Ⅰ. The nature of gross features

木材宏观特征的属性

Ⅱ. The gross structural features of wood valuable in identification

具有木材识别价值的宏观结构特征

Ⅲ. The physical properties of wood valuable in identification

具有木材识别价值的物理性能

Ⅳ. Principles of wood identification 木材识别原理

Chapter 3 The Gross Features of Wood 木材宏观特征

Ⅰ. The nature of gross features

In wood identification of gross level, we often need to use lots of gross features of wood, so it necessary for us to know well some basic features of wood.

The gross features of wood are of two kinds:

— Structural features those traceable to wood structure e.g.: wood rays, pores, annual rings

— physical features those no relation to structure e.g.: color, odor, weight

Ⅱ. The gross structural features of wood

1. The three standard planes of wood In wood anatomical research, all the wood structural features are discussed on this three standard planes.

• Cross Section ： cut at right angles to the grain (axis) .• Tangential Section ： cut along the grain and right to wood rays• Radial Section ： cut along the grain and following a radius

2. Growth increments （生长轮） In most species in temperate climates, the difference between wood that is formed early in a growing season and that formed later is sufficient to produce well-marked annual growth rings. The age of a tree at the stump or the age at any cross section of the trunk may be determined by counting these rings.

2-1 Annual rings of normal type ( 正常年轮 )

• Conceptions of growth increments and annual rings The former is the layer of wood produced in one growth season, an

d the latter is the layer of wood produced in one year. In cold and temperate areas, there is only one growing season in a y

ear, so in this case, growth increments and annual rings are the same thing; while in tropical and some subtropical areas, there are more than one growing season in a year, and in this case, growth increments and annual rings are two different conceptions.

• The appearance of annual rings on different planes

Concentric rings Parallel strips Parabolas mounted one after another

2-2 Earlywood and latewood ( 早材与晚材 )

• Earlywood The inner part of the growth ring formed first in the growing season is called earlywood (spring wood). Earlywood is characterized by cells with relatively large cavities and thin walls.

• Latewood The outer part of the growth ring formed later in the growing season is called latewood (summer wood). Latewood cells have smaller cavities and thicker walls.

2-3 Annual rings of abnormal type ( 非正常年轮 )

• Discontinuous rings It is the ring which was interrupted at one or more points because that the growth of the tree was stopped at local places by fire or insects attack, while the growth of other parts of the tree continued normally.

• False rings The tree growth in diameter may be interrupted by the influence of drought or defoliation because of insect attack. When the influence was over, the tree growth continued again, and so, more than one ring was formed in the same season. In such an event, the inner rings usually do not have sharply defined boundaries and are termed false rings.

• Identification of false rings False rings can be distinguished from true rings in that the cells composing the false summerwood grade gradually, not only to the inside but also to the outside.

2-4 Annual rings in relation to quality of wood

The quality of wood is affected by ring width in most and probably in all tree-species.

Generally speaking, rings of unusual width frequently mean lumber of inferior quality, while lumber with narrow rings usually means high mechanical strength and high quality.

For the same tree species, the faster a tree grows, the wider the annual rings, and the lower the quality of wood produced.

3-1 Conception of sapwood and heartwood

3. Sapwood and heartwood （边材与心材）

Sapwood

Heartwood

3-2 Formation of heartwood

Heartwood arises from sapwood. When a tree is young, all the section of the tree stem was used to conduct sap, so that all wood belongs to sapwood.

As the tree grows on, the tree stem becomes thicker and thicker, and part of the stem near the pith is not needed to play conduction function anymore. At this time, some kinds of extractives would deposit in the area that had no conduction function, and gradually this part of the stem turns into heartwood.

As the tree grows older and older, more and more heartwood would be produced in this way.

3-3 Main differences of heartwood from sapwood

Compared with sapwood, usually heartwood exhibits significant difference in the following 7 aspects:

• color is darker;

• infiltration content is higher;

• weight is heavier;

• strength is higher;

• natural durability is better;

• permeability is lower;

• moisture content of green wood is much lower.

3-4 Some conceptions

• Heartwood species( 心材树种）： The wood species that possess significant difference between sapwood and heartwood in color.

• Sapwood species( 边材树种）： The wood species that possess no significant difference in color and moisture content between the two parts near pith and bark.

• Heartwood concealed species( 隐心材树种）： No difference in color but with difference in M.C. between sapwood and heartwood.

• False heartwood( 假心材）： pathologically darkened wood near the center in sapwood species.

• Included sapwood( 内含边材）： fungus affected light colored wood occurred in heartwood of heartwood species.

4. Wood rays （木射线）

4-1 Conception

The ribbon-like tissues extending in the radial direction, i.e., from the pith toward the bark running at more or less right angles to the growth increments, when viewed on the transverse section.

4-2 The textile structure of wood

In structure, wood bears some analogy to a textile in which the threads run at right angles.

In this analogy the rays would represent the cross threads, and the remaining tissues the long threads.

4-3 Functions of wood rays

— Radial conduction; — Storage of nutrients; — Strengthening in transverse.

4-4 Appearances of wood rays on different planes

C: rays from pith to bark; R: flecks or ribbons at right angles to the grain; T: staggered small lines along the grain.

5. Wood parenchyma ( 木薄壁组织 )

5-1 Ray parenchyma （射线薄壁组织） : the main body of wood rays.

5-2 Epithelial parenchyma （伴生薄壁组织） : the secretory cells composing resin canals and gum canals. 5-3 Longitudinal parenchyma （轴向薄壁组织） : the parenchymatous cells extending along the grain in the form of strands.

5-4 Distribution of longitudinal parenchyma

The distribution patterns of longitudinal parenchyma can be divided into two groups:

— Apotracheal parenchyma （离管型薄壁组织）： Diffuse parenchyma （星散型） Diffuse-in-aggregate （星散聚合型） Apotracheal banded （离管带状） Initial （轮始型） Terminal （轮末型）

— Paratracheal parenchyma （傍管型薄壁组织） Scanty parenchyma （稀疏傍管） One-sided （单侧傍管） Vasicentric （环管型） Aliform （翼状） Confluent aliform （聚翼状） Paratracheal banded （傍管带状）

6. Pores ( 管孔）

6-1 Definition

Pores are the bird-eye views of vessel elements.

6-2 Main difference between softwood and hardwood

• Softwood — Nonporous wood

without pores, except Ephedraceae （麻黄科）• Hardwood — Porous wood

with pores, except Tetracentron sinensis （水青树）

6-3 Arrangement of pores （管孔的排列）

• Ring-porous wood — 环孔材• Diffuse-porous wood — 散孔材• Semi-porous wood — 半环孔材• Radiant porous wood — 辐射孔材• Tangent porous wood — 切线孔材• Staggered porous wood — 交叉孔材

6-4 Distribution of pores （管孔的分布）

Usually refers to the pores in latewood of ring-porous wood.

Flame-shaped Scattered star-like tangent line –like

火焰状 星散型 弦切型

6-5 Combination of pores （管孔的组合）

Usually refers to the relationships between pores.

— Solitary pores / 单管孔

— Compound pores / 复管孔

— Pore chains / 管孔链

— Clustered pores / 管孔团

7. Resin canals （树脂道）

7-1 Normal resin canals Structure Function: Storage room of resin Wood species with normal resin canals (Pinaceae)

Pinus ( 松属 ) ； Picea( 云杉属 ) ； Cathaya( 银杉属 ) ； Larix( 落叶松属 )

Pseudotsuga( 黄杉属 ) ； Ketereeria( 油杉属 ) — 无径向树脂道

7-2 Traumatic resin canals Formation: They are formed only when the tree was injured Appearance: Lager and connected in tangential direction Distribution: They occur only in the ring that suffered injury

8. Texture and grain （结构与纹理）8-1 Texture•  Definition: Texture is concerned with the size of wood cells and degree of dif

ference in size of cells.

• Terms of wood texture Fine textured, Coarse textured Even textured, Uneven textured Smooth textured, Harsh textured

8-2 Grain• Definition:

Grain refers to the longitudinal alignment of wood cells.• Terms of wood grain

Straight grain, Diagonal grain, Spiral grain, interlocked grain, cross grain （斜纹）

9. Figure in wood （木材花纹）

9-1 Definition: In a general sense, any distinctive markings of wood may be

described as figure. Commercially, the term figure is restricted to the highly decorative patterns.

9-2 All kinds of wood figure

Ⅲ. The physical properties of wood

1. Color

• Formation: Extractives; Fungi attack; Chemicals; Dyes

• Variation: Sapwood and heartwood; Weathering; Aging

• Practical value: Asset: as in Hongmu, the dark the color of the wood, the higher the value. Liability: as in surface decoration, dark color should be avoided. Wood identification: color is used as a supplementary feature.

2. Luster

• Definition: Luster is the property of wood that enables it to reflect light, in other words, t

he property of exhibiting sheen.

• Variation: Structure of wood; Infiltrated products; Section plane; Incident light angles; Aging

• Practical value: Wood quality evaluation: lustrous → sound Wood identification: used as supplementary features, e.g., catalpa-sassafras

3. Odor and taste （气味和滋味）• Odor: tested with nose At ordinary temperatures, wood substance itself has no sce

nt; i.e., it does not emit free molecules into the air. When an odor is present, it is due to substances deposited in the wood (infiltration products) or formed through the action of fungi or microorganisms.

The odor from the former is favorable: cupress, sandalwood. The odor from the latter is unfavorable: it means decay.

• Taste: tested with tongue The taste of wood mainly comes from the extractives, and can

be used as a supplementary feature in wood identification. Wood with unfavorable taste is avoided in wooden container o

f comestible products.

4. Weight （重量）• Value in wood identification particularly when the discrepancy between species under comparison is unusually great.

• Grades of wood weight light: d < 0.3; middle: d = 0.3~0.5; heavy: d> 0.5

• To wood quality, the heavier the wood, the better of the wood. Standards of Hongmu: d > 0.8 Guajacum （绿檀）： d=1.3 Hsiemu （蚬木）： d=1.0 Balsa wood （轻木）： d=0.12

5. Hardness• The relative hardness or softness of wood is a useful indicator of its physical properties. • A useful idea of the approximate hardness of wood can be gained by testing it with a knife or the thumbnail.

Ⅳ Principles of Wood identification

1. Bi-search key — 对分检索表法

表 3-3六种紫檀属红木对分检索表

1. 木射线主为单列，偶见多列 .........................................................................................................2

1. 木射线主为多列（2列），单列较少 ..............................................................................刺猬紫檀

2. 散孔材，半环孔材倾向可见或明显..........................................................................................3

2. 散孔材 ...........................................................................................................................檀香紫檀

3. 新切面有香气或香气浓郁 .............................................................................................................4

3. 新切面无香气 ...................................................................................................................囊状紫檀

4. 木刨花或木屑冷水浸出液为红色 .............................................................................................5

4. 木刨花或木屑冷水浸出液蓝绿色荧光很明显............................................................鸟足紫檀

5. 轴向薄壁组织主为傍管细线状，稀少翼状及环管状....................................................越柬紫檀

5. 轴向薄壁组织主为傍管带状、聚翼状或者细线状及环管状........................................大果紫檀

2. Perforation cards — 穿孔卡片法

3. Wood identification with computer — 木材计算机识别

Reflection and practice:

• How to generate the cross, radial and tangential sections on a log?

• The difference between annual rings and growth increments?

• Appearance of annual rings on cross, radial and tangential sections?

• How to distinguish false ring from true ring?

• How does the heartwood form in a tree?

• Main differences between sapwood and heartwood?

• Functions of wood rays in a living tree?

• Appearance of wood rays on cross, radial and tangential sections?

• How many kinds of parenchyma are there in wood, their names and functions?

• The most significant difference between softwoods and hardwoods?

• What is pores in the field of wood structure?

• Distribution patterns of pores in ring porous, semi-ring porous, and diffuse porous woods?

• Structure of resin canals?

• Name the six genera of softwood species that have normal resin canals in China in Latin and Chinese.