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Brian W Van Wilgen John Measey David M R Biography & Facts

Eucalyptus () 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. Description Size and habit Eucalypts vary in size and habit from shrubs to tall trees. Trees usually have a single main stem or trunk but many eucalypts are mallees that are multistemmed from ground level and rarely taller than 10 metres (33 feet). There is no clear distinction between a mallee and a shrub but in eucalypts, a shrub is a mature plant less than 1 m (3 ft 3 in) tall and growing in an extreme environment. Eucalyptus vernicosa in the Tasmanian highlands, E. yalatensis on the Nullarbor and E. surgens growing on coastal cliffs in Western Australia are examples of eucalypt shrubs. The terms "mallet" and "marlock" are only applied to Western Australian eucalypts. A mallet is a tree with a single thin trunk with a steeply branching habit but lacks both a lignotuber and epicormic buds. Eucalyptus astringens is an example of a mallet. A marlock is a shrub or small tree with a single, short trunk, that lacks a lignotuber and has spreading, densely leafy branches that often reach almost to the ground. Eucalyptus platypus is an example of a marlock. Eucalyptus trees, including mallets and marlocks, are single-stemmed and include Eucalyptus regnans, the tallest known flowering plant on Earth. The tallest reliably measured tree in Europe, Karri Knight, can be found in Coimbra, Portugal in Vale de Canas. It is an Eucalyptus diversicolor of 72.9 meters height and of 5.71 meters girth. Tree sizes follow the convention of: Small: to 10 m (33 ft) in height Medium-sized: 10–30 m (33–98 ft) Tall: 30–60 m (98–197 ft) Very tall: over 60 m (200 ft) Bark All eucalypts add a layer of bark every year and the outermost layer dies. In about half of the species, the dead bark is shed exposing a new layer of fresh, living bark. The dead bark may be shed in large slabs, in ribbons or in small flakes. These species are known as "smooth barks" and include E. sheathiana, E. diversicolor, E. cosmophylla and E. cladocalyx. The remaining species retain the dead bark which dries out and accumulates. In some of these species, the fibres in the bark are loosely intertwined (in stringybarks such as E. macrorhyncha or peppermints such as E. radiata) or more tightly adherent (as in the "boxes" such as E. leptophleba). In some species (the "ironbarks" such as E. crebra and E. jensenii) the rough bark is infused with gum resin. Many species are ‘half-barks’ or ‘blackbutts’ in which the dead bark is retained in the lower half of the trunks or stems—for example, E. brachycalyx, E. ochrophloia, and E. occidentalis—or only in a thick, black accumulation at the base, as in E. clelandii. In some species in this category, for example E. youngiana and E. viminalis, the rough basal bark is very ribbony at the top, where it gives way to the smooth upper stems. The smooth upper bark of the half-barks and that of the completely smooth-barked trees and mallees can produce remarkable colour and interest, for example E. deglupta. E. globulus bark cells are able to photosynthesize in the absence of foliage, conferring an "increased capacity to re-fix internal CO2 following partial defoliation". This allows the tree to grow in less-than-ideal climates, in addition to providing a better chance of recovery from damage sustained to its leaves in an event such as a fire. Different commonly recognised types of bark include: Stringybark—consists of long fibres and can be pulled off in long pieces. It is usually thick with a spongy texture. Ironbark—is hard, rough, and deeply furrowed. It is impregnated with dried kino (a sap exuded by the tree) which gives a dark red or even black colour. Tessellated—bark is broken up into many distinct flakes. They are corkish and can flake off. Box—has short fibres. Some also show tessellation. Ribbon—has the bark coming off in long, thin pieces, but is still loosely attached in some places. They can be long ribbons, firmer strips, or twisted curls. Leaves 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 leav.... Discover the Brian W Van Wilgen John Measey David M R popular books. Find the top 100 most popular Brian W Van Wilgen John Measey David M R books.