areas with a positive rainfall balance . Where there is sufficient water, the temperature is the limiting factor in their range. High summer temperatures or summer drought result in lower growth heights and lower lifespans.
The American quivering aspen can still be found in warm parts of the permafrost zone of Canada and Alaska ; its distribution area extends to the eastern provinces of Canada, which with their mild and humid climate also have very high amounts of snow. In the central Rocky Mountains ( Wyoming , Colorado ) it can be found at altitudes of 2000 to 3500 meters. In Baja California it is no less than 2,440 meters and in New Mexico and Arizona no less than 2000 meters. Its eastern limit of distribution in the USA corresponds roughly to the 24 ° C isotherm (average temperature in July).
Soils and topography
Populus tremuloides grows mainly on alfisol , podsol and inceptisol ; but overall it also occurs on very shallow and rocky soils such as deep loamy sands or heavy clay soils. When reforested, it also grows in landfills. For young or shallow soils, basic soils of basaltic origin are preferred to granite. Good poplar soils are usually not too moist, calcareous loamy soils with a high humus content and a good supply of nutrients. Because of its rapid growth and nutritional requirements, it is an important factor in the nutrient cycle.
The soil water flow is a critical point in the demands of the poplar. Distances from the groundwater surface of less than 0.6 meters are just as problematic as those over 2.6 meters. Heavy and wet clay soils are not well suited because of their lack of oxygen.
Forest societies
Populus tremuloides grows in a wide variety of forest communities across America. It is very common in "eastern" and "western poplar forests", in "spruce-poplar forests" of the American forest communities. It has a smaller share in a further 35 forest communities and is rarely found in three of these 255 formations recorded as forest cover types . The American quaking aspen resembles the quaking aspen P. tremula in its behavior .
Associated shrubs are Corylus cornuta , Corylus americana , Acer spicatum , Alnus rugosa , Alnus crispa , Diervilla lonicera , Rubus , Ribes and Salix . In areas of the prairie it is also associated with Symphoricarpos , Viburnum edule , Lonicera dioica , Cornus stolonifera , Amelanchier alnifolia , Prunus virginiana , Salix bebbiana and Rosa ; in Alaska it is also associated with Salix scouleriana , Shepherdia canadensis and Vaccinium vitis-idaea . In the Rocky Mountains these are Symphoricarpos oreophilus , Amelanchier alnifolia , Juniperus communis , Sambucus pubens and others.
Herbaceous plants that share the habitat with P. tremuloides are Aster macrophyllus , Aralia nudicaulis , Maianthemum canadense , Cornus canadensis , Clintonia borealis , Solidago , Carex and others. In the western area of distribution the herbaceous companions are too numerous to list them.
use
In the foreseeable future, most locations of the species Populus tremuloides should be extensively farmed. The wood from Populus tremuloides is used as a pulp supplier, for the production of wood fiber or chipboard and sawn timber . Populus tremuloides is harvested either as wood chips or as round wood . The best trees can be promoted by thinning the stock in order to produce higher quality round wood.
An alcoholic extract from the aspen leaves was also used in the past in the preparation of prostagutt drops for medicinal use against prostate enlargement.
literature
- DA Perala: Quaking Aspen. In: RM Burns, BH Honkala (Ed.): Silvics of North America. Agriculture Handbook 654, USDA Forest Service, Washington, DC ( online ).
Web links
Individual evidence
- ↑ a b Horst Bartels, 1993: Wood Science - Introduction to Dendrology. Ulmer, Stuttgart. ISBN 3-8001-2648-6
- ^ Society of American Foresters Forest Cover Types (SAF 1980) ( Memento of the original from January 15, 2009 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF; 437 kB)
- ^ Lykke Aresin , Helga Hörz , Hannes Hüttner , Hans Szewczyk : Lexikon der Humansexuologie. Volk und Gesundheit Verlag, Berlin 1990, p. 164 ( Quaking aspen ).
