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THE SCHOOL BOOK OF FORESTRY
By
CHARLES LATHROP PACK
PRESIDENT OF THE AMERICAN TREE ASSOCIATION
1922
[Illustration: FOREST FIRE GUARD STATIONED IN A TREE TOP]
THE AUTHOR GRATEFULLY ACKNOWLEDGES INFORMATION AND ASSISTANCE
FROM THE WRITINGS AND REPORTS OF COL. W.B. GREELEY, U.S.
FORESTER; COL. HENRY S. GRAVES, FORMER U.S. FORESTER; GIFFORD
PINCHOT, FORMER U.S. FORESTER; DR. B.E. FERNOW, DR. J.W. TOUMEY,
F.W. BESLEY, W.I. HUTCHINSON, R.H.D. BOERKER, PROF. NELSON C.
BROWN, PROF. R.S. HOSMER, E.A. STERLING, R.S. KELLOGG, E.T.
ALLEN, S. GORDON DORRANCE, DR. HUGH P. BAKER, ALFRED GASKILL,
J.S. ILLICK, AND MANY OTHER LEADERS IN FORESTRY.
"THE PART OF GOOD CITIZENS"
A people without children would face a hopeless future; a country
without trees is almost as helpless; forests which are so used
that they cannot renew themselves will soon vanish, and with them
all their benefits. When you help to preserve our forests or
plant new ones you are acting the part of good citizens.
--THEODORE ROOSEVELT.
INTRODUCTION
Our forests, with their billions of trees, are the backbone of
agriculture, the skeleton of lumbering, and the heart of
industry. Even now, in spite of their depletion, they are the
cream of our natural resources. They furnish wood for the nation,
pasture for thousands of cattle and sheep, and water supply for
countless cities and farms. They are the dominions of wild life.
Millions of birds, game animals, and fish live in the forests and
the forest streams. The time is coming when our forests will be
the greatest playgrounds of America. It is necessary that we
preserve, protect, and expand our timberlands. By so doing we
shall provide for the needs of future generations.
The forest is one of the most faithful friends of man. It
provides him with materials to build homes. It furnishes fuel. It
aids agriculture by preventing floods and storing the surplus
rainfall in the soil for the use of farm crops. It supplies the
foundation for all our railroads. It is the producer of fertile
soils. It gives employment to millions of workmen. It is a
resource which bountifully repays kind treatment. It is the best
organized feature of the plant world. The forest is not merely a
collection of different kinds of trees. It is a permanent asset
which will yield large returns over long periods when properly
managed.
Our forest fortune has been thoughtlessly squandered by
successive generations of spendthrifts. Fortunately, it is not
too late to rebuild it through coöperative effort.
The work has been well begun, but it is a work of years, and it
is to the youth of the country that we must look for its
continuous expansion and perpetuation. A part of our effort must
be directed toward familiarizing them with the needs and rewards
of an intelligent forestry policy.
CONTENTS
INTRODUCTION
CHAPTER
I. HOW TREES GROW AND MULTIPLY
II. THE FOREST FAMILIES
III. FORESTS AND FLOODS
IV. WILD LIFE OF THE FOREST
V. IMPORTANT FOREST TREES AND THEIR USES
VI. THE GREATEST ENEMY OF THE FOREST--FIRE
VII. INSECTS AND DISEASES THAT DESTROY FORESTS
VIII. THE GROWTH OF THE FORESTRY IDEA
IX. OUR NATIONAL FORESTS
X. THE NATIONAL FORESTS OF ALASKA
XI. PROGRESS IN STATE FORESTRY
XII. THE PLAYGROUNDS OF THE NATION
XIII. SOLVING OUR FORESTRY PROBLEMS
XIV. WHY THE UNITED STATES SHOULD PRACTICE FORESTRY
XV. WHY THE LUMBERMAN SHOULD PRACTICE FORESTRY
XVI. WHY THE FARMER SHOULD PRACTICE FORESTRY
XVII. PUTTING WOOD WASTE TO WORK
XVIII. WOOD FOR THE NATION
ILLUSTRATIONS
Forest Fire Guard Stationed in a Tree Top
Section of a Virgin Forest
The Sequoias of California
A Forest Ranger and His Forest Cabin
Pine Which Yields Turpentine and Timber
Forest Fires Destroy Millions of Dollars Worth of Timber Every Year
Blackened Ruins of a Fire Swept Forest
Forest Management Provides for Cutting Mature Trees
Seed Beds in a Forest Nursery
Sowing Forest Seed in an Effort to Grow a New Forest
A Camping Ground in a National Forest
Good Forests Mean Good Hunting and Fishing
Young White Pine Seeded from Adjoining Pine Trees
What Some Kinds of Timber Cutting Do to a Forest
On Poor Soil Trees are More Profitable Than Farm Crops
A Forest Crop on its Way to the Market
[Transcriber's note: "Section of a Virgin Forest" is the seventh
(not the second) illustration in the book.]
CHAPTER I
HOW TREES GROW AND MULTIPLY
The trees of the forest grow by forming new layers of wood
directly under the bark. Trees are held upright in the soil by
means of roots which reach to a depth of many feet where the soil
is loose and porous. These roots are the supports of the tree.
They hold it rigidly in position. They also supply the tree with
food. Through delicate hairs on the roots, they absorb soil
moisture and plant food from the earth and pass them along to the
tree. The body of the tree acts as a passage way through which
the food and drink are conveyed to the top or crown. The crown is
the place where the food is digested and the regeneration of
trees effected.
The leaves contain a material known as chlorophyll, which, in the
presence of light and heat, changes mineral substances into plant
food. Chlorophyll gives the leaves their green color. The cells
of the plant that are rich in chlorophyll have the power to
convert carbonic-acid gas into carbon and oxygen. These cells
combine the carbon and the soil water into chemical mixtures
which are partially digested when they reach the crown of the
tree. The water, containing salts, which is gathered by the
roots is brought up to the leaves. Here it combines with the
carbonic-acid gas taken from the air. Under the action of
chlorophyll and sunlight these substances are split up, the
carbon, oxygen and hydrogen being combined into plant food. It is
either used immediately or stored away for future emergency.
Trees breathe somewhat like human beings. They take in oxygen and
give off carbonic-acid gas. The air enters the tree through the
leaves and small openings in the bark, which are easily seen in
such trees as the cherry and birch. Trees breathe constantly, but
they digest and assimilate food only during the day and in the
presence of light. In the process of digestion and assimilation
they give off oxygen in abundance, but they retain most of the
carbonic acid gas, which is a plant food, and whatever part of it
is not used immediately is stored up by the tree and used for its
growth and development. Trees also give off their excess
moisture through the leaves and bark. Otherwise they would become
waterlogged during periods when the water is rising rapidly from
the roots.
After the first year, trees grow by increasing the thickness of
the older buds. Increase in height and density of crown cover is
due to the development of the younger twigs. New growth on the
tree is spread evenly between the wood and bark over the entire
body of the plant. This process of wood production resembles a
factory enterprise in which three layers of material are engaged.
In the first two of these delicate tissues the wood is actually
made. The inner side of the middle layer produces new wood while
the outer side grows bark. The third layer is responsible for the
production of the tough, outer bark. Year after year new layers
of wood are formed around the first layers. This first layer
finally develops into heartwood, which, so far as growth is
concerned, is dead material. Its cells are blocked up and prevent
the flow of sap. It aids in supporting the tree. The living
sapwood surrounds the heartwood. Each year one ring of this
sapwood develops. This process of growth may continue until the
annual layers amount to 50 or 100, or more, according to the life
of the tree.
One can tell the age of a tree by counting the number of annual
rings. Sometimes, because of the interruption of normal growth,
two false rings may be produced instead of a single true ring.
However, such blemishes are easy for the trained eye to
recognize. Heartwood does not occur in all varieties of trees. In
some cases, where both heartwood and sapwood appear, it is
difficult to distinguish between them as their colors are so
nearly alike. Because it takes up so much moisture and plant
food, sapwood rots much more quickly than heartwood. The sapwood
really acts as a pipe line to carry water from the roots to the
top of the tree. In some of our largest trees the moisture is
raised as high as 300 feet or more through the sapwood.
Strange though it may seem, trees fight with each other for a
place in the sunlight. Sprightly trees that shoot skyward at a
swift pace are the ones that develop into the monarchs of the
forest. They excel their mates in growth because at all times
they are exposed to plenty of light. The less fortunate trees,
that are more stocky and sturdy, and less speedy in their climb
toward the sky, are killed out in large numbers each year. The
weaker, spindly trees of the forest, which are slow growers,
often are smothered out by the more vigorous trees.
Some trees are able to grow in the shade. They develop near or
under the large trees of the forest. When the giants of the
woodland die, these smaller trees, which previously were shaded,
develop rapidly as a result of their freedom from suppression. In
many cases they grow almost as large and high as the huge trees
that they replace. In our eastern forests the hemlock often
follows the white pine in this way. Spruce trees may live for
many years in dense shade. Then finally, when they have access to
plenty of light they may develop into sturdy trees. A tree that
is a pigmy in one locality may rank as a giant in another region
due to different conditions of growth and climate. For example,
the canoe birch at its northern limit is a runt. It never grows
higher than a few feet above the ground. Under the most favorable
conditions in Florida, where this species thrives, such trees
often tower to a height of 125 feet.
In sheltered regions the seeds of trees may fall, sprout and take
root close to their parent trees. As a rule, the wind plays a
prominent part in distributing seed in every section of the
country. Pine and fir seeds are equipped with wings like those
of a bird or an airplane. They enable the seeds to fly long
distances on the wind before they drop to the ground and are
covered with leaves. Maple seeds fly by means of double-winged
sails which carry them far afield before they settle. Ash seeds
have peculiar appendages which act like a skate-sail in
transporting them to distant sections. Cottonwood seeds have
downy wings which aid their flight, while basswood seeds are
distributed over the country by means of parachute-like wings.
The pods of the locust tree fall on the frozen ground or snow
crust and are blown long distances from their source. On the
other hand, oak, hickory, and chestnut trees produce heavy seeds
which generally remain where they fall.
Squirrels are the most industrious foresters in the animal world.
Each year they bury great quantities of tree seeds in hoards or
caches hidden away in hollow logs or in the moss and leaves of
the forest floor. Birds also scatter tree seed here, there, and
everywhere over the forests and the surrounding country. Running
streams and rivers carry seeds uninjured for many miles and
finally deposit them in places where they sprout and grow into
trees. Many seeds are carried by the ocean currents to distant
foreign shores.
The decay of leaves and woodland vegetation forms rich and
fertile soils in the forests, in which conditions are favorable
for the development of new tree growth. When living tree seeds
are exposed to proper amounts of moisture, warmth and air in a
fertile soil, they will sprout and grow. A root develops which
pushes its way down into the soil, while the leaf-bud of the
plant, which springs from the other end of the seed, works its
way upward toward the light and air. This leafy part of the seed
finally forms the stem of the tree. But trees may produce plenty
of seed and yet fail to maintain their proper proportion in the
forest. This results because much of the seed is unsound. Even
where a satisfactory supply of sound fertile seed is produced, it
does not follow that the trees of that variety will be maintained
in the forest, as the seed supply may be scattered in unfavorable
positions for germination. Millions of little seedlings, however,
start to grow in the forest each year, but only a small number
survive and become large trees. This is because so many of the
seedlings are destroyed by forest fires, cattle and sheep
grazing, unfavorable soil and weather conditions, and many other
causes.
Beech and chestnut trees and others of the broad-leaved type
reproduce by means of sprouts as well as by seed. Generally, the
young stumps of broad-leaved trees produce more sprouts than the
stumps of older trees which have stood for some time. Among the
cone-bearing trees reproduction by sprouts is rare. The redwood
of California is one of the few exceptions. The pitch pine of the
Eastern States produces many sprouts, few of which live and
develop into marketable timber.
When trees are grown in nurseries, the practice is to sow the
seed in special beds filled with rich soil. Lath screens are used
as shade. They protect the young seedlings from the sun just as
the parent trees would do in the forest. The seedbeds are kept
well cultivated and free of weeds so that the seedlings may have
the best opportunities for rapid growth. Generally the seeds are
sown in the spring between March and May. Such seeds as the elms
and soft maples, which ripen in the early summer, are sown as
soon as possible after they are gathered. Practical tests have
shown that thick sowings of tree seeds give the best results.
There is little danger of weeds smothering out the seedlings
under such conditions. After the seed has germinated the beds may
be thinned so that the seedlings will have more room to develop.
During the fall of the same year, or in the following spring, the
seedlings should be transplanted to nursery rows. Thereafter it
is customary to transplant the young trees at least once again
during damp weather. When the trees finally are robust and
vigorous and have reached the age of two to five years, they are
dug up carefully and set out permanently. The usual practice is
to keep the seedlings one year in the seedbed and two years
in the nursery rows before they are set out. Whether the
transplanting should take place during the spring or fall depends
largely on the climate and geography of the locality. Practical
experience is the best guide in such matters.
Some farmers and land owners are now interested in setting out
hardwood forests for commercial purposes. If they do not wish to
purchase their seedlings from a reliable nursery-man, they can
grow them from carefully selected seed planted in well-prepared
seedbeds. The popular practice is to sow the seed in drills about
2 to 3 feet apart so that horses may be used for cultivation. The
seeds are sown to a depth of 2 to 3 times their thickness. They
are placed close enough in the drill so that from 12 to 15
seedlings to the linear foot result. In order to hasten the
sprouting of the seeds, some planters soak them in cold water for
several days before sowing. In the case of such hard-coated seed
as the black locust or honey locust, it is best to soak them in
hot water before planting.