Common ash ( Fraxinus excelsior )
The common ash , common ash or high ash ( Fraxinus excelsior ) is a tree species native to Europe which, with a height of up to 40 m, is one of the tallest deciduous trees in Europe; at more exposed locations, however, it often only reaches 15 to 20 m. Due to the high competitive strength of the beech , with which it is often associated, it can be found in larger stands predominantly in forest communities on more humid ( hardwood floodplain , alluvial forest ) or drier locations (shallow limestone soils), where the competitive strength of the beech decreases. Due to its positive properties, ash wood is counted among the noble hardwoods . After beech and oak , it is one of the most important deciduous timber in Central Europe. Ash wood is particularly used when the highest demands are placed on strength and elasticity. It is often used in the manufacture of tool handles, sports equipment, and molded parts.
Since the beginning of the 1990s, the ash has been threatened by an ash mortality that first occurred in Poland and is now widespread in large parts of Europe, caused by the hose fungus Hymenoscyphus fraxineus .
The common ash reaches a height of up to 40 m and a trunk diameter of 2 m. After 100 years it has an average height of 30 m and a chest height diameter of 30 cm to 40 cm. The maximum age is around 250 to 300 years. The trunk axis is usually straight and does not fork. In the fringes of the distribution area, however, the values mentioned above are clearly undercut, or it only occurs in shrub form , for example in Norway. The growth is usually tied, that is, the bud of a year is completely laid out in the bud of the previous year. Only under favorable conditions does growth take place freely and the shoots develop without a rest period in the same year. The appearance of enrichment shoots and locust shoots can be observed in young trees .
In addition to long and short shoots , the ash also forms so-called linear shoots, which are longer than short shoots, but do not form branches like long shoots do. The branches are at right angles to the trunk; the branches point straight up. Branches that do not get enough light die and break off in a row. This usually starts after about three to five years.
Bark and wood
The bark of young trees is greenish to shiny gray with only a few cork pores . Corking starts after about 15 to 40 years; a web bark is formed. The bark itself is thick and rich in sclerenchyme , without bast fibers .
The wood is ring-pored, the early wood usually shows multi-row, coarse vessels that stand out clearly from the late wood. This makes the annual rings clearly visible. The vessels of the latewood are scattered, small and barely recognizable. The rays are narrow. The ash is a heartwood tree whose core hardly differs from the broad, light yellowish sapwood . Only older trees from 70 to 80 years and above show a light brown core, which is seen as a color defect when the wood is used. Ash trees that grow on dry, calcareous soils show narrower rings and, with age, can form a core that resembles the wood of the olive tree ( Olea europaea ). One then speaks of olive ash; Depending on fashion trends, their wood is particularly popular for making furniture.
The main root first grows vertically into the ground, but after a few cm changes to horizontal growth and develops a typical sinker root system with strong side roots running close to the surface. From this and from the trunk arise strong roots that grow vertically downwards. The fine roots are concentrated in certain areas and absent in others. The root system of a 90-year-old ash tree extends a maximum of about 350 cm from the base of the trunk and reaches a depth of 140 cm.
Buds and leaves
The short buds are covered with thick, black and felty hairs that are formed to protect against frost and evaporation. With a length and width of around 1 cm, the terminal buds are significantly larger than the side buds, which only reach up to 5 mm. Flower buds are more blunt and more spherical than other buds. The buds are ready by the end of July. The buds of a knot on the main shoots are often offset from one another.
The leaves are crosswise opposite , only on particularly vigorous shoots are threefold leaf whorls . The leaves are up to 40 cm long with the 5 cm to 10 cm long stem and are usually 9 to 15 pinnate, rarely fewer leaflets occur. The individual leaflets are 4 cm to 10 cm long and 1.2 cm to 3.5 cm wide. They are eilanzettlich , long pointed and at the base wedge-shaped, small and sharply serrated. The top is bare and deep green. The underside is light bluish green, the middle nerve and some of the side nerves can be hairy with loose felts. The lateral leaflets are short stalked or sessile, the terminal leaflet is longer stalked. The leaf spindle has a hairy furrow with cork pores , stipules are missing. The leaves usually fall green from the tree, only in the continental east of the distribution area (see below) the leaves sometimes turn yellow.
Flowers and fruits
The ash tree becomes manable when free-standing at 20 to 30 years of age , in groups with other trees after 30 to 35 years. It is hermaphroditic, although one gender can be reduced depending on the individual ( trioce ). The flowers have a greenish, two carpels incurred syncarp ovary and two stamens . The anthers stand on short stamens and are initially purple. Sepals and petals are missing. The common ash is the only species in the olive family that is pollinated by wind ( anemophilia ). Lateral panicles are formed as inflorescences , which appear before the leaves on the sprouts of the previous year. At first they stand upright and later hang over.
As a fruit -seeded, winged be Nuts formed on thin stems. They are 19 mm to 35 mm long and 4 mm to 6 mm wide, narrowly oblong to oblong obscure-wedge-shaped, shiny brown and slightly twisted in one direction (twisted). The nut is 8 mm to 15 mm long and 2 mm to 3 mm wide, rounded at the base and arched at the top when compressed. The wing edge is tongue-shaped, often sanded, less often pointed and runs down to a maximum of half the nut. The fruits ripen from October to November and fall off throughout the winter. They are helicopter fliers and can reach distances of 60 m, in rare cases up to 125 m.
Germination and growth
The common ash germinates epigeously . The seeds are sprout inhibited and rest for about two winters before they sprout, but they can remain viable in the soil for six years. The inhibition of germination is partly due to the fact that the embryo only reaches half of its later size at the time of fruit ripening and is not fully developed. In addition, the abscisic acid it contains promotes the dormant state of the seed .
The two cotyledons of the seedling are narrow, elongated and network-veined and reach a length of 5 cm and a width of 7 mm. They are similar to those of the maple , but differ from them in their reticulate veins. The primary leaves are undivided, the following leaves are triple pinnate. Under favorable light conditions in open spaces or in heavily thinned old stands, the ash grows rapidly in height; growth is strongest between 2 and 15 years of age. The ash can then develop shoot lengths of up to 1.5 m per year. In dense stands the growth in thickness is set back compared to growth in height; Under favorable conditions, however, the ash can form annual rings up to 9 mm wide.
The chromosome number of the common ash is 2n = 46.
Distribution and location requirements
The common ash can already be detected in the Cretaceous and Tertiary periods in the northern hemisphere of the earth. During the last ice age it was pushed back to south and south-west Europe, but returned to central Europe after the ice age, about 7000 to 6000 years before our era. There it was able to spread and occupy a larger proportion of the Central European forests before it was displaced by the beech . The ash was pushed back further by slash and burn , during antiquity and the Middle Ages, especially by systematic clearing to gain arable land. However, it was still preserved in hedges and smaller forests as a fodder and wood supplier. Due to the heavy use and expansion of goat farming, deforestation reached a peak at the beginning of the 19th century. To avoid flooding and soil erosion, ash trees from higher elevations were resettled along rivers from this time on. With the migration of the rural population and the abandonment of arable land, especially on steep slopes and damp areas, the ash was able to spread again.
The ash is a tree species found throughout Central Europe and beyond. The northern border of the distribution area runs from Scotland to the Trondheimfjord in Norway and includes the south of Norrland in Sweden . In Finland the border runs through Satakunta and Hämeenlinna to Lake Ladoga . Ash is absent in the northeastern parts of Russia ; also in the steppe areas, the eastern limit of distribution is probably determined by the dryness of the hot summers and extends to the Volga , the Crimea and the Caucasus . In southern Europe the distribution area extends over the Balkan Peninsula and Italy , on the Iberian Peninsula to the line Central Galicia - Cantabrian Mountains - Ebro .
In Styria , Carinthia and Lower Austria the ash grows up to heights of 1000 m, in Tyrol up to 1700 m. In central German mountains they can be found up to 800 m and in the Bavarian Alps up to 1400 m. In the Allgäu Alps in Bavaria, at the southern foot of the Höfats, it still occurs at an altitude of 1300 m. In the Caucasus it reaches altitudes of 1800 m.
The ash needs mineral, deep, fresh to moist soils in not too warm, rather humid, light and late frost-free locations in order to reach their maximum height. But it also grows on dry, shallow rendzines from weathered limestone soils. The occurrence in these very different locations led to the consideration of dividing the species into two races , the "Kalkesche" and the "Wasseresche". However, the existence of different races could not be confirmed. “Kalkeschen” thrive well on moist soils and vice versa. The ash transpires a lot of water, so a good water supply is crucial for growth. However, small amounts are sufficient for survival, and it can also insist on the shallow rendzinen. However, the rainfall in May and June is important. It prefers well-aerated soils and avoids soils with a pH below 4.2. In the course of its life the ash changes its light requirements. As a young tree it is very shade-tolerant, needs more light with increasing age and ultimately needs a completely free crown for satisfactory growth.
Socialization with other tree species
In Scandinavia , the ash is found in coastal forests together with the black alder ( Alnus glutinosa ) or in mixed forests with the mountain elm ( Ulmus glabra ) and the common oak ( Quercus robur ). In the Baltic States it thrives in mixed forests with the quivering aspen ( Populus tremula ), the silver birch ( Betula pendula ), and the common hazel ( Corylus avellana ) or in wetlands together with the black alder. In Spain it is found in association with the field maple ( Acer campestre ) and the common hazel.
In Central Europe, Heinz Ellenberg names four types of mixed forests in which the ash occurs:
- the ash-maple-Schatthangwald on submontane to montane, north-west to east-facing steep slopes with strongly humic, alkaline rock and rubble soils
- the corydalis Acer negundo-Talsohlenwald fertile filled Auenlehm soles shaded V-shaped valleys in lime-poor areas, such as the resin
- the maple-ash slope foot forest on colline to submontane, colluvial , deep slope floors that are rich in nutrients and at least moist in spring
- the ash creek channel forest along narrow creek channels notched in clay in submontane and planar beech areas
Other locations can be found in beech-dominated companies, especially in lime-beech forests.
The common ash is part of a complex ecosystem. Just as Fraxinus excelsior is dependent on very specific site conditions, numerous animal and plant species live with it. A study commissioned by the British environmental agency Joint Nature Conservation Committee and published in 2014 estimated that around 1,000 species are associated with ash or ash forests, including 12 birds, 55 mammals , 78 vascular plants , 58 mosses , 68 fungi, 239 invertebrates and 548 lichens . Of these species, 44 were classified as obligatory on living or dead ash trees (4 lichens, 11 fungi and 19 invertebrate species). Another 62 were “closely associated” with the ash (13 lichens, 19 mushrooms, 6 mosses and 24 invertebrates).
The ash is often attacked by so-called ash cancer, which can be traced back to two causes, on the one hand to bacterial attack and on the other to fungal attack. The bacterium Pseudomonas syringae penetrates the cortical tissue through wounds, leaf scars or cork pores and causes the cambium cells to die off, with subsequent increased but impaired wound healing. This leads to the formation of blackish swellings. The fungus Nectria galligena penetrates through broken branches or other openings and causes the bark to die off. This creates crater-like wounds up to 30 cm wide. Annually created elliptical bulges made of callus tissue are characteristic , from the number of which the age of the tree canker can be deduced and which give the canker a typical appearance ("target canker").
The variegated ash bast beetle ( Leperisinus varius ) eats 6 cm to 10 cm long, double-armed transverse tunnels in the bark of the trees, but spares the cambium. The larval ducts are shorter and about 4 cm long, the ripening feed occurs on the still green bark of branches and young trunks. Repeated infestation changes the appearance of the bark, which is then referred to as "ash grind" or "bark roses". The infestation can lead to the death of the tree. The caterpillars of the first generation of prays fraxinella ( Prays fraxinella ) feed on the leaves of the ash, the caterpillars of the second generation drill at the beginning of October in terminal buds, to hibernate and eat them, resulting in Zwiesel leads formation. The rush plant hoppers ( Cicadella viridis ) lays their eggs in the bark, which can lead to the bark dying off. In rare cases, it can cause significant damage to ash crops. In case of infestation by the Eschenblattnestlaus ( Prociphilus fraxini ) and Esch Two Glaus ( Prociphilus bumeliae ) sheet nests caused by petiole compression and petiole curvature. Hoofed game , but also rabbits and various species of mice, damage particularly young trees through browsing and gnawing, which can lead to significant formal defects such as twosomes.
In the early 1990s, ash trees began to die in large numbers in the north-western part of Poland . The symptoms that occur are dead spots on trunks and twigs without the flow of mucus , withering and falling off of the leaves as well as the death of twigs and canopy shoots, which can lead to the death of younger trees in particular. The wood lying under the damaged bark can turn brown. This disease is commonly referred to as ash dieback or ash dieback. It spread from Poland to Sweden , Austria , Germany , Denmark , Finland , Lithuania and the Czech Republic and is now also threatening the population in the United Kingdom . In Denmark, at least 95% of all ash trees had died of ash by the end of 2013, and for Germany researchers expect that around a third of the ash population will perish by 2017.
In the damaged areas of the ash trees, in addition to other types of fungus, a new type of a by- fruit form of a hose fungus was often found, which in 2006 received the species name Chalara fraxinea . The species could not be found in all damaged areas, and the damaged areas were also colonized by other potentially damaging fungal species of the genera Cytospora , Diplodia , Fusarium , Phomopsis and Armillaria . Vaccination experiments ( inoculation ) with Chalara fraxinea have shown that the fungus causes damage that is identical to that found in ash dieback . However, after infection, chalara fraxinea can be completely displaced by competing species. After Chalara fraxinea had been considered to be the secondary fruit form of the white stem cup ( Hymenoscyphus albidus ), which has been known since 1851 , it was discovered in 2010 that the true main fruit form is the previously unknown hose fungus Hymenoscyphus pseudoalbidus , which cannot be differentiated from Hymenoscyphus albidus with the naked eye and the microscope can be distinguished, but only by examining the genetic make-up . The new fungus has appeared in Switzerland since at least 1978 and grows to the core of the trees. Why this fungus became the cause of a new disease is still unclear. A possible cause could be a change through mutation or hybridization with an as yet unknown species. Environmental influences could also have increased the harmfulness of the fungus. However, it is now assumed that Chalara fraxinea originally comes from Asia, where it is native to at least Korea and Japan. The ash species there seem to have developed a kind of resistance due to their long coexistence and are only slightly damaged by the fungus. Researchers are in the process of selecting and breeding European ash trees that are naturally resistant to the fungus.
A large-scale scientific study published in March 2016 with the aim of recording the ash stocks in the British Isles came to the conclusion that it was "highly likely" that the entire European ash stocks in the coming decades will grow out of Chalara fraxinea on the one hand and slowly On the other hand, Asian ash jewel beetles immigrating to Europe will fall victim to Asia . The common ash would largely become extinct in Europe, which would result in changes to entire cultural landscapes and complex ecosystems. A similar scenario as with the " Dutch elm disease " in the 20th century threatens .
Genome sequencing of the common ash
The genome of Fraxinus excelsior is decrypted by two research groups in the United Kingdom since 2013. A group led by Richard Buggs at Queen Mary University of London are sequencing an offshoot of an ash tree from the Cotswolds in Worcestershire . The second group under Allan Downie at the John Innes Center are sequencing "Tree 35", an ash tree from Denmark that has survived the Hymenoscyphus pseudoalbidus infestation for eight years and is therefore largely resistant. The genome of Hymenoscyphus pseudoalbidus was also deciphered in 2013.
Man and ash
Ash lances are mentioned as early as the 7th century BC by Hesiod in his book Works and Days as the armament of the “third human race”. However, the ash tree is of particular importance as the world tree Yggdrasil in Nordic mythology , which has been preserved through the Icelandic Edda , a literary work written in Old Icelandic. According to Edda, the branches of the world ash Yggdrasil extend over the whole sky and extend over the whole world. The tree rests on three roots from which springs arise. The source of Mimir gives wisdom and knowledge, the main Norse god Odin gives one of his eyes as a pledge to drink from the source. The gods hold judgment at the primeval fountain , and this is where the Norns live . Under the third root lies the Hvergelmir spring , from which all rivers spring. The dragon Nidhöggr gnaws at the roots and an eagle sits in the crown of the tree. In Norse mythology, humans also descend from the ash tree. Three gods - including Odin - find two tree trunks Ask and Embla on the beach . Ask can be identified as ash; It is unclear which tree Embla is. It could be the elm or alder . The gods form the first man from Ask, the first woman from Embla.
The ash in medicine
Various parts of the ash were used for medicinal purposes as early as ancient times. It is mentioned in the Corpus Hippocraticum , and also in the De Materia Medica of the Greek doctor Dioscurides . In the twelfth century, the abbess Hildegard von Bingen describes the use of ash leaves to make a diuretic tea. Konrad von Megenberg recommended the ashes of the bark for treating broken bones. In the 16th century, the German doctor Hieronymus Bock used the distillate of ash bark for jaundice and stone ailments and tea made from ash fruits as a diuretic . Pietro Andrea Mattioli , the court doctor of Emperor Maximilian II , describes ash bark as a remedy in his New Kreuterbuch . Hufeland recommends tea infusions made from bark and leaves for muscular rheumatism and gout . At the beginning of the 18th century, consideration was given to using the ash bark as an inexpensive substitute for the expensive cinchona bark as an antipyretic agent for malaria . The oil obtained from the wood of the ash has also been used as a medicine since ancient times.
Several places have the ash in their name, including: Eschbach , Eschede , Eschwege and Eschweiler as well as Essen an der Ruhr , around 800 AD Asnithi (= Eschen-Ort ). Eschwege and Eschede also have an ash branch in their coat of arms .
The Common Ash is a kind in the family of Oleaceae . In the genus of the ash ( Fraxinus ) it belongs with the narrow-leaved ash , the Manchurian ash and the black ash to the subsection Bumelioides in the section Fraxinus .
One can distinguish three subspecies:
- Fraxinus excelsior subsp. coriariifolia (Scheele) AEMurray (Syn .: Fraxinus coriariifolia Scheele ): It occurs from Bulgaria to the Crimea and from northeast Turkey to Iran.
- Fraxinus excelsior subsp. excelsior : It occurs from Europe to Iran.
- Fraxinus excelsior subsp. siciliensis Ilardi & Raimondo : This subspecies, first described in 2007, only occurs in Sicily.
A division into two races, the "water ash" and the "lime ash", could not be confirmed either by differences in growth performance or by phenological or morphological characteristics. A pronounced genetic differentiation is also unlikely, since the contiguous distribution area of the ash was only separated from beech ( Fagus ) and hornbeam ( Carpinus ) due to competition between 3,000 and 4,000 years ago . However, current research gives indications of a particularly flood-tolerant, hereditary fixed ecotype of the ash in the alluvial forests on the Upper Rhine.
There are several types of gardens, including:
- 'Allgold' a 10 to 12 m high tree with intensely golden yellow colored shoots. The leaves are green in summer and yellow in autumn.
- 'Altea' with a straight trunk and stiff, upright habit.
- 'Aurea' is an 8 m high tree with branches that are yellow in winter. The leaves are initially yellow-green and turn intense yellow in autumn.
- 'Diversifolia' or single-leaf ash, a 20 m to 25 m high tree with 14 cm to 18 cm long leaves that consist only of the terminal leaflet and often another, smaller pair of leaflets. The leaf margin is irregular or double serrated.
- 'Eureka' with a straight trunk and stiffly upright habit.
- 'Globosa' is a dwarf form with a high trunk and a densely branched, flattened, spherical crown that is up to 4 m wide.
- 'Jaspidea' a tree up to 15 m high. Young shoots and twigs have a yellow-green striped bark. The leaves are large, yellow at first, yellow-green in summer and yellow in autumn.
- 'Nana' or spherical ash, a dwarf form with a high trunk and a spherical, compact crown that can be 2.5 m to 4.5 m wide.
- 'Pendula' or hanging ash , a 12 to 15 m high tree with branches and twigs that grow downward in an arch and often reach the ground.
- 'Westhofs Glorie' with a continuous trunk and stiff, upright growth.
|Bulk density (12-15% HF )||690||kg / m³|
|modulus of elasticity||13,000-14,000||N / mm²|
|Compressive strength||44-52||N / mm²|
|tensile strenght||130-165||N / mm²|
|Flexural strength||102-120||N / mm²|
|Fracture impact work||68||kJ / m²|
|Brinell hardness||lengthways 65, crossways 37–41||N / mm²|
With an average bulk density of 690 kg / m³, ash wood is heavy and hard wood with favorable strength properties. Its tensile strength and flexural strength exceed that of oak. It is elastic, abrasion-resistant and, thanks to its high impact strength, tougher than most other domestic wood species. The wider the annual rings, the more favorable the mechanical properties. Annual rings with a width of more than 1.5 mm, as they often appear in "water ash", are a sign of good wood quality. A pronounced color core does not affect the quality of the wood.
Ash wood can be worked well by hand as well as by machine, and when steamed it can be bent just as easily as beech. The surfaces are easy to treat, which is especially true for pickling . The wood is resistant to weak alkalis and acids . However, it is only slightly weatherproof and the wood is quickly damaged even if it comes into contact with the ground. Because it is difficult to impregnate , the wood is rarely used outdoors.
Ash wood is often used both as solid wood and in the form of veneers , for example for kitchen, living room and bedroom furniture or in a curved shape for seating furniture. It is also used for wall and ceiling cladding and for the production of parquet and plank floors . For all these applications, light wood without a colored core is preferred.
Ash wood is used especially when high demands are placed on strength, toughness and elasticity, for example for the production of handles for hammers, hatchets, shovels, hoes and axes, scythes, rakes and other garden tools. Also, sports and gymnastics equipment such as wall bars , bats or slides are made of ash wood.
In the wheelwright was the ash is of paramount importance and was considered the most suitable for the production of hubs , rims , spokes , shafts and wagon . It was also of great importance in vehicle and wagon construction. The Deutsche Reichsbahn even stipulated the use of ash for many applications. It was also used in mechanical engineering, for example for the manufacture of threshing machines or looms .
The rotation period is usually 100–140 years.
Ash leaves used to be an important animal feed for winter. The foliage was cut in summer (among other things in the form of snowflakes ), dried and stored for later use. The ash is also a common street and city tree - especially in Northern and Eastern Europe and in higher elevations in the low mountain range.
Ash trees are also often used to fortify slopes and embankments of flowing waters. The foliage of the ash decomposes quickly, has a humus-forming and soil-improving effect.
Mighty and famous ash trees
The mightiest ash is in the Białowieża National Park in the Białowieża Primeval Forest in north-eastern Poland. In 2016, at a height of 40.50 m, it reached a circumference of 5.40 m (measuring height 1.30 m). The tree was planted in 1800 ± 10 years. In the same area there is a 45.20 m high specimen, which, however, only has a trunk circumference of 4.30 m (measuring height 1.30 m, measurement 2014).
The other common German names for the common ash also exist or existed : Aerschen, Aeschach ( Middle High German ), Aeschbaum, Aesche, Aeschern, Asca, Asch ( Old High German ), Ascha (Old High German), Aschbaum, Asche (Old High German), Ask (Old High German) , Eesch (Middle High German), Edelesche, Ehsse (Middle High German), Eisch (Middle High German), Esche ( Austria , Lower Weser ), Eschein (Middle High German), Eschelterpaum (Middle High German), Eschenbaum, Eschenbom, Eschern ( Ulm ), Eschernbaum, Eske ( East Frisia ) , Eskenbaum (Unterweser), Espe ( Traun ), Esschenbaum (Middle High German), Essenbaum (Middle High German), Estken ( Middle Low German ), Fladerbaum (Middle High German), Flädrein (Middle High German), Fly Tree (Eichstädt), Früssen (Middle High German), Geissbaum, Gersche, Gerschen, hanging ash (hanging variant), Hohesche, Jeschbum ( Transylvania ), Langespe, Liesche ( Eifel ), Lischen (Eifel), Oesch ( Switzerland ), Oeschling ( Pinzgau , Pongau ), Schwin dholz (Austria, Zillertal ), Schwundholz (Austria near Linz ), Slintpaum (Old High German), sparrow-tongue tree, stone ash ( Alsace ), Tageesch ( Mecklenburg ), weeping ash (hanging variant), bird's tongue tree (Austria), forest ash, wound tree (Ulm, Alsace) and woundwood tree.
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