Wood \Wood\, n. [OE. wode, wude, AS. wudu, wiodu;
akin to OHG. witu, Icel. vi?r, Dan. & Sw. ved wood, and
probably to Ir. & Gael. fiodh, W. gwydd trees, shrubs.] [1913
Webster]
A large and thick collection of trees; a forest
or grove; -- frequently used in the plural. [1913 Webster] Light
thickens, and the crow Makes wing to the rooky wood. --Shak. [1913
Webster]
The substance of trees and the like; the hard
fibrous substance which composes the body of a tree and its
branches, and which is covered by the bark; timber. "To worship
their own work in wood and stone for gods." --Milton. [1913
Webster]
(Bot.) The fibrous material which makes up the
greater part of the stems and branches of trees and shrubby plants,
and is found to a less extent in herbaceous stems. It consists of
elongated tubular or needle-shaped cells of various kinds, usually
interwoven with the shinning bands called silver grain. [1913
Webster] Note: Wood consists chiefly of the carbohydrates cellulose
and lignin, which are isomeric with starch. [1913 Webster]
Trees cut or sawed for the fire or other uses.
[1913 Webster] Wood acid,
Wood
vinegar (Chem.), a complex acid liquid obtained in the dry
distillation of wood, and containing large quantities of acetic
acid; hence, specifically, acetic acid. Formerly called pyroligneous
acid. Wood anemone
(Bot.), a delicate flower (Anemone
nemorosa) of early spring; -- also called windflower. See Illust. of
Anemone. Wood ant
(Zool.), a large ant (Formica
rufa) which lives in woods and forests, and constructs large
nests. Wood apple
(Bot.). See Elephant
apple, under Elephant. Wood baboon
(Zool.), the drill. Wood betony.
(Bot.) (a) Same as Betony. (b) The common American
lousewort (Pedicularis
Canadensis), a low perennial herb with yellowish or purplish
flowers. Wood borer.
(Zool.) (a) The larva of any one of numerous species of boring
beetles, esp. elaters, longicorn beetles, buprestidans, and certain
weevils. See Apple borer,
under Apple, and Pine weevil,
under Pine. (b) The larva
of any one of various species of lepidopterous insects, especially
of the clearwing moths, as the peach-tree borer (see under Peach), and of the goat moths. (c)
The larva of various species of hymenopterous of the tribe
Urocerata. See Tremex.
(d) Any one of several bivalve shells which bore in wood, as the
teredos, and species of Xylophaga. (e) Any one of several species
of small Crustacea, as the Limnoria, and the boring
amphipod (Chelura
terebrans). Wood carpet,
a kind of floor covering made of thin pieces of wood secured to a
flexible backing, as of cloth. --Knight. Wood cell
(Bot.), a slender cylindrical or prismatic cell usually tapering to
a point at both ends. It is the principal constituent of woody
fiber. Wood choir,
the choir, or chorus, of birds in the woods. [Poetic] --Coleridge.
Wood
coal, charcoal; also, lignite, or brown coal. Wood cricket
(Zool.), a small European cricket (Nemobius
sylvestris). Wood culver
(Zool.), the wood pigeon. Wood cut, an
engraving on wood; also, a print from such an engraving. Wood dove
(Zool.), the stockdove. Wood drink, a
decoction or infusion of medicinal woods. Wood duck
(Zool.) (a) A very beautiful American duck (Aix sponsa).
The male has a large crest, and its plumage is varied with green,
purple, black, white, and red. It builds its nest in trees, whence
the name. Called also bridal duck,
summer
duck, and wood
widgeon. (b) The hooded merganser. (c) The Australian maned
goose (Chlamydochen
jubata). Wood echo, an
echo from the wood. Wood
engraver. (a) An engraver on wood. (b) (Zool.) Any of several
species of small beetles whose larvae bore beneath the bark of
trees, and excavate furrows in the wood often more or less
resembling coarse engravings; especially, Xyleborus
xylographus. Wood
engraving. (a) The act or art engraving on wood; xylography.
(b) An engraving on wood; a wood cut; also, a print from such an
engraving. Wood fern.
(Bot.) See Shield fern,
under Shield. Wood fiber.
(a) (Bot.) Fibrovascular tissue. (b) Wood comminuted, and reduced
to a powdery or dusty mass. Wood fretter
(Zool.), any one of numerous species of beetles whose larvae bore
in the wood, or beneath the bark, of trees. Wood frog
(Zool.), a common North American frog (Rana
sylvatica) which lives chiefly in the woods, except during the
breeding season. It is drab or yellowish brown, with a black stripe
on each side of the head. Wood
germander. (Bot.) See under Germander. Wood god, a
fabled sylvan deity. Wood grass.
(Bot.) See under Grass.
Wood
grouse. (Zool.) (a) The capercailzie. (b) The spruce partridge.
See under Spruce.
Wood
guest (Zool.), the ringdove. [Prov. Eng.] Wood hen.
(Zool.) (a) Any one of several species of Old World short-winged
rails of the genus Ocydromus, including the weka
and allied species. (b) The American woodcock. Wood hoopoe
(Zool.), any one of several species of Old World arboreal birds
belonging to Irrisor and
allied genera. They are closely allied to the common hoopoe, but
have a curved beak, and a longer tail. Wood ibis
(Zool.), any one of several species of large, long-legged, wading
birds belonging to the genus Tantalus. The head and neck are
naked or scantily covered with feathers. The American wood ibis
(Tantalus
loculator) is common in Florida. Wood lark
(Zool.), a small European lark (Alauda
arborea), which, like, the skylark, utters its notes while on
the wing. So called from its habit of perching on trees. Wood laurel
(Bot.), a European evergreen shrub (Daphne
Laureola). Wood leopard
(Zool.), a European spotted moth (Zeuzera
aesculi) allied to the goat moth. Its large fleshy larva bores
in the wood of the apple, pear, and other fruit trees. Wood lily
(Bot.), the lily of the valley. Wood lock
(Naut.), a piece of wood close fitted and sheathed with copper, in
the throating or score of the pintle, to keep the rudder from
rising. Wood louse
(Zool.) (a) Any one of numerous species of terrestrial isopod
Crustacea belonging to Oniscus, Armadillo, and related genera.
See Sow
bug, under Sow, and Pill bug, under
Pill. (b) Any one of
several species of small, wingless, pseudoneuropterous insects of
the family Psocidae,
which live in the crevices of walls and among old books and papers.
Some of the species are called also book lice, and
deathticks, or
deathwatches.
Wood
mite (Zool.), any one of numerous small mites of the family
Oribatidae. They are
found chiefly in woods, on tree trunks and stones. Wood mote.
(Eng. Law) (a) Formerly, the forest court. (b) The court of
attachment. Wood nettle.
(Bot.) See under Nettle.
Wood
nightshade (Bot.), woody nightshade. Wood nut (Bot.),
the filbert. Wood nymph.
(a) A nymph inhabiting the woods; a fabled goddess of the woods; a
dryad. "The wood nymphs, decked with daisies trim." --Milton. (b)
(Zool.) Any one of several species of handsomely colored moths
belonging to the genus Eudryas. The larvae are
bright-colored, and some of the species, as Eudryas
grata, and Eudryas
unio, feed on the leaves of the grapevine. (c) (Zool.) Any one
of several species of handsomely colored South American humming
birds belonging to the genus Thalurania. The males are
bright blue, or green and blue. Wood
offering, wood burnt on the altar. [1913 Webster] We cast the
lots . . . for the wood offering. --Neh. x.
[1913 Webster] Wood oil (Bot.),
a resinous oil obtained from several East Indian trees of the genus
Dipterocarpus,
having properties similar to those of copaiba, and sometimes
substituted for it. It is also used for mixing paint. See Gurjun. Wood opal
(Min.), a striped variety of coarse opal, having some resemblance
to wood. Wood paper,
paper made of wood pulp. See Wood pulp,
below. Wood pewee
(Zool.), a North American tyrant flycatcher (Contopus
virens). It closely resembles the pewee, but is smaller.
Wood pie
(Zool.), any black and white woodpecker, especially the European
great spotted woodpecker. Wood pigeon.
(Zool.) (a) Any one of numerous species of Old World pigeons
belonging to Palumbus
and allied genera of the family Columbidae. (b) The ringdove.
Wood
puceron (Zool.), a plant louse. Wood pulp
(Technol.), vegetable fiber obtained from the poplar and other
white woods, and so softened by digestion with a hot solution of
alkali that it can be formed into sheet paper, etc. It is now
produced on an immense scale. Wood quail
(Zool.), any one of several species of East Indian crested quails
belonging to Rollulus
and allied genera, as the red-crested wood quail (Rollulus
roulroul), the male of which is bright green, with a long crest
of red hairlike feathers. Wood rabbit
(Zool.), the cottontail. Wood rat
(Zool.), any one of several species of American wild rats of the
genus Neotoma found in
the Southern United States; -- called also bush rat. The
Florida wood rat (Neotoma
Floridana) is the best-known species. Wood reed
grass (Bot.), a tall grass (Cinna
arundinacea) growing in moist woods. Wood reeve,
the steward or overseer of a wood. [Eng.] Wood rush
(Bot.), any plant of the genus Luzula, differing from the true
rushes of the genus Juncus chiefly in having very few
seeds in each capsule. Wood sage
(Bot.), a name given to several labiate plants of the genus
Teucrium. See Germander. Wood screw, a
metal screw formed with a sharp thread, and usually with a slotted
head, for insertion in wood. Wood
sheldrake (Zool.), the hooded merganser. Wood shock
(Zool.), the fisher. See Fisher,
Wood shrike
(Zool.), any one of numerous species of Old World singing birds
belonging to Grallina,
Collyricincla,
Prionops, and allied
genera, common in India and Australia. They are allied to the true
shrikes, but feed upon both insects and berries. Wood snipe.
(Zool.) (a) The American woodcock. (b) An Asiatic snipe (Gallinago
nemoricola). Wood soot, soot
from burnt wood. Wood sore.
(Zool.) See Cuckoo spit,
under Cuckoo. Wood sorrel
(Bot.), a plant of the genus Oxalis (Oxalis
Acetosella), having an acid taste. See Illust. (a) of Shamrock. Wood spirit.
(Chem.) See Methyl
alcohol, under Methyl. Wood stamp, a
carved or engraved block or stamp of wood, for impressing figures
or colors on fabrics. Wood star
(Zool.), any one of several species of small South American humming
birds belonging to the genus Calothorax. The male has a
brilliant gorget of blue, purple, and other colors. Wood sucker
(Zool.), the yaffle. Wood swallow
(Zool.), any one of numerous species of Old World passerine birds
belonging to the genus Artamus and allied genera of the
family Artamidae. They
are common in the East Indies, Asia, and Australia. In form and
habits they resemble swallows, but in structure they resemble
shrikes. They are usually black above and white beneath. Wood tapper
(Zool.), any woodpecker. Wood tar. See
under Tar. Wood thrush,
(Zool.) (a) An American thrush (Turdus
mustelinus) noted for the sweetness of its song. See under
Thrush. (b) The missel
thrush. Wood tick. See
in Vocabulary. Wood tin.
(Min.). See Cassiterite. Wood
titmouse (Zool.), the goldcgest. Wood
tortoise (Zool.), the sculptured tortoise. See under Sculptured. Wood vine
(Bot.), the white bryony. Wood
vinegar. See Wood acid,
above. Wood
warbler. (Zool.) (a) Any one of numerous species of American
warblers of the genus Dendroica. See Warbler. (b) A European warbler
(Phylloscopus
sibilatrix); -- called also green wren,
wood
wren, and yellow wren.
Wood
worm (Zool.), a larva that bores in wood; a wood borer.
Wood
wren. (Zool.) (a) The wood warbler. (b) The willow warbler.
[1913 Webster]
Wood \Wood\ (w[oo^]d), a. [OE. wod, AS. w[=o]d;
akin to OHG. wuot, Icel. [=o][eth]r, Goth. w[=o]ds, D. woede
madness, G. wuth, wut, also to AS. w[=o][eth] song, Icel.
[=o][eth]r, L. vates a seer, a poet. Cf. Wednesday.] Mad; insane;
possessed; rabid; furious; frantic. [Obs.] [Written also wode.] [1913 Webster] Our hoste gan
to swear as [if] he were wood. --Chaucer. [1913 Webster]
Wood \Wood\, v. t. [imp. & p. p. Wooded; p. pr. & vb. n.
Wooding.] To supply with
wood, or get supplies of wood for; as, to wood a steamboat or a
locomotive. [1913 Webster] [1913 Webster]
Wood \Wood\, v. i. To take or get a supply of
wood. [1913 Webster]
Word Net
woodNoun
1 the hard fibrous lignified substance under the
bark of trees
3 United States film actress (1938-1981) [syn:
Natalie
Wood]
4 English conductor (1869-1944) [syn: Sir Henry
Wood, Sir
Henry Joseph Wood]
5 English writer of novels about murders and
thefts and forgeries (1814-1887) [syn: Mrs. Henry
Wood, Ellen
Price Wood]
6 United States painter noted for works based on
life in the Midwest (1892-1942) [syn: Grant
Wood]
7 any wind instrument other than the brass
instruments [syn: woodwind, woodwind
instrument]
8 a golf club with a long shaft used to hit long
shots; originally made with a wooden head; metal woods are now
available
Moby Thesaurus
acacia, afforestation, alder, arboretum, ash, backlog, balsa, balsam, banyan, bass, basswood, bavin, beam, beech, beechwood, billet, birch, board, boarding, boondocks, brush, brushwood, burl, bush, bushveld, buttonwood, chase, cherry, chestnut, clapboard, climax forest, cloud forest, cord, cordwood, cork, cypress, deal, dendrology, dogwood, driftwood, ebony, elm, eucalyptus, fagot, fir, firewood, forest, forest land, forest preserve, forestry, fringing forest, gallery forest, greenwood, gum, gumwood, hanger, hardwood, hazel, hemlock, hickory, index forest, ironwood, jungle, jungles, juniper, kindling, kindlings, lancewood, larch, lath, lathing, lathwork, linden, locust, log, logwood, lumber, magnolia, mahogany, maple, national forest, oak, olive, palmetto barrens, panelboard, paneling, panelwork, park, park forest, pecan, pine, pine barrens, plank, planking, plyboard, plywood, pole, poplar, post, primeval forest, protection forest, puncheon, rain forest, redwood, reforestation, sandalwood, scrub, scrubland, selection forest, shake, sheathing, sheathing board, sheeting, shingle, shrubland, sideboard, siding, silviculture, slab, slat, softwood, splat, sprout forest, spruce, stand of timber, state forest, stave, stick, stick of wood, stovewood, sumac, sycamore, teak, three-by-four, timber, timbering, timberland, timberwork, tree veld, two-by-four, virgin forest, walnut, weatherboard, wildwood, woodland, woods, yew, yule clog, yule logsee Wood
English
Homophones
Noun
- The substance making up the central part of the trunk and branches of a tree. Used as a material for construction, to manufacture various items, etc. or as fuel.
- As the previous but referring to wood of a particular species.
- Teak is much used for outdoor benches, but a number of other woods are also suitable, such as ipé, redwood, etc.
- A forested or wooded
area, most often used in the plural.
- He got lost in the woods beyond Seattle.
- Firewood.
- A type of golf club, the head of which is frequently made of wood.
- A woodwind instrument.
- An erection.
Derived terms
- bentwood
- greasewood
- hardwood
- heartwood
- kingwood
- knock on wood
- ironwood
- olivewood
- out of the woods
- purplewood
- softwood
- whitewood
- woodchopper
- woodcock
- wooded
- wooden
- woodpecker
- woody
Translations
substance
- Albanian: dru
- Arabic: خشب
- Basque: zur
- Blackfoot: mĭstcĭs
- Breton: koad , koadeier / koadoù
- Catalan: fusta
- Chinese: 木 (mù)
- Crimean Tatar: taqta
- Croatian: drvo
- Czech: dřevo
- Dutch: hout
- Esperanto: ligno
- Estonian: puit
- Finnish: puu
- French: bois
- German: Holz
- Greek: ,
- Classical: ξύλον
(xýlon)
- Modern: ξύλο (xýlo), ξυλεία (xylía)
- Classical: ξύλον
(xýlon)
- Guarani: yvyra
- Hebrew: עץ (‘ets), קרש (khorsh)
- Hindi: लक्डी (luckdee)
- Hopi: koho
- Hungarian: fa
- Ilocano: kayo
- Indonesian: kayu
- Interlingua: ligno
- Irish: adhmad
- Italian: legno, bosco
- Japanese: 木, 木材 (もくざい, mokuzai)
- Korean: 나무 (namu), 목재 (木材, mokjae)
- Kurdish: دار
- Lakota: čą
- Lithuanian: medis
- Malay: kayu
- Marathi: लाकुड (Lākud)
- Mingo: úwẽ'kææ', uyêta'
- Mohawk: oyente
- Norwegian: tre, treverk
- Occitan: fusta
- Ossetian: (khaed)
- Piemontese: bosch
- Polish: drewno
- Portuguese: madeira
- Romanian: lemn
- Romansch: lain
- Russian: дерево
- Sardinian: linna
- Scottish Gaelic: fiodh
- Slovene: les
- Spanish: madera
- Swedish: trä
- Tatar: агач (agaç)
- Tupinambá: ybyrá
- Turkish: odun
- Welsh: coed
- West Frisian: hout
- Yucatec: čeʼ
wood from a particular species
- Finnish: puulaji
- German: Holz
woodland
firewood
type of golf club
- Finnish: puu, puumaila
- German: Holz
music: woodwind instrument
- Finnish: puupuhallin
slang: an erection
- Finnish: stondis
- German: Latte
Adjective
- Made of wood.
Synonyms
Translations
made of wood
Verb
- To cover or plant with trees.
Translations
Etymology 2
Old English wōd.Adjective
en-adj erWood is hard, fibrous, lignified
structural tissue produced as secondary xylem in the stems of woody plants,
notably trees but also
shrubs. It conducts water
to the leaves and other growing tissues and acts as a support
function, enabling plants to reach large sizes. Wood may also refer
to other plant materials and tissues with comparable
properties.
Wood is a heterogeneous, hygroscopic, cellular
and anisotropic
material. It is composed of fibers of cellulose (40% – 50%) and
hemicellulose (15%
– 25%) impregnated with lignin (15% – 30%).
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 and boats. Nearly all boats were made
out of wood till the late 1800s, and wood
remains in common use today in boat construction. New domestic
housing in many parts of the world today is commonly made from
timber-framed construction. 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 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.
Wood unsuitable for construction in its native
form 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 chipboard,
engineered
wood, hardboard,
medium-density
fiberboard (MDF), oriented
strand board (OSB). 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 also be used for kinds of flooring,
for example laminate
flooring.
Wood is also used for cutlery, such as chopsticks, toothpicks, and other
utensils, like the wooden
spoon.
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 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
textured and almost
invariably lighter in colour 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. In white
pines 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 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
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 (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 (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
than where 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, direction of fiber, 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.
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 fiber than upon
defects in the beam. The effect of knots is to reduce the
difference between the fiber stress at elastic limit and the
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 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
Heartwood is wood that has died and become resistant to decay as a result of genetically programmed processes. It appears in a cross-section as a discolored circle, following annual rings in shape. Heartwood is usually much darker than 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 roots to the 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 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 trees as chestnut,
black
locust, mulberry,
osage-orange,
and sassafras, while
in maple, 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 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.
There may be decided differences in the 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,
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 tree 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
building. The densest wood may be black
ironwood.
Wood is commonly classified as either softwood or hardwood. The wood
from conifers (e.g.
pine) is called softwood, and the wood from 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 most hardwoods.
Wood products such as plywood are typically classified
as engineered wood and not considered raw wood.
Colour
In species which show a distinct difference between heartwood and sapwood the natural colour 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.Since the late wood of a growth ring is usually
darker in colour 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 colour of wood is no
indication of strength.
Abnormal discolouration 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 discolouration 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 colours 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 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 the hardwoods is more complex.
They are more or less filled with vessels: in some cases (oak,
chestnut, 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, 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.
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.
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 fibers 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
fibers which form one-half or more of the wood. In inferior oak,
such fiber 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
spokes. 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 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."
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."
See also
References
- 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
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