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[[Image:Drva.JPG|thumb|240px|Trunks]]
[[Image:VeluweTreeTrunk.jpg|thumb|240px|right|A tree trunk as found at the [[Veluwe]], [[The Netherlands]]]]'''Wood''' is a solid material derived from [[woody plant]]s, notably [[tree]]s but also [[shrub]]s. Wood from the latter is only produced in small sizes, reducing the diversity of uses.
In its most common meaning, "wood" is the secondary [[xylem]] of a woody plant, but this is an approximation only: in the wider sense, wood may refer to other materials and tissues with comparable properties.
Wood is a [[heterogeneous]], [[hygroscopic]], [[cellular]] and [[anisotropic]] material. Wood is composed of fibers of [[cellulose]] (40%–50%) and [[hemicellulose]] (15%–25%) held together by [[lignin]] (15%–30%).<ref>[http://www.extension.umn.edu/distribution/naturalresources/components/6413ch1.html Lesson 1: ''Tree Growth and Wood Material'' at University of Minnesota Extension] </ref>
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==Uses==
[[Image:Woodcarvings of cranes.jpg|left|thumb|[[Artist]]s can use wood to create delicate [[sculpture]]s.]]
[[Image:CIMG1460.jpg|thumb|240px|wrought pieces of wood ready for use]]
Wood has been used for millennia for many purposes. One of its primary uses is as [[fuel]]. It is also used as for making artworks, furniture, tools, and weapons, and as a [[construction]] material.
Wood has been an important [[construction]] material since humans began building shelters, houses, boats. Nearly all boats were made out of wood till the late 1800's. It remains in common use today for wooden boats and wooden houses. In buildings made of other materials, wood will still be found as a supporting material (notably in roof construction) or exterior decoration. Wood to be used for construction work is commonly known as ''lumber'' in [[North America]]. Elsewhere, ''[[lumber]]'' will usually refer to felled trees, and the word for sawn planks (etc) ready for use will be ''[[timber]]''.
Wood which in its native form is unsuitable for construction may be broken down mechanically (into fibres or chips) or chemically (into cellulose) and used as a raw material for other building materials such as [[particle board|chipboard]], [[engineered wood]], [[hardboard]], [[medium-density fibreboard]] (MDF), [[oriented strand board]] (OSB). Also, wood fibres are an important component of most [[paper]], and cellulose is used as a component of some [[Synthesis|synthetic]] materials.
It can also be used for kinds of flooring for example [[laminate flooring]]
==Formation==
A tree increases in [[diameter]] by the formation, between the old wood and the inner bark, of new woody layers which envelop the entire stem, living branches, and roots. Where there are clear seasons, this can happen in a discrete pattern, leading to what is known as [[Dendrochronology|growth rings]], as can be seen on the end of a log. If these seasons are annual these growth rings are annual rings. Where there is no seasonal difference growth rings are likely to be indistinct or absent.
Within a growth ring it may be possible to see two parts. The part nearest the center of the tree is more open [[texture]]d and almost invariably lighter in color than that near the outer portion of the ring. The inner portion is formed early in the season, when growth is comparatively rapid; it is known as '''early wood''' or '''spring wood'''. The outer portion is the '''late wood''' or '''summer wood''', being produced in the [[summer]].<ref>[http://www.farmforestline.com.au/pages/2.1.2.1_wood.html Wood growth and structure] www.farmforestline.com.au</ref> In [[Pinus classification|white pine]]s there is not much contrast in the different parts of the ring, and as a result the wood is very uniform in [[texture]] and is easy to work. In [[Pinus classification|hard pines]], on the other hand, the late wood is very dense and is deep-colored, presenting a very decided contrast to the soft, straw-colored early wood. In ring-porous woods each season's growth is always well defined, because the large pores of the spring abut on the denser tissue of the fall before. In the diffuse-porous woods, the demarcation between rings is not always so clear and in some cases is almost (if not entirely) invisible to the unaided eye.
===Knots===
[[Image:TreeKnot.jpg|thumb|240px|A knot on a tree at the [[Garden of the Gods]] public park in [[Colorado Springs]], [[Colorado]] (October 2006).]]
A knot is a particular type of imperfection in a piece of timber, which reduces its strength, but which may be exploited for artistic effect. In a longitudinally-sawn plank, a knot will appear as a roughly circular "solid" (usually darker) piece of wood around which the roughly parallel fibres ([[Wood grain|grain]]) of the rest of the "flows" (parts and rejoins).
A knot is actually a portion of a side [[branch]] (or a dormant bud) included in the wood of the stem or larger branch. The included portion is irregularly conical in shape (hence the roughly circular cross-section) with the tip at the point in stem diameter at which the plant's [[cambium]] was located when the branch formed as a bud. Within a knot, the fibre direction ([[Wood grain|grain]]) is up to 90 degrees different from the fibres of the stem, thus producing local cross grain.
During the development of a tree, the lower limbs often die, but may persist for a time, sometimes years. Subsequent layers of growth of the attaching stem are no longer intimately joined with the dead limb, but are grown around it. Hence, dead branches produce knots which are not attached, and likely to drop out after the tree has been sawn into boards.
In grading [[lumber]] and structural [[timber]], knots are classified according to their form, size, soundness, and the firmness with which they are held in place. This firmness is affected by, among other factors, the length of time for which the branch was dead while the attaching stem continued to grow.
Knots materially affect cracking (known in the industry as checking) and warping, ease in working, and cleavability of timber. They are defects which weaken timber and lower its value for structural purposes where strength is an important consideration. The weakening effect is much more serious when timber is subjected to forces perpendicular to the grain and/or [[tension (mechanics)|tension]] than where under load along the grain and/or [[physical compression|compression]]. The extent to which knots affect the strength of a [[Beam (structure)|beam]] depends upon their position, size, number, direction of [[fibre]], and condition. A knot on the upper side is compressed, while one on the lower side is subjected to tension. The knot, especially (as is often the case) if there is a season check in it, offers little resistance to this tensile stress. Small knots, however, may be so located in a beam along the neutral plane as actually to increase the strength by tending to prevent longitudinal [[shear stress|shearing]]. Knots in a board or plank are least injurious when they extend through it at right angles to its broadest surface. Knots which occur near the ends of a beam do not weaken it. Sound knots which occur in the central portion one-fourth the height of the beam from either edge are not serious defects.
Knots do not necessarily influence the stiffness of structural timber. Only defects of the most serious character affect the elastic limit of beams. Stiffness and elastic strength are more dependent upon the quality of the wood fibre than upon defects in the beam. The effect of knots is to reduce the difference between the fibre stress at elastic limit and the [[Young's modulus|modulus]] of rupture of beams. The breaking strength is very susceptible to defects. Sound knots do not weaken wood when subject to compression parallel to the [[Wood grain|grain]].
For purposes for which appearance is more important than strength, such as wall panelling, knots are considered a benefit, as they add visual texture to the wood, giving it a more interesting appearance.
The traditional style of playing the Basque xylophon ''[[txalaparta]]'' involves hitting the right knots to obtain different tones.
===Heartwood and sapwood===
[[Image:Taxus wood.jpg|300px|thumb|right|A section of a [[Taxus|Yew]] branch showing 27 annual growth rings, pale sapwood and dark heartwood, and [[pith]] (centre dark spot). The dark radial lines are small knots.]]
Heartwood is wood that, as a result of genetically programmed processes, has died and become resistant to decay. It appears in a cross-section as a discolored circle, following annual rings in shape. Heartwood is usually much darker than still living wood, and forms with age. Many woody plants do not form heartwood, but other processes, such as decay, can discolor wood in similar ways, leading to confusion. Some uncertainty still exists as to whether heartwood is truly dead, as it can still chemically react to decay organisms, but only once (Shigo 1986, 54).
Sapwood is living wood in the growing tree. All wood in a tree is first formed as sapwood. Its principal functions are to conduct water from the [[root]]s to the [[leaf|leaves]] and to store up and give back according to the season the food prepared in the leaves. The more leaves a tree bears and the more vigorous its growth, the larger the volume of sapwood required. Hence trees making rapid growth in the open have thicker sapwood for their size than trees of the same species growing in dense forests. Sometimes trees grown in the open may become of considerable size, 30 cm or more in diameter, before any heartwood begins to form, for example, in second-growth [[hickory]], or open-grown [[pine]]s.
As a tree increases in age and diameter an inner portion of the sapwood becomes inactive and finally ceases to function, as the cells die. This inert or dead portion is called heartwood. Its name derives solely from its position and not from any vital importance to the tree. This is shown by the fact that a tree can thrive with its heart completely decayed. Some species begin to form heartwood very early in life, so having only a thin layer of live sapwood, while in others the change comes slowly. Thin sapwood is characteristic of such trees as [[chestnut]], [[black locust]], [[mulberry]], [[osage-orange]], and [[sassafras]], while in [[maple]], [[Ash tree|ash]], [[hickory]], [[hackberry]], [[beech]], and [[pine]], thick sapwood is the rule.
There is no definite relation between the annual rings of growth and the amount of sapwood. Within the same species the cross-sectional area of the sapwood is very roughly proportional to the size of the crown of the tree. If the rings are narrow, more of them are required than where they are wide. As the tree gets larger, the sapwood must necessarily become thinner or increase materially in volume. Sapwood is thicker in the upper portion of the trunk of a tree than near the base, because the age and the diameter of the upper sections are less.
When a tree is very young it is covered with limbs almost, if not entirely, to the ground, but as it grows older some or all of them will eventually die and are either broken off or fall off. Subsequent growth of wood may completely conceal the stubs which will however remain as knots. No matter how smooth and clear a log is on the outside, it is more or less knotty near the middle. Consequently the sapwood of an old tree, and particularly of a forest-grown tree, will be freer from knots than the heartwood. Since in most uses of wood, knots are defects that weaken the timber and interfere with its ease of working and other properties, it follows that sapwood, because of its position in the tree, may have certain advantages over heartwood.
It is remarkable that the inner heartwood of old trees remains as sound as it usually does, since in many cases it is hundreds of years, and in a few instances thousands of years, old. Every broken limb or root, or deep wound from fire, insects, or falling timber, may afford an entrance for decay, which, once started, may penetrate to all parts of the trunk. The larvae of many insects bo
re into the trees and their tunnels remain indefinitely as sources of weakness. Whatever advantages, however, that sapwood may have in this connection are due solely to its relative age and position.
If a tree grows all its life in the open and the conditions of [[soil]] and site remain unchanged, it will make its most rapid growth in youth, and gradually decline. The annual rings of growth are for many years quite wide, but later they become narrower and narrower. Since each succeeding ring is laid down on the outside of the wood previously formed, it follows that unless a tree materially increases its production of wood from year to year, the rings must necessarily become thinner as the trunk gets wider. As a tree reaches maturity its crown becomes more open and the annual wood production is lessened, thereby reducing still more the width of the growth rings. In the case of forest-grown trees so much depends upon the competition of the trees in their struggle for light and nourishment that periods of rapid and slow growth may alternate. Some trees, such as southern [[oak]]s, maintain the same width of ring for hundreds of years. Upon the whole, however, as a tree gets larger in diameter the width of the growth rings decreases.
There may be decided differences in the [[Wood grain|grain]] of heartwood and sapwood cut from a large tree, particularly one that is mature. In some trees, the wood laid on late in the life of a tree is softer, lighter, weaker, and more even-textured than that produced earlier, but in other species, the reverse applies. In a large log the sapwood, because of the time in the life of the tree when it was grown, may be inferior in [[hardness]], [[Strength of materials|strength]], and toughness to equally sound heartwood from the same log.
==Different woods==
There is a strong relationship between the properties of wood and the properties of the particular tree that yielded it. For every trees species there is a range of density for the wood it yields. There is a rough correlation between density of a wood and its strength (mechanical properties). For example, while [[mahogany]] is a medium-dense hardwood which is excellent for fine furniture crafting, [[balsa]] is light, making it useful for [[model (physical)|model]] building. The densest wood may be [[Black Ironwood|black ironwood]].
Wood is commonly classified as either [[softwood]] or [[hardwood]]. The wood from [[conifer]]s (e.g. [[pine]]) is called softwood, and the wood from [[angiosperm|broad-leaved trees]] (e.g. [[oak]]) is called hardwood. These names are a bit misleading, as hardwoods are not necessarily hard, and softwoods are not necessarily soft. The well-known [[balsa]] (a hardwood) is actually softer than any commercial softwood. Conversely, some softwoods (e.g. [[Taxus baccata|yew]]) are harder than most hardwoods.
Wood products such as [[plywood]] are typically classified as [[engineered wood]] and not considered raw wood.
===Color===
In species which show a distinct difference between heartwood and sapwood the natural color of heartwood is usually darker than that of the sapwood, and very frequently the contrast is conspicuous. This is produced by deposits in the heartwood of various materials resulting from the process of growth, increased possibly by [[oxidation]] and other chemical changes, which usually have little or no appreciable effect on the mechanical properties of the wood. Some experiments on very resinous [[Longleaf Pine]] specimens, however, indicate an increase in strength. This is due to the [[resin]] which increases the strength when dry. Such resin-saturated heartwood is called "fat lighter". Structures built of fat lighter are almost impervious to rot and termites; however they are very flammable. Stumps of old longleaf pines are often dug, split into small pieces and sold as kindling for fires. Stumps thus dug may actually remain a century or more since being cut. [[Spruce]] impregnated with crude resin and dried is also greatly increased in strength thereby.
[[Image:Sequoia wood.jpg|300px|left|thumb|Th
e wood of [[Coast Redwood]] is distinctively red in colour]]
Since the late wood of a growth ring is usually darker in color than the early wood, this fact may be used in judging the density, and therefore the hardness and strength of the material. This is particularly the case with coniferous woods. In ring-porous woods the vessels of the early wood not infrequently appear on a finished surface as darker than the denser late wood, though on cross sections of heartwood the reverse is commonly true. Except in the manner just stated the color of wood is no indication of strength.
Abnormal discoloration of wood often denotes a diseased condition, indicating unsoundness. The black check in western [[Tsuga|hemlock]] is the result of insect attacks. The reddish-brown streaks so common in [[hickory]] and certain other woods are mostly the result of injury by birds. The discoloration is merely an indication of an injury, and in all probability does not of itself affect the properties of the wood. Certain rot-producing [[fungus|fungi]] impart to wood characteristic colors which thus become symptomatic of weakness; however an attractive effect known as [[spalting]] produced by this process is often considered a desirable characteristic. Ordinary sap-staining is due to fungous growth, but does not necessarily produce a weakening effect.
===Structure===
In [[conifer]]ous or [[softwood]] species the wood cells are mostly of one kind, [[tracheid]]s, and as a result the material is much more uniform in structure than that of most [[hardwood]]s. There are no [[phloem|vessel]]s ("pores") in coniferous wood such as one sees so prominently in [[oak]] and [[Ash tree|ash]], for example.
[[Image:BlkWalnut-x-section.jpg|left|thumb|Magnified cross-section of a diffuse-porous hardwood wood ([[Black Walnut]]), showing the vessels, rays (white lines) and annual rings]]
The structure of the hardwoods is more complex.<ref>[http://www.uwsp.edu/papersci/biasca/ps350/Hardwood%20Structure.htm Hardwood Structure] www.uwsp.edu</ref> They are more or less filled with vessels: in some cases ([[oak]], [[chestnut]], [[Ash tree|ash]]) quite large and distinct, in others ([[buckeye]], [[poplar]], [[willow]]) too small to be seen plainly without a small hand lens. In discussing such woods it is customary to divide them into two large classes, ''ring-porous'' and ''diffuse-porous''. In ring-porous species, such as [[Ash tree|ash]], [[black locust]], [[catalpa]], [[chestnut]], [[elm]], [[hickory]], [[mulberry]], and [[oak]], the larger vessels or pores (as cross sections of vessels are called) are localized in the part of the growth ring formed in spring, thus forming a region of more or less open and porous tissue. The rest of the ring, produced in summer, is made up of smaller vessels and a much greater proportion of wood fibres. These fibres are the elements which give strength and toughness to wood, while the vessels are a source of weakness.
In diffuse-porous woods the pores are scattered throughout the growth ring instead of being collected in a band or row. Examples of this kind of wood are [[basswood]], [[birch]], [[buckeye]], [[maple]], [[poplar]], and [[willow]]. Some species, such as [[walnut]] and [[cherry]], are on the border between the two classes, forming an intermediate group.
If a heavy piece of pine is compared with a light specimen it will be seen at once that the heavier one contains a larger proportion of late wood than the other, and is therefore considerably darker. The late wood of all species is denser than that formed early in the season, hence the greater the proportion of late wood the greater the density and strength. When examined under a microscope the cells of the late wood are seen to be very thick-walled and with very small cavities, while those formed first in the season have thin walls and large cavities. The strength is in the walls, not the cavities. In choosing a piece of pine where strength or stiffness is the important consideration, the principal thing to observe is the comparative amounts of early and late wood. The width of ring is not nearly so important as the proportion of the late wood in the ring.
[[Image:LightningVolt Wood Floor.jpg|thumb|right|Wood can be cut into straight planks and made into a [[hardwood]] [[floor]] ([[parquetry]]).]]
It is not only the proportion of late wood, but also its quality, that counts. In specimens that show a very large proportion of late wood it may be noticeably more porous and weigh considerably less than the late wood in pieces that contain but little. One can judge comparative density, and therefore to some extent weight and strength, by visual inspection.
[[Image:LightningVolt Twisting Branch Lilac tree.jpg|thumb|250px|left|The twisty branch of a [[Lilac]] tree]]
No satisfactory explanation can as yet be given for the real causes underlying the formation of early and late wood. Several factors may be involved. In conifers, at least, rate of growth alone does not determine the proportion of the two portions of the ring, for in some cases the wood of slow growth is very hard and heavy, while in others the opposite is true. The quality of the site where the tree grows undoubtedly affects the character of the wood formed, though it is not possible to formulate a rule governing it. In general, however, it may be said that where strength or ease of working is essential, woods of moderate to slow growth should be chosen. But in choosing a particular specimen it is not the width of ring, but the proportion and character of the late wood which should govern.
In the case of the ring-porous hardwoods there seems to exist a pretty definite relation between the rate of growth of timber and its properties. This may be briefly summed up in the general statement that the more rapid the growth or the wider the rings of growth, the heavier, harder, stronger, and stiffer the wood. This, it must be remembered, applies only to ring-porous woods such as oak, ash, hickory, and others of the same group, and is, of course, subject to some exceptions and limitations.
In ring-porous woods of good growth it is usually the middle portion of the ring in which the thick-walled, strength-giving fibres are most abundant. As the breadth of ring diminishes, this middle portion is reduced so that very slow growth produces comparatively light, porous wood composed of thin-walled vessels and wood parenchyma. In good oak these large vessels of the early wood occupy from 6 to 10 per cent of the volume of the log, while in inferior material they may make up 25 per cent or more. The late wood of good oak, except for [[radial]] grayish patches of small pores, is dark colored and firm, and consists of thick-walled fibres which form one-half or more of the wood. In inferior oak, such fibre areas are much reduced both in quantity and quality. Such variation is very largely the result of rate of growth.
Wide-ringed wood is often called "second-growth", because the growth of the young timber in open stands after the old trees have been removed is more rapid than in trees in the [[forest]], and in the manufacture of articles where strength is an important consideration such "second-growth" hardwood material is preferred. This is particularly the case in the choice of hickory for handles and [[spoke]]s. Here not only strength, but toughness and resilience are important. The results of a series of tests on hickory by the U.S. Forest Service show that:
:"The work or shock-resisting ability is greatest in wide-ringed wood that has from 5 to 14 rings per [[inch]] (rings 1.8-5 [[millimetre|mm]] thick), is fairly constant from 14 to 38 rings per inch (rings 0.7-1.8 mm thick), and decreases rapidly from 38 to 47 rings per inch (rings 0.5-0.7 mm thick). The strength at maximum load is not so great with the most rapid-growing wood; it is maximum with from 14 to 20 rings per inch (rings 1.3-1.8 mm thick), and again becomes less as the wood becomes more closely ringed. The natural deduction is that wood of first-class mechanical value shows from 5 to 20 rings per inch (rings 1.3-5 mm thick) and that slower growth yields poorer stock. Thus the
inspector or buyer of hickory should discriminate against timber that has more than 20 rings per inch (rings less than 1.3 mm thick). Exceptions exist, however, in the case of normal growth upon dry situations, in which the slow-growing material may be strong and tough."<ref name=USforest>U.S. Department of Agriculture, Forest Products Laboratory. ''[http://www.fpl.fs.fed.us/documn/ts/fplgtr/fplgtr113/fplgtr113.htm The Wood Handbook: Wood as an engineering material]''. General Technical Report 113. Madison, WI.</ref>
The effect of rate of growth on the qualities of chestnut wood is summarized by the same authority as follows:
:"When the rings are wide, the transition from spring wood to summer wood is gradual, while in the narrow rings the spring wood passes into summer wood abruptly. The width of the spring wood changes but little with the width of the annual ring, so that the narrowing or broadening of the annual ring is always at the expense of the summer wood. The narrow vessels of the summer wood make it richer in wood substance than the spring wood composed of wide vessels. Therefore, rapid-growing specimens with wide rings have more wood substance than slow-growing trees with narrow rings. Since the more the wood substance the greater the weight, and the greater the weight the stronger the wood, chestnuts with wide rings must have stronger wood than chestnuts with narrow rings. This agrees with the accepted view that sprouts (which always have wide rings) yield better and stronger wood than seedling chestnuts, which grow more slowly in diameter."<ref name=USforest/>
In diffuse-porous woods, as has been stated, the vessels or pores are scattered throughout the ring instead of collected in the early wood. The effect of rate of growth is, therefore, not the same as in the ring-porous woods, approaching more nearly the conditions in the [[conifer]]s. In general it may be stated that such woods of medium growth afford stronger material than when very rapidly or very slowly grown. In many uses of wood, strength is not the main consideration. If ease of working is prized, wood should be chosen with regard to its uniformity of texture and straightness of [[Wood grain|grain]], which will in most cases occur when there is little contrast between the late wood of one season's growth and the early wood of the next.
===Monocot wood===
Structural tissue resembling ordinary 'dicot' wood is produced by a number of [[monocot]] plants, and these are also usually called wood. Of these, the wood of [[bamboo]] has considerable economic importance. Other plant groups that produce woody tissue are [[palm]]s, and members of the [[Liliales]], such as [[Dracaena]] and [[Cordyline]]. With all these woods, the structure and compositon of the structural tissue is quite different from ordinary wood.
==Water content==
[[Water]] occurs in living wood in three conditions, namely: (1) in the [[cell wall]]s, (2) in the [[protoplasm]]ic contents of the [[Cell (biology)|cells]], and (3) as free water in the cell cavities and spaces. In heartwood it occurs only in the first and last forms. Wood that is thoroughly air-dried retains from 8-16% of water in the cell walls, and none, or practically none, in the other forms. Even oven-dried wood retains a small percentage of moisture, but for all except chemical purposes, may be considered absolutely dry.
The general effect of the water content upon the wood substance is to render it softer and more pliable. A similar effect of common observation is in the softening action of water on [[paper]] or [[cloth]]. Within certain limits the greater the water content the greater its softening effect.
Drying produces a decided increase in the strength of wood, particularly in small specimens. An extreme example is the case of a completely dry [[spruce]] block 5 cm in section, which will sustain a permanent load four times as great as that which a green block of the same size will support.
The greatest increase due to drying is in the ultimate crushing strength, and strength at [[elastic limit]] in endwise
compression; these are followed by the modulus of rupture, and stress at elastic limit in cross-bending, while the [[modulus of elasticity]] is least affected.
==See also==
[[Image:Wooden Miracle Kizhi.jpg|thumb|right|275px|The churches of [[Kizhi]], [[Russia]] are among a handful of [[World Heritage Site]]s built entirely of wood, without metal joints.]]
{{wiktionary}}
* [[Tree]]
* [[List of woods]]
* [[Forest]]
* [[Forestry]]
* [[Woodworm]]
* [[Wood plastic composite]]
* [[Bamboo]]
* [[Engineered wood]]
* [[Wood as a medium]]
* [[Plywood]]
* [[Wood drying]]
* [[Wood warping]]
* [[Timber]]
* [[Lumber]]
* [[Xiloteque]]
* [[Driftwood]]
<br>
<br>
==References==
{{reflist}}
* Hoadley, R. Bruce. (2000) ''Understanding Wood: A Craftsman’s Guide to Wood Technology''. Taunton Press. ISBN 1-56158-358-8
* Shigo, Alex. (1986) ''A New Tree Biology Dictionary''. Shigo and Trees, Associates. ISBN 0-943563-12-7
==External links==
{{Commonscat|Wood}}
* [http://www.awc.org American Wood Council], wood as construction material
* [http://www.australianhardwood.net Australian Hardwood & Cypress Manual]
* [http://www.woodcollectors.org International Wood Collectors Society]
* [http://www.mayang.com/textures/Wood/html/Flat%20Wood%20Textures/ Mayang textures - wood] (many wood closeup pictures)
* [http://www.trada.co.uk/ TRADA: Timber Research And Development Association]
* [http://www.fpl.fs.fed.us/ US Forest Service, Forest Products Laboratory]
* [http://wood.rleeden.no-ip.com Wood Identification Website]
* [http://www.sankey.ws/wetwood.html Wood moisture]
* [http://www.xiloteca.com Xiloteca Manuel Soler] (One of the largest private collection of wood samples)
* [http://www.matbase.com/material/wood/ Matbase: Environmental, Mechanical and Physical Properties of Wood Types]
[[Category:Forestry]]
[[Category:Wood| ]]
[[Image:VeluweTreeTrunk.jpg|thumb|240px|right|A tree trunk as found at the [[Veluwe]], [[The Netherlands]]]]'''Wood''' is a solid material derived from [[woody plant]]s, notably [[tree]]s but also [[shrub]]s. Wood from the latter is only produced in small sizes, reducing the diversity of uses.
In its most common meaning, "wood" is the secondary [[xylem]] of a woody plant, but this is an approximation only: in the wider sense, wood may refer to other materials and tissues with comparable properties.
Wood is a [[heterogeneous]], [[hygroscopic]], [[cellular]] and [[anisotropic]] material. Wood is composed of fibers of [[cellulose]] (40%–50%) and [[hemicellulose]] (15%–25%) held together by [[lignin]] (15%–30%).<ref>[http://www.extension.umn.edu/distribution/naturalresources/components/6413ch1.html Lesson 1: ''Tree Growth and Wood Material'' at University of Minnesota Extension] </ref>
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==Uses==
[[Image:Woodcarvings of cranes.jpg|left|thumb|[[Artist]]s can use wood to create delicate [[sculpture]]s.]]
[[Image:CIMG1460.jpg|thumb|240px|wrought pieces of wood ready for use]]
Wood has been used for millennia for many purposes. One of its primary uses is as [[fuel]]. It is also used as for making artworks, furniture, tools, and weapons, and as a [[construction]] material.
Wood has been an important [[construction]] material since humans began building shelters, houses, boats. Nearly all boats were made out of wood till the late 1800's. It remains in common use today for wooden boats and wooden houses. In buildings made of other materials, wood will still be found as a supporting material (notably in roof construction) or exterior decoration. Wood to be used for construction work is commonly known as ''lumber'' in [[North America]]. Elsewhere, ''[[lumber]]'' will usually refer to felled trees, and the word for sawn planks (etc) ready for use will be ''[[timber]]''.
Wood which in its native form is unsuitable for construction may be broken down mechanically (into fibres or chips) or chemically (into cellulose) and used as a raw material for other building materials such as [[particle board|chipboard]], [[engineered wood]], [[hardboard]], [[medium-density fibreboard]] (MDF), [[oriented strand board]] (OSB). Also, wood fibres are an important component of most [[paper]], and cellulose is used as a component of some [[Synthesis|synthetic]] materials.
It can also be used for kinds of flooring for example [[laminate flooring]]
==Formation==
A tree increases in [[diameter]] by the formation, between the old wood and the inner bark, of new woody layers which envelop the entire stem, living branches, and roots. Where there are clear seasons, this can happen in a discrete pattern, leading to what is known as [[Dendrochronology|growth rings]], as can be seen on the end of a log. If these seasons are annual these growth rings are annual rings. Where there is no seasonal difference growth rings are likely to be indistinct or absent.
Within a growth ring it may be possible to see two parts. The part nearest the center of the tree is more open [[texture]]d and almost invariably lighter in color than that near the outer portion of the ring. The inner portion is formed early in the season, when growth is comparatively rapid; it is known as '''early wood''' or '''spring wood'''. The outer portion is the '''late wood''' or '''summer wood''', being produced in the [[summer]].<ref>[http://www.farmforestline.com.au/pages/2.1.2.1_wood.html Wood growth and structure] www.farmforestline.com.au</ref> In [[Pinus classification|white pine]]s there is not much contrast in the different parts of the ring, and as a result the wood is very uniform in [[texture]] and is easy to work. In [[Pinus classification|hard pines]], on the other hand, the late wood is very dense and is deep-colored, presenting a very decided contrast to the soft, straw-colored early wood. In ring-porous woods each season's growth is always well defined, because the large pores of the spring abut on the denser tissue of the fall before. In the diffuse-porous woods, the demarcation between rings is not always so clear and in some cases is almost (if not entirely) invisible to the unaided eye.
===Knots===
[[Image:TreeKnot.jpg|thumb|240px|A knot on a tree at the [[Garden of the Gods]] public park in [[Colorado Springs]], [[Colorado]] (October 2006).]]
A knot is a particular type of imperfection in a piece of timber, which reduces its strength, but which may be exploited for artistic effect. In a longitudinally-sawn plank, a knot will appear as a roughly circular "solid" (usually darker) piece of wood around which the roughly parallel fibres ([[Wood grain|grain]]) of the rest of the "flows" (parts and rejoins).
A knot is actually a portion of a side [[branch]] (or a dormant bud) included in the wood of the stem or larger branch. The included portion is irregularly conical in shape (hence the roughly circular cross-section) with the tip at the point in stem diameter at which the plant's [[cambium]] was located when the branch formed as a bud. Within a knot, the fibre direction ([[Wood grain|grain]]) is up to 90 degrees different from the fibres of the stem, thus producing local cross grain.
During the development of a tree, the lower limbs often die, but may persist for a time, sometimes years. Subsequent layers of growth of the attaching stem are no longer intimately joined with the dead limb, but are grown around it. Hence, dead branches produce knots which are not attached, and likely to drop out after the tree has been sawn into boards.
In grading [[lumber]] and structural [[timber]], knots are classified according to their form, size, soundness, and the firmness with which they are held in place. This firmness is affected by, among other factors, the length of time for which the branch was dead while the attaching stem continued to grow.
Knots materially affect cracking (known in the industry as checking) and warping, ease in working, and cleavability of timber. They are defects which weaken timber and lower its value for structural purposes where strength is an important consideration. The weakening effect is much more serious when timber is subjected to forces perpendicular to the grain and/or [[tension (mechanics)|tension]] than where under load along the grain and/or [[physical compression|compression]]. The extent to which knots affect the strength of a [[Beam (structure)|beam]] depends upon their position, size, number, direction of [[fibre]], and condition. A knot on the upper side is compressed, while one on the lower side is subjected to tension. The knot, especially (as is often the case) if there is a season check in it, offers little resistance to this tensile stress. Small knots, however, may be so located in a beam along the neutral plane as actually to increase the strength by tending to prevent longitudinal [[shear stress|shearing]]. Knots in a board or plank are least injurious when they extend through it at right angles to its broadest surface. Knots which occur near the ends of a beam do not weaken it. Sound knots which occur in the central portion one-fourth the height of the beam from either edge are not serious defects.
Knots do not necessarily influence the stiffness of structural timber. Only defects of the most serious character affect the elastic limit of beams. Stiffness and elastic strength are more dependent upon the quality of the wood fibre than upon defects in the beam. The effect of knots is to reduce the difference between the fibre stress at elastic limit and the [[Young's modulus|modulus]] of rupture of beams. The breaking strength is very susceptible to defects. Sound knots do not weaken wood when subject to compression parallel to the [[Wood grain|grain]].
For purposes for which appearance is more important than strength, such as wall panelling, knots are considered a benefit, as they add visual texture to the wood, giving it a more interesting appearance.
The traditional style of playing the Basque xylophon ''[[txalaparta]]'' involves hitting the right knots to obtain different tones.
===Heartwood and sapwood===
[[Image:Taxus wood.jpg|300px|thumb|right|A section of a [[Taxus|Yew]] branch showing 27 annual growth rings, pale sapwood and dark heartwood, and [[pith]] (centre dark spot). The dark radial lines are small knots.]]
Heartwood is wood that, as a result of genetically programmed processes, has died and become resistant to decay. It appears in a cross-section as a discolored circle, following annual rings in shape. Heartwood is usually much darker than still living wood, and forms with age. Many woody plants do not form heartwood, but other processes, such as decay, can discolor wood in similar ways, leading to confusion. Some uncertainty still exists as to whether heartwood is truly dead, as it can still chemically react to decay organisms, but only once (Shigo 1986, 54).
Sapwood is living wood in the growing tree. All wood in a tree is first formed as sapwood. Its principal functions are to conduct water from the [[root]]s to the [[leaf|leaves]] and to store up and give back according to the season the food prepared in the leaves. The more leaves a tree bears and the more vigorous its growth, the larger the volume of sapwood required. Hence trees making rapid growth in the open have thicker sapwood for their size than trees of the same species growing in dense forests. Sometimes trees grown in the open may become of considerable size, 30 cm or more in diameter, before any heartwood begins to form, for example, in second-growth [[hickory]], or open-grown [[pine]]s.
As a tree increases in age and diameter an inner portion of the sapwood becomes inactive and finally ceases to function, as the cells die. This inert or dead portion is called heartwood. Its name derives solely from its position and not from any vital importance to the tree. This is shown by the fact that a tree can thrive with its heart completely decayed. Some species begin to form heartwood very early in life, so having only a thin layer of live sapwood, while in others the change comes slowly. Thin sapwood is characteristic of such trees as [[chestnut]], [[black locust]], [[mulberry]], [[osage-orange]], and [[sassafras]], while in [[maple]], [[Ash tree|ash]], [[hickory]], [[hackberry]], [[beech]], and [[pine]], thick sapwood is the rule.
There is no definite relation between the annual rings of growth and the amount of sapwood. Within the same species the cross-sectional area of the sapwood is very roughly proportional to the size of the crown of the tree. If the rings are narrow, more of them are required than where they are wide. As the tree gets larger, the sapwood must necessarily become thinner or increase materially in volume. Sapwood is thicker in the upper portion of the trunk of a tree than near the base, because the age and the diameter of the upper sections are less.
When a tree is very young it is covered with limbs almost, if not entirely, to the ground, but as it grows older some or all of them will eventually die and are either broken off or fall off. Subsequent growth of wood may completely conceal the stubs which will however remain as knots. No matter how smooth and clear a log is on the outside, it is more or less knotty near the middle. Consequently the sapwood of an old tree, and particularly of a forest-grown tree, will be freer from knots than the heartwood. Since in most uses of wood, knots are defects that weaken the timber and interfere with its ease of working and other properties, it follows that sapwood, because of its position in the tree, may have certain advantages over heartwood.
It is remarkable that the inner heartwood of old trees remains as sound as it usually does, since in many cases it is hundreds of years, and in a few instances thousands of years, old. Every broken limb or root, or deep wound from fire, insects, or falling timber, may afford an entrance for decay, which, once started, may penetrate to all parts of the trunk. The larvae of many insects bo
re into the trees and their tunnels remain indefinitely as sources of weakness. Whatever advantages, however, that sapwood may have in this connection are due solely to its relative age and position.
If a tree grows all its life in the open and the conditions of [[soil]] and site remain unchanged, it will make its most rapid growth in youth, and gradually decline. The annual rings of growth are for many years quite wide, but later they become narrower and narrower. Since each succeeding ring is laid down on the outside of the wood previously formed, it follows that unless a tree materially increases its production of wood from year to year, the rings must necessarily become thinner as the trunk gets wider. As a tree reaches maturity its crown becomes more open and the annual wood production is lessened, thereby reducing still more the width of the growth rings. In the case of forest-grown trees so much depends upon the competition of the trees in their struggle for light and nourishment that periods of rapid and slow growth may alternate. Some trees, such as southern [[oak]]s, maintain the same width of ring for hundreds of years. Upon the whole, however, as a tree gets larger in diameter the width of the growth rings decreases.
There may be decided differences in the [[Wood grain|grain]] of heartwood and sapwood cut from a large tree, particularly one that is mature. In some trees, the wood laid on late in the life of a tree is softer, lighter, weaker, and more even-textured than that produced earlier, but in other species, the reverse applies. In a large log the sapwood, because of the time in the life of the tree when it was grown, may be inferior in [[hardness]], [[Strength of materials|strength]], and toughness to equally sound heartwood from the same log.
==Different woods==
There is a strong relationship between the properties of wood and the properties of the particular tree that yielded it. For every trees species there is a range of density for the wood it yields. There is a rough correlation between density of a wood and its strength (mechanical properties). For example, while [[mahogany]] is a medium-dense hardwood which is excellent for fine furniture crafting, [[balsa]] is light, making it useful for [[model (physical)|model]] building. The densest wood may be [[Black Ironwood|black ironwood]].
Wood is commonly classified as either [[softwood]] or [[hardwood]]. The wood from [[conifer]]s (e.g. [[pine]]) is called softwood, and the wood from [[angiosperm|broad-leaved trees]] (e.g. [[oak]]) is called hardwood. These names are a bit misleading, as hardwoods are not necessarily hard, and softwoods are not necessarily soft. The well-known [[balsa]] (a hardwood) is actually softer than any commercial softwood. Conversely, some softwoods (e.g. [[Taxus baccata|yew]]) are harder than most hardwoods.
Wood products such as [[plywood]] are typically classified as [[engineered wood]] and not considered raw wood.
===Color===
In species which show a distinct difference between heartwood and sapwood the natural color of heartwood is usually darker than that of the sapwood, and very frequently the contrast is conspicuous. This is produced by deposits in the heartwood of various materials resulting from the process of growth, increased possibly by [[oxidation]] and other chemical changes, which usually have little or no appreciable effect on the mechanical properties of the wood. Some experiments on very resinous [[Longleaf Pine]] specimens, however, indicate an increase in strength. This is due to the [[resin]] which increases the strength when dry. Such resin-saturated heartwood is called "fat lighter". Structures built of fat lighter are almost impervious to rot and termites; however they are very flammable. Stumps of old longleaf pines are often dug, split into small pieces and sold as kindling for fires. Stumps thus dug may actually remain a century or more since being cut. [[Spruce]] impregnated with crude resin and dried is also greatly increased in strength thereby.
[[Image:Sequoia wood.jpg|300px|left|thumb|Th
e wood of [[Coast Redwood]] is distinctively red in colour]]
Since the late wood of a growth ring is usually darker in color than the early wood, this fact may be used in judging the density, and therefore the hardness and strength of the material. This is particularly the case with coniferous woods. In ring-porous woods the vessels of the early wood not infrequently appear on a finished surface as darker than the denser late wood, though on cross sections of heartwood the reverse is commonly true. Except in the manner just stated the color of wood is no indication of strength.
Abnormal discoloration of wood often denotes a diseased condition, indicating unsoundness. The black check in western [[Tsuga|hemlock]] is the result of insect attacks. The reddish-brown streaks so common in [[hickory]] and certain other woods are mostly the result of injury by birds. The discoloration is merely an indication of an injury, and in all probability does not of itself affect the properties of the wood. Certain rot-producing [[fungus|fungi]] impart to wood characteristic colors which thus become symptomatic of weakness; however an attractive effect known as [[spalting]] produced by this process is often considered a desirable characteristic. Ordinary sap-staining is due to fungous growth, but does not necessarily produce a weakening effect.
===Structure===
In [[conifer]]ous or [[softwood]] species the wood cells are mostly of one kind, [[tracheid]]s, and as a result the material is much more uniform in structure than that of most [[hardwood]]s. There are no [[phloem|vessel]]s ("pores") in coniferous wood such as one sees so prominently in [[oak]] and [[Ash tree|ash]], for example.
[[Image:BlkWalnut-x-section.jpg|left|thumb|Magnified cross-section of a diffuse-porous hardwood wood ([[Black Walnut]]), showing the vessels, rays (white lines) and annual rings]]
The structure of the hardwoods is more complex.<ref>[http://www.uwsp.edu/papersci/biasca/ps350/Hardwood%20Structure.htm Hardwood Structure] www.uwsp.edu</ref> They are more or less filled with vessels: in some cases ([[oak]], [[chestnut]], [[Ash tree|ash]]) quite large and distinct, in others ([[buckeye]], [[poplar]], [[willow]]) too small to be seen plainly without a small hand lens. In discussing such woods it is customary to divide them into two large classes, ''ring-porous'' and ''diffuse-porous''. In ring-porous species, such as [[Ash tree|ash]], [[black locust]], [[catalpa]], [[chestnut]], [[elm]], [[hickory]], [[mulberry]], and [[oak]], the larger vessels or pores (as cross sections of vessels are called) are localized in the part of the growth ring formed in spring, thus forming a region of more or less open and porous tissue. The rest of the ring, produced in summer, is made up of smaller vessels and a much greater proportion of wood fibres. These fibres are the elements which give strength and toughness to wood, while the vessels are a source of weakness.
In diffuse-porous woods the pores are scattered throughout the growth ring instead of being collected in a band or row. Examples of this kind of wood are [[basswood]], [[birch]], [[buckeye]], [[maple]], [[poplar]], and [[willow]]. Some species, such as [[walnut]] and [[cherry]], are on the border between the two classes, forming an intermediate group.
If a heavy piece of pine is compared with a light specimen it will be seen at once that the heavier one contains a larger proportion of late wood than the other, and is therefore considerably darker. The late wood of all species is denser than that formed early in the season, hence the greater the proportion of late wood the greater the density and strength. When examined under a microscope the cells of the late wood are seen to be very thick-walled and with very small cavities, while those formed first in the season have thin walls and large cavities. The strength is in the walls, not the cavities. In choosing a piece of pine where strength or stiffness is the important consideration, the principal thing to observe is the comparative amounts of early and late wood. The width of ring is not nearly so important as the proportion of the late wood in the ring.
[[Image:LightningVolt Wood Floor.jpg|thumb|right|Wood can be cut into straight planks and made into a [[hardwood]] [[floor]] ([[parquetry]]).]]
It is not only the proportion of late wood, but also its quality, that counts. In specimens that show a very large proportion of late wood it may be noticeably more porous and weigh considerably less than the late wood in pieces that contain but little. One can judge comparative density, and therefore to some extent weight and strength, by visual inspection.
[[Image:LightningVolt Twisting Branch Lilac tree.jpg|thumb|250px|left|The twisty branch of a [[Lilac]] tree]]
No satisfactory explanation can as yet be given for the real causes underlying the formation of early and late wood. Several factors may be involved. In conifers, at least, rate of growth alone does not determine the proportion of the two portions of the ring, for in some cases the wood of slow growth is very hard and heavy, while in others the opposite is true. The quality of the site where the tree grows undoubtedly affects the character of the wood formed, though it is not possible to formulate a rule governing it. In general, however, it may be said that where strength or ease of working is essential, woods of moderate to slow growth should be chosen. But in choosing a particular specimen it is not the width of ring, but the proportion and character of the late wood which should govern.
In the case of the ring-porous hardwoods there seems to exist a pretty definite relation between the rate of growth of timber and its properties. This may be briefly summed up in the general statement that the more rapid the growth or the wider the rings of growth, the heavier, harder, stronger, and stiffer the wood. This, it must be remembered, applies only to ring-porous woods such as oak, ash, hickory, and others of the same group, and is, of course, subject to some exceptions and limitations.
In ring-porous woods of good growth it is usually the middle portion of the ring in which the thick-walled, strength-giving fibres are most abundant. As the breadth of ring diminishes, this middle portion is reduced so that very slow growth produces comparatively light, porous wood composed of thin-walled vessels and wood parenchyma. In good oak these large vessels of the early wood occupy from 6 to 10 per cent of the volume of the log, while in inferior material they may make up 25 per cent or more. The late wood of good oak, except for [[radial]] grayish patches of small pores, is dark colored and firm, and consists of thick-walled fibres which form one-half or more of the wood. In inferior oak, such fibre areas are much reduced both in quantity and quality. Such variation is very largely the result of rate of growth.
Wide-ringed wood is often called "second-growth", because the growth of the young timber in open stands after the old trees have been removed is more rapid than in trees in the [[forest]], and in the manufacture of articles where strength is an important consideration such "second-growth" hardwood material is preferred. This is particularly the case in the choice of hickory for handles and [[spoke]]s. Here not only strength, but toughness and resilience are important. The results of a series of tests on hickory by the U.S. Forest Service show that:
:"The work or shock-resisting ability is greatest in wide-ringed wood that has from 5 to 14 rings per [[inch]] (rings 1.8-5 [[millimetre|mm]] thick), is fairly constant from 14 to 38 rings per inch (rings 0.7-1.8 mm thick), and decreases rapidly from 38 to 47 rings per inch (rings 0.5-0.7 mm thick). The strength at maximum load is not so great with the most rapid-growing wood; it is maximum with from 14 to 20 rings per inch (rings 1.3-1.8 mm thick), and again becomes less as the wood becomes more closely ringed. The natural deduction is that wood of first-class mechanical value shows from 5 to 20 rings per inch (rings 1.3-5 mm thick) and that slower growth yields poorer stock. Thus the
inspector or buyer of hickory should discriminate against timber that has more than 20 rings per inch (rings less than 1.3 mm thick). Exceptions exist, however, in the case of normal growth upon dry situations, in which the slow-growing material may be strong and tough."<ref name=USforest>U.S. Department of Agriculture, Forest Products Laboratory. ''[http://www.fpl.fs.fed.us/documn/ts/fplgtr/fplgtr113/fplgtr113.htm The Wood Handbook: Wood as an engineering material]''. General Technical Report 113. Madison, WI.</ref>
The effect of rate of growth on the qualities of chestnut wood is summarized by the same authority as follows:
:"When the rings are wide, the transition from spring wood to summer wood is gradual, while in the narrow rings the spring wood passes into summer wood abruptly. The width of the spring wood changes but little with the width of the annual ring, so that the narrowing or broadening of the annual ring is always at the expense of the summer wood. The narrow vessels of the summer wood make it richer in wood substance than the spring wood composed of wide vessels. Therefore, rapid-growing specimens with wide rings have more wood substance than slow-growing trees with narrow rings. Since the more the wood substance the greater the weight, and the greater the weight the stronger the wood, chestnuts with wide rings must have stronger wood than chestnuts with narrow rings. This agrees with the accepted view that sprouts (which always have wide rings) yield better and stronger wood than seedling chestnuts, which grow more slowly in diameter."<ref name=USforest/>
In diffuse-porous woods, as has been stated, the vessels or pores are scattered throughout the ring instead of collected in the early wood. The effect of rate of growth is, therefore, not the same as in the ring-porous woods, approaching more nearly the conditions in the [[conifer]]s. In general it may be stated that such woods of medium growth afford stronger material than when very rapidly or very slowly grown. In many uses of wood, strength is not the main consideration. If ease of working is prized, wood should be chosen with regard to its uniformity of texture and straightness of [[Wood grain|grain]], which will in most cases occur when there is little contrast between the late wood of one season's growth and the early wood of the next.
===Monocot wood===
Structural tissue resembling ordinary 'dicot' wood is produced by a number of [[monocot]] plants, and these are also usually called wood. Of these, the wood of [[bamboo]] has considerable economic importance. Other plant groups that produce woody tissue are [[palm]]s, and members of the [[Liliales]], such as [[Dracaena]] and [[Cordyline]]. With all these woods, the structure and compositon of the structural tissue is quite different from ordinary wood.
==Water content==
[[Water]] occurs in living wood in three conditions, namely: (1) in the [[cell wall]]s, (2) in the [[protoplasm]]ic contents of the [[Cell (biology)|cells]], and (3) as free water in the cell cavities and spaces. In heartwood it occurs only in the first and last forms. Wood that is thoroughly air-dried retains from 8-16% of water in the cell walls, and none, or practically none, in the other forms. Even oven-dried wood retains a small percentage of moisture, but for all except chemical purposes, may be considered absolutely dry.
The general effect of the water content upon the wood substance is to render it softer and more pliable. A similar effect of common observation is in the softening action of water on [[paper]] or [[cloth]]. Within certain limits the greater the water content the greater its softening effect.
Drying produces a decided increase in the strength of wood, particularly in small specimens. An extreme example is the case of a completely dry [[spruce]] block 5 cm in section, which will sustain a permanent load four times as great as that which a green block of the same size will support.
The greatest increase due to drying is in the ultimate crushing strength, and strength at [[elastic limit]] in endwise
compression; these are followed by the modulus of rupture, and stress at elastic limit in cross-bending, while the [[modulus of elasticity]] is least affected.
==See also==
[[Image:Wooden Miracle Kizhi.jpg|thumb|right|275px|The churches of [[Kizhi]], [[Russia]] are among a handful of [[World Heritage Site]]s built entirely of wood, without metal joints.]]
{{wiktionary}}
* [[Tree]]
* [[List of woods]]
* [[Forest]]
* [[Forestry]]
* [[Woodworm]]
* [[Wood plastic composite]]
* [[Bamboo]]
* [[Engineered wood]]
* [[Wood as a medium]]
* [[Plywood]]
* [[Wood drying]]
* [[Wood warping]]
* [[Timber]]
* [[Lumber]]
* [[Xiloteque]]
* [[Driftwood]]
<br>
<br>
==References==
{{reflist}}
* Hoadley, R. Bruce. (2000) ''Understanding Wood: A Craftsman’s Guide to Wood Technology''. Taunton Press. ISBN 1-56158-358-8
* Shigo, Alex. (1986) ''A New Tree Biology Dictionary''. Shigo and Trees, Associates. ISBN 0-943563-12-7
==External links==
{{Commonscat|Wood}}
* [http://www.awc.org American Wood Council], wood as construction material
* [http://www.australianhardwood.net Australian Hardwood & Cypress Manual]
* [http://www.woodcollectors.org International Wood Collectors Society]
* [http://www.mayang.com/textures/Wood/html/Flat%20Wood%20Textures/ Mayang textures - wood] (many wood closeup pictures)
* [http://www.trada.co.uk/ TRADA: Timber Research And Development Association]
* [http://www.fpl.fs.fed.us/ US Forest Service, Forest Products Laboratory]
* [http://wood.rleeden.no-ip.com Wood Identification Website]
* [http://www.sankey.ws/wetwood.html Wood moisture]
* [http://www.xiloteca.com Xiloteca Manuel Soler] (One of the largest private collection of wood samples)
* [http://www.matbase.com/material/wood/ Matbase: Environmental, Mechanical and Physical Properties of Wood Types]
[[Category:Forestry]]
[[Category:Wood| ]]
