Demonstration of some uses of wood. Optional exercise on
structure of wood. Method of cutting determined by
examination. Home work on study of furniture trim, etc.
Visit to Museum to study some economic uses of wood.
Visit to Museum or field trip to learn some common trees.
[Illustration: A forest in North Carolina. (U. S. G. S.)]
The Economic Value of Trees. Protection and Regulation of Water
Supply.--Trees form a protective covering for parts of the earth's surface.
They prevent soil from being washed away, and they hold moisture in the
ground. The devastation of immense areas in China and considerable damage
by floods in parts of Switzerland, France, and in Pennsylvania has resulted
where the forest covering has been removed. No one who has tramped through
our Adirondack forest can escape noticing the differences in the condition
of streams surrounded by forest and those which flow through areas from
which trees have been cut. The latter streams often dry up entirely in hot
weather, while the forest-shaded stream has a never failing supply of
crystal water.
[Illustration: Working to prevent erosion after the removal of the forest
in the French Alps.]
[Illustration: Erosion at Sayre, Pennsylvania, by the Chemung River.
(Photograph by W. C. Barbour.)]
The city of New York owes much of its importance to its position at the
mouth of a great river with a harbor large enough to float the navies of
the world. This river is supplied with water largely from the Adirondack
and Catskill forests. Should these forests be destroyed, it is not
impossible that the frequent freshets which would follow would so fill the
Hudson River with silt and debris that the ship channels in the bay,
already costing the government hundreds of thousands of dollars a year to
keep dredged, would become too shallow for ships. If this _should_ occur,
the greatest city in this country would soon lose its place and become of
second-rate importance.
The story of how this very thing happened to the old Greek
city of Poseidonia is graphically told in the following lines:--
"It was such a strange, tremendous story, that of the Greek
Poseidonia, later the Roman Paestum. Long ago those
adventuring mariners from Greece had seized the fertile
plain, which at that time was covered with forests of great
oak and watered by two clear and shining rivers. They drove
the Italian natives back into the distant hills, for the
white man's burden even then included the taking of all the
desirable things that were being wasted by incompetent
natives, and they brought over colonists--whom the
philosophers and moralists at home maligned, no doubt, in
the same pleasant fashion of our own day. And the colonists
cut down the oaks, and plowed the land, and built cities,
and made harbors, and finally dusted their busy hands and
busy souls of the grime of labor and wrought splendid
temples in honor of the benign gods who had given them the
possessions of the Italians and filled them with power and
fatness.
"Every once in so often the natives looked lustfully down
from the hills upon this fatness, made an armed snatch at
it, were driven back with bloody contumely, and the heaping
of riches upon riches went on. And more and more the oaks
were cut down--mark that! for the stories of nations are so
inextricably bound up with the stories of trees--until all
the plain was cleared and tilled; and then the foothills
were denuded, and the wave of destruction crept up the
mountain sides, and they, too, were left naked to the sun
and the rains.
"At first these rains, sweeping down torrentially,
unhindered by the lost forests, only enriched the plain with
the long-hoarded sweetness of the trees; but by and by the
living rivers grew heavy and thick, vomiting mud into the
ever shallowing harbors, and the land soured with the
undrained stagnant water. Commerce turned more and more to
deeper ports, and mosquitoes began to breed in the brackish
soil that was making fast between the city and the sea.
"Who of all those powerful landowners and rich merchants
could ever have dreamed that little buzzing insects could
sting a great city to death? But they did. Fevers grew more
and more prevalent. The malaria haunted population went more
and more languidly about their business. The natives, hardy
and vigorous in the hills, were but feebly repulsed.
Carthage demanded tribute, and Rome took it, and changed the
city's name from Poseidonia to Paestum. After Rome grew weak,
Saracen corsairs came in by sea and grasped the slackly
defended riches, and the little winged poisoners of the
night struck again and again, until grass grew in the
streets, and the wharves crumbled where they stood. Finally,
the wretched remnant of a great people wandered away into
the more wholesome hills, the marshes rotted in the heat and
grew up in coarse reeds where corn and vine had flourished,
and the city melted back into the wasted earth."[16]
Footnote 16: Elizabeth Bisland and Anne Hoyt, _Seekers in
Sicily_. John Lane Company.
[Illustration: Result of deforestation in China. This land has been ruined
by erosion. (Carnegie Institution Research in China.)]
Prevention of Erosion by Covering of Organic Soil.--We have shown how
ungoverned streams might dig out soil and carry it far from its original
source. Examples of what streams have done may be seen in the deltas formed
at the mouths of great rivers. The forest prevents this by holding the
water supply and letting it out gradually. This it does by covering the
inorganic soil with humus or decayed organic material. In this way the
forest floor becomes like a sponge, holding water through long periods of
drought. The roots of the trees, too, help hold the soil in place. The
gradual evaporation of water through the stomata of the leaves cools the
atmosphere, and this tends to precipitate the moisture in the air.
Eventually the dead bodies of the trees themselves are added to the organic
covering, and new trees take their place.
[Illustration: The forest regions of the United States.]
Other Uses of the Forest.--In some localities forests are used as
windbreaks and to protect mountain towns against avalanches. In winter they
moderate the cold, and in summer reduce the heat and lessen the danger from
storms. Birds nesting in the woods protect many valuable plants which
otherwise might be destroyed by insects.
Forests have great commercial importance. Pyrogallic and other acids are
obtained from trees, as are tar, creosote, resin, turpentine, and many
useful oils. The making of maple sirup and sugar forms a profitable
industry in several states.
The Forest Regions of the United States.--The combined area of all the
forests in the United States, exclusive of Alaska, is about 500,000,000
acres. This seemingly immense area is rapidly decreasing in acreage and in
quality, thanks to the demands of an increasing population, a woeful
ignorance on the part of the owners of the land, and wastefulness on the
part of cutters and users alike.
A glance at the map on page 109 shows the distribution of our principal
forests. Washington ranks first in the production of lumber. Here the great
Douglas fir, one of the "evergreens," forms the chief source of supply. In
the Southern states, especially Louisiana and Mississippi, yellow pine and
cypress are the trees most lumbered.
Which states produce the most hardwoods? From which states do we get most
of our yellow pine, spruce, red fir, redwood? Where are the heaviest
forests of the United States?
[Illustration: Transportation of lumber in the West. A logging train.]
[Illustration: Transportation of lumber in the East. Logs are mostly
floated down rivers to the mills.]
Uses of Wood.--Even in this day of coal, wood is still by far the most used
fuel. It is useful in building. It outlasts iron under water, in addition
to being durable and light. It is cheap and, with care of the forests,
inexhaustible, while our mineral wealth may some day be used up. Distilled
wood gives wood alcohol. Partially burned wood is charcoal. In our forests
much of the soft wood (the cone-bearing trees, spruce, balsam, hemlock, and
pine), and poplars, aspens, basswood, with some other species, make paper
pulp. The daily newspaper and cheap books are responsible for inroads on
our forests which cannot well be repaired. It is not necessary to take the
largest trees to make pulp wood. Hence many young trees of not more than
six inches in diameter are sacrificed. Of the hundreds of species of trees
in our forests, the conifers are probably most sought after for lumber.
Pine, especially, is probably used more extensively than any other wood. It
is used in all heavy construction work, frames of houses, bridges, masts,
spars and timber of ships, floors, railway ties, and many other purposes.
Cedar is used for shingles, cabinetwork, lead pencils, etc.; hemlock and
spruce for heavy timbers and, as we have seen, for paper pulp. Another use
for our lumber, especially odds and ends of all kinds, is in the
packing-box industry. It is estimated that nearly 50 per cent of all lumber
cut ultimately finds its way into the construction of boxes. Hemlock bark
is used for tanning.
The hard woods--ash, basswood, beech, birch, cherry, chestnut, elm, maple,
oak, and walnut--are used largely for the "trim" of our houses, for
manufacture of furniture, wagon or car work, and endless other purposes.
[Illustration: Diagrams of sections of timber. _a_, cross section; _b_,
radial; _c_, tangential. (From Pinchot, U. S. Dept. of Agriculture.)]
Methods of cutting Timber.--A glance at the diagram of the sections of
timber shows us that a tree may be cut radially through the middle of the
trunk or tangentially to the middle portion. Most lumber is cut
tangentially. In wood cut in this manner the yearly rings take a more or
less irregular course. The grain in wood is caused by the fibers not taking
straight lines in their course in the tree trunk. In many cases the fibers
of the wood take a spiral course up the trunk, or they may wave outward to
form little projections. Boards cut out of such a piece of wood will show
the effect seen in many of the school desks, where the annual rings appear
to form elliptical markings. Quite a difference in color and structure is
often seen between the heartwood, composed of the dead walls of cells
occupying the central part of the tree trunk, and the sapwood, the living
part of the stem.
[Illustration: Section of a tree trunk showing knot.]
Knots.--Knots, as can be seen from the diagram, are branches which at one
time started in their outward growth and were for some reason killed.
Later, the tree, continuing in its outward growth, surrounded them and
covered them up. A dead limb should be pruned before such growth occurs.
The markings in bird's-eye maple are caused by buds which have not
developed, and have been overgrown with the wood of the tree.
Destruction of the Forest.--_By Waste in Cutting._--Man is responsible for
the destruction of one of this nation's most valuable assets. This is
primarily due to wrong and wasteful lumbering. Hundreds of thousands of
dollars' worth of lumber is left to rot annually because the lumbermen do
not cut the trees close enough to the ground, or because through careless
felling of trees many other smaller trees are injured. There is great waste
in the mills. In fact, man wastes in every step from the forest to the
finished product.
[Illustration: A forest in the far west totally destroyed by fire and
wasteful lumbering.]
_By Fire._--Indirectly, man is responsible for fire, one of the greatest
enemies of the forest. Most of the great forest fires of recent years, the
losses from which total in the hundreds of millions, have been due either
to railroads or to carelessness in making fires in the woods. It is
estimated that in forest lands traversed by railroads from 25 per cent to
90 per cent of the fires are caused by coal-burning locomotives. For this
reason laws have been made in New York State requiring locomotives passing
through the Adirondack forest preserve to burn oil instead of coal. This
has resulted in a considerable reduction in the number of fires. In
addition to the loss in timber, the fires often burn out the organic matter
in the soil (the "duff") forming the forest floor, thus preventing the
growth of forest there for many years to come. In New York and other states
fires are fought by an organized corps of fire wardens, whose duty it is to
watch the forest and to fight forest fires.
Other Enemies.--Other enemies of the forest are numerous fungus plants,
insect parasites which bore into the wood or destroy the leaves, and
grazing animals, particularly sheep. Wind and snow also annually kill many
trees.
Forestry.--In some parts of central Europe, the value of the forests was
seen as early as the year 1300 A.D., and many towns consequently bought up
the surrounding forests. The city of Zurich has owned forests in its
vicinity for at least 600 years and has found them a profitable investment.
In this country only recently has the importance of preserving and caring
for our forests been noted by our government. Now, however, we have a
Forest Survey of the Department of Agriculture and numerous state and
university schools of forestry which are rapidly teaching the people of
this country the best methods for the preservation of our forests. The
Federal government has set aside a number of tracts of mountain forest in
some of the Western states, making a total area of over 167,000,000 acres.
New York has established for the same purpose the Adirondack Park, with
nearly 1,500,000 acres of timberland. Pennsylvania has one of 700,000
acres, and many other states have followed their example.
[Illustration: The forest primeval. Trees are killing each other in the
struggle for light and air.]
[Illustration: A German beech forest. The trees are kept thinned out so as
to allow the young trees to get a start. Contrast this with the picture
above.]
Methods for Keeping and Protecting the Forests.--Forests should be kept
thinned. Too many trees are as bad as too few. They struggle with one
another for foothold and light, which only a few can enjoy. In cutting the
forest, it should be considered as a harvest. The oldest trees are the
"ripe grain," the younger trees being left to grow to maturity. Several
methods of renewing the forest are in use in this country. (1) Trees may be
cut down and young ones allowed to sprout from cut stumps. This is called
coppice growth. This growth is well seen in parts of New Jersey. (2) Areas
or strips may be cut out so that seeds from neighboring trees are carried
there to start new growth. (3) Forests may be artificially planted. Two
seedlings planted for every tree cut is a rule followed in Europe. (4) The
most economical method is that shown in the lower picture on page 114,
where the largest trees are thinned out over a large area so as to make
room for the younger ones to grow up. The greatest dangers to the forests
are from fire and from careless cutting, and these dangers may be kept in
check by the efficient work of our national and state foresters.
[Illustration: We must protect our city trees. This tree was badly wounded
by being gnawed by a horse.]
A City's Need for Trees.--The city of Paris, well known as one of the most
beautiful of European capitals, spends over $100,000 annually in caring for
and replacing some of the 90,000 trees owned by the city. All over the
United States the city governments are beginning to realize what European
cities have long known, that trees are of great value to a city. They are
now following the example of European cities by planting trees and by
protecting the trees after they are planted. Thousands of city trees are
annually killed by horses which gnaw the bark. This may be prevented by
proper protection of the trunk by means of screens or wire guards. Chicago
has appointed a city forester, who has given the following excellent
reasons why trees should be planted in the city:--
(1) Trees are beautiful in form and color, inspiring a constant
appreciation of nature.
(2) Trees enhance the beauty of architecture.
(3) Trees create sentiment, love of country, state, city, and home.
(4) Trees have an educational influence upon citizens of all ages,
especially children.
(5) Trees encourage outdoor life.
(6) Trees purify the air.
(7) Trees cool the air in summer and radiate warmth in winter.
(8) Trees improve climate and conserve soil and moisture.
(9) Trees furnish resting places and shelter for birds.
(10) Trees increase the value of real estate.
(11) Trees protect the pavement from the heat of the sun.
(12) Trees counteract adverse conditions of city life.
Let us all try to make Arbor Day what it should be, a day for
caring for and planting trees, for thus we may preserve this most
important heritage of our nation.