Biermann Ch. Handbook of Pulping and Papermaking

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574 26. SOFTWOOD ANATOMY

mercial production is principally in the southern

Appalachian and Cumberland Mountain regions.

Another species, southern redcedar (J. silicicold),

grows over a limited area in the South Atlantic

and Gulf Coastal Plains.

Uses. The wood is moderately heavy, mod-

erately low in strength, hard, and high in shock

resistance, but low in stiffness. It has very small

shrinkage and stays in place well after seasoning.

The texture is fine and uniform. Grain is usually

straight, except where deflected by knots, which

are numerous. Eastern redcedar heartwood is very

resistant to decay. The greatest quantity of eastern

redcedar is used for fenceposts. Lumber is manu-

factured into chests, wardrobes, and closet lining.

Other uses are flooring, novelties, pencils, and

small boats. Southern redcedar is used for the

same purposes.

Color. The heartwood of redcedar is bright

to dull red, and the thin sapwood is nearly white.

Macroscopic structure. The longitudinal

parenchyma are visible as several dark lines,

particularly in the sapwood.

LIBOCEDRUS

Many species in this family are similar in

appearance. Heartwood color and odor help to

distinguish them.

Incense cedar (Figs. 26-45 and 26-46)

Incense—cedar

(Libocedrus

decurrens) grows

in California and southwestern Oregon and a little

in Nevada. Most incense—cedar lumber comes

from the northern half of California and the

remainder from southern Oregon.

Uses. Incense—cedar is light in weight,

moderately low in strength, soft, low in shock

resistance, and low in stiffness. It has small

shrinkage and is easy to season with little checking

or warping. Incense—cedar is used for lumber

and fenceposts. Nearly all the high—grade lumber

is used for pencils and Venetian blinds. Some is

used for chests and toys. Much of the

incense—cedar lumber is more or less pecky; that

is,

it contains pockets or areas of disintegrated

wood caused by advanced states of localized decay

Fig. 26-44. Eastern redcedar (Jii/iiperiisvirgimana) (50X).

ANATOMY OF SOFTWOOD SPECIES 575

in the living tree. Peck development is arrested

once the lumber is seasoned. This lumber is used

locally for rough construction where cheapness

and decay resistance are important. Because of its

resistance to decay, incense—-cedar is well suited

for fenceposts. Other products are railroad ties,

poles,

and split shingles.

Color. The sapwood of incense—cedar is

white or cream colored, and the heartwood is light

brown, often tinged with red or pale purple. The

wood has a fine, uniform texture, a spicy odor,

and acrid taste.

Macroscopic features. The transition from

earlywood to latewood is more or less abrupt, and

the growth rings are prominent on flatsawn surfac-

es.

Incense—cedar is similar to western redcedar,

but the latter lacks the acrid taste. Longitudinal

parenchyma are visible in the latewood as dark

reddish lines or zones.

Microscopic structure. Incense—cedar lacks

indentures in the ray parenchyma, which distin-

guishes it from other species with nodular ray cell

end walls on transverse surfaces of longitudinal

parenchyma.

Fig. 26-45. Libocedrus decurrens.

Fig. 26-46. Incense-cedar (Libocedrus decurrens) (50X).

576 26. SOFTWOOD ANATOMY

THUJA

Western redcedar (Figs. 26-47 and 26-48)

Western redcedar {Thuja plicata) grows in

the Pacific Northwest and along the Pacific coast

to Alaska. Western redcedar is also called canoe

cedar, giant arborvitae, shinglewood, and Pacific

redcedar. Western redcedar lumber is produced

principally in Washington, followed by Oregon,

Idaho, and Montana.

The wood is generally straight grained and

has a uniform but rather coarse texture and very

small shrinkage. It is light in weight, moderately

soft, low in strength when used as a beam or post,

and low in shock resistance. It has a higher

density in the pith that decreases outward. It has

a sweet odor that some say is like chocolate.

Western redcedar is used principally for shingles,

lumber, poles, posts, and piles. The lumber is

used for exterior siding, interior finish, greenhouse

construction, ship and boat building, boxes and

crates,

sash, doors, and millwork.

Color. The heartwood of western redcedar

is reddish or pinkish brown to dull brown and very

Fig. 26-47. Thuja plicata.

Fig. 26-48. Western redcedar {Thujaplicata) (50

x).

ANATOMY OF SOFTWOOD SPECIES 577

resistant to decay. The sapwood is nearly white

and narrow, often 1/4—1 in. wide.

Similar woods. Western redcedar closely

resembles northern white—cedar but the latter is

of slower growth and has a plain light brown color

usually without a reddish tinge. Dark grades

resemble redwood but redwood lacks the charac-

teristic odor and taste.

Northern white—cedar

This species is very similar in properties and

uses to Atlantic white—cedar; both grow in the

eastern

U.S.

The two species are used for similar

purposes, mostly for poles, ties, lumber, posts,

and decorative fencing. Northern white—cedar

(Thuja occidentalis) is also known as arborvitae,

or simply cedar. It grows from Maine along the

Appalachian Mountain Range and westward

through the northern part of the Lake States.

Production of northern white—cedar lumber is

probably greatest in Maine and the lake States.

Uses. The wood is light in weight, rather

soft and low in strength, and low in shock resis-

tance. It shrinks little in drying. It is easily

worked, holds paint well, and the heartwood is

highly resistant to decay.

Color. The heartwood of white—cedar is

light brown, and the sapwood is white or nearly

so.

The sapwood is usually thin, not over 1 in.

except in very fast growth.

Similar

woods.

C. thyoides is similar but has

a more pinkish hue, a spicy odor, and, as a rule,

wider growth rings. Western redcedar generally

has wider growth rings and a reddish hue. Bald

cypress has a more dingy color and a rancid odor

that is much different from that of cedar.

CUPRESSUS

Arizona cypress

Arizona cypress (C arizonica) grows in the

southwest U.S. The heartwoods merges into the

sapwood and both are yellowish in color.

Many of the microscopic features resemble

those of Juniperus, although the parenchyma end

walls are not as obviously nodular and the rays are

not as high.

TAXODIACEAE

TAXODIUM

Baldcypress (Figs. 26-49 and 26-50)

Baldcypress (Jaxodium distichum) is com-

monly known as cypress, also as southern cypress,

red cypress, yellow cypress, and white cypress.

Commercially, the terms tidewater red cypress,

gulf cypress, red cypress (coast type), and yellow

cypress (inland type) are often used. About

one—half of the cypress lumber comes from the

Southern States and one—fourth from the South

Atlantic States, although the supply has decreased.

Uses. The wood is moderately heavy, mod-

erately strong, and moderately hard. The heart-

wood of old—growth timber is one of our most

decay—resistant woods. Shrinkage is moderately

small: greater than that of cedar and less than that

of southern pine. Often the wood of certain

cypress trees contains pockets or localized areas

that have been attacked by a fungus. Such wood

is known as pecky cypress. The decay caused by

this fungus is arrested when the wood is cut into

lumber and dried. Pecky cypress is durable and

useful where watertightness is unnecessary and

appearance is not important or a novel effect is

desired. Cypress has been used principally for

building construction, especially where resistance

to decay is required. It was used for beams,

posts,

and other members in docks, warehouses,

factories, bridges, and heavy construction.

Color. The sapwood of baldcypress is

narrow (1—2 in., gradually merging into heart-

wood) and nearly white. The color of the heart-

wood varies widely, ranging from light yellowish

brown to dark brownish red, brown, or chocolate.

The wood is dull, lacking sheen or luster.

Macroscopic features. The darker heartwood

has a more or less rancid odor; the longitudinal

surfaces feel distinctly greasy or waxy. The wood

lacks resin canals and has an abrupt transition

from earlywood to latewood. The growth rings

are distinct and irregular in outline and width.

Longitudinal parenchyma are often visible with a

lens on longitudinal surfaces as strands.

578 26. SOFTWOOD ANATOMY

Similar

woods.

Cypress has a high degree of

variability. It resembles the cedars, but the odor

is entirely different. Some species of Cupressus

spp.

of the western U.S. are called cypress, but

are much different from bald cypress.

SEQUOIA

Redwood (Figs. 26-51 and 26-52)

Redwood {Sequoia sempervirens) is a very

large tree growing on the coast of northern Cali-

fornia. Another sequoia, giant sequoia {Sequoia

gigantea),

grows in a limited area in the Sierra

Nevada of California, but is used in very limited

quantities. Other names for redwood are coast

redwood, California redwood, and sequoia.

Production of redwood lumber is limited to Cali-

fornia, but a nationwide market exists.

Uses. Typical old—growth redwood is

moderately light in weight, moderately strong and

stiff,

and moderately hard. The wood is easy to

work, generally straight grained, and shrinks and

swells comparatively little. The heartwood has

high decay resistance. Redwood lumber is used

for building. It is remanufactured extensively into

Fig. 26-49.

Taxodium

distichum.

/llAHIIli Sif

Fig. 26-50. Baldcypress

{Taxodium distichum)

(50x).

ANATOMY OF SOFTWOOD SPECIES 579

siding, sash, doors, blinds, finish, casket stock,

and containers. Because of its durability, it is

useful for cooling towers, tanks, silos,

wood—stave pipe, and outdoor furniture. It is

used in agriculture for buildings and equipment.

Its use as timbers and large dimension in bridges

and trestles is relatively minor. The wood splits

readily and the manufacture of split products

(posts and fence material) is an important business

in the redwood area. Some redwood decorative

veneer is used.

Color. The unique color of redwood heart-

wood varies from a light cherry to a dark mahoga-

ny and distinguishes it from baldcypress. The

narrow sapwood (1—3 in.) is almost white.

Macroscopic features. The wood is without

normal resin canals and has no distinctive odor,

taste,

or feel. The wood is coarse—textured. The

transition to the narrow, dark latewood is abrupt.

Western redcedar heartwood may approach red-

wood in color, but the odor of the former is

distinct. The longitudinal parenchyma are visible

on longitudinal surfaces with a lens as strands.

Microscopic features. Bi— or triseriate

Fig.

26-51.

Sequoia sempervirens.

Fig. 26-52. Coast redwood

(Sequoia sempervirens)

(50x).

580 26. SOFTWOOD ANATOMY

pitting of

tracheids,

ray cell smooth end walls, and

taxodioid pitting on the cross—fields are present.

TAXACEAE

TAXUS

Yew (Figs. 26-53 and 26-54)

The yew is a genus of minor wood impor-

tance in the U.S. Florida yew (T. floridana) is

rare and confined to a few counties in northwest-

em Florida. Pacific yew {T. hrevifolia) is native

to the U.S. A compound called taxol, which is

extracted from the bark and needles, has been

used in the last few years to treat certain types of

cancer. Taxol will be synthesized in the laborato-

ry and the yew tree will not be harvested for this

drug in the future. Pacific yew grows from

southeast Alaska to northern California

Microscopic features. The spiral thickening

of yew tracheids and the lack of resin canals are

shared with the rare Torreya, but yew has cross-

field pits that are 8—10 /xm, larger than those of

Torreya (6

ptm).

The spiral thickenings of

Torreya

are less numerous and steep than those of yew.

Fig. 26-53. Taxus hrevifoia.

Fig. 26-54. Pacific yew {Taxus hrevifolia) (50x).

NON AMERICAN SPECIES 581

26.4 NON-AMERICAN SPECIES

Information on non—North American species

is available in Kukachka (1970).

PINACEAE

PINUS

Pine, Radiata

Radiata or Monterey pine (P. radiata) is

native to a small area of California but is planted

extensively in the southern hemisphere, mainly in

Chile, New Zealand, Australia, and South Africa.

Plantation—grown trees may reach a height of 80

to 90 feet in 20 years. The species is not com-

mercially significant in its native U.S. in part due

to its large number of knots.

Plantation—grown heartwood is variable in

color among trees and is light brown to pinkish

brown. It is distinct from the paler creamy sap-

wood in older trees (more than 40 years old).

Growth rings are mostly wide and distinct. False

growth rings may be common. Texture is moder-

ately even and fme, and the grain is usually

straight.

Plantation—grown radiata pine averages

about 30 Ib/ft^ at 12%

MCQD

(specific gravity of

0.48). The strength is comparable to red pine (P.

resinosa) although there may be considerable

variation due to location and growth rates. The

sapwood is prone to attack by stain fungi and

vulnerable to boring insects. Radiata pine can be

used for the same purposes as other pines of the

United States.

Bamber and Burley (1983) review the proper-

ties of this species. It had been introduced to

Australia in the 1850s. In 1979 there were

430,000 hectares in Australia, 800,000 in New

Zealand, and 600,000 in Chile. It is mostly

three—needled, with markedly dentate walls in the

ray tracheids and 1—4 pinoid cross—field pits of

small size. The uniseriate rays have marginal

tracheids. The fusiform rays may be 3 to

5—seriate and 15—20 cells high. The earlywood

longitudinal tracheids average 3.0 mm long, 0.045

mm in diameter, and 0.003 mm in thickness. The

latewood longitudinal tracheids average 3.5 mm

long, 0.013 mm in diameter, and 0.005 mm in

thickness. The cellulose content in mature wood

is over 50% and the lignin content is about 26%.

Caribbean

pine

Caribbean pine (P. caribaea) occurs along

the Caribbean side of Central America from Belize

to northeastern Nicaragua. It is also native to the

Bahamas and Cuba. It is also called slash pine

and British Honduras pitch pine. This tree of the

low elevations is widely introduced as a plantation

species throughout the world tropics.

The heartwood is golden brown to red brown

and distinct from the sapwood, which is 1 to 2

inches in thickness and a light yellow. The soft-

wood species has a strong resinous odor and a

greasy feel. The weight varies considerably and

may vary from 24 to 51 Ib/ft^ at 12% MCQD,

although the higher density is much more com-

mon.

Caribbean pine may be appreciably heavier

than slash pine (P. elliotti) but the mechanical

properties of these two species are rather similar.

The durability and resistance to insect attack vary

with resin content but generally the heartwood is

rated moderately durable. The sapwood is highly

permeable. Caribbean pine is used for the same

purposes as the southern pines of the U.S.

Scots

pine

Scots pine (P. sylvestris), also called red

deal, yellow deal, or redwood, grows in Europe.

PICEA

Norway spruce

Norway spruce (P. abies) is also called white

deal or whitewood and grows in Europe.

LARIX

European

larch

European larch (L. decidua) is also called

common larch and grows in Europe.

CUPRESSACEAE

CYPRESSUS

Bentham

cypress

Bentham cypress (C. lusitanica) grows in

Mexico and Guatemala. The heartwood is distinct

from the sapwood and light reddish brown. The

wood is aromatic.

The end walls of the ray parenchyma are not

nodular and indenture is lacking or not obvious.

582 26. SOFTWOOD ANATOMY

FITZROYA

Alerce

Alerce (F.

cupressoides)

is native to southern

Chile. The heartwood is reddish brown and

sharply defined from the narrow and very

light—colored sapwood. The density is 26 Ib/ft^.

Alerce is much like redwood in most regards and

used as redwood is used, but redwood rays are

two or three times taller. Alerce has indenture

and nodular end walls in ray cells. The rays are

mostly under 12 cells high.

ARAUCARIACEAE

All three of the species listed in this section

lack growth rings and have vertical tracheids with

2—4 bordered pits across their widths in alternate

arrangement that are distinctive for this family.

AGATHIS

Almaciga, sakar

Almaciga or sakar

(Agathis philippinesis)

from the Philippine Islands. Agathis lacks the

leaf scars that cause the pin knots. Klinki pine

lacks the reddish streaks.

ARAVCARIA

A unique characteristic of Araucaria and

Agathis amongst all other conifers is the

2—4—seriate, alternate intertracheid pitting.

Resinous tracheids (near parenchyma) occur

in the heartwood of Agathis and Araucaria of

Araucariaceae. They are filled with reddish

brown to black amorphous deposits.

Parana—pine

Parana—pine (A. angustifolia) is not a true

pine.

It is a softwood that comes from southeast-

ern Brazil and adjacent areas of Paraguay and

Argentina. It is available in large clear boards of

uniform texture. The small pinhead knots that

appear

flat—sawn surfaces (caused

leaf scars)

and the light brown or reddish brown heartwood,

which is frequently streaked with red, provide

desirable figured effects for matching in paneling

and interior finishes. The growth rings are fairly

distinct and more nearly like those of white pine

(P.

strobus) rather than those of the yellow pines.

The wood has relatively straight grain, takes paint

well, glues easily, and is free from resin ducts,

pitch pockets, and streaks.

The sapwood is yellowish and not always

distinct from the heartwood, which is a very light

brown and frequently shows bright streaks of red.

The strength is similar to that of other U.S.

softwoods of similar density (loblolly and shortleaf

pine),

except for its deficiency in compression

strength across the grain. Splitting and warping of

the kiln—dried wood is due to the presence of

compression wood. The principal uses include

framing lumber, interior trim, furniture, case

goods, and veneer.

Klinki—pine

Klinki pine of hoop—pine

(Araucaria

klinkii)

is fron: Australia, New Guinea, New Caledonia,

and Norfolk Island. It typically grows to 150 ft

with a trunk diameter of 3 ft. The heartwood is

light yellowish brown, not sharply demarcated

from the straw—colored sapwood. The basic

specific gravity is 0.42.

PODOCARPACEAE

PODOCARPUS

Podocarp

A variety of podocarp species (P. spp) have

limited use as pulpwood. Common names include

podo,

yellow wood, and manio. The anatomy of

the species varies greatly. Some have resin

canals, others do not. The cross—field pitting can

be of almost any type, except pinoid. P. amarus

grows in New Zealand, South Africa, and Chile

and looks somewhat like eastern white pine.

References for this chapter are found on pages 537-540 of Chapter 25.

HARDWOOD ANATOMY

27.1 GROSS ANATOMY OF HARDWOODS

Introduction

The references for this chapter are found

on pages 537-540 of Chapter 25.

Hardwoods are identified by the presence of

vessels (pores), although a few (commercially

unimportant) species lack them. Vessels are the

long tubes (which may extend the length of the

tree) for conduction of water made up of individu-

al vessel elements (or members) attached end to

end. Vessels may be barely visible with a lens in

some species and quite obvious in others.

Vessel

size

distribution

(seen in cross section, x)

Ring—porous woods (oaks, ash, elm, hicko-

ry, hackberry) have large--diameter vessels in the

earlywood that soon decrease in diameter toward

the latewood.

Semi—ring—porous

woods have a

gradual decrease in vessel diameter through the

width of the growth ring, with the earlywood

vessels of moderately larger diameter than the

latewood. Diffuse—porous woods have vessels

that do not change much in diameter throughout

the growth ring (maple, yellow—poplar, sweet-

gum).

Obviously the distinction is somewhat

arbitrary, but Fig. 27-1 shows representative

Fig. 27-1. Rmg—porous {Ulmus americana), semi—rmg—porous (Juglans nigra), and diffuse-

porous (Prunusserotina) woods. Tyloses fiU many of the vessels of the first two examples.

583