Wood

of these articles treats the raw material wood, further meanings under wood (term clarifying)
Verschiedene Holzarten

wood (v. althochdt.: wood = knocking off) marks the solid hard substance of the trunk, the branches and branches of trees and bushes. It becomes in the plants in an educated manner by the cells of the Meristems.

As more versatile, in particular however regenerating raw material is wood one of the most important plant products and wood belongs to the oldest useful plants.

In the forest one does not call wood present and living also Totholz.

Table of contents

wood

wood consists of:

resinous wood

Evolutionary resinous woods are older than hardwood, have therefore a simpler anatomical cell structure and to possess only two cell kinds.

  1. Tracheiden:Elongated one (prosenchymatische) to thatEnds pointedly approaching cells, which are filled with air or water only. They have a portion of 90 100% of the Holzsubstanz. Over Tüpfelpaare and/or Hoftüpfel so mentioned takes place the water exchange between the cells. In radial direction ensure the wood jets (Quertracheiden)for the water transportation. They have a portion of 4 12% at the entire Holzsubstanz.
  2. Parenchymzellen:Usually rectangular cells, which take over the line of feeding and stature materials as well as the storage of strength and fats. In radial direction they form for wood jets likewiseand the resin channels surround, here speak one then also of epithelium cells. These epithelium cells produce the resin, which they separate into the resin channel. Also coniferous trees, which do not possess resin channels (e.g.), Trauma tables of resin channels can form fir in such a way in case of a Verwundung.

The coniferous trees spruce, larch, Kiefer and douglas fir do not possess resin channels, Eibe, fir and Wacholder .

hardwood

The cells of hardwood are substantially more differentiated than from resinous wood. One can do it in three functional groupsdivide.

  1. Guidance fabric: Containers (tracheae), Gefässtracheiden, vasizentrische Tracheiden. The two latters are intermediate stages in the development of the Tracheide to the container.
  2. Strengthening fabric: Libroformfasern, Fasertracheiden
  3. Memory fabric: Holzstrahlenparenchymzellen, Längsparenchymzellen, epithelium cells

Of hardwood are not characteristic in resinous woods existing containers. They often are to recognize with the naked eye as small holes in the wood cross section and as grooves in the tangential cut. One differentiates here, depending upon arrangement of these tracheae, ring-porous woods (z. B. Oak, Edelkastanie, ash, Robinie, elm tree …), half ring-porous woods (z.B.Nut tree, cherry …) and absent-minded-porous woods (z. B.Birke, Erle, lime tree, Pappel, red beech, pasture …).

tropical wood

The term tropical wood is rather imprecise and not alternative to leaves or resinous woodto understand. It designates the wood growing in the tropical or subtropical regions of the earth from Central European view. Many tropical woods are characterised by favourable mechanical characteristics and higher stability against weathering, insect or fungal attack, often become also thoseColor or grain as responding felt. The consumption of tropical wood was discussed critically in the industrialized countries for the 1970er years, since the existence of the tropical rain forests is endangered by predatory exploitation among other things. On the other hand wood places an important restaurant factor for manytropical countries and is (as also in the moderate zones) an important source of income for the rural population.

Examples: Mahagoni, Teak, Balsaholz, Bangkirai, Bongossi, Abachi, Framiere

emergence of wood

0 = Mark; 1 Jahresringgrenze; 2 Harzkanäle; 3 Primäre Holzstrahlen; 4 Sekundäre Holzstrahlen; 5 Kambium; 6 Holzstrahlen des Bastes; 7 Korkkambium; 8 Bast; 9 Borke
0 = Mark; 1 yearly ring border; 2 resin channels; 3 primary wood jets; 4 secondary wood jets; 5 Kambium; 6 wood jets of the phloem; 7 Korkkambium; 8 phloem; 9 bark

the emergence of Holzsubstanz finds in divisionable cells of the plantinstead of. One differentiates here two different kinds from education fabrics (Meristeme):

  • The Scheitelmeristem (vegetation cone) provides for length growth (primary growth) at the sprouting, branch and root points.
  • The Kambium, which is between wood and crust, provides for thickness growth (secondaryGrowth).
    During the division of a Kambiumzelle two equal cells develop, from which however only their division ability keeps and grows up to a new initial cell.
    From the other one a continuous cell becomes still in or several times divides. Finally develops everaccording to layer a phloem cell (Phloem), from which the interior crust and the bark developing later from it exists, or a wood cell (Xylem). Here it is to be noted that the cell division inward, thus the formation of wood cells substantially more frequentlyand so the crust portion of the entire trunk only about 5 takes place 15% amounts to.
    After the continuous cell the latter divided times, a differentiation of the wood cell takes place to a line, a strengthening or a memory cell.

In our widths it gives climaticallycauses four growth phases:

  • Dwell phase (November February)
  • mobilization phase (March, April)
  • growth phase (May July): Wood cells, those in this season develop are grosslumig, thin-walled and from bright color and form the Frühholz in such a way specified.
  • Deposition phase (August Octobers): Wood cells, those in this season develop are kleinlumig,thick-walled and of dark color and form the Spätholz in such a way specified (and/or. Herbstholz).

From this cyclic growth behavior result Jahresringe, which are clearly in a cross section recognizable by a trunk (see also dendrochronology).

structure of the cell wall

If one moves from the outside into the inside of a wood cell, one crosses several layers those together the cell wall forms and under an electron microscope is recognizable. Between the cells the central lamella, those is together with the primary wall in such a way specifiedCentral layer forms. Afterwards the secondary wall 1 (S 1) and secondary wall 2 (S 2) follows, whereby S 2 - layer the most powerful and dominierenste is. The following Tertiary period wall (S 3) is covered by a wart layer and forms thatAbschluss.Die individual layers or lamellas consist of Fibrillen (Mikrofibrillen), which are formed again from Elementarfibrillen (Mizellen). Elementarfibrillen are bundles from several cellulose macromolecules, those from 10 - 14,000 glucose components consist and into a matrix of Hemizellulosen and lignin embeddedare and form amorphous and crystalline ranges. A water storage does not leave itself a pouring and shrinking the wood with water absorption and delivery practically by the orientation of these crystalline ranges, within which the Elementarfibrillen run strictly parallel, is closely packed andtakes place, in which S 2 dominaten - layer explain. Here these ranges are arranged so well parallel to the master axle; amorphous ranges in those more waters to be clearly bound and the volume knows is increased in such a way is in more radial and tangentialMaster direction thus more frequently to find than in master longitudinal direction, in which the wood therefore 10 - 20mal fewer swelling deformations exhibits. In relatively thin S 1 - and S 3 - layer the crystalline ranges run orthogonal to those in thick S2 - Layer.

Verkernung

as Splintholz one designates the range of the trunk, which participates actively in the water and nutrient transport. With split pin wood trees (z. B. Sycamore, Birke, Erle, Pappel, pointed maple, white beech…) it is the whole master cross section. Ita uniform colour does not exhibit and it takes place Verkernung.

Of the Verkernung of wood one speaks, if the internal water guidance courses of the trunk are interrupted and the cells to die. This is done with resinous woods via locking the Hoftüpfel andHardwood by a Verthyllung and filling the cell lumens at an age of approx. 20-40 years. Afterwards core contents materials are formed and stored into the cell walls, which often leads to an increase of the natural durability. The core range is clear by onedarken colouring to recognize, one speaks of heartwood trees (z. B. Oak, Walnuss, Kiefer, cherry tree, douglas fir, larch, Robinie…).

If no difference in color is to be recognized, but over the reduced moisture content on it to be closed that that is verkernt internal area, speaks one can of hoar frost wood trees (z. B. Spruces, fir, lime tree, Birnbaum, red beech…).

With core hoar frost wood trees (z. B. Ash, elm tree…) the core is not coloured set off, followed from a hoar frost wood range, just like the core the any more at nutrient transport participates and an outsideSplit pin range.

Fig. 1:
Cross section by an oak trunk (heartwood tree).
Fig. 2:
Cross section by a Kiefernstamm (heartwood tree).
Fig. 3:
Cross section by a spruce trunk (hoar frost wood tree).

production and use

with the production of wood for industrielle or other purposes are betweento differentiate lasting forestry and devastierendem predatory exploitation.

also

Aufgerichtetes Holz
wood has

areas of application put up wood like every other material its pro and cons.

Under ecological criterion the reproductibility is surely an important point, but also the easy workability andthe associated low power requirement with the production as well as with the processing play here an important role. If the wood finally moves on the garbage or of wastes result with the production, it can be disposed problem-free. Ideally it can to be even kompostiert. If escort substances do not permit such as wood preservatives, lacquers or glues this, modern flue gas purification makes a thermal use possible also in these cases. The long-term use of wood represents over the natural decomposition going out CO 2 - to storage.

Due to its small heat guidance ability wood is a outstanding damming material (z. B. Fiber damming plates, Balsa for the isolation of liquid gas tanks). Besides wood is relatively resistant to chemicals, then wood is only attacked at a pH value under 2 or over 9.

Sender Gleiwitz
Transmitter Gleiwitz

in contrast to metals is wood electrically not conductive. For this reason one built numerous transmitting towers for medium-wave transmitters from wood in the thirties, whereby the antenna wire was hung up inside the tower. With exception of the transmitting tower of the Transmitters Gleiwitz became all these buildings either at the end 2. World war destroys or in the meantime torn off. Further the German Telekom AG uses high wood towers, which were manufactured without use of metal parts in bridges two 54 meters. These serve as the admissionof antennas which can be measured. By the metal-free construction of the towers unimpaired measuring of the antenna patterns is possible.

To the fire danger by timber buildings it is to be marked that wood is classified with large dimensions as fire-restraining, since on its surface under Feuereinwirkung a carbon film develops.Also by the kind of the building method and by certain painting the resistance period of a timber construction can be increased. Building stability sinks in the case of fire slowly and assessably by the reduction of the mass. With structural steelworks against it heat-conditioned deformations can lead to the sudden collapse.Combustibility can be laid out naturally also as disadvantage.

In principle does not oppose the building from multistoried buildings from wood anything; this is however meaningful from static view only for the highest floors at all and due to care susceptibility (wood preservative)not economically. The highest wood building of the world is located in Magdeburg, Germany. This concerns the thousands of years tower (1999 open in the context of the Bundesgartenschau on the area of the Elbauenparks).

Also stature characteristics or wood defects can being rated positively like negatively.

[[Ein]]substantially larger disadvantage of wood is its susceptibility opposite bio tables factors, it can thus from z. B. Insects, mushrooms or bacteria to be attacked and in its substance be lastingly destroyed.

During a long period also UV-RADIATION damages the wood.The lignin reacts to z as cement substance and can thereafter. B. by the rain water to be rinsed out. Besides the wood under UV effect becomes grey like concrete. The effect of the sunlight is limited to the outside layers, their can by lacquer finish be met.

A further point of minus is working, thus the deformations of the wood. On the one hand wood shrinks in principle with increasing age, and can throw itself also by the dismantling of the tensions developed in the living wood. On the other hand the hygroscopic characteristic causesof wood - D. h. it can take up and deliver water - over the whole life span deformation. The moisture content of wood adapts to its environment climate. These humidity variations below the fiber saturation point accompany with form fluctuations (it pours and shrinks), also stillon the three anatomical basic directions of the wood are dependent. Thus wood z shrinks. B. in tangential direction at most. More details is located in the section structure of the cell wall further above.

These disadvantages leave themselves by constructional wood preservation - application often oldKnowledge, how wood to block actual goes around. A new possibility of making wood more insensitive to moisture effects is that thermal wood - process.

wood working and wood processing

wood in the wood working and wood processing used as:

used wood is called as mature timber and serves cut up raw material for the wood-based materials industry. Mature timber is used increasingly in addition, as fuel material in biomass power stations to the regenerativ and CO 2 - neutral power production.

see also

  • woods - overWood as building material
  • forestry - management from forests to the production of wood
  • wood processing - treatment of wood and materials from wood (chip boards etc.)

literature

  • DIN of 68364 “characteristic values of wood”
  • R. Bruce Hoadley: Wood as material.O. MeierPublishing house, Ravensburg 1990, ISBN 3473425605
  • P. Niemz: Physics of the wood and the timber materials. DRW publishing house, Stuttgart 1993, ISBN 3871813249
  • car-lead wood Atlas technical book publishing house Leipzig, Leipzig 1996, ISBN 3-446-00900-0
  • H.H. Bad hard Holzkunde part of 1-3 Birkhäuser publishing house, Stuttgart 1982, ISBN 3-7643-1328-5
  • Paul Lehfeldt: Timber construction art [Reprint]. Reprint publishing house Leipzig, Leipzig and Holzminden o.J., ISBN 3-8262-1210-X
  • Anselm jump, Maximilian glass: Wood. The fifth element. Frederking & Thaler, Munich 2005, ISBN 3-89405-523-5
  • Udo one rope, Jörg Wagner, Janett Baumann: Material flow model WOOD: Determination of arising,the use and the whereabouts of wood products. Garbage and waste 37 (6), S. 309 - 315 (2005), ISSN 0027-2957

Web on the left of

Wiktionary: Wood - word origin, synonyms and translations
Wikiquote: Wood - quotations
Commons: Wood - pictures, videos and/or audio files
Generally
wood
science
economics
 

  > German to English > de.wikipedia.org (Machine translated into English)