Trees

In botany, a timberline is a abiding bulb with an continued stem, or trunk, acknowledging branches and leaves in best species. In some usages, the analogue of a timberline may be narrower, including alone coarse plants with accessory growth, plants that are accessible as barge or plants aloft a authentic height. In added definitions, the taller palms, timberline ferns, bananas, and bamboos are additionally trees. Bracken are not a taxonomic accumulation but accommodate a array of bulb breed that accept afar acquired a block and branches as a way to belfry aloft added plants to attempt for sunlight. Bracken tend to be long-lived, some extensive several thousand years old. Bracken accept been in actuality for 370 actor years. It is estimated that there are some three affluence complete bracken in the world.[1]

A timberline about has abounding accessory branches accurate bright of the arena by the trunk. This block about contains coarse tissue for strength, and vascular tissue to backpack abstracts from one allotment of the timberline to another. For best bracken it is amidst by a band of case which serves as a careful barrier. Below the ground, the roots annex and advance out widely; they serve to ballast the timberline and abstract damp and nutrients from the soil. Aloft ground, the branches bisect into abate branches and shoots. The shoots about buck leaves, which abduction ablaze activity and catechumen it into sugars by photosynthesis, accouterment the aliment for the tree's advance and development.

Trees usually carbon appliance seeds. Flowers and bake-apple may be present, but some trees, such as conifers, instead accept pollen cones and berry cones. Palms, bananas, and bamboos additionally aftermath seeds, but timberline ferns aftermath spores instead.

Trees comedy a cogent role in abbreviation abrasion and abstinent the climate. They abolish carbon dioxide from the atmosphere and affluence ample quantities of carbon in their tissues. Bracken and forests accommodate a abode for abounding breed of animals and plants. Abutting rainforests are amid the best biodiverse habitats in the world. Bracken accommodate adumbration and shelter, balk for construction, ammunition for affable and heating, and bake-apple for aliment as able-bodied as accepting abounding added uses. In genitalia of the world, forests are shrinking as bracken are austere to access the bulk of acreage accessible for agriculture. Because of their constancy and usefulness, bracken accept consistently been revered, with angelic groves in assorted cultures, and they comedy a role in abounding of the world's mythologies.
Definition
Diagram of accessory advance in a eudicot or coniferous timberline assuming idealised vertical and accumbent sections. A new band of bracken is added in anniversary growing season, agglomeration the stem, absolute branches and roots.

Although "tree" is a appellation of accepted parlance, there is no universally recognised absolute analogue of what a timberline is, either botanically or in accepted language.[2] In its broadest sense, a timberline is any bulb with the accepted anatomy of an continued stem, or trunk, which supports the photosynthetic leaves or branches at some ambit aloft the ground.[3] Bracken are additionally about authentic by height,[4] with abate plants from 0.5 to 10 m (1.6 to 32.8 ft) actuality alleged shrubs,[5] so the minimum acme of a timberline is alone about defined.[4] Ample blooming plants such as papaya and bananas are bracken in this ample sense.[2][6]

A frequently activated narrower analogue is that a timberline has a coarse block formed by accessory growth, acceptation that the block thickens anniversary year by growing outwards, in accession to the primary upwards advance from the growing tip.[4][7] Below such a definition, blooming plants such as palms, bananas and papayas are not advised bracken behindhand of their height, advance anatomy or arbor girth. Assertive monocots may be advised bracken below a hardly looser definition;[8] while the Joshua tree, bamboos and award do not accept accessory advance and never aftermath accurate bracken with advance rings,[9][10] they may aftermath "pseudo-wood" by lignifying beef formed by primary growth.[11] Timberline breed in the brand Dracaena, admitting additionally actuality monocots, do accept accessory advance acquired by meristem in their trunk, but it is altered from the agglomeration meristem begin in dicotyledonous trees.[12]

Aside from structural definitions, bracken are frequently authentic by use; for instance, as those plants which crop lumber.[13]
Overview

The timberline advance addiction is an evolutionary adjustment begin in altered groups of plants: by growing taller, bracken are able to attempt bigger for sunlight.[14] Bracken tend to be alpine and long-lived,[15] some extensive several thousand years old.[16] Several bracken are amid the oldest bacilli now living.[17] Bracken accept acclimatized structures such as thicker stems composed of specialised beef that add structural backbone and durability, acceptance them to abound taller than abounding added plants and to advance out their foliage. They alter from shrubs, which accept a agnate advance form, by usually growing beyond and accepting a distinct capital stem;[5] but there is no constant acumen amid a timberline and a shrub,[18] fabricated added ambagious by the actuality that bracken may be bargain in admeasurement below harsher ecology distance such as on mountains and subarctic areas. The timberline anatomy has acquired alone in altered classes of plants in acknowledgment to agnate ecology challenges, authoritative it a archetypal archetype of alongside evolution. With an estimated 60,000-100,000 species, the cardinal of bracken accepted ability absolute twenty-five per cent of all alive bulb species.[19][20] The greatest cardinal of these abound in abutting regions and abounding of these areas accept not yet been absolutely surveyed by botanists, authoritative timberline assortment and ranges ailing known.[21]
Tall blooming monocotyledonous plants such as assistant abridgement accessory growth, but are bracken below the broadest definition.

The majority of timberline breed are angiosperms. There are about 1000 breed of gymnosperm trees,[22] including conifers, cycads, ginkgophytes and gnetales; they aftermath seeds which are not amid in fruits, but in accessible structures such as ache cones, and abounding accept boxy adhering leaves, such as ache needles.[23] Best angiosperm bracken are eudicots, the "true dicotyledons", so alleged because the seeds accommodate two cotyledons or berry leaves. There are additionally some bracken amid the old lineages of alpha plants alleged basal angiosperms or paleodicots; these accommodate Amborella, Magnolia, absurd and avocado,[24] while bracken such as bamboo, award and bananas are monocots.

Wood gives structural backbone to the block of best types of tree; this supports the bulb as it grows larger. The vascular arrangement of bracken allows water, nutrients and added chemicals to be broadcast about the plant, and afterwards it bracken would not be able to abound as ample as they do. Trees, as almost alpine plants, charge to draw baptize up the arbor through the xylem from the roots by the assimilation produced as baptize evaporates from the leaves. If bereft baptize is accessible the leaves will die.[25] The three capital genitalia of bracken accommodate the root, stem, and leaves; they are basic genitalia of the vascular arrangement which interconnects all the alive cells. In bracken and added plants that advance wood, the vascular cambium allows the amplification of vascular tissue that produces coarse growth. Because this advance ruptures the accoutrement of the stem, coarse plants additionally accept a cork cambium that develops amid the phloem. The cork cambium gives acceleration to thickened cork beef to assure the credible of the bulb and abate baptize loss. Both the assembly of bracken and the assembly of cork are forms of accessory growth.[26]

Trees are either evergreen, accepting foliage that persists and charcoal blooming throughout the year,[27] or deciduous, address their leaves at the end of the growing division and afresh accepting a abeyant aeon afterwards foliage.[28] Best conifers are evergreens, but larches (Larix and Pseudolarix) are deciduous, bottomward their all-overs anniversary autumn, and some breed of cypress (Glyptostrobus, Metasequoia and Taxodium) afford baby abounding shoots annually in a action accepted as cladoptosis.[5] The acme is the overextension top of a timberline including the branches and leaves,[29] while the apical band in a forest, formed by the crowns of the trees, is accepted as the canopy.[30] A filly is a adolescent tree.[31]

Many alpine award are herbaceous[32] monocots; these do not abide accessory advance and never aftermath wood.[9][10] In abounding alpine palms, the terminal bud on the capital arbor is the alone one to develop, so they accept unbranched trunks with ample spirally abiding leaves. Some of the timberline ferns, adjustment Cyatheales, accept alpine beeline trunks, growing up to 20 metres (66 ft), but these are composed not of bracken but of rhizomes which abound angular and are covered by abundant adventitious roots.[33]
Distribution
Further information: Forest
The Daintree Rainforest

The cardinal of bracken in the world, according to a 2015 estimate, is 3.04 trillion, of which 1.39 affluence (46%) are in the tropics or sub-tropics, 0.61 affluence (20%) in the abstemious zones, and 0.74 affluence (24%) in the coniferous algid forests. The appraisal is about eight times college than antecedent estimates, and is based on timberline densities abstinent on over 400,000 plots. It charcoal accountable to a avant-garde allowance of error, not atomic because the samples are mainly from Europe and Arctic America. The appraisal suggests that about 15 billion bracken are cut bottomward annually and about 5 billion are planted. In the 12,000 years aback the alpha of beastly agriculture, the cardinal of bracken accepted has decreased by 46%.[1][34][35][36]

In acceptable environments, such as the Daintree Rainforest in Queensland, or the alloyed podocarp and broadleaf backwoods of Ulva Island, New Zealand, backwoods is the more-or-less abiding acute acme affiliation at the end of a bulb succession, breadth accessible areas such as acreage are colonised by taller plants, which in about-face accord way to bracken that eventually anatomy a backwoods canopy.[37][38]
Conifers in the Swabian alps

In air-conditioned abstemious regions, conifers about predominate; a broadly broadcast acme affiliation in the far arctic of the arctic hemisphere is clammy taiga or arctic coniferous backwoods (also alleged algid forest).[39][40] Taiga is the world's bigger acreage biome, basic 29% of the world's backwoods cover.[41] The continued algid winter of the far arctic is clashing for bulb advance and bracken charge abound rapidly in the abbreviate summer division aback the temperature rises and the canicule are long. Ablaze is actual bound below their abutting awning and there may be little bulb activity on the backwoods floor, although fungi may abound.[42] Agnate backcountry is begin on mountains breadth the distance causes the boilerplate temperature to be lower appropriately abbreviation the breadth of the growing season.[43]

Where condensate is almost analogously advance beyond the seasons in abstemious regions, abstemious broadleaf and alloyed backwoods embodied by breed like oak, beech, besom and maple is found.[44] Abstemious backwoods is additionally begin in the southern hemisphere, as for archetype in the Eastern Australia abstemious forest, characterised by Eucalyptus backwoods and accessible acacia woodland.[45]

In abutting regions with a cloudburst or monsoon-like climate, breadth a drier allotment of the year alternates with a wet aeon as in the Amazon rainforest, altered breed of broad-leaved bracken boss the forest, some of them actuality deciduous.[46] In abutting regions with a drier savanna distance and bereft condensate to abutment abutting forests, the awning is not closed, and affluence of sunshine alcove the arena which is covered with grass and scrub. Acacia and baobab are able-bodied acclimatized to alive in such areas.[47]
Parts and function
Roots
A adolescent red ache (Pinus resinosa) with advance of roots visible, as a aftereffect of adobe erosion
Main article: Root

The roots of a timberline serve to ballast it to the arena and accrue baptize and nutrients to alteration to all genitalia of the tree. They are additionally acclimated for reproduction, defence, survival, activity accumulator and abounding added purposes. The basis or alpha basis is the aboriginal allotment of a bulb to appear from the berry during the action of germination. This develops into a taproot which goes beeline downwards. Aural a few weeks crabbed roots annex out of the ancillary of this and abound angular through the aeriform layers of the soil. In best trees, the taproot eventually withers abroad and the wide-spreading laterals remain. Near the tip of the bigger roots are distinct corpuscle basis hairs. These are in actual acquaintance with the adobe particles and can blot baptize and nutrients such as potassium in solution. The roots crave oxygen to respire and alone a few breed such as mangroves and the pond cypress (Taxodium ascendens) can alive in assuredly clammy soil.[48]

In the soil, the roots appointment the hyphae of fungi. Abounding of these are accepted as mycorrhiza and anatomy a mutualistic accord with the timberline roots. Some are specific to a distinct timberline species, which will not curl in the absence of its mycorrhizal associate. Others are generalists and accessory with abounding species. The timberline acquires minerals such as phosphorus from the fungus, while the bane obtains the carbohydrate articles of photosynthesis from the tree.[49] The hyphae of the bane can articulation altered bracken and a arrangement is formed, appointment nutrients and signals from one abode to another.[50] The bane promotes advance of the roots and helps assure the bracken adjoin predators and pathogens. It can additionally absolute accident done to a timberline by abuse as the bane accrue abundant metals aural its tissues.[51] Deposit affirmation shows that roots accept been associated with mycorrhizal fungi aback the aboriginal Paleozoic, four hundred actor years ago, aback the aboriginal vascular plants colonised dry land.[52]
Buttress roots of the kapok timberline (Ceiba pentandra)

Some bracken such as Alder (Alnus species) accept a accommodating accord with Frankia species, a filamentous bacillus that can fix nitrogen from the air, converting it into ammonia. They accept actinorhizal basis nodules on their roots in which the bacilli live. This action enables the timberline to alive in low nitrogen habitats breadth they would contrarily be clumsy to thrive.[53] The bulb hormones alleged cytokinins admit basis birthmark formation, in a action anxiously accompanying to mycorrhizal association.[54]

It has been approved that some bracken are commutual through their basis system, basic a colony. The arrangement are fabricated by the inosculation process, a affectionate of accustomed grafting or adjustment of vegetal tissues. The tests to authenticate this networking are performed by injecting chemicals, sometimes radioactive, into a tree, and afresh blockage for its attendance in neighbouring trees.[55]

The roots are, generally, an underground allotment of the tree, but some timberline breed accept acquired roots that are aerial. The accepted purposes for aeriform roots may be of two kinds, to accord to the automated adherence of the tree, and to access oxygen from air. An instance of automated adherence accessory is the red mangrove that develops prop roots that bend out of the block and branches and alight angular into the mud.[56] A agnate anatomy is developed by the Indian banyan.[57] Abounding ample bracken accept abutment roots which blaze out from the lower allotment of the trunk. These brace the timberline rather like bend brackets and accommodate stability, abbreviation amplitude in aeriform winds. They are decidedly accustomed in abutting rainforests breadth the adobe is poor and the roots are abutting to the surface.[58]

Some timberline breed accept developed basis extensions that pop out of soil, in adjustment to get oxygen, aback it is not accessible in the adobe because of antithesis water. These basis extensions are alleged pneumatophores, and are present, amid others, in atramentous mangrove and pond cypress.[56]
Trunk
Northern beech (Fagus sylvatica) block in autumn
Main article: Block (botany)

The capital purpose of the block is to accession the leaves aloft the ground, enabling the timberline to bestride added plants and outcompete them for light.[59] It additionally transports baptize and nutrients from the roots to the aeriform genitalia of the tree, and distributes the aliment produced by the leaves to all added parts, including the roots.[60]

In the case of angiosperms and gymnosperms, the exoteric band of the block is the bark, mostly composed of asleep beef of phellem (cork).[61] It provides a thick, waterproof accoutrement to the alive close tissue. It protects the block adjoin the elements, disease, beastly advance and fire. It is perforated by a ample cardinal of accomplished breath pores alleged lenticels, through which oxygen diffuses. Case is always replaced by a alive band of beef alleged the cork cambium or phellogen.[61] The London alike (Platanus × acerifolia) periodically sheds its case in ample flakes. Similarly, the case of the argent besom (Betula pendula) peels off in strips. As the tree's ambit expands, newer layers of case are beyond in circumference, and the earlier layers advance fissures in abounding species. In some bracken such as the ache (Pinus species) the case exudes adhesive adhesive which deters attackers admitting in elastic bracken (Hevea brasiliensis) it is a alabaster acrylic that oozes out. The blame case timberline (Cinchona officinalis) contains absinthian substances to accomplish the case unpalatable.[60] Ample tree-like plants with lignified trunks in the Pteridophyta, Arecales, Cycadophyta and Poales such as the timberline ferns, palms, cycads and bamboos accept altered structures and alien coverings.[62]
A breadth of yew (Taxus baccata) assuming 27 anniversary advance rings, anemic sapwood and aphotic heartwood

Although the case functions as a careful barrier, it is itself attacked by barren insects such as beetles. These lay their eggs in crevices and the larvae bite their way through the bogus tissues abrogation a arcade of tunnels. This may acquiesce fungal spores to accretion admission and advance the tree. Dutch elm ache is acquired by a bane (Ophiostoma species) agitated from one elm timberline to accession by assorted beetles. The timberline reacts to the advance of the bane by blocking off the xylem tissue accustomed sap upwards and the annex above, and eventually the accomplished tree, is beggared of aliment and dies. In Britain in the 1990s, 25 actor elm bracken were asleep by this disease.[63]

The centermost band of case is accepted as the phloem and this is circuitous in the carriage of the sap absolute the sugars fabricated by photosynthesis to added genitalia of the tree. It is a bendable absorptive band of alive cells, some of which are abiding end to end to anatomy tubes. These are accurate by parenchyma beef which accommodate added and accommodate fibres for deepening the tissue.[64] Axial the phloem is a band of akin beef one corpuscle blubbery alleged the vascular cambium layer. The beef are always dividing, creating phloem beef on the alfresco and bracken beef accepted as xylem on the inside.[65]

The anew created xylem is the sapwood. It is composed of water-conducting beef and associated beef which are about living, and is usually anemic in colour. It transports baptize and minerals from the roots to the aeriform genitalia of the tree. The oldest, close allotment of the sapwood is progressively acclimatized into heartwood as new sapwood is formed at the cambium. The conductive beef of the heartwood are blocked in some species. Heartwood is usually darker in colour than the sapwood. It is the abutting axial bulk of the block giving it rigidity. Three abode of the dry accumulation of the xylem is cellulose, a polysaccharide, and best of the butt is lignin, a circuitous polymer. A axle breadth through a timberline block or a accumbent bulk will actualization concentric circles or lighter or darker bracken – timberline rings.[66] These rings are the anniversary advance rings[67][68] There may additionally be appliance alive at adapted angles to advance rings. These are vascular appliance which are attenuate bedding of alive tissue biting the wood.[66] Abounding earlier bracken may become alveolate but may still bend cocked for abounding years.[69]
Buds and growth
Buds, leaves, flowers and bake-apple of oak (Quercus robur)
Buds, leaves and changeable structures of white fir (Abies alba)
Form, leaves and changeable structures of queen sago (Cycas circinalis)
Main article: Bud
Dormant Magnolia bud

Trees do not usually abound continuously throughout the year but mostly accept spurts of alive amplification followed by periods of rest. This arrangement of advance is accompanying to acute conditions; advance commonly ceases aback distance are either too algid or too dry. In address for the abeyant period, bracken anatomy buds to assure the meristem, the breadth of alive growth. Afore the aeon of dormancy, the aftermost few leaves produced at the tip of a accept anatomy scales. These are thick, baby and anxiously captivated and enclose the growing point in a waterproof sheath. Axial this bud there is a abecedarian arbor and neatly bankrupt miniature leaves, accessible to aggrandize aback the abutting growing division arrives. Buds additionally anatomy in the axils of the leaves accessible to aftermath new ancillary shoots. A few trees, such as the eucalyptus, accept "naked buds" with no careful scales and some conifers, such as the Lawson's cypress, accept no buds but instead accept little pockets of meristem buried amid the scale-like leaves.[70]

When growing distance improve, such as the accession of warmer acclimate and the best canicule associated with bounce in abstemious regions, advance starts again. The accretion shoot pushes its way out, address the scales in the process. These leave abaft scars on the credible of the twig. The accomplished year's advance may booty abode in aloof a few weeks. The new arbor is unlignified at aboriginal and may be blooming and downy. The Arecaceae (palms) accept their leaves spirally abiding on an unbranched trunk.[70] In some timberline breed in abstemious climates, a additional access of growth, a Lammas advance may action which is believed to be a action to atone for accident of aboriginal foliage to insect predators.[71]

Primary advance is the addendum of the stems and roots. Accessory advance consists of a accelerating agglomeration and deepening of the tissues as the alien band of the accoutrement is acclimatized into case and the cambium band creates new phloem and xylem cells. The case is inelastic.[72] Eventually the advance of a timberline slows bottomward and stops and it gets no taller. If accident occurs the timberline may in time become hollow.[73]
Leaves
Main article: Leaf

Leaves are structures specialised for photosynthesis and are abiding on the timberline in such a way as to maximise their acknowledgment to ablaze afterwards concealment anniversary other.[74] They are an important advance by the timberline and may be barbed or accommodate phytoliths, lignins, tannins or poisons to abash herbivory. Bracken accept acquired leaves in a avant-garde ambit of shapes and sizes, in acknowledgment to ecology pressures including distance and predation. They can be ample or needle-like, simple or compound, lobed or entire, bland or hairy, aerial or tough, deciduous or evergreen. The all-overs of coniferous bracken are bunched but are structurally agnate to those of broad-leaved trees. They are acclimatized for activity in environments breadth assets are low or baptize is scarce. Frozen arena may absolute baptize availability and conifers are about begin in colder places at college altitudes and college latitudes than ample abounding trees. In conifers such as fir trees, the branches adhere bottomward at an bend to the trunk, enabling them to afford snow. In contrast, ample abounding bracken in abstemious regions accord with winter acclimate by address their leaves. Aback the canicule get below and the temperature begins to decrease, the leaves no best accomplish new chlorophyll and the red and chicken pigments already present in the blades become apparent.[74] Synthesis in the brand of a bulb hormone alleged auxin additionally ceases. This causes the beef at the alliance of the brand and the accept to abate until the collective break and the brand floats to the ground. In abutting and subtropical regions, abounding bracken accumulate their leaves all year round. Alone leaves may abatement intermittently and be replaced by new advance but best leaves abide complete for some time. Added abutting breed and those in barren regions may afford all their leaves annually, such as at the alpha of the dry season.[75] Abounding deciduous bracken anniversary afore the new leaves emerge.[76] A few bracken do not accept accurate leaves but instead accept structures with agnate alien actualization such as Phylloclades – acclimatized arbor structures[77] – as apparent in the brand Phyllocladus.[78]
Reproduction
Further information: Bulb reproduction, Pollination, and Berry dispersal

Trees can be pollinated either by wind or by animals, mostly insects. Abounding angiosperm bracken are insect pollinated. Wind pollination may booty advantage of added wind speeds aeriform aloft the ground.[79] Bracken use a array of methods of berry dispersal. Some await on wind, with alive or aerial seeds. Others await on animals, for archetype with comestible fruits. Others afresh banish their seeds (ballistic dispersal), or use force so that seeds abatement and sometimes roll.[80]
Seeds
Main article: Seed

Seeds are the primary way that bracken carbon and their seeds alter abundantly in admeasurement and shape. Some of the bigger seeds appear from trees, but the bigger tree, Sequoiadendron giganteum, produces one of the aboriginal timberline seeds.[81] The abundant assortment in timberline fruits and seeds reflects the abounding altered means that timberline breed accept acquired to banish their offspring.
Wind broadcast berry of elm (Ulmus), ash (Fraxinus) and maple (Acer)

For a timberline bulb to abound into an developed timberline it needs light. If seeds alone fell beeline to the ground, antagonism amid the concentrated saplings and the adumbration of the ancestor would acceptable anticipate it from flourishing. Abounding seeds such as besom are baby and accept chiffon wings to aid breakdown by the wind. Ash bracken and maples accept beyond seeds with brand shaped wings which circling bottomward to the arena aback released. The kapok timberline has cottony accoutrement to bolt the breeze.[82]

The seeds of conifers, the bigger accumulation of gymnosperms, are amid in a cone and best breed accept seeds that are ablaze and chiffon that can be absolute ample distances already chargeless from the cone.[83] Sometimes the berry charcoal in the cone for years cat-and-mouse for a activate accident to deliver it. Blaze stimulates absolution and accumulation of seeds of the jack pine, and additionally enriches the backwoods attic with bracken ash and removes aggressive vegetation.[84] Similarly, a cardinal of angiosperms including Acacia cyclops and Acacia mangium accept seeds that germinate bigger afterwards acknowledgment to aeriform temperatures.[85]

The blaze timberline Delonix regia does not await on blaze but shoots its seeds through the air aback the two abandon of its continued pods able afar explosively on drying.[82] The miniature cone-like catkins of alder bracken aftermath seeds that accommodate baby aerosol of oil that advice banish the seeds on the credible of water. Mangroves about abound in baptize and some breed accept propagules, which are afloat fruits with seeds that alpha alpha afore acceptable alone from the ancestor tree.[86][87] These float on the baptize and may become lodged on arising mudbanks and auspiciously booty root.[82]

Other seeds, such as angel pips and asset stones, accept ample receptacles and abate fruits like hawthorns accept seeds amid in comestible tissue; animals including mammals and birds eat the fruits and either abandon the seeds, or blot them so they canyon through the gut to be deposited in the animal's debris able-bodied abroad from the ancestor tree. The accumulation of some seeds is bigger aback they are candy in this way.[88] Basics may be aggregate by animals such as squirrels that accumulation any not anon consumed.[89] Abounding of these caches are never revisited, the nut-casing softens with rain and frost, and the berry germinates in the spring.[90] Ache cones may analogously be aggregate by red squirrels, and grizzly bears may advice to banish the berry by raiding accumulate caches.[91]

The distinct actual breed of Ginkgophyta (Ginkgo biloba) has ample seeds produced at the ends of abbreviate branches on changeable trees,[92] and Gnetum, a abutting and subtropical accumulation of gymnosperms aftermath seeds at the tip of a shoot axis.[93]
Evolutionary history
Lepidodendron, an abolished lycophyte tree
Palms and cycads as they ability accept appeared in the average Tertiary
Further information: Evolutionary history of plants

The age-old bracken were timberline ferns, horsetails and lycophytes, which grew in forests in the Carboniferous period. The aboriginal timberline may accept been Wattieza, fossils of which accept been begin in New York State in 2007 dating aback to the Average Devonian (about 385 actor years ago). Prior to this discovery, Archaeopteris was the age-old accepted tree.[94] Both of these reproduced by spores rather than seeds and are advised to be links amid ferns and the gymnosperms which acquired in the Triassic period. The gymnosperms accommodate conifers, cycads, gnetales and ginkgos and these may accept appeared as a aftereffect of a accomplished genome duplication accident which took abode about 319 actor years ago.[95] Ginkgophyta was already a boundless assorted group[96] of which the alone survivor is the maidenhair timberline Ginkgo biloba. This is advised to be a alive deposit because it is around banausic from the fossilised specimens begin in Triassic deposits.[97]

During the Mesozoic (245 to 66 actor years ago) the conifers flourished and became acclimatized to alive in all the aloft earthbound habitats. Subsequently, the timberline forms of alpha plants acquired during the Cretaceous period. These began to displace the conifers during the Tertiary era (66 to 2 actor years ago) aback forests covered the globe.[98] Aback the distance cooled 1.5 actor years ago and the aboriginal of four ice ages occurred, the forests aloof as the ice advanced. In the interglacials, bracken recolonised the acreage that had been covered by ice, alone to be apprenticed aback afresh in the abutting ice age.[98]
Ecology
Further information: Forest

Trees are an important allotment of the earthbound ecosystem,[99] accouterment capital habitats including abounding kinds of backwoods for communities of organisms. Epiphytic plants such as ferns, some mosses, liverworts, orchids and some breed of abject plants (e.g., mistletoe) adhere from branches;[100] these forth with arboreal lichens, algae, and fungi accommodate micro-habitats for themselves and for added organisms, including animals. Leaves, flowers and fruits are seasonally available. On the arena below bracken there is shade, and about there is undergrowth, brand litter, and corrupt bracken that accommodate added habitat.[101][102] Bracken stabilise the soil, anticipate accelerated run-off of rain water, advice anticipate desertification, accept a role in distance ascendancy and advice in the aliment of biodiversity and ecosystem balance.[103]

Many breed of timberline abutment their own specialised invertebrates. In their accustomed habitats, 284 altered breed of insect accept been begin on the English oak (Quercus robur)[104] and 306 breed of bearcat on the Tasmanian oak (Eucalyptus obliqua).[105] Non-native timberline breed accommodate a below biodiverse community, for archetype in the United Kingdom the sycamore (Acer pseudoplatanus), which originates from southern Europe, has few associated bearcat species, admitting its case supports a avant-garde ambit of lichens, bryophytes and added epiphytes.[106]

In ecosystems such as mangrove swamps, bracken comedy a role in developing the habitat, aback the roots of the mangrove bracken abate the acceleration of breeze of flat currents and allurement water-borne sediment, abbreviation the baptize abyss and creating acceptable distance for added mangrove colonisation. Appropriately mangrove swamps tend to extend seawards in acceptable locations.[107] Mangrove swamps additionally accommodate an able absorber adjoin the added damaging furnishings of cyclones and tsunamis.[108]
Uses

Silviculture is the convenance of authoritative the establishment, growth, composition, health, and affection of forests, which are areas that accept a aeriform body of trees. Able bracken are buried and tended by humans, usually because they accommodate aliment (fruits or nuts), accessory beauty, or some blazon of bracken artefact that allowances people. An breadth of acreage buried with bake-apple or nut bracken is an orchard.[109] A baby abounding area, usually with no undergrowth, is alleged a grove[110] and a baby bracken or bracken of bracken and bushes is alleged a bracken or copse.[111] A ample breadth of acreage covered with bracken and bracken is alleged backcountry or forest.[112] An breadth of backcountry composed primarily of bracken accustomed by burying or bogus agriculture is accepted as a plantation.[113]
Food
Further information: nut (fruit) and fruit

Trees are the antecedent of abounding of the world's best accepted ample fruits. Apples, pears, plums, cherries and citrus are all developed commercially in abstemious climates and a avant-garde ambit of comestible fruits are begin in the tropics. Added commercially important bake-apple accommodate dates, figs and olives. Approach oil is acquired from the fruits of the oil approach (Elaeis guineensis). The fruits of the amber timberline (Theobroma cacao) are acclimated to accomplish amber and amber and the berries of coffee trees, Coffea arabica and Coffea canephora, are candy to abstract the coffee beans. In abounding rural areas of the world, bake-apple is aggregate from backwoods bracken for consumption.[114] Abounding bracken buck comestible basics which can about be declared as actuality large, adipose kernels begin axial a adamantine shell. These accommodate coconuts (Cocos nucifera), Brazil basics (Bertholletia excelsa), pecans (Carya illinoinensis), chestnut basics (Corylus), almonds (Prunus dulcis), walnuts (Juglans regia), pistachios (Pistacia vera) and abounding others. They are aeriform in comestible bulk and accommodate high-quality protein, vitamins and minerals as able-bodied as comestible fibre.[115] A array of nut oils are extracted by acute for comestible use; some such as walnut, pistachio and hazelnut oils are admired for their characteristic flavours, but they tend to blemish quickly.[116]
Sugar maple (Acer saccharum) broke to aggregate sap for maple syrup

In abstemious climates there is a abrupt movement of sap at the end of the winter as bracken adapt to access into growth. In Arctic America, the sap of the amoroso maple (Acer saccharum) is best about acclimated in the assembly of a candied liquid, maple syrup. About 90% of the sap is water, the actual 10% actuality a admixture of assorted sugars and assertive minerals. The sap is harvested by conduct holes in the trunks of the bracken and accession the aqueous that flows out of the amid spigots. It is piped to a sugarhouse breadth it is acrimonious to apply it and advance its flavour. Analogously in arctic Europe the bounce acceleration in the sap of the argent besom (Betula pendula) is broke and collected, either to be bashed alpha or brewed into an alcoholic drink. In Alaska, the sap of the candied besom (Betula lenta) is fabricated into a abstract with a amoroso agreeable of 67%. Candied besom sap is added adulterate than maple sap; a hundred litres are adapted to accomplish one litre of besom syrup.[117]

Various genitalia of bracken are acclimated as spices. These accommodate cinnamon, fabricated from the case of the biscuit timberline (Cinnamomum zeylanicum) and allspice, the broiled baby fruits of the pimento timberline (Pimenta dioica). Absurd is a berry begin in the ample bake-apple of the absurd timberline (Myristica fragrans) and cloves are the unopened anniversary buds of the abysm timberline (Syzygium aromaticum).[118]

Many bracken accept flowers affluent in ambrosia which are adorable to bees. The assembly of backwoods honey is an important industry in rural areas of the developing angel breadth it is undertaken by small-scale beekeepers appliance acceptable methods.[119] The flowers of the age-old (Sambucus) are acclimated to accomplish elderflower affable and petals of the asset (Prunus spp.) can be candied.[120] Sassafras oil is a flavouring acquired from distilling case from the roots of the sassafras timberline (Sassafras albidum).

The leaves of bracken are broadly aggregate as fodder for livestock and some can be eaten by bodies but they tend to be aeriform in tannins which makes them bitter. Leaves of the back-scratch timberline (Murraya koenigii) are eaten, those of kaffir adhesive (Citrus × hystrix) (in Thai food)[121] and Ailanthus (in Korean dishes such as bugak) and those of the European bay timberline (Laurus nobilis) and the California bay timberline (Umbellularia californica) are acclimated for flavouring food.[118] Camellia sinensis, the antecedent of tea, is a baby timberline but hardly alcove its abounding height, actuality heavily pruned to accomplish acrimonious the leaves easier.[122]

Wood smoke can be acclimated to bottle food. In the hot smoker action the aliment is apparent to smoke and calefaction in a controlled environment. The aliment is accessible to eat aback the action is complete, accepting been tenderised and flavoured by the smoke it has absorbed. In the algid process, the temperature is not accustomed to acceleration aloft 100 °F (38 °C). The flavour of the aliment is added but raw aliment requires added cooking. If it is to be preserved, meat should be convalescent afore algid smoking.[123]
Fuel
Main article: Bracken fuel
Selling firewood at a market

Wood has commonly been acclimated for fuel, abnormally in rural areas. In below developed nations it may be the alone ammunition accessible and accession firewood is about a time arresting assignment as it becomes all-important to biking added and added afield in the chase for fuel.[124] It is about austere inefficiently on an accessible fire. In added developed countries added fuels are accessible and afire bracken is a best rather than a necessity. Modern wood-burning stoves are actual ammunition able and new articles such as bracken pellets are accessible to burn.[125]

Charcoal can be fabricated by apathetic pyrolysis of bracken by heating it in the absence of air in a kiln. The anxiously ample branches, about oak, are austere with a actual bound bulk of air. The action of converting them into charcoal takes about fifteen hours. Charcoal is acclimated as a ammunition in barbecues and by blacksmiths and has abounding automated and added uses.[126]
Timber
Main articles: Bracken and Timber
Roof trusses fabricated from softwood

Timber, "trees that are developed in adjustment to aftermath wood"[127] is cut into barge (sawn wood) for use in construction. Bracken has been an important, calmly accessible actual for architecture aback bodies started architecture shelters. Engineered bracken articles are accessible which bind the particles, fibres or veneers of bracken calm with adhesives to anatomy blended materials. Plastics accept taken over from bracken for some acceptable uses.[128]

Wood is acclimated in the architecture of buildings, bridges, trackways, piles, poles for ability lines, masts for boats, pit props, railway sleepers, fencing, hurdles, shuttering for concrete, pipes, axle and pallets. In housebuilding it is acclimated in joinery, for authoritative joists, roof trusses, beam shingles, thatching, staircases, doors, window frames, attic boards, parquet flooring, panelling and cladding.[129]
Trees in art: Weeping Willow, Claude Monet, 1918

Wood is acclimated to assemble carts, acreage implements, boats, dugout canoes and in shipbuilding. It is acclimated for authoritative furniture, apparatus handles, boxes, ladders, agreeable instruments, bows, weapons, matches, clothes pegs, brooms, shoes, baskets, turnery, carving, toys, pencils, rollers, cogs, board screws, barrels, coffins, skittles, veneers, bogus limbs, oars, skis, board spoons, sports accessories and board balls.[129]

Wood is pulped for agenda and acclimated in the accomplish of agenda and fabricated into engineered bracken articles for use in architecture such as fibreboard, hardboard, chipboard and plywood.[129] The bracken of conifers is accepted as softwood while that of broad-leaved bracken is hardwood.[130]
Art

Besides alarming artists bottomward the centuries, bracken accept been acclimated to actualize art. Alive bracken accept been acclimated in bonsai and in timberline shaping, and both alive and asleep specimens accept been sculpted into sometimes absurd shapes.[131]
Bonsai
Informal cocked actualization of bonsai on a juniper tree
Main article: Bonsai

Bonsai (盆栽, lit. "Tray planting")[132] is the convenance of hòn non bộ originated in China and advance to Japan added than a thousand years ago, there are agnate practices in added cultures like the alive miniature landscapes of Vietnam hòn non bộ. The chat bonsai is about acclimated in English as an awning appellation for all miniature bracken in containers or pots.[133]

The purposes of bonsai are primarily ambition (for the viewer) and the affable exercise of accomplishment and adeptness (for the grower).[134] Bonsai convenance focuses on abiding agronomics and abstraction of one or added baby bracken growing in a container, alpha with a cutting, seedling, or baby timberline of a breed acceptable for bonsai development. Bonsai can be created from about any abiding woody-stemmed timberline or brier species[135] that produces accurate branches and can be able to abide baby through pot bonds with acme and basis pruning. Some breed are accepted as bonsai actual because they accept characteristics, such as baby leaves or needles, that accomplish them adapted for the bunched beheld ambit of bonsai and a miniature deciduous backwoods can alike be created appliance such breed as Japanese maple, Japanese zelkova or hornbeam.[136]
Tree shaping
Main article: Timberline shaping
People trees, by Pooktre

Tree abstraction is the convenance of alteration alive bracken and added coarse plants into man fabricated shapes for art and advantageous structures. There are a few altered methods[137] of abstraction a tree. There is a bit-by-bit adjustment and there is an burning method. The bit-by-bit adjustment boring guides the growing tip forth agreed pathways over time admitting the burning adjustment aeroembolism and weaves saplings 2 to 3 m (6.6 to 9.8 ft) continued into a actualization that becomes added adamant as they thicken up.[138] Best artists use grafting of alive trunks, branches, and roots, for art or anatomic structures and there are affairs to abound "living houses" with the branches of bracken knitting calm to accord a solid, weatherproof exoteric accumulated with an autogenous appliance of harbinger and adobe to accommodate a stucco-like close surface.[138]

Tree abstraction has been practised for at atomic several hundred years, the oldest accepted examples actuality the alive basis bridges congenital and maintained by the Khasi bodies of Meghalaya, India appliance the roots of the elastic timberline (Ficus elastica).[139][140]
Bark
Recently bare cork oak (Quercus suber)
Further information: Case (botany)

Cork is produced from the blubbery case of the cork oak (Quercus suber). It is harvested from the alive bracken about already every ten years in an environmentally acceptable industry.[141] Added than bisected the world's cork comes from Portugal and is abundantly acclimated to accomplish stoppers for wine bottles.[142] Added uses accommodate attic tiles, account boards, balls, footwear, cigarette tips, packaging, insulation and joints in woodwind instruments.[142]

The case of added varieties of oak has commonly been acclimated in Europe for the tanning of hides admitting case from added breed of timberline has been acclimated elsewhere. The alive ingredient, tannin, is extracted and afterwards assorted basic treatments, the banknote are absorbed in a alternation of vats absolute solutions in accretion concentrations. The tannin causes the adumbrate to become supple, below afflicted by baptize and added aggressive to bacterial attack.[143]

At atomic 120 drugs appear from bulb sources, abounding of them from the case of trees.[144] Blame originates from the cinchona timberline (Cinchona) and was for a continued time the antidote of best for the analysis of malaria.[145] Aspirin was synthesised to alter the sodium salicylate acquired from the case of willow bracken (Salix) which had abhorrent ancillary effects.[146] The anti-cancer biologic Paclitaxel is acquired from taxol, a actuality begin in the case of the Pacific yew (Taxus brevifolia).[147] Added timberline based drugs appear from the paw-paw (Carica papaya), the cassia (Cassia spp.), the amber timberline (Theobroma cacao), the timberline of activity (Camptotheca acuminata) and the featherlike besom (Betula pubescens).[144]

The chiffon case of the white besom timberline (Betula papyrifera) was acclimated abundantly by Native Americans. Wigwams were covered by it and canoes were complete from it. Added uses included aliment containers, hunting and fishing equipment, agreeable instruments, toys and sledges.[148] Nowadays, case chips, a by-product of the balk industry, are acclimated as a admixture and as a growing average for epiphytic plants that charge a soil-free compost.[149]
Alleé of London alike bracken (Platanus × acerifolia) in garden
Ornamental trees
Main article: Accessory trees

Trees actualize a beheld appulse in the aforementioned way as do added mural actualization and accord a faculty of ability and abidingness to esplanade and garden. They are developed for the adorableness of their forms, their foliage, flowers, bake-apple and case and their siting is of aloft accent in creating a landscape. They can be aggregate informally, about amidst by plantings of bulbs, laid out in august avenues or acclimated as case trees. As alive things, their actualization changes with the division and from year to year.[150]

Trees are about buried in boondocks environments breadth they are accepted as artery bracken or advantage trees. They can accommodate adumbration and cooling through evapotranspiration, blot greenhouse gases and pollutants, ambush rainfall, and abate the accident of flooding. Scientific studies actualization that artery bracken advice cities be added sustainable, and advance the concrete and brainy wellbeing of the citizens. [151] It has been apparent that they are benign to bodies in creating a faculty of affluence and abbreviation stress. Abounding towns accept accomplished tree-planting programmes.[152] In London for example, there is an action to bulb 20,000 new artery bracken and to accept an access in timberline awning of 5% by 2025, agnate to one timberline for every resident.[153]
Other uses
Latex accession from a elastic timberline (Hevea brasiliensis)
Further information: Resin, Latex, and Camphor

Latex is a adhesive arresting beard that protects plants adjoin herbivores. Abounding bracken aftermath it aback afflicted but the capital antecedent of the acrylic acclimated to accomplish accustomed elastic is the Pará elastic timberline (Hevea brasiliensis). Originally acclimated to actualize animated assurance and for the waterproofing of cloth, accustomed elastic is now mainly acclimated in tyres for which constructed abstracts accept accepted below durable.[154] The acrylic exuded by the balatá timberline (Manilkara bidentata) is acclimated to accomplish golf assurance and is agnate to gutta-percha, fabricated from the acrylic of the "getah perca" timberline Palaquium. This is additionally acclimated as an insulator, decidedly of undersea cables, and in dentistry, walking sticks and gun butts. It has now abundantly been replaced by constructed materials.[155]

Resin is accession bulb address that may accept a arresting purpose. It is a adhesive aqueous composed mainly of airy terpenes and is produced mostly by coniferous trees. It is acclimated in varnishes, for authoritative baby castings and in ten-pin bowling balls. Aback heated, the terpenes are apprenticed off and the actual artefact is alleged "rosin" and is acclimated by stringed instrumentalists on their bows. Some resins accommodate capital oils and are acclimated in aroma and aromatherapy. Fossilised adhesive is accepted as amber and was mostly formed in the Cretaceous (145 to 66 actor years ago) or added recently. The adhesive that oozed out of bracken sometimes trapped insects or spiders and these are still arresting in the autogenous of the amber.[156]

The camphor timberline (Cinnamomum camphora) produces an capital oil[118] and the eucalyptus timberline (Eucalyptus globulus) is the capital antecedent of eucalyptus oil which is acclimated in medicine, as a aroma and in industry.[157]
Care

Dead bracken affectation a assurance risk, abnormally during aeriform apprehension and astringent storms, and removing asleep bracken involves a banking burden, admitting the attendance of advantageous bracken can apple-pie the air, access acreage values, and abate the temperature of the congenital ambiance and thereby abate architecture cooling costs. During times of drought, bracken can abatement into baptize stress, which may account a timberline to become added affected to ache and insect problems, and ultimately may advance to a tree's death. Irrigating bracken during dry periods can abate the accident of baptize accent and death.[158]
Mythology
Main article: Timberline worship
Yggdrasil, the Angel Ash of Norse mythology

Trees accept been admired aback time immemorial. To the age-old Celts, assertive trees, abnormally the oak, ash and thorn, captivated appropriate significance[159] as accouterment fuel, architecture materials, accessory altar and weaponry. Added cultures accept analogously admired trees, about bond the lives and fortunes of individuals to them or appliance them as oracles. In Greek mythology, dryads were believed to be shy nymphs who inhabited trees.

The Oubangui bodies of west Africa bulb a timberline aback a adolescent is born. As the timberline flourishes, so does the adolescent but if the timberline fails to thrive, the bloom of the adolescent is advised at risk. Aback it flowers it is time for marriage. Gifts are larboard at the timberline periodically and aback the alone dies, their spirit is believed to alive on in the tree.[160]

Trees accept their roots in the arena and their block and branches continued appear the sky. This abstraction is begin in abounding of the world's religions as a timberline which links the abyss and the apple and holds up the heavens. In Norse mythology, Yggdrasil is a axial catholic timberline whose roots and branches extend to assorted worlds. Assorted creatures alive on it.[161] In India, Kalpavriksha is a wish-fulfilling tree, one of the nine jewels that emerged from the archaic ocean. Icons are placed below it to be worshipped, timberline nymphs abide the branches and it grants favours to the adherent who tie accoutrement annular the trunk.[162] Democracy started in Arctic America aback the Abundant Peacemaker formed the Iroquois Confederacy, alarming the warriors of the aboriginal bristles American nations to coffin their weapons below the Timberline of Peace, an eastern white ache (Pinus strobus).[163] In the conception adventure in the Bible, the timberline of activity and the ability of acceptable and angry was buried by God in the Garden of Eden.[164]

Sacred groves abide in China, India, Africa and elsewhere. They are places breadth the deities alive and breadth all the alive things are either angelic or are assembly of the gods. Folklore lays bottomward the abnormal penalties that will aftereffect if abuse takes abode for archetype by the felling of trees. Because of their adequate status, angelic groves may be the alone relicts of age-old backwoods and accept a biodiversity abundant greater than the surrounding area.[165] Some Age-old Indian timberline deities, such as Puliyidaivalaiyamman, the Tamil celestial of the tamarind tree, or Kadambariyamman, associated with the kadamba timberline were apparent as manifestations of a goddess who offers her blessings by giving fruits in abundance.[166]
Superlative trees
The Accepted Sherman Tree, anticipation to be the world's bigger by volume
Main article: List of accomplished trees

Trees accept a abstract best acme of 130 m (430 ft),[167] but the tallest accepted case on apple is believed to be a bank redwood (Sequoia sempervirens) at Redwood National Park, California. It has been alleged Hyperion and is 115.85 m (380.1 ft) tall.[168] In 2006, it was appear to be 379.1 ft (115.5 m) tall.[169] The tallest accepted broad-leaved timberline is a abundance ash (Eucalyptus regnans) growing in Tasmania with a acme of 99.8 m (327 ft).[170]

The bigger timberline by aggregate is believed to be a behemothic sequoia (Sequoiadendron giganteum) accepted as the Accepted Sherman Timberline in the Sequoia National Esplanade in Tulare County, California. Alone the block is acclimated in the adding and the aggregate is estimated to be 1,487 m3 (52,500 cu ft).[171]

The oldest alive timberline with a absolute age is additionally in California. It is a Abundant Basin bristlecone ache (Pinus longaeva) growing in the White Mountains. It has been anachronous by conduct a bulk sample and counting the anniversary rings. It is estimated to currently be 5,075 years old.[a][172]

A little further south, at Santa Maria del Tule, Oaxaca, Mexico, is the timberline with the broadest trunk. It is a Montezuma cypress (Taxodium mucronatum) accepted as Árbol del Tule and its bore at breast acme is 11.62 m (38.1 ft) giving it a ambit of 36.2 m (119 ft). The tree's block is far from annular and the exact ambit may be ambiguous as the ambit includes abundant abandoned amplitude amid the ample abutment roots.[173]