Dendrology And

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Dendrology and

Wood Anatomy

WSEng-4203

Dr Manoj Kumar Dubey


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Credit Value

No. of hours/week

Lectures: 2

Tutorial: 0

Practice or laboratory: 3

Home study: 4


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Course Structure

PART A DENDROLOGY 1. INTRODUCTION: DEFINITION AND OBJECTIVES

2. CLASSIFICATION AND NOMENCLATURE

3. TERMINOLOGY OF FLOWERING PLANTS AND METHODS OFIDENTIFICATION

4. SPECIMEN PREPARATION AND HERBARIUM MANAGEMENT 5. IMPORTANT TREE SPECIES OF ETHIOPIA

PART B WOOD ANATOMY AND IDENTIFICATION 1. INTRODUCTION TO WOOD AND WOOD ANATOMY

2.MACROSCOPIC CHARACTER OF WOOD

3. MICROSTRUCTURE OF SOFT WOOD 4.MICROSCOPIC STRUCTURE OF HARD WOOD

5.JUVENILE WOOD, REACTION WOOD AND WOOD OF BRANCHESAND ROOTS

6.WOOD IDENTIFICATION


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Chapter 1

INTRODUCTION TO WOOD ANDWOOD ANATOMY

PART B WOOD ANATOMY

AND IDENTIFICATION


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Wood Anatomy

What is wood ?

A solid lignocellulosic

material

naturally produced intrees and some shrubs

(Stem, branches and

roots)

made of up to 40%-50% cellulose, 20%-

30% hemicellulose,

and 20% -30% lignin.


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LOG & LUMBER

Log: Stem of a tree that isfelled and ready forconversion

Lumber: Product of thesaw and planing mill,manufactured by sawing,resawing, passinglengthwise through astandard planingmachine, crosscutting tolength, and matching.


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Timber

A type of lumber

Commercial form of

wood suitable for

construction work and

sawn wood of

specified width and

thickness (minimum

5 least dimension)


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Softwoods

Wood produced by one of thebotanical groups of trees thatin most cases have needlelikeor scalelike leaves

Also known as conifers

Pines, spruces, firs

Term has no reference to theactual hardness of the wood.

Normal softwoods (OD density30lb/cft) Scot pine, douglus fir

Many exceptions: Pitch Pine,Yew (OD density 42-48 lb/cft)


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Hardwoods

Wood produced by one of thebotanical groups of trees thathave broad leaves

Also called Angiosperms orDeciduous

Misnomer

Normal hardwoods (AverageOD density 45lb/cft) Teak,Oak, Walnut, Eucalypts

Many exceptions:

Cricket willow, Aspen (25-28lb/cft)

Balsa (8lb/cft) Lightest wood

Lignum vitae (80lb/cft) Hardestwood


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Importance of wood

Served humankind since ancient times

Modern times continue to be raw material for many productsin spite of other competitive materials (metal , cement ,plastic)

After harvesting from forest wood is converted into range ofproducts through processing (sawing, slicing, gluing, chipping,pulping, chemical impregnation and modification)

Product of primary processing: poles, posts, lumber, veneer,plywood, particleboard, fibreboard, pulp & paper

Product of secondary processing include the final end use

products such as furniture, cabinets etc Wood is an important source of fuel in developing economies.

About half of worlds wood production is used as fuel.


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Characteristic

properties of wood


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1. Composed ofWood cells

All wood is cellular in structure

Cell walls composed of a characteristic

mixture of polymers of holocelluloses, non-cellulosic carbohydrates, and lignin,

This accounts for a combination of elastic

and plastic responses of the cell wall to

applied forces.


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2. Anisotropic in nature

Wood exhibits different mechanicalproperties and dimensional changes in itsits three major directional axes.

This behavior arises from the structure and organization of wood

components (cellulose fibers) in cell wall

elongated shape of the wood cell typical arrangements of wood cells in differentdirections


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3. Hygroscopic substance

Wood loses and gains moisture as a result

of changes in the atmospheric humidity

and temperature.

This phenomenon leads to dimensional

instability of wood

This affects physical and mechanical

properties of wood


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4. Biodegradable

Wood may be reduced to its component throughattack by organisms such as fungi, bacteria, andcertain insects, for instance, termites.

It can also be degraded by hydrolysis andoxidation resulting from condition to which it isexposed.

Wood requires treatment with wood

preservatives to reduce its degradation Thus disposal of wood after end of its life-cycle

is no major environmental threat


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5.Combustible

Good calorific value

This property makes wood one of the major

sources of fuel in the developing economy

It also opens many possibilities for deriving basic

chemicals from wood, such as alcohols and

gaseous compounds

On the other hand, combustibility of wood mustbe taken into account when it is employed in

lconstruction


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6. Inert to chemicals

Inert to mild acids and doesnt oxidize

For this reason it is well suited for manyindustrial applications where resistance to

the disintegrating action of chemicals and

to corrosion is important.


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7. Excellent insulating properties

Wood is good insulating material for heat and electricity due to itsfibrous structure and the quantity of entrapped air in cell lumens

Other building materials used in house construction are not goodinsulators.

In comparison to wood, the heat loss through

common brick is 6 times more a glass window 8 times more

Similarly, compared to wood thermal conductivity of Concrete (sand and gravel aggregate) is 15 times more

Steel 390 times more

aluminum 1700 times more.

This property is very important for construction in cold countrieswhere wooden constructions are helpful in preventing heat loss


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Variability of Properties

Wood characteristics and properties varies at thedifferent levels Between species

Between different trees of same species

Between different geographical location Between different parts of the same tree (butt, dbh and top )

Wood is inherently variable substance due to due to its biological origin as a product of metabolism and

physiology of the living tree.

external factors affecting its growth such weather, biologicalorganisms

Thus, wood is a material with an almost infinite range ofproperties and characteristics


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Wood as an industrial

raw material

The versatile characteristics of wood make

it important raw material for many

industries such as

Saw mills

Wood treatment industries

Paper and pulp

Reconstitute wood such as plywood, LVL and

engineered wood panels (such as

particleboard, MDF)


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Advantages of Wood as a

construction material &

other applications


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1. Easy to cut and worked into

various shapes Carpenter friendly material Can be worked easily with simple tools or power-driven

machinery with low consumption of energy

Thus it can covert easily not only in a factory/mill but

also to on-the-site fabrication. Wood can be easily joined with nails, screw, bolts, and

connectors, by simple tools

Wood can also be joined with adhesives, which canproduce a continuous bond over the entire surface. This

property is employed in making plywood, LVL Prefabrication of large wood trusses, laminated beamsand arches etc have made wood constructioncompetitive in building.


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2.High strength-weight ratio

Flexural rigidity in relation to the weight of the

material, is one of the outstanding mechanical

properties of wood.

Douglas-fir is superior to steel in bending by aratio of 2.6 to 1.

The high flexural rigidity of wood is most

effective in members in which the length is far in

excess of depth of the cross section, such as in

beams and long slender column.


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3. Wood is a good energy-

absorbing material The exceptional impact strength of wood gives it

a considerable mechanical and economicadvantage for structures designed to resist earthquakes

for situations where abrupt loads are imposed suchas aircraft carrier decking, s

Wood is at least nine times as good an energy-absorbing material than steel.

Unlike steel, wood also possesses excellentvibration-damping characteristics.

This property is of utmost importance in bridgesand other structures subject to dynamic loads.


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4. Dimensionally stable to

temperature variation

Dimensional changes that may take place as aresult of rise in temperature are less significantin wood construction than other materials

When heated, wood expands only little in thelongitudinal direction, which is important inconstruction.

Moreover, in wood, increase in dimensions withrise in temperature is frequently balanced to a

considerable degree by shrinkage caused bydrying, with a corresponding increase instrength.


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Other advantages

Aesthetically unrivalled as available in

many colour, textures and figures

Good acoustic properties, thus used inmusical instruments

Renewable, can be produced cheaply with

solar energy in contrast to petroleum, coal,

mineral ores which will gradually

exhausted


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Wood Anatomy

Study of structure or

architectural organization

of wood

It deals with nature andarrangement of its

physical and chemical

building components

Study is done at

macroscopic, microscopicand ultra-structural level


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Wood Anatomy

MACROSCOPIC MICROSCOPIC ULTRAMICROSCOPICMACROSCOPICMACROSCOPIC ULTRAMICROSCOPIC


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Importance of wood anatomy

Explains the characteristics behavior of wood as amaterial due to close relationship of structure, propertiesand utilization

Identification of wood species

Selection of wood for particular purpose. For example:Wood with long fibres is suitable for paper and pulpindustry

Understanding the mechanism of tree growth and cancontribute in the quality of wood produced in a forest.

It explains how different anatomical features influencewood properties and, in turn, how these properties reactto different treatments of the wood such as wood drying,wood preservation , wood working and finishing.


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Thank you !

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