Wood

Wood is a porous and fibrous structural tissue found in the stems and roots of trees and other woody plants. It is an organic material, a natural composite of cellulose fibers that are strong in tension and embedded in a matrix of lignin that resists compression. Wood is sometimes defined as only the secondary xylem in the stems of trees,[1] or it is defined more broadly to include the same type of tissue elsewhere such as in the roots of trees or shrubs. In a living tree it performs a support function, enabling woody plants to grow large or to stand up by themselves. It also conveys water and nutrients between the leaves, other growing tissues, and the roots. Wood may also refer to other plant materials with comparable properties, and to material engineered from wood, or wood chips or fiber.

Wood has been used for thousands of years for fuel, as a construction material, for making tools and weapons, furniture and paper. More recently it emerged as a feedstock for the production of purified cellulose and its derivatives, such as cellophane and cellulose acetate.

As of 2005, the growing stock of forests worldwide was about 434 billion cubic meters, 47% of which was commercial.[2] As an abundant, carbon-neutral renewable resource, woody materials have been of intense interest as a source of renewable energy. In 1991 approximately 3.5 billion cubic meters of wood were harvested. Dominant uses were for furniture and building construction.[3]

 Pine 
 Spruce 
 Larch 
 Aspen 
 Birch 
 Alder 
 Beech 
 Oak 
 Elm 
 Cherry 
 Pear 
 Maple 
 Linden 
 Ash 

History

A 2011 discovery in the Canadian province of New Brunswick yielded the earliest known plants to have grown wood, approximately 395 to 400 million years ago.[4][5]

Wood can be dated by carbon dating and in some species by dendrochronology to determine when a wooden object was created.

People have used wood for thousands of years for many purposes, including as a fuel or as a construction material for making houses, tools, weapons, furniture, packaging, artworks, and paper. Known constructions using wood date back ten thousand years. Buildings like the European Neolithic long house were made primarily of wood.

Recent use of wood has been enhanced by the addition of steel and bronze into construction.[6]

The year-to-year variation in tree-ring widths and isotopic abundances gives clues to the prevailing climate at the time a tree was cut.[7]

Physical properties

Tree secondary growth diagram
Diagram of secondary growth in a tree showing idealized vertical and horizontal sections. A new layer of wood is added in each growing season, thickening the stem, existing branches and roots, to form a growth ring.

Growth rings

Wood, in the strict sense, is yielded by trees, which increase in diameter by the formation, between the existing wood and the inner bark, of new woody layers which envelop the entire stem, living branches, and roots. This process is known as secondary growth; it is the result of cell division in the vascular cambium, a lateral meristem, and subsequent expansion of the new cells. These cells then go on to form thickened secondary cell walls, composed mainly of cellulose, hemicellulose and lignin.

Where the differences between the four seasons are distinct, e.g. New Zealand, growth can occur in a discrete annual or seasonal pattern, leading to growth rings; these can usually be most clearly seen on the end of a log, but are also visible on the other surfaces. If the distinctiveness between seasons is annual (as is the case in equatorial regions, e.g. Singapore), these growth rings are referred to as annual rings. Where there is little seasonal difference growth rings are likely to be indistinct or absent. If the bark of the tree has been removed in a particular area, the rings will likely be deformed as the plant overgrows the scar.

If there are differences within a growth ring, then the part of a growth ring nearest the center of the tree, and formed early in the growing season when growth is rapid, is usually composed of wider elements. It is usually lighter in color than that near the outer portion of the ring, and is known as earlywood or springwood. The outer portion formed later in the season is then known as the latewood or summerwood.[8] However, there are major differences, depending on the kind of wood (see below).

Knots

TreeKnot
A knot on a tree trunk

As a tree grows, lower branches often die, and their bases may become overgrown and enclosed by subsequent layers of trunk wood, forming a type of imperfection known as a knot. The dead branch may not be attached to the trunk wood except at its base, and can drop out after the tree has been sawn into boards. Knots affect the technical properties of the wood, usually reducing the local strength and increasing the tendency for splitting along the wood grain, but may be exploited for visual effect. In a longitudinally sawn plank, a knot will appear as a roughly circular "solid" (usually darker) piece of wood around which the grain of the rest of the wood "flows" (parts and rejoins). Within a knot, the direction of the wood (grain direction) is up to 90 degrees different from the grain direction of the regular wood.

In the tree a knot is either the base of a side branch or a dormant bud. A knot (when the base of a side branch) is conical in shape (hence the roughly circular cross-section) with the inner tip at the point in stem diameter at which the plant's vascular cambium was located when the branch formed as a bud.

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.

Wood Knot
Wood knot in vertical section

Knots materially affect cracking 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 than when under load along the grain and/or compression. The extent to which knots affect the strength of a beam depends upon their position, size, number, and condition. A knot on the upper side is compressed, while one on the lower side is subjected to tension. If there is a season check in the knot, as is often the case, it will offer little resistance to this tensile stress. Small knots, however, may be located along the neutral plane of a beam and increase the strength by preventing longitudinal 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.

— Samuel J. Record, The Mechanical Properties of Wood[9]

Knots do not necessarily influence the stiffness of structural timber, this will depend on the size and location. Stiffness and elastic strength are more dependent upon the sound wood than upon localized defects. The breaking strength is very susceptible to defects. Sound knots do not weaken wood when subject to compression parallel to the grain.

In some decorative applications, wood with knots may be desirable to add visual interest. In applications where wood is painted, such as skirting boards, fascia boards, door frames and furniture, resins present in the timber may continue to 'bleed' through to the surface of a knot for months or even years after manufacture and show as a yellow or brownish stain. A knot primer paint or solution (knotting), correctly applied during preparation, may do much to reduce this problem but it is difficult to control completely, especially when using mass-produced kiln-dried timber stocks.

Heartwood and sapwood

Taxus wood
A section of a Yew branch showing 27 annual growth rings, pale sapwood, dark heartwood, and pith (center dark spot). The dark radial lines are small knots.

Heartwood (or duramen[10]) is wood that as a result of a naturally occurring chemical transformation has become more resistant to decay. Heartwood formation is a genetically programmed process that occurs spontaneously. Some uncertainty exists as to whether the wood dies during heartwood formation, as it can still chemically react to decay organisms, but only once.[11]

Heartwood is often visually distinct from the living sapwood, and can be distinguished in a cross-section where the boundary will tend to follow the growth rings. For example, it is sometimes much darker. However, other processes such as decay or insect invasion can also discolor wood, even in woody plants that do not form heartwood, which may lead to confusion.

Sapwood (or alburnum[12]) is the younger, outermost wood; in the growing tree it is living wood,[13] and its principal functions are to conduct water from the roots to the leaves and to store up and give back according to the season the reserves prepared in the leaves. However, by the time they become competent to conduct water, all xylem tracheids and vessels have lost their cytoplasm and the cells are therefore functionally dead. All wood in a tree is first formed as sapwood. 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 (of species that do form heartwood) grown in the open may become of considerable size, 30 cm (12 in) or more in diameter, before any heartwood begins to form, for example, in second-growth hickory, or open-grown pines.

The term heartwood derives solely from its position and not from any vital importance to the tree. This is evidenced 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 species as chestnut, black locust, mulberry, osage-orange, and sassafras, while in maple, ash, hickory, hackberry, beech, and pine, thick sapwood is the rule.[14] Others never form heartwood.

No definite relation exists 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 relatively 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 inner 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 a given piece of sapwood, because of its position in the tree, may well be stronger than a piece of heartwood from the same tree.

It is remarkable that the inner heartwood of old trees remains as sound as it usually does, since in many cases it is hundreds, 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 bore 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 oaks, 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.

Different pieces of wood cut from a large tree may differ decidedly, particularly if the tree is big and 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 trees, the reverse applies. This may or may not correspond to heartwood and sapwood. 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, and toughness to equally sound heartwood from the same log. In a smaller tree, the reverse may be true.

Color

Sequoia wood
The wood of coast redwood is distinctively red.

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 (see section of yew log above). This is produced by deposits in the heartwood of chemical substances, so that a dramatic color variation does not imply a significant difference in the mechanical properties of heartwood and sapwood, although there may be a marked biochemical difference between the two.

Some experiments on very resinous longleaf pine specimens indicate an increase in strength, 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.

Since the latewood of a growth ring is usually darker in color than the earlywood, this fact may be used in visually 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 often appear on a finished surface as darker than the denser latewood, though on cross sections of heartwood the reverse is commonly true. Otherwise 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 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 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 fungal growth, but does not necessarily produce a weakening effect.

Water content

Water occurs in living wood in three locations, namely:

In heartwood it occurs only in the first and last forms. Wood that is thoroughly air-dried retains 8–16% of the 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 occurs in the softening action of water on rawhide, 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 a green (undried) block of the same size will.

The greatest strength 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.[9]

Structure

BlkWalnut-x-section
Magnified cross-section of black walnut, showing the vessels, rays (white lines) and annual rings: this is intermediate between diffuse-porous and ring-porous, with vessel size declining gradually

Wood is a heterogeneous, hygroscopic, cellular and anisotropic material. It consists of cells, and the cell walls are composed of micro-fibrils of cellulose (40–50%) and hemicellulose (15–25%) impregnated with lignin (15–30%).[15]

In coniferous or softwood species the wood cells are mostly of one kind, tracheids, and as a result the material is much more uniform in structure than that of most hardwoods. There are no vessels ("pores") in coniferous wood such as one sees so prominently in oak and ash, for example.

The structure of hardwoods is more complex.[16] The water conducting capability is mostly taken care of by vessels: in some cases (oak, chestnut, ash) these are quite large and distinct, in others (buckeye, poplar, willow) too small to be seen without a hand lens. In discussing such woods it is customary to divide them into two large classes, ring-porous and diffuse-porous.[17]

In ring-porous species, such as ash, black locust, catalpa, chestnut, elm, hickory, mulberry, and oak,[17] 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 fibers. These fibers 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 evenly sized so that the water conducting capability is scattered throughout the growth ring instead of being collected in a band or row. Examples of this kind of wood are alder,[17] basswood,[18] birch,[17] buckeye, maple, willow, and the Populus species such as aspen, cottonwood and poplar.[17] Some species, such as walnut and cherry, are on the border between the two classes, forming an intermediate group.[18]

Earlywood and latewood

In softwood

Wood Pseudotsuga taxifolia
Earlywood and latewood in a softwood; radial view, growth rings closely spaced in Rocky Mountain Douglas-fir

In temperate softwoods, there often is a marked difference between latewood and earlywood. The latewood will be denser than that formed early in the season. When examined under a microscope, the cells of dense latewood are seen to be very thick-walled and with very small cell cavities, while those formed first in the season have thin walls and large cell cavities. The strength is in the walls, not the cavities. Hence the greater the proportion of latewood, the greater the density and strength. In choosing a piece of pine where strength or stiffness is the important consideration, the principal thing to observe is the comparative amounts of earlywood and latewood. The width of ring is not nearly so important as the proportion and nature of the latewood in the ring.

If a heavy piece of pine is compared with a lightweight piece it will be seen at once that the heavier one contains a larger proportion of latewood than the other, and is therefore showing more clearly demarcated growth rings. In white pines there is not much contrast between the different parts of the ring, and as a result the wood is very uniform in texture and is easy to work. In hard pines, on the other hand, the latewood is very dense and is deep-colored, presenting a very decided contrast to the soft, straw-colored earlywood.

It is not only the proportion of latewood, but also its quality, that counts. In specimens that show a very large proportion of latewood it may be noticeably more porous and weigh considerably less than the latewood in pieces that contain less latewood. One can judge comparative density, and therefore to some extent strength, by visual inspection.

No satisfactory explanation can as yet be given for the exact mechanisms determining the formation of earlywood and latewood. 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.

In ring-porous woods

Wood Fraxinus excelsior
Earlywood and latewood in a ring-porous wood (ash) in a Fraxinus excelsior; tangential view, wide growth rings

In ring-porous woods, each season's growth is always well defined, because the large pores formed early in the season abut on the denser tissue of the year before.

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 latewood in which the thick-walled, strength-giving fibers are most abundant. As the breadth of ring diminishes, this latewood 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 earlywood occupy from 6 to 10 percent of the volume of the log, while in inferior material they may make up 25% or more. The latewood of good oak is dark colored and firm, and consists mostly of thick-walled fibers which form one-half or more of the wood. In inferior oak, this latewood is 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 a closed 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 spokes. Here not only strength, but toughness and resilience are important.[9]

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 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."[19]

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."[19]

In diffuse-porous woods

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. Conversely, when there is a clear demarcation there may not be a noticeable difference in structure within the growth ring.

In diffuse-porous woods, as has been stated, the vessels or pores are even-sized, so that the water conducting capability is scattered throughout the ring instead of collected in the earlywood. The effect of rate of growth is, therefore, not the same as in the ring-porous woods, approaching more nearly the conditions in the conifers. 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, total 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 grain, which will in most cases occur when there is little contrast between the latewood of one season's growth and the earlywood of the next.

Monocot wood

Gelugu (coconut wood) in Klaten, Java
Trunks of the coconut palm, a monocot, in Java. From this perspective these look not much different from trunks of a dicot or conifer

Structural material that resembles ordinary, "dicot" or conifer timber in its gross handling characteristics is produced by a number of monocot plants, and these also are colloquially called wood. Of these, bamboo, botanically a member of the grass family, has considerable economic importance, larger culms being widely used as a building and construction material and in the manufacture of engineered flooring, panels and veneer. Another major plant group that produces material that often is called wood are the palms. Of much less importance are plants such as Pandanus, Dracaena and Cordyline. With all this material, the structure and composition of the processed raw material is quite different from ordinary wood.

Specific gravity

The single most revealing property of wood as an indicator of wood quality is specific gravity (Timell 1986),[20] as both pulp yield and lumber strength are determined by it. Specific gravity is the ratio of the mass of a substance to the mass of an equal volume of water; density is the ratio of a mass of a quantity of a substance to the volume of that quantity and is expressed in mass per unit substance, e.g., grams per milliliter (g/cm3 or g/ml). The terms are essentially equivalent as long as the metric system is used. Upon drying, wood shrinks and its density increases. Minimum values are associated with green (water-saturated) wood and are referred to as basic specific gravity (Timell 1986).[20]

Wood density

Wood density is determined by multiple growth and physiological factors compounded into “one fairly easily measured wood characteristic” (Elliott 1970).[21]

Age, diameter, height, radial (trunk) growth, geographical location, site and growing conditions, silvicultural treatment, and seed source all to some degree influence wood density. Variation is to be expected. Within an individual tree, the variation in wood density is often as great as or even greater than that between different trees (Timell 1986).[20] Variation of specific gravity within the bole of a tree can occur in either the horizontal or vertical direction.

Hard and soft woods

It is common to classify wood as either softwood or hardwood. The wood from conifers (e.g. pine) is called softwood, and the wood from dicotyledons (usually 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. yew) are harder than many hardwoods.

There is a strong relationship between the properties of wood and the properties of the particular tree that yielded it. The density of wood varies with species. The density of a wood correlates with its strength (mechanical properties). For example, mahogany is a medium-dense hardwood that is excellent for fine furniture crafting, whereas balsa is light, making it useful for model building. One of the densest woods is black ironwood.

Chemistry of wood

Lignin
Chemical structure of lignin, which comprises about 25% of wood dry matter and is responsible for many of its properties.

The chemical composition of wood varies from species to species, but is approximately 50% carbon, 42% oxygen, 6% hydrogen, 1% nitrogen, and 1% other elements (mainly calcium, potassium, sodium, magnesium, iron, and manganese) by weight.[22] Wood also contains sulfur, chlorine, silicon, phosphorus, and other elements in small quantity.

Aside from water, wood has three main components. Cellulose, a crystalline polymer derived from glucose, constitutes about 41–43%. Next in abundance is hemicellulose, which is around 20% in deciduous trees but near 30% in conifers. It is mainly five-carbon sugars that are linked in an irregular manner, in contrast to the cellulose. Lignin is the third component at around 27% in coniferous wood vs. 23% in deciduous trees. Lignin confers the hydrophobic properties reflecting the fact that it is based on aromatic rings. These three components are interwoven, and direct covalent linkages exist between the lignin and the hemicellulose. A major focus of the paper industry is the separation of the lignin from the cellulose, from which paper is made.

In chemical terms, the difference between hardwood and softwood is reflected in the composition of the constituent lignin. Hardwood lignin is primarily derived from sinapyl alcohol and coniferyl alcohol. Softwood lignin is mainly derived from coniferyl alcohol.[23]

Extractives

Aside from the lignocellulose, wood consists of a variety of low molecular weight organic compounds, called extractives. The wood extractives are fatty acids, resin acids, waxes and terpenes.[24] For example, rosin is exuded by conifers as protection from insects. The extraction of these organic materials from wood provides tall oil, turpentine, and rosin.[25]

Uses

Fuel

Wood has a long history of being used as fuel,[26] which continues to this day, mostly in rural areas of the world. Hardwood is preferred over softwood because it creates less smoke and burns longer. Adding a woodstove or fireplace to a home is often felt to add ambiance and warmth.

Construction

Saitta House Dyker Heights
The Saitta House, Dyker Heights, Brooklyn, New York built in 1899 is made of and decorated in wood.[27]

Wood has been an important construction material since humans began building shelters, houses and boats. Nearly all boats were made out of wood until the late 19th century, and wood remains in common use today in boat construction. Elm in particular was used for this purpose as it resisted decay as long as it was kept wet (it also served for water pipe before the advent of more modern plumbing).

Wood to be used for construction work is commonly known as lumber in North America. Elsewhere, lumber usually refers to felled trees, and the word for sawn planks ready for use is timber.[28] In Medieval Europe oak was the wood of choice for all wood construction, including beams, walls, doors, and floors. Today a wider variety of woods is used: solid wood doors are often made from poplar, small-knotted pine, and Douglas fir.

Преображенская церковь (деревянная) (1714 г.) 01
The churches of Kizhi, Russia are among a handful of World Heritage Sites built entirely of wood, without metal joints. See Kizhi Pogost for more details.

New domestic housing in many parts of the world today is commonly made from timber-framed construction. Engineered wood products are becoming a bigger part of the construction industry. They may be used in both residential and commercial buildings as structural and aesthetic materials.

In buildings made of other materials, wood will still be found as a supporting material, especially in roof construction, in interior doors and their frames, and as exterior cladding.

Wood is also commonly used as shuttering material to form the mold into which concrete is poured during reinforced concrete construction.

Wood flooring

LightningVolt Wood Floor
Wood can be cut into straight planks and made into a wood flooring.

A solid wood floor is a floor laid with planks or battens created from a single piece of timber, usually a hardwood. Since wood is hydroscopic (it acquires and loses moisture from the ambient conditions around it) this potential instability effectively limits the length and width of the boards.

Solid hardwood flooring is usually cheaper than engineered timbers and damaged areas can be sanded down and refinished repeatedly, the number of times being limited only by the thickness of wood above the tongue.

Solid hardwood floors were originally used for structural purposes, being installed perpendicular to the wooden support beams of a building (the joists or bearers) and solid construction timber is still often used for sports floors as well as most traditional wood blocks, mosaics and parquetry.

Engineered wood

Engineered wood products, glued building products "engineered" for application-specific performance requirements, are often used in construction and industrial applications. Glued engineered wood products are manufactured by bonding together wood strands, veneers, lumber or other forms of wood fiber with glue to form a larger, more efficient composite structural unit.[29]

These products include glued laminated timber (glulam), wood structural panels (including plywood, oriented strand board and composite panels), laminated veneer lumber (LVL) and other structural composite lumber (SCL) products, parallel strand lumber, and I-joists.[29] Approximately 100 million cubic meters of wood was consumed for this purpose in 1991.[3] The trends suggest that particle board and fiber board will overtake plywood.

Wood unsuitable for construction in its native form may be broken down mechanically (into fibers or chips) or chemically (into cellulose) and used as a raw material for other building materials, such as engineered wood, as well as chipboard, hardboard, and medium-density fiberboard (MDF). Such wood derivatives are widely used: wood fibers are an important component of most paper, and cellulose is used as a component of some synthetic materials. Wood derivatives can be used for kinds of flooring, for example laminate flooring.

Furniture and utensils

Wood has always been used extensively for furniture, such as chairs and beds. It is also used for tool handles and cutlery, such as chopsticks, toothpicks, and other utensils, like the wooden spoon and pencil.

Next generation wood products

Further developments include new lignin glue applications, recyclable food packaging, rubber tire replacement applications, anti-bacterial medical agents, and high strength fabrics or composites.[30] As scientists and engineers further learn and develop new techniques to extract various components from wood, or alternatively to modify wood, for example by adding components to wood, new more advanced products will appear on the marketplace. Moisture content electronic monitoring can also enhance next generation wood protection.[31]

In the arts

Wood has long been used as an artistic medium. It has been used to make sculptures and carvings for millennia. Examples include the totem poles carved by North American indigenous people from conifer trunks, often Western Red Cedar (Thuja plicata).

Other uses of wood in the arts include:

Sports and recreational equipment

Many types of sports equipment are made of wood, or were constructed of wood in the past. For example, cricket bats are typically made of white willow. The baseball bats which are legal for use in Major League Baseball are frequently made of ash wood or hickory, and in recent years have been constructed from maple even though that wood is somewhat more fragile. NBA courts have been traditionally made out of parquetry.

Many other types of sports and recreation equipment, such as skis, ice hockey sticks, lacrosse sticks and archery bows, were commonly made of wood in the past, but have since been replaced with more modern materials such as aluminium, titanium or composite materials such as fiberglass and carbon fiber. One noteworthy example of this trend is the family of golf clubs commonly known as the woods, the heads of which were traditionally made of persimmon wood in the early days of the game of golf, but are now generally made of metal or (especially in the case of drivers) carbon-fiber composites.

Bacterial degradation

Little is known about the bacteria that degrade cellulose. Symbiotic bacteria in Xylophaga may play a role in the degradation of sunken wood; while bacteria such as Alphaproteobacteria, Flavobacteria, Actinobacteria, Clostridia, and Bacteroidetes have been detected in wood submerged over a year.[32]

See also

References

  1. ^ Hickey, M.; King, C. (2001). The Cambridge Illustrated Glossary of Botanical Terms. Cambridge University Press.
  2. ^ "Global Forest Resources Assessment 2005/Food and Agriculture Organization of the United Nations" (PDF).
  3. ^ a b Horst H. Nimz, Uwe Schmitt, Eckart Schwab, Otto Wittmann, Franz Wolf "Wood" in Ullmann's Encyclopedia of Industrial Chemistry 2005, Wiley-VCH, Weinheim. doi:10.1002/14356007.a28_305
  4. ^ "N.B. fossils show origins of wood". CBC.ca. August 12, 2011. Archived from the original on August 13, 2011. Retrieved August 12, 2011.
  5. ^ Philippe Gerrienne; et al. (Aug 12, 2011). "A Simple Type of Wood in Two Early Devonian Plants". Science. 333 (6044): 837. Bibcode:2011Sci...333..837G. doi:10.1126/science.1208882. PMID 21836008.
  6. ^ Woods, Sarah. "A History of Wood from the Stone Age to the 21st Century". EcoBUILDING. A Publication of The American Institute of Architects. Archived from the original on March 29, 2017. Retrieved March 28, 2017.
  7. ^ Briffa, K.; Shishov, V.V.; Melvin, T.M.; Vaganov, E.A.; Grudd, H.; Hantemirov (2008). "Trends in recent temperature and radial tree growth spanning 2000 years across northwest Eurasia". Philosophical Transactions of the Royal Society B: Biological Sciences. 363 (1501): 2271–2284. doi:10.1098/rstb.2007.2199. PMC 2606779. PMID 18048299.
  8. ^ Wood growth and structure Archived December 12, 2009, at the Wayback Machine www.farmforestline.com.au
  9. ^ a b c Record, Samuel J (1914). The Mechanical Properties of Wood. J. Wiley & Sons. p. 165. ASIN B000863N3W.
  10. ^ Wikisource "Duramen" . Encyclopædia Britannica. 8 (11th ed.). 1911. p. 692.
  11. ^ Shigo, Alex. (1986) A New Tree Biology Dictionary. Shigo and Trees, Associates. ISBN 0-943563-12-7
  12. ^ Wikisource "Alburnum" . Encyclopædia Britannica. 1 (11th ed.). 1911. p. 516.
  13. ^ Capon, Brian (2005), Botany for Gardeners (2nd ed.), Portland, OR: Timber Publishing, p. 65 ISBN 0-88192-655-8
  14. ^ Record, Samuel James (1914). The Mechanical Properties of Wood: Including a Discussion of the Factors Affecting the Mechanical Properties, and Methods of Timber Testing. J. Wiley & Sons, Incorporated. Archived from the original on December 11, 2017.
  15. ^ "Wood Properties Growth and Structure 2015". treetesting.com. Archived from the original on March 13, 2016.
  16. ^ "Timber Plus Toolbox, Selecting timber, Characteristics of timber, Structure of hardwoods". nationalvetcontent.edu.au. Archived from the original on August 10, 2014.
  17. ^ a b c d e Sperry, John S.; Nichols, Kirk L.; Sullivan, June E.; Eastlack, Sondra E. (1994). "Xylem Embolism in ring-porous, diffuse-porous, and coniferous trees of Northern Utah and Interior Alaska" (PDF). Ecology. 75 (6): 1736–1752. doi:10.2307/1939633. JSTOR 1939633.
  18. ^ a b Samuel James Record (1914). The mechanical properties of wood, including a discussion of the factors affecting the mechanical properties, and methods of timber testing. J. Wiley & sons, inc. pp. 44–. Archived from the original on March 15, 2017.
  19. ^ a b U.S. Department of Agriculture, Forest Products Laboratory. The Wood Handbook: Wood as an engineering material Archived March 15, 2007, at the Wayback Machine. General Technical Report 113. Madison, WI.
  20. ^ a b c Timell, T.E. 1986. Compression wood in gymnosperms. Springer-Verlag, Berlin. 2150 p.
  21. ^ Elliott, G.K. 1970. Wood density in conifers. Commonwealth For. Bureau, Oxford, U.K., Tech. Commun. 8. 44 p.
  22. ^ Jean-Pierre Barette; Claude Hazard et Jérôme Mayer (1996). Mémotech Bois et Matériaux Associés. Paris: Éditions Casteilla. p. 22. ISBN 978-2-7135-1645-0.
  23. ^ W. Boerjan; J. Ralph; M. Baucher (June 2003). "Lignin biosynthesis". Annu. Rev. Plant Biol. 54 (1): 519–549. doi:10.1146/annurev.arplant.54.031902.134938. PMID 14503002.
  24. ^ Mimms, Agneta; Michael J. Kuckurek; Jef A. Pyiatte; Elizabeth E. Wright (1993). Kraft Pulping. A Compilation of Notes. TAPPI Press. pp. 6–7. ISBN 978-0-89852-322-5.
  25. ^ Fiebach, Klemens; Grimm, Dieter (2000). "Resins, Natural". Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.a23_073. ISBN 978-3-527-30673-2.
  26. ^ Sterrett, Frances S. (October 12, 1994). Alternative Fuels and the Environment. CRC Press. ISBN 978-0-87371-978-0.
  27. ^ "Saitta House – Report Part 1 Archived December 16, 2008, at the Wayback Machine",DykerHeightsCivicAssociation.com
  28. ^ Binggeli, Corky (2013). Materials for Interior Environments. John Wiley & Sons. ISBN 978-1-118-42160-4.
  29. ^ a b "APA – The Engineered Wood Association" (PDF). apawood.org. Archived (PDF) from the original on June 27, 2006.
  30. ^ "FPInnovations" (PDF). forintek.ca. Archived from the original (PDF) on March 19, 2009.
  31. ^ "System for remotely monitoring moisture content on wooden elements" I Arakistain, O Munne EP Patent EPO1382108.0
  32. ^ Christina Bienhold; Petra Pop Ristova; Frank Wenzhöfer; Thorsten Dittmar; Antje Boetius (January 2, 2013). "How Deep-Sea Wood Falls Sustain Chemosynthetic Life". PLOS ONE. 8 (1): e53590. Bibcode:2013PLoSO...853590B. doi:10.1371/journal.pone.0053590. PMC 3534711. PMID 23301092.

External links

Charcoal

Charcoal is the lightweight black carbon and ash residue hydrocarbon produced by removing water and other volatile constituents from animal and vegetation substances. Charcoal is usually produced by slow pyrolysis — the heating of wood or other substances in the absence of oxygen. This process is called charcoal burning. The finished charcoal consists largely of carbon.

The advantage of using charcoal instead of just burning wood is the removal of the water and other components. This allows charcoal to burn to a higher temperature, and give off very little smoke (regular wood gives off a good amount of steam, organic volatiles, and unburnt carbon particles — soot — in its smoke).

Chris Wood (footballer, born 1991)

Christopher Grant Wood (born 7 December 1991) is a New Zealand professional footballer who plays as a striker for English Premier League club Burnley and the New Zealand national team, of which he is vice-captain.

Wood was born in Auckland and started his senior career with Cambridge FC, Waikato FC and Hamilton Wanderers before moving to England to play for Premier League side West Bromwich Albion. He spent his time on loan to six different clubs before joining Leicester City in 2015. After a loan spell with Ipswich Town in 2015, he signed for Championship club Leeds United where he became top scorer in the 2016–17 season. He then joined Burnley for a club record fee in the Premier League.

Wood has been capped 56 times for the New Zealand national team, scoring 24 goals. He played for the side at the 2010 FIFA World Cup.

Edward Wood, 1st Earl of Halifax

Edward Frederick Lindley Wood, 1st Earl of Halifax, (16 April 1881 – 23 December 1959), styled Lord Irwin from 1925 until 1934 and Viscount Halifax from 1934 until 1944, was one of the most senior British Conservative politicians of the 1930s. He held several senior ministerial posts during this time, most notably those of Viceroy of India from 1925 to 1931 and of Foreign Secretary between 1938 and 1940. He was one of the architects of the policy of appeasement of Adolf Hitler in 1936–38, working closely with Prime Minister Neville Chamberlain. However, after the German occupation of Czechoslovakia in March 1939 he was one of those who pushed for a new policy of attempting to deter further German aggression by promising to go to war to defend the Second Polish Republic.

On Chamberlain's resignation early in May 1940, Halifax declined the position of Prime Minister as he felt that Churchill would be a more suitable war leader (his membership in the House of Lords was given as the official reason). A few weeks later, with the Allies facing apparently catastrophic defeat and British forces falling back to Dunkirk, Halifax favoured approaching the Kingdom of Italy to see if acceptable peace terms could be negotiated. He was overruled by Churchill after a series of stormy meetings of the War Cabinet. From 1941 to 1946, he served as British Ambassador in Washington.

Elijah Wood

Elijah Jordan Wood (born January 28, 1981) is an American actor, film producer, and DJ. He is known for portraying Frodo Baggins in the Lord of the Rings film trilogy (2001–2003).

Wood made his film debut in 1989 with a small part in Back to the Future Part II. He went on to achieve recognition as a child actor with roles in Avalon (1990), Paradise (1991), Radio Flyer, Forever Young (both 1992), The Adventures of Huck Finn and The Good Son (both 1993). As a teenager, he starred in films such as North, The War (both 1994), Flipper (1996), The Ice Storm (1997), Deep Impact and The Faculty (both 1998). Following the success of Lord of the Rings, Wood has appeared in a wide range of films, including Eternal Sunshine of the Spotless Mind (2004), Sin City, Green Street, Everything Is Illuminated (all 2005), Paris, je t'aime, Bobby (both 2006), Celeste and Jesse Forever, Maniac (both 2012), Grand Piano (2013), The Last Witch Hunter (2015), The Trust (2016), and I Don't Feel at Home in This World Anymore (2017).

Wood's voice work includes the role of Mumble in Happy Feet (2006) and its sequel; the title character in 9 (2009); and Spyro in the Legend of Spyro video game trilogy (2006–2008). In addition, he provided the voice of Beck on Disney XD's Tron: Uprising (2012–2013), and Wirt in the Cartoon Network miniseries Over the Garden Wall (2014). From 2011–2014, Wood played the role of Ryan Newman on the FX television series Wilfred, for which he received a Satellite Award nomination for Best Actor. From 2016–17, he starred as Todd Brotzman on the BBC America series Dirk Gently's Holistic Detective Agency.

Wood has his own record label, Simian Records, which he founded in 2005. In 2010, he founded the production company SpectreVision, which specializes in producing horror films.

Evan Rachel Wood

Evan Rachel Wood (born September 7, 1987) is an American actress, model, and musician. She began acting in the 1990s, appearing in several television series, including American Gothic (1995–96) and Once and Again (1999–2002). Wood made her debut as a leading film actress at the age of eleven in Digging to China (1998) and garnered acclaim for her Golden Globe-nominated role as the troubled teenager Tracy Freeland in the teen drama film Thirteen (2003).Wood continued acting mostly in independent films, including Pretty Persuasion (2005), Down in the Valley (2005), Running with Scissors (2006), and in the big studio production Across the Universe (2007). Since 2008, Wood has appeared in more mainstream films, including The Wrestler (2008), Whatever Works (2009) and The Ides of March (2011). She also returned to television, playing the supporting role of Queen Sophie-Anne on True Blood from 2009 to 2011 and playing the daughter of Mildred Pierce in the HBO miniseries Mildred Pierce (2011), for which she was nominated for the Golden Globe and Emmy Award for Best Supporting Actress. As of 2016, she plays the sentient android Dolores Abernathy in the HBO series Westworld, for which she won a Critics' Choice Award and earned a Golden Globe and Emmy Award nominations.

Groundhog

The groundhog (Marmota monax), also known as a woodchuck, is a rodent of the family Sciuridae, belonging to the group of large ground squirrels known as marmots. It was first scientifically described by Carl Linnaeus in 1758. The groundhog is also referred to as a chuck, wood-shock, groundpig, whistlepig, whistler, thickwood badger, Canada marmot, monax, moonack, weenusk, red monk and, among French Canadians in eastern Canada, siffleux. The name "thickwood badger" was given in the Northwest to distinguish the animal from the prairie badger. Monax (Móonack) is an Algonquian name of the woodchuck, which meant "digger" (cf. Lenape monachgeu). Young groundhogs may be called chucklings. Other marmots, such as the yellow-bellied and hoary marmots, live in rocky and mountainous areas, but the groundhog is a lowland creature. It is found through much of the eastern United States across Canada and into Alaska

Hardwood

Hardwood is wood from dicot trees. These are usually found in broad-leaved temperate and tropical forests. In temperate and boreal latitudes they are mostly deciduous, but in tropics and subtropics mostly evergreen. Hardwood contrasts with softwood (which is from gymnosperm trees).

House

A house is a building that functions as a home. They can range from simple dwellings such as rudimentary huts of nomadic tribes and the improvised shacks in shantytowns to complex, fixed structures of wood, brick, concrete or other materials containing plumbing, ventilation, and electrical systems. Houses use a range of different roofing systems to keep precipitation such as rain from getting into the dwelling space. Houses may have doors or locks to secure the dwelling space and protect its inhabitants and contents from burglars or other trespassers. Most conventional modern houses in Western cultures will contain one or more bedrooms and bathrooms, a kitchen or cooking area, and a living room. A house may have a separate dining room, or the eating area may be integrated into another room. Some large houses in North America have a recreation room. In traditional agriculture-oriented societies, domestic animals such as chickens or larger livestock (like cattle) may share part of the house with humans. The social unit that lives in a house is known as a household.

Most commonly, a household is a family unit of some kind, although households may also be other social groups, such as roommates or, in a rooming house, unconnected individuals. Some houses only have a dwelling space for one family or similar-sized group; larger houses called townhouses or row houses may contain numerous family dwellings in the same structure. A house may be accompanied by outbuildings, such as a garage for vehicles or a shed for gardening equipment and tools. A house may have a backyard or frontyard, which serve as additional areas where inhabitants can relax or eat.

Lumber

Lumber (American English; used only in North America) or timber (used in the rest of the English-speaking world) is a type of wood that has been processed into beams and planks, a stage in the process of wood production. Lumber is mainly used for structural purposes but has many other uses as well.

There are two main types of lumber. It may be supplied either rough-sawn, or surfaced on one or more of its faces. Besides pulpwood, rough lumber is the raw material for furniture-making and other items requiring additional cutting and shaping. It is available in many species, usually hardwoods; but it is also readily available in softwoods, such as white pine and red pine, because of their low cost.Finished lumber is supplied in standard sizes, mostly for the construction industry – primarily softwood, from coniferous species, including pine, fir and spruce (collectively spruce-pine-fir), cedar, and hemlock, but also some hardwood, for high-grade flooring. It is more commonly made from softwood than hardwoods, and 80% of lumber comes from softwood.

Methanol

Methanol, also known as methyl alcohol among others, is a chemical with the formula CH3OH (a methyl group linked to a hydroxyl group, often abbreviated MeOH). Methanol acquired the name wood alcohol because it was once produced chiefly by the destructive distillation of wood. Today, methanol is mainly produced industrially by hydrogenation of carbon monoxide.Methanol is the simplest alcohol, consisting of a methyl group linked to a hydroxyl group. It is a light, volatile, colorless, flammable liquid with a distinctive odor similar to that of ethanol (drinking alcohol). Methanol is however far more toxic than ethanol. At room temperature, it is a polar liquid. With more than 20 million tons produced annually, it is used as a precursor to other commodity chemicals, including formaldehyde, acetic acid, methyl tert-butyl ether, as well as a host of more specialized chemicals.

Monkey (zodiac)

The Monkey (猴) is the ninth of the 12-year cycle of animals which appear in the Chinese zodiac related to the Chinese calendar. The Year of the Monkey is associated with the Earthly Branch symbol 申.

Natalie Wood

Natalie Wood (born Natalia Nikolaevna Zakharenko; July 20, 1938 – November 29, 1981) was an American actress.

Born in San Francisco to Russian immigrant parents, Wood began her career in film as a child and became a successful Hollywood star as a young adult, receiving three Academy Award nominations before she turned 25 years old. She began acting in films at the age of four and, at age eight, was given a co-starring role in the 1947 classic Christmas film Miracle on 34th Street. As a teenager, she earned a nomination for the Academy Award for Best Supporting Actress for her performance in Rebel Without a Cause (1955). She starred in the musical films West Side Story (1961) and Gypsy (1962), and received Academy Award for Best Actress nominations for her performances in Splendor in the Grass (1961) and Love with the Proper Stranger (1963). Her career continued with films such as Bob & Carol & Ted & Alice (1969).

After this, she took a break from acting and had two children with different husbands, appearing in only three theatrical films during the 1970s. She was married to actor Robert Wagner, then to producer Richard Gregson, and then back to Wagner. She had one daughter with Gregson, actress Natasha Gregson Wagner. Wood gave birth to Courtney Wagner during her second marriage to Wagner. Wood starred in several television productions, including a remake of the film From Here to Eternity (1979), which earned her a Golden Globe Award. During her career, her films represented a "coming of age" for both her and Hollywood films in general.Wood drowned on November 29, 1981, at the age of 43; the events surrounding her death have been controversial due to conflicting witness statements, prompting the Sheriff's Department in 2012 to declare the cause of her death as "drowning and other undetermined factors".

Oak

An oak is a tree or shrub in the genus Quercus (; Latin "oak tree") of the beech family, Fagaceae. There are approximately 600 extant species of oaks. The common name "oak" also appears in the names of species in related genera, notably Lithocarpus (stone oaks), as well as in those of unrelated species such as Grevillea robusta (silky oaks) and the Casuarinaceae (she-oaks). The genus Quercus is native to the Northern Hemisphere, and includes deciduous and evergreen species extending from cool temperate to tropical latitudes in the Americas, Asia, Europe, and North Africa. North America contains the largest number of oak species, with approximately 90 occurring in the United States, while Mexico has 160 species of which 109 are endemic. The second greatest center of oak diversity is China, which contains approximately 100 species.

Oaks have spirally arranged leaves, with lobate margins in many species; some have serrated leaves or entire leaves with smooth margins. Many deciduous species are marcescent, not dropping dead leaves until spring. In spring, a single oak tree produces both male flowers (in the form of catkins) and small female flowers. The fruit is a nut called an acorn or oak nut borne in a cup-like structure known as a cupule; each acorn contains one seed (rarely two or three) and takes 6–18 months to mature, depending on their species. The acorns and leaves contain tannic acid, which helps to guard from fungi and insects. The live oaks are distinguished for being evergreen, but are not actually a distinct group and instead are dispersed across the genus.

Pig (zodiac)

The Pig (豬) is the twelfth of the 12-year cycle of animals which appear in the Chinese zodiac related to the Chinese calendar. In the continuous sexagenary cycle of sixty years, every twelfth year corresponds to hai, 亥 (the twelfth of the twelve Earthly Branches); this re-recurring twelfth year is commonly called the Year of the Pig (豬年). There are five types of Pigs, named after the Chinese elements. In order, they are: Metal, Water, Wood, Fire, and Earth. These correspond to the Heavenly Stems. Thus, there are five pig years in every sexegenary cycle. For example, in the year 2019, the Earthly Branch is the twelfth, hài, and the Heavenly Stem is the sixth, jǐ 己. The Chinese New Year in 2019 is February fifth: this corresponds with the beginning of both the sexegenary year of jǐ hài and also the zodiac year of the Earth Pig.

In the Japanese zodiac and the Tibetan zodiac, the Pig is replaced by the boar. In the Dai zodiac, the Pig is replaced by the elephant. In the Gurung zodiac, the Pig is replaced by the deer.

Pine

A pine is any conifer in the genus Pinus () of the family Pinaceae. Pinus is the sole genus in the subfamily Pinoideae. The Plant List compiled by the Royal Botanic Gardens, Kew and Missouri Botanical Garden accepts 126 species names of pines as current, together with 35 unresolved species and many more synonyms.

Ronnie Wood

Ronald David Wood (born 1 June 1947) is an English rock musician, songwriter, multi-instrumentalist, artist, author and radio personality best known as a member of The Rolling Stones since 1975, as well as a member of Faces and the Jeff Beck Group.

Wood began his career in 1964, when he joined The Birds on guitar. He then joined the mod group The Creation, but remained with the group only for a short time and appeared on a small number of singles. Wood joined the Jeff Beck Group in 1967 as a bass player. The band released two albums, Truth and Beck-Ola, which became moderate successes.

The group split in 1969, and Wood departed along with lead vocalist Rod Stewart to join former Small Faces members Ronnie Lane, Ian McLagan and Kenney Jones in a new group named Faces. The group found great success in the UK and mainland Europe, though were relegated to cult status in the United States. Faces released its debut album, First Step, in 1970. The group went on to release Long Player and A Nod Is As Good As a Wink... to a Blind Horse in 1971. Their last LP, titled Ooh La La, was released in 1973.

As the group began to split, Wood started several solo projects, eventually recording his first solo LP, I've Got My Own Album to Do, in 1974. The album featured bandmate McLagan as well as former Beatle George Harrison and Keith Richards of The Rolling Stones, a longtime friend of Wood's. Richards soon invited Wood to join the Rolling Stones, after the departure of Mick Taylor. Wood joined in 1975 and has remained a member ever since.Besides I've Got My Own Album to Do, Wood has recorded several other solo efforts. Now Look was released in 1975, and peaked at NO. 118 on Billboard, and Wood collaborated with Ronnie Lane for the soundtrack album Mahoney's Last Stand. He released Gimme Some Neck in 1979, which hit No. 45 in the US, 1234 was released in 1981, peaking at No. 164. He released Slide on This in 1992, Not for Beginners came out in 2002. and I Feel Like Playing in 2010. As a member of the Rolling Stones, Wood was inducted into the Rock and Roll Hall of Fame in 1989, and was inducted a second time, as a member of Faces, in April 2012.

Teak

Teak (Tectona grandis) is a tropical hardwood tree species placed in the flowering plant family Lamiaceae. Some forms of teak are known as Burmese teak, Central Province teak (CP teak), as well as Nagpur teak. T. grandis is a large, deciduous tree that occurs in mixed hardwood forests. It has small, fragrant white flowers arranged in dense clusters (panicles) at the end of the branches. These flowers contain both types of reproductive organs (perfect flowers). The large, papery leaves of teak trees are often hairy on the lower surface. Teak wood has a leather-like smell when it is freshly milled and is particularly valued for its durability and water resistance. The wood is used for boat building, exterior construction, veneer, furniture, carving, turnings, and other small wood projects.Tectona grandis is native to south and southeast Asia, mainly India, Sri Lanka, Indonesia, Malaysia, Thailand, Myanmar and Bangladesh but is naturalised and cultivated in many countries in Africa and the Caribbean. Myanmar's teak forests account for nearly half of the world's naturally occurring teak. Molecular studies show that there are two centres of genetic origin of teak: one in India and the other in Myanmar and Laos.The English word teak comes from Tamil tekku (தேக்கு), Malayalam thekku (തേക്ക്), Sinhala thekka (තේක්ක), and Kannada tega (ತೇಗ) via the Portuguese teca. In Bangladesh and West Bengal, the species is known as segun (সেগুন). Central Province teak and Nagpur teak are named for those regions of India.

Tree

In botany, a tree is a perennial plant with an elongated stem, or trunk, supporting branches and leaves in most species. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are usable as lumber or plants above a specified height. Trees are not a taxonomic group but include a variety of plant species that have independently evolved a woody trunk and branches as a way to tower above other plants to compete for sunlight. Trees tend to be long-lived, some reaching several thousand years old. In wider definitions, the taller palms, tree ferns, bananas, and bamboos are also trees. Trees have been in existence for 370 million years. It is estimated that there are just over 3 trillion mature trees in the world.A tree typically has many secondary branches supported clear of the ground by the trunk. This trunk typically contains woody tissue for strength, and vascular tissue to carry materials from one part of the tree to another. For most trees it is surrounded by a layer of bark which serves as a protective barrier. Below the ground, the roots branch and spread out widely; they serve to anchor the tree and extract moisture and nutrients from the soil. Above ground, the branches divide into smaller branches and shoots. The shoots typically bear leaves, which capture light energy and convert it into sugars by photosynthesis, providing the food for the tree's growth and development.

Trees usually reproduce using seeds. Flowers and fruit may be present, but some trees, such as conifers, instead have pollen cones and seed cones. Palms, bananas, and bamboos also produce seeds, but tree ferns produce spores instead.

Trees play a significant role in reducing erosion and moderating the climate. They remove carbon dioxide from the atmosphere and store large quantities of carbon in their tissues. Trees and forests provide a habitat for many species of animals and plants. Tropical rainforests are among the most biodiverse habitats in the world. Trees provide shade and shelter, timber for construction, fuel for cooking and heating, and fruit for food as well as having many other uses. In parts of the world, forests are shrinking as trees are cleared to increase the amount of land available for agriculture. Because of their longevity and usefulness, trees have always been revered, with sacred groves in various cultures, and they play a role in many of the world's mythologies.

Woodworking

Woodworking is the activity or skill of making items from wood, and includes cabinet making (cabinetry and furniture), wood carving, joinery, carpentry, and woodturning.

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