Эвкалипт: Род растений семейства Миртовые

Genus of flowering plants in the myrtle familythe plant genus
Automatic taxobox
| oldest fossil = Eocene
| image = Eucalyptus tereticornis flowers, capsules, buds and foliage. jpeg
| image caption = Buds, capsules, flowers and foliage of E. tereticornis
| display parents = 2
| taxon = Eucalyptus
| authority = L'Hér. | type species = Eucalyptus obliqua
| type species authority = L'Hér. 1789
| subdivision ranks = Species
| subdivision = *List of Eucalyptus species
| synonyms = * Aromadendrum W. Anderson ex R. Br., 1810
Eudesmia R. Br., 1814
Symphyomyrtus Schauer in J. G. C. Lehmann, 1844
| synonyms ref = is a genus of more than 700 species of flowering plants in the family Myrtaceae. Most species of Eucalyptus are trees, often mallees, and a few are shrubs. Along with several other genera in the tribe Eucalypteae, including Corymbia and Angophora, they are commonly known as eucalypts or "gum trees". Plants in the genus Eucalyptus have bark that is either smooth, fibrous, hard, or stringy, the leaves have oil glands, and the sepals and petals are fused to form a "cap" or operculum over the stamens. The fruit is a woody capsule commonly referred to as a "gumnut". Most species of Eucalyptus are native to Australia, and every state and territory has representative species. About three quarters of Australian forests are eucalypt forests. Many eucalypt species have adapted to wildfire, are able to resprout after fire, or have seeds that survive fire. A few species are native to islands north of Australia, and a smaller number are only found outside the continent. Eucalypts have been grown in plantations in many other countries because they are fast growing, have valuable timber, or can be used for pulpwood, honey production, or essential oils. In some countries, however, they have been removed because of the danger of forest fires due to their high flammability.

Nearly all Eucalyptus are evergreen, but some tropical species lose their leaves at the end of the dry season. As in other members of the myrtle family, Eucalyptus leaves are covered with oil glands. The copious oils produced are an important feature of the genus. Although mature Eucalyptus trees may be towering and fully leafed, their shade is characteristically patchy because the leaves usually hang downwards. The leaves on a mature Eucalyptus plant are commonly lanceolate, petiolate, apparently alternate and waxy or glossy green. In contrast, the leaves of seedlings are often opposite, sessile and glaucous. But many exceptions to this pattern exist. Many species such as E. melanophloia and E. setosa retain the juvenile leaf form even when the plant is reproductively mature. Some species, such as E. macrocarpa, E. rhodantha, and E. crucis, are sought after ornamentals due to this lifelong juvenile leaf form. A few species, such as E. petraea, E. dundasii, and E. lansdowneana, have shiny green leaves throughout their life cycle. Eucalyptus caesia exhibits the opposite pattern of leaf development to most Eucalyptus, with shiny green leaves in the seedling stage and dull, glaucous leaves in mature crowns. The contrast between juvenile and adult leaf phases is valuable in field identification. Four leaf phases are recognised in the development of a Eucalyptus plant: the ‘seedling’, ‘juvenile’, ‘intermediate’, and ‘adult’ phases. However, no definite transitional point occurs between the phases. The intermediate phase, when the largest leaves are often formed, links the juvenile and adult phases. In all except a few species, the leaves form in pairs on opposite sides of a square stem, consecutive pairs being at right angles to each other (decussate). In some narrow leaved species, for example E. oleosa, the seedling leaves after the second leaf pair are often clustered in a detectable spiral arrangement about a five sided stem. After the spiral phase, which may last from several to many nodes, the arrangement reverts to decussate by the absorption of some of the leaf bearing faces of the stem. In those species with opposite adult foliage the leaf pairs, which have been formed opposite at the stem apex, become separated at their bases by unequal elongation of the stem to produce the apparently alternate adult leaves.

The most readily recognisable characteristics of Eucalyptus species are the distinctive flowers and fruit (capsules or "gumnuts"). Flowers have numerous fluffy stamens which may be white, cream, yellow, pink, or red; in bud, the stamens are enclosed in a cap known as an operculum which is composed of the fused sepals or petals, or both. Thus, flowers have no petals, but instead decorate themselves with the many showy stamens. As the stamens expand, the operculum is forced off, splitting away from the cup like base of the flower; this is one of the features that unites the genus. The woody fruits or capsules are roughly cone shaped and have valves at the end which open to release the seeds, which are waxy, rod shaped, about 1 mm in length, and yellow brown in colour. Most species do not flower until adult foliage starts to appear; E. cinerea and E. perriniana are notable exceptions.

The genus Eucalyptus was first formally described in 1789 by Charles Louis L'Héritier de Brutelle who published the description in his book Sertum Anglicum, seu, Plantae rariores quae in hortis juxta Londinum along with a description of the type species, Eucalyptus obliqua. The name Eucalyptus is derived from the Ancient Greek words eu meaning 'good' and kalypto meaning '(I) cover, conceal, hide' referring to the operculum covering the flower buds. He coined the generic name from the Greek roots eu and calyptos, meaning "well" and "covered" in reference to the operculum of the flower bud which protects the developing flower parts as the flower develops and is shed by the pressure of the emerging stamens at flowering. It was most likely an accident that L'Héritier chose a feature common to all eucalypts. The name obliqua was derived from the Latin obliquus, meaning "oblique", which is the botanical term describing a leaf base where the two sides of the leaf blade are of unequal length and do not meet the petiole at the same place. E. obliqua was published in 1788–89, which coincided with the European colonisation of Australia. Between then and the turn of the 19th century, several more species of Eucalyptus were named and published. Most of these were by the English botanist James Edward Smith and most were, as might be expected, trees of the Sydney region. These include the economically valuable E. pilularis, E. saligna and E. tereticornis. The first endemic Western Australian Eucalyptus to be collected and subsequently named was the Yate (E. cornuta) by the French botanist Jacques Labillardière, who collected in what is now the Esperance area in 1792. and the ratio of the amount of leucoanthocyanins varies considerably in certain species.

Eucalyptus is one of three similar genera that are commonly referred to as "eucalypts", the others being Corymbia and Angophora. Many species, though by no means all, are known as gum trees because they exude copious kino from any break in the bark (e. g., scribbly gum). The generic name is derived from the Greek words ευ (eu) "well" and καλύπτω (kalýpto) "to cover", referring to the operculum on the calyx that initially conceals the flower.

There are more than 700 species of Eucalyptus and most are native to Australia; a very small number are found in adjacent areas of New Guinea and Indonesia. One species, Eucalyptus deglupta, ranges as far north as the Philippines. Of the 15 species found outside Australia, just nine are exclusively non Australian. Species of Eucalyptus are cultivated widely in the tropical and temperate world, including the Americas, Europe, Africa, the Mediterranean Basin, the Middle East, China, and the Indian subcontinent. However, the range over which many eucalypts can be planted in the temperate zone is constrained by their limited cold tolerance. The Blue Mountains of southeastern Australia have been a centre of eucalypt diversification; their name is in reference to the blue haze prevalent in the area, believed derived from the volatile terpenoids emitted by these trees.

The oldest definitive Eucalyptus fossils are from Patagonia in South America, where eucalypts are no longer native, though they have been introduced from Australia. The fossils are from the early Eocene (51.9 Mya), and were found in the Laguna del Hunco Formation in Chubut Province in Argentina. This shows that the genus had a Gondwanan distribution. Fossil leaves also occur in the Miocene of New Zealand, where the genus is not native today, but again have been introduced from Australia. Despite the prominence of Eucalyptus in modern Australia, estimated to contribute some 75% of the modern vegetation, the fossil record is very scarce throughout much of the Cenozoic, and suggests that this rise to dominance is a geologically more recent phenomenon. The oldest reliably dated macrofossil of Eucalyptus is a 21 million year old tree stump encased in basalt in the upper Lachlan Valley in New South Wales. Other fossils have been found, but many are either unreliably dated or else unreliably identified. It is useful to consider where Eucalyptus fossils have not been found. Extensive research has gone into the fossil floras of the Paleocene to Oligocene of South Eastern Australia, and has failed to uncover a single Eucalyptus specimen. Although the evidence is sparse, the best hypothesis is that in the mid Tertiary, the continental margins of Australia only supported more mesic noneucalypt vegetation, and that eucalypts probably contributed to the drier vegetation of the arid continental interior. With the progressive drying out of the continent since the Miocene, eucalypts were displaced to the continental margins, and much of the mesic and rainforest vegetation that was once there was eliminated. Coast Douglas fir is about the same height; only coast redwood is taller, and they are conifers (gymnosperms). Six other eucalypt species exceed 80 metres in height: Eucalyptus obliqua, Eucalyptus delegatensis, Eucalyptus diversicolor, Eucalyptus nitens, Eucalyptus globulus and Eucalyptus viminalis.

Most eucalypts are not tolerant of severe cold. Eucalypts do well in a range of climates but are usually damaged by anything beyond a light frost of ; Two subspecies, E. pauciflora subsp. niphophila and E. pauciflora subsp. debeuzevillei in particular are even hardier and can tolerate even quite severe winters. Several other species, especially from the high plateau and mountains of central Tasmania such as Eucalyptus coccifera, Eucalyptus subcrenulata and Eucalyptus gunnii, have also produced extreme cold hardy forms and it is seed procured from these genetically hardy strains that are planted for ornament in colder parts of the world.

An essential oil extracted from Eucalyptus leaves contains compounds that are powerful natural disinfectants and can be toxic in large quantities. Several marsupial herbivores, notably koalas and some possums, are relatively tolerant of it. The close correlation of these oils with other more potent toxins called formylated phloroglucinol compounds (euglobals, macrocarpals and sideroxylonals) allows koalas and other marsupial species to make food choices based on the smell of the leaves. For koalas, these compounds are the most important factor in leaf choice. Eucalyptus flowers produce a great abundance of nectar, providing food for many pollinators including insects, birds, bats and possums. Many lizard species in Australia feed on Eucalyptus sap as well, famously in the case of the Dubious dtella. Although Eucalyptus trees are seemingly well defended from herbivores by the oils and phenolic compounds, they have insect pests. These include the eucalyptus longhorn borer Phoracantha semipunctata and the aphid like psyllids that create "bell lerps", both of which have become established as pests throughout the world wherever eucalypts are cultivated. The eusocial beetle Austroplatypus incompertus makes and defends its galleries exclusively inside eucalypts, including some species of Eucalyptus and Corymbia. The trunks and branches of the Eucalyptus tree allow the largest known moth, Zelotypia stacyi (the bentwing ghost moth, having a wingspan up to 250 mm) to feed and protect their larvae and pupae, respectively.

Fungal species Mycosphaerella and Teratosphaeria have been associated with leaf disease on various Eucalyptus species. Several fungal species from Teratosphaeriaceae family are causal agents in leaf diseases and stem cankers of Eucalyptus in Uruguay, and Australia.

Eucalypts originated between 35 and 50 million years ago, not long after Australia New Guinea separated from Gondwana, their rise coinciding with an increase in fossil charcoal deposits (suggesting that fire was a factor even then), but they remained a minor component of the Tertiary rainforest until about 20 million years ago, when the gradual drying of the continent and depletion of soil nutrients led to the development of a more open forest type, predominantly Casuarina and Acacia species. The two valuable timber trees, alpine ash E. delegatensis and Australian mountain ash E. regnans, are killed by fire and only regenerate from seed. The same 2003 bushfire that had little impact on forests around Canberra resulted in thousands of hectares of dead ash forests. However, a small amount of ash survived and put out new ash trees as well.

Eucalyptus oil is highly flammable and at high enough temperatures the oil expands quickening the spread of wildfires. Bushfires can travel easily through the oil rich air of the tree crowns. Eucalypts obtain long term fire survivability from their ability to regenerate from epicormic buds situated deep within their thick bark, or from lignotubers,

In seasonally dry climates oaks are often fire resistant, particularly in open grasslands, as a grass fire is insufficient to ignite the scattered trees. In contrast, a Eucalyptus forest tends to promote fire because of the volatile and highly combustible oils produced by the leaves, as well as the production of large amounts of litter high in phenolics, preventing its breakdown by fungi and thus accumulating as large amounts of dry, combustible fuel. Consequently, dense eucalypt plantings may be subject to catastrophic firestorms. In fact, almost thirty years before the Oakland firestorm of 1991, a study of Eucalyptus in the area warned that the litter beneath the trees builds up very rapidly and should be regularly monitored and removed. It has been estimated that 70% of the energy released through the combustion of vegetation in the Oakland fire was due to Eucalyptus. In a National Park Service study, it was found that the fuel load (in tons per acre) of non native Eucalyptus woods is almost three times as great as native oak woodland.

Some species of Eucalyptus drop branches unexpectedly. In Australia, Parks Victoria warns campers not to camp under river red gums. Some councils in Australia such as Gosnells, Western Australia, have removed eucalypts after reports of damage from dropped branches, even in the face of lengthy, well publicised protests to protect particular trees. A former Australian National Botanic Gardens director and consulting arborist, Robert Boden, has been quoted referring to "summer branch drop". Dropping of branches is recognised in Australia literature through the fictional death of Judy in Seven Little Australians. Although all large trees can drop branches, the density of Eucalyptus wood is high due to its high resin content, increasing the hazard.

Eucalypts were introduced from Australia to the rest of the world following the Cook expedition in 1770. Collected by Sir Joseph Banks, botanist on the expedition, they were subsequently introduced to many parts of the world, notably California, southern Europe, Africa, the Middle East, South Asia and South America. About 250 species are under cultivation in California. In Portugal and also Spain, eucalypts have been grown in plantations for the production of pulpwood. Eucalyptus are the basis for several industries, such as sawmilling, pulp, charcoal and others. Several species have become invasive and are causing major problems for local ecosystems, mainly due to the absence of wildlife corridors and rotations management. Eucalypts have many uses which have made them economically important trees, and they have become a cash crop in poor areas such as Timbuktu, Mali and the Peruvian Andes, despite concerns that the trees are invasive in some environments like those of South Africa. elsewhere in Europe, in the Caucasus (Western Georgia), and California. Drainage removes swamps which provide a habitat for mosquito larvae, but can also destroy ecologically productive areas. This drainage is not limited to the soil surface, because the Eucalyptus roots are up to in length and can, depending on the location, even reach the phreatic zone.

Eucalyptus is the most common short fibre source for pulpwood to make pulp. The types most often used in papermaking are Eucalyptus globulus (in temperate areas) and the Eucalyptus urophylla x Eucalyptus grandis hybrid (in the tropics). The fibre length of Eucalyptus is relatively short and uniform with low coarseness compared with other hardwoods commonly used as pulpwood. The fibres are slender, yet relatively thick walled. This gives uniform paper formation and high opacity that are important for all types of fine papers. The low coarseness is important for high quality coated papers. and serves as an active ingredient in some commercial mosquito repellents. Aromatherapists have adopted Eucalyptus oils for a wide range of purposes. Eucalyptus globulus is the principal source of Eucalyptus oil worldwide.

Eucalypt wood is also commonly used to make didgeridoos, a traditional Australian Aboriginal wind instrument. The trunk of the tree is hollowed out by termites, and then cut down if the bore is of the correct size and shape. Eucalypt wood is also being used as a tonewood and a fingerboard material for acoustic guitars, notably by the California based Taylor company.

All parts of Eucalyptus may be used to make dyes that are substantive on protein fibres (such as silk and wool), simply by processing the plant part with water. Colours to be achieved range from yellow and orange through green, tan, chocolate and deep rust red. The material remaining after processing can be safely used as mulch or fertiliser.

Eucalyptus trees in the Australian outback draw up gold from tens of metres underground through their root system and deposit it as particles in their leaves and branches. A Maia detector for x ray elemental imaging at the Australian Synchrotron clearly showed deposits of gold and other metals in the structure of Eucalyptus leaves from the Kalgoorlie region of Western Australia that would have been untraceable using other methods. The microscopic leaf bound "nuggets", about 8 micrometres wide on average, are not worth collecting themselves, but may provide an environmentally benign way of locating subsurface mineral deposits.

In the 20th century, scientists around the world experimented with Eucalyptus species. They hoped to grow them in the tropics, but most experimental results failed until breakthroughs in the 1960s 1980s in species selection, silviculture, and breeding programs "unlocked" the potential of eucalypts in the tropics. Prior to then, as Brett Bennett noted in a 2010 article, eucalypts were something of the "El Dorado" of forestry. Today, Eucalyptus is the most widely planted type of tree in plantations around the world, in South America (mainly in Brazil, Argentina, Paraguay and Uruguay), South Africa, Australia, India, Galicia, Portugal and many more.

In Italy, the Eucalyptus only arrived at the turn of the 19th century and large scale plantations were started at the beginning of the 20th century with the aim of drying up swampy ground to defeat malaria. During the 1930s, Benito Mussolini had thousands of Eucalyptus planted in the marshes around Rome. This, their rapid growth in the Italian climate and excellent function as windbreaks, has made them a common sight in the south of the country, including the islands of Sardinia and Sicily. They are also valued for the characteristic smelling and tasting honey that is produced from them. The variety of Eucalyptus most commonly found in Italy is E. camaldulensis.

In Greece, eucalypts are widely found, especially in southern Greece and Crete. They are cultivated and used for various purposes, including as an ingredient in pharmaceutical products (e. g., creams, elixirs and sprays) and for leather production. They were imported in 1862 by botanist Theodoros Georgios Orphanides. The principal species is E. globulus.

Eucalyptus has been grown in Ireland since trials in the 1930s and now grows wild in South Western Ireland in the mild climate.

Eucalyptus seeds of the species E. globulus were imported into Palestine in the 1860s, but did not acclimatise well. Later, E. camaldulensis was introduced more successfully and it is still a very common tree in Israel. Many Zionist colonies also adopted the practice in the following years under the guidance of the Mikveh Israel Agricultural School. Eucalyptus trees are now considered an invasive species in the region. In India, the Institute of Forest Genetics and Tree Breeding, Coimbatore started a Eucalyptus breeding program in the 1990s. The organisation released four varieties of conventionally bred, high yielding and genetically improved clones for commercial and research interests in 2010. Eucalyptus trees were introduced to Sri Lanka in the late 19th century by tea and coffee planters, for wind protection, shade and fuel. Forestry replanting of Eucalyptus began in the 1930s in deforested mountain areas, and currently there are about 10 species present in the island. They account for 20% of major reforestation plantings. They provide railway sleepers, utility poles, sawn timber and fuelwood, but are controversial because of their adverse effect on biodiversity, hydrology and soil fertility. They are associated with another invasive species, the eucalyptus gall wasp, Leptocybe invasa.

In Hawaii, some 90 species of Eucalyptus have been introduced to the islands, where they have displaced some native species due to their higher maximum height, fast growth and lower water needs. Particularly noticeable is the rainbow eucalyptus (Eucalyptus deglupta), native to Indonesia and the Philippines, whose bark falls off to reveal a trunk that can be green, red, orange, yellow, pink and purple.

Due to similar favourable climatic conditions, Eucalyptus plantations have often replaced oak woodlands, for example in California, Spain and Portugal. The resulting monocultures have raised concerns about loss of biological diversity, through loss of acorns that mammals and birds feed on, absence of hollows that in oak trees provide shelter and nesting sites for birds and small mammals and for bee colonies, as well as lack of downed trees in managed plantations. A study of the relationship between birds and Eucalyptus in the San Francisco Bay Area found that bird diversity was similar in native forest versus Eucalyptus forest, but the species were different. One way in which the avifauna (local assortment of bird species) changes is that cavity nesting birds including woodpeckers, owls, chickadees, wood ducks, etc. are depauperate in Eucalyptus groves because the decay resistant wood of these trees prevents cavity formation by decay or excavation. Also, those bird species that glean insects from foliage, such as warblers and vireos, experience population declines when Eucalyptus groves replace oak forest. Birds that thrive in Eucalyptus groves in California tend to prefer tall vertical habitat. These avian species include herons and egrets, which also nest in redwoods. The Point Reyes Bird Observatory observes that sometimes short billed birds like the ruby crowned kinglet are found dead beneath Eucalyptus trees with their nostrils clogged with pitch. E. cladocalyx and E. diversicolor are considered Fynbos invaders, and use up to 20% more water than the native fynbos vegetation; with invasive species including Eucalyptus being cleared that reduce Cape Town's water resource by 55 billion litres or two months worth of water supply.