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Title: USDA Farmers' Bulletin No. 67 - Forestry For Farmers
Author: Fernow, Bernhard E.
Language: English
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U. S. DEPARTMENT OF AGRICULTURE.
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FARMERS' BULLETIN No. 67.
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FORESTRY FOR FARMERS.
BY
B. E. FERNOW,
_Chief of the Division of Forestry._
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[Reprinted from the Yearbooks of the U. S. Department of Agriculture
for 1894 and 1895.]
[Illustration]
WASHINGTON:
GOVERNMENT PRINTING OFFICE.
1898.
----------
LETTER OF TRANSMITTAL.
U. S. Department of Agriculture,
Division of Forestry,
_Washington, D. C., December 4, 1897._
Sir: I have the honor to recommend that the two articles contributed
by me to the Yearbooks for 1894 and for 1895 on forestry for farmers
be reprinted as a Farmers' Bulletin. The articles contain information
in popular form regarding the growth of trees, the planting of a
forest, treatment of the wood lot, the cultivation of the wood crop,
influence of trees, etc. A wider distribution of this information, for
which there is still considerable demand, would, I believe, result in
acquainting farmers with a subject the importance of which has not
always been duly recognized.
Very respectfully,
B. E. Fernow, _Chief_.
Approved:
James Wilson, _Secretary_.
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CONTENTS.
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Page.
How trees grow 3
Food materials and conditions of growth 3
Soil conditions 4
Light conditions 6
Physiology of tree growth 9
"Sap up and sap down" 10
Progress of development 11
Growth in length and ramification 11
Growth in thickness 14
Form development 17
Rate of growth 19
Reproduction 21
How to plant a forest 22
What trees to plant 23
Methods of planting 26
How to treat the wood lot 28
Improvement cuttings 29
Methods of reproducing the wood crop 31
Size of openings 34
Wind mantle 34
Coppice 35
Plan of management 37
How to cultivate the wood crop 37
Effect of light on wood production 38
Number of trees per acre 38
Weeding and cleaning the crop 40
Methods of thinning 40
What trees to remove 41
The relation of forests to farms 42
The forest waters the farm 44
The forest tempers the farm 45
The forest protects the farm 45
The forest supplies the farm with useful material 46
FORESTRY FOR FARMERS.
The following five chapters have been written with the view of aiding
farmers who own small timber tracts or wood lots, or who wish to plant
some part of their land to forest. This country varies so greatly in
soil, climate, and flora that it is only possible, within the limits
assigned for the present discussion, to outline general principles
everywhere applicable. Nevertheless, wherever suggestions have
approximated the laying down of rules of practice, the writer has had
mainly in mind the conditions prevalent in our northeastern States.
Moreover, for the reason already referred to, limitation of space, it
has not been possible to give more than a comprehensive view, without
much detail.
The succeeding chapters should be read connectedly, as they are more
or less interdependent. The first treats of the behavior of a forest
plant; the second, of the principles which should guide the planter
in setting a crop; the third, of the manner in which a natural forest
crop should be produced; the fourth points out how the crop should be
managed afterwards in order to secure the best results in quantity
and quality of material; while the fifth chapter is devoted to a
consideration of the relation of forests to farms.
1. HOW TREES GROW.
Trees, like most other plants, originate from seed, build up a body
of cell tissues, form foliage, flower, and fruit, and take up food
material from the soil and air, which they convert into cellulose and
other compounds, from which all their parts are formed. They rely, like
other plants, upon moisture, heat, and light as the means of performing
the functions of growth. Yet there are some peculiarities in their
behavior, their life and growth, which require special attention on the
part of a tree grower or forest planter, and these we shall briefly
discuss.
FOOD MATERIALS AND CONDITIONS OF GROWTH.
Trees derive their food and solid substance in part from the air and
in part from the soil. The solid part of their bodies is made up
of cellulose, which consists largely of carbon (44 per cent of its
weight), with hydrogen and oxygen added in almost the same proportions
as in water. The carbon is derived from the carbonic acid of the air,
which enters into the leaves and, under the influence of light, air,
and water, is there decomposed; the oxygen is exhaled; the carbon is
retained and combined with elements derived from the water, forming
compounds, such as starch, sugar, etc., which are used as food
materials, passing down the tree through its outer layers to the very
tips of the roots, making new wood all along the branches, trunk, and
roots.
This process of food preparation, called "assimilation," can be
carried on only in the green parts, and in these only when exposed to
light and air; hence foliage, air, and light at the top are essential
prerequisites for tree growth, and hence, other conditions being
favorable, the more foliage and the better developed it is, and the
more light this foliage has at its disposal for its work, the more
vigorously will the tree grow.
In general, therefore, pruning, since it reduces the amount of foliage,
reduces also, for the time, the amount of wood formed; and just so
shading, reducing the activity of foliage, reduces the growth of wood.
SOIL CONDITIONS.
From the soil trees take mainly water, which enters through the roots
and is carried through the younger part of the tree to the leaves, to
be used in part on its passage for food and wood formation and in part
to be given up to the air by transpiration.
In a vigorously growing tree the solid wood substance itself will
contain half its weight in the form of water chemically combined, and
the tree, in addition, will contain from 40 to 65 per cent and more of
its dry weight in water mechanically or "hygroscopically" held. This
last, when the tree is cut, very largely evaporates; yet well-seasoned
wood still contains 10 to 12 per cent of such water. The weight of a
green tree, a pine, for instance, is made up, in round numbers, of
about 30 per cent of carbon and 70 per cent or water, either chemically
or hygroscopically held, while a birch contains a still larger
percentage of water.
The largest part of the water which passes through the tree is
transpired--i. e., given off to the air in vapor. The amounts thus
transpired during the season vary greatly with the species of tree,
its age, the amount of foliage at work, the amount of light at its
disposal, the climatic conditions (rain, temperature, winds, relative
humidity), and the season. These amounts are, however, very large when
compared with the quantity retained; so that while an acre of forest
may store in its trees, say, 1,000 pounds of carbon, 15 to 20 pounds
of mineral substances, and 5,000 pounds of water in a year, it will
have transpired--taken up from, the soil and returned to the air--from
500,000 to 1,500,000 pounds of water (one-quarter to one-half as much
as agricultural crops).
Mineral substances are taken up only in very small quantities, and
these are mostly the commoner sorts, such as lime, potash, magnesia,
and nitrogen. These are carried in solution to the leaves, where they
are used (as perhaps also on their passage through the tree), with a
part of the water, in food preparation. The main part of the mineral
substances taken up remains, however, as the water transpires, in the
leaves and young twigs, and is returned to the soil when the leaves are
shed or when the tree is cut and the brush left to decompose and make
humus.
Hence the improvement of the fertility of the soil by wood crops is
explained, the minerals being returned in more soluble form to the
soil; as also the fact that wood crops do not exhaust the soil of its
minerals, provided the leaves and litter are allowed to remain on the
ground.
For this reason there is no necessity of alternating wood crops, as far
as their mineral needs are concerned; the same kind of trees can be
grown on the same soil continuously, provided the soil is not allowed
to deteriorate from other causes.
As the foliage can perform its work of food assimilation only when
sufficient water is at its disposal, the amount of growth is also
dependent not only on the presence of sufficient sources of supply, but
also on the opportunity had by the roots to utilize the supply, and
this opportunity is dependent upon the condition of the soil. If the
soil is compact, so that the rain water can not penetrate readily, and
runs off superficially, or if it is of coarse grain and so deep that
the water rapidly sinks out of reach of the roots and can not be drawn
up by capillary action, the water supply is of no avail to the plants;
but if the soil is porous and moderately deep (depth being the distance
from the surface to the impenetrable subsoil, rock, or ground water)
the water not only can penetrate but also can readily be reached and
taken up by the roots.
The moisture of the soil being the most important element in it for
tree growth, the greatest attention must be given to its conservation
and most advantageous distribution through the soil.
No trees grow to the best advantage in very dry or very wet soil,
although some can live and almost thrive in such unfavorable
situations. A moderately but evenly moist soil, porous and deep enough
or fissured enough to be well drained, and yet of such a structure that
the water supplies from the depths can readily be drawn up and become
available to the roots--that is the soil on which all trees grow most
thriftily.
The agriculturist procures this condition of the soil as far as
possible by plowing, drainage, and irrigation, and he tries by
cultivating to keep the soil from compacting again, as it does under
the influence of the beating rain and of the drying out of the upper
layers by sun and wind.
The forest grower can not rely upon such methods, because they are
either too expensive or entirely impracticable. He may, indeed, plow
for his first planting, and cultivate the young trees, but in a few
years this last operation will become impossible and the effects of the
first operation will be lost. He must, therefore, attain his object in
another manner, namely, by shading and mulching the soil. The shading
is done at first by planting very closely, so that the ground may be
protected as soon as possible from sun and wind, and by maintaining the
shade well throughout the period of growth. This shade is maintained,
if necessary, by more planting, and in case the main crop in later life
thins out inordinately in the crowns or tops, or by the accidental
death of trees, it may even become desirable to introduce an underbrush.
The mulching is done by allowing the fallen leaves and twigs to remain
and decay, and form a cover of rich mold or humus. This protective
cover permits the rain and snow waters to penetrate without at the same
time compacting the soil, keeping it granular and in best condition for
conducting water, and at the same time preventing evaporation at the
surface.
The soil moisture, therefore, is best maintained by proper soil cover,
which, however, is needful only in naturally dry soils. Wet soils,
although supporting tree growth, do not, if constantly wet, produce
satisfactory wood crops, the growth being very slow. Hence they must be
drained and their water level sunk below the depth of the root system.
Irrigation is generally too expensive to be applied to wood crops,
except perhaps in the arid regions, where the benefit of the shelter
belt may warrant the expense.
Attention to favorable moisture conditions in the soil requires the
selection of such kinds of trees as shade well for a long time, to
plant closely, to protect the woody undergrowth (but not weeds), and to
leave the litter on the ground as a mulch.
Different species, to be sure, adapt themselves to different degrees of
soil moisture, and the crop should therefore be selected with reference
to its adaptation to available moisture supplies.
While, as stated, all trees thrive best with a moderate and even supply
of moisture, some can get along with very little, like the conifers,
especially pines; others can exist even with an excessive supply, as
the bald cypress, honey locust, some oaks, etc. The climate, however,
must also be considered in this connection, for a tree species,
although succeeding well enough on a dry soil in an atmosphere which
does not require much transpiration, may not do so in a drier climate
on the same soil.
In the selection of different kinds of trees for different soils, the
water conditions of the soil should, therefore, determine the choice.
LIGHT CONDITIONS.
To insure the largest amount of growth, full enjoyment of sunlight is
needed. But as light is almost always accompanied by heat and relative
dryness of air, which demands water from the plant, and may increase
transpiration from the leaves inordinately, making them pump too hard,
as it were, young seedlings of tree species whose foliage is not built
for such strains require partial shading for the first year or two. The
conifers belong to this class.
In later life the light conditions exert a threefold influence on the
development of the tree, namely, with reference to soil conditions,
with reference to form development, and with reference to amount of
growth.
The art of the forester consists in regulating the light conditions so
as to secure the full benefit of the stimulating effect of light on
growth, without its deteriorating influences on the soil and on form
development.
As we have seen, shade is desirable in order to preserve soil moisture.
Now, while young trees of all kinds, during the "brush" stage of
development, have a rather dense foliage, as they grow older they
vary in habit, especially when growing in the forest. Some, like the
beech, the sugar maple, the hemlock, and the spruce, keep up a dense
crown; others, like the chestnut, the oaks, the walnut, the tulip
tree, and the white pine, thin out more and more, and when fully
grown have a much less dense foliage; Anally, there are some which do
not keep up a dense shade for any length of time, like the black and
honey locust, with their small, thin leaves; the catalpa, with its
large but few leaves at the end of the branchlets only, and the larch,
with its short, scattered bunches of needles. So we can establish a
comparative scale of trees with reference to the amount of shade which
they can give continuously, as densely foliaged and thinly foliaged,
in various gradations. If we planted all beech or sugar maple, the
desirable shading of the soil would never be lacking, while if we
planted all locust or catalpa the sun would soon reach the soil and
dry it out, or permit a growth of grass or weeds, which is worse,
because those transpire still larger quantities of water than the bare
ground evaporates or an undergrowth of woody plants would transpire.
Of course, a densely foliaged tree has many more leaves to shed than a
thinly foliaged one, and therefore makes more litter, which increases
the favorable mulch cover of the soil. Another reason for keeping the
ground well shaded is that the litter then decomposes slowly, but into
a desirable humus, which acts favorably upon the soil, while if the
litter is exposed to light, an undesirable, partly decomposed "raw"
humus is apt to be formed.
Favorable soil conditions, then, require shade, while wood growth is
increased by full enjoyment of light; to satisfy both requirements,
mixed planting, with proper selection of shade-enduring and
light-needing species, is resorted to.
As the different species afford shade in different degrees, so they
require for their development different degrees of light. The dense
foliage of the beech, with a large number of leaves in the interior
of the crown, proves that the leaves can exist and perform their work
with a small amount of light; the beech is a shade-enduring tree. The
scanty foliage of the birches, poplars, or pines shows that these are
light-needing trees; hence they are never found under the dense shade
of the former, while the shade-enduring can develop satisfactorily
under the light shade of the thin-foliaged kinds. Very favorable soil
conditions increase the shade endurance of the latter, and climatic
conditions also modify their relative position in the scale.
All trees ultimately thrive best--i. e., grow most vigorously--in the
full enjoyment of light, but their energy then goes into branching.
Crowded together, with the side light cut off, the lower lateral
branches soon die and fall, while the main energy of growth is put into
the shaft and the height growth is stimulated. The denser shade of the
shade-enduring kinds, if placed as neighbors to light-needing ones, is
most effective in producing this result, provided that the light is not
cut off at the top; and thus, in practice, advantage is taken of the
relative requirements for light of the various species.[1]
[1] This relation of the different species to varying light conditions;
their comparative shading value and shade endurance, is one of the most
important facts to be observed and utilized by the forester. European
foresters have done this, but since they had to deal with only a few
species and over a limited territory, they could quite readily classify
their trees with reference to their shade endurance, and take it for
granted that shade endurance and density of foliage or shading value
were more or less identical. With our great wealth of useful species it
will be necessary and profitable to be more exact in the classification.
The forester finds in close planting and in mixed growth a means of
securing tall, clear trunks, free from knots, and he is able, moreover,
by proper regulation of light conditions, to influence the form
development, and also the quality of his crop, since slow growth and
rapid growth produce wood of different character.
There are some species which, although light-foliaged and giving
comparatively little shade, are yet shade-enduring--i. e., can subsist,
although not develop favorably, under shade; the oaks are examples
of this kind. Others, like the black cherry, bear a dense crown for
the first twenty years, perhaps, seemingly indicating great shade
endurance; but the fact that the species named soon clears itself
of its branches and finally has a thin crown, indicates that it is
light-needing, though a good shader for the first period of its life.
Others, again, like the catalpa, which is shady and shade-enduring, as
the difficulty with which it clears itself indicates, leaf out so late
and lose their foliage so early that their shading value is thereby
impaired. Black locust and honey locust, on the other hand, leave
no doubt either as to their light-needing or their inferior shading
quality.
That soil conditions and climatic conditions also modify crown
development and shade endurance has been well recognized abroad, but in
our country this influence is of much more importance on account of the
great variation in those conditions. Thus the box elder, an excellent
shader in certain portions of the West, is a failure as soil cover in
others where it nevertheless will grow.
We see, then, that in determining the shading value as well as the
shade endurance of one species in comparison with another, with
reference to forestry purposes, not only soil and climate but also the
character of foliage and its length of season must be considered.
PHYSIOLOGY OF TREE GROWTH.
As we have seen, root and foliage are the main life organs of the tree.
The trunk and branches serve to carry the crown upward and expose it to
the light, which is necessary in order to prepare the food and increase
the volume of the tree, and also as conductors of food materials up
and down between root and foliage. A large part of the roots, too,
aside from giving stability to the tree, serve only as conductors of
water and food material; only the youngest parts, the fibrous roots,
beset with innumerable fine hairs, serve to take up the water and
minerals from the soil. These fine roots, root hairs, and young parts
are therefore the essential portion of the root system. A tree may
have a fine, vigorous-looking root system, yet if the young parts and
fibrous roots are cut off or allowed to dry out, which they readily
do--some kinds more so than others--thereby losing their power to take
up water, such a tree is apt to die. Under very favorable moisture
and temperature conditions, however, the old roots may throw out now
sprouts and replace the fibrous roots. Some species, like the willows,
poplars, locusts, and others, are especially capable of doing so.
All trees that "transplant easily" probably possess this capacity of
renewing the fibrous roots readily, or else are less subject to drying
out. But it may be stated as a probable fact that most transplanted
trees which die soon after the planting do so because the fibrous roots
have been curtailed too much in taking up, or else have been allowed to
dry out on the way from the nursery or forest to the place of planting;
they were really dead before being set. Conifers--pines, spruces,
etc.--are especially sensitive; maples, oaks, catalpas, and apples
will, in this respect, stand a good deal of abuse.
Hence, in transplanting, the first and foremost care of the forest,
grower, besides taking the sapling up with least injury, is the proper
protection of its root fibers against drying out.
The water, with the minerals in solution, is taken up by the roots
when the soil is warm enough, but to enable the roots to act they must
be closely packed with the soil. It is conveyed mostly through the
outer, which are the younger, layers of the wood of root, trunk, and
branches to the leaves. Here, as we have seen, under the influence of
light and heat it is in large part transpired and in part combined
with the carbon into organic compounds, sugar, etc., which serve as
food materials. These travel from the leaf into the branchlet, and
down through the outer layers of the trunk to the very tips of the
root, forming new wood all the way, new buds, which lengthen into
shoots, leaves, and flowers, and also new rootlets. To live and grow,
therefore, the roots need the food elaborated in the leaves, just as
the leaves need the water sent up from the roots.
Hence the interdependence of root system and crown, which must be kept
in proportion when transplanting. At least, the root system must be
sufficient to supply the needs of the crown.
"SAP UP AND SAP DOWN."
The growing tree, in all its parts, is more or less saturated with
water, and as the leaves, under the influence of sun and wind and
atmospheric conditions generally transpire, new supplies are taken in
through the roots and conveyed to the crown. This movement takes place
even in winter, in a slight degree, to supply the loss of water by
evaporation from the branches. In the growing season it is so active
as to become noticeable; hence the saying that the sap is "up," or
"rising," and when, toward the end of the season, the movement becomes
less, the sap is said to be "down." But this movement of water is
always upward; hence the notion that there is a stream upward at one
season and in one part of the tree, and a stream downward at another
season and perhaps in another part of the tree, is erroneous. The
downward movement is of food materials, and the two movements of water
upward and food downward take place simultaneously, and depend, in
part at least, one upon the other, the food being carried to the young
parts, wherever required, by a process of diffusion from cell to cell
known as "osmosis."
[Illustration: Fig. 1.--Physiological importance of different parts of
the tree; pathways of water and food materials. (Schematic.)]
These food materials are, by the life processes of the active cells,
changed in chemical composition as need be, from sugar, which is
soluble, into starch, which is insoluble, and back into sugar, and
combined with nitrogenous substances to make the cell-forming material,
protoplasm (fig. 1).
In the fall, when the leaves cease to elaborate food, both the upward
and the downward movement, more or less simultaneously, come to rest
(the surplus of food materials, as starch, and sometimes as sugar,
being stored for the winter in certain cell tissues), to begin again
simultaneously when in spring the temperature is high enough to
reawaken activity, when the stored food of last year is dissolved
and started on its voyage. The exact manner in which this movement of
water upward and food materials downward takes place, and the forces
at work, are not yet fully understood, nor is there absolute certainty
as to the parts of the tree in which the movement takes place. It
appears, however, that while all the so-called "sapwood" is capable
of conducting water (the heartwood is probably not), the most active
movement of both water and food materials takes place in the cambium
(the growing cells immediately beneath the bark) and youngest parts of
the bark.
The deductions from these processes important to the planter are:
That injury to the living bark or bast means injury to growth, if not
destruction to life; that during the period of vegetation transplanting
can be done only with great caution; that the best time to move trees
is in the fall, when the leaves have dropped and the movement of
water and food materials has mostly ceased, or in spring, before the
movement begins again, the winter being objectionable only because of
the difficulty of working the soil and of keeping the roots protected
against frost. All things considered, spring planting, before activity
in the tree has begun, is the best, although it is not impossible to
plant at other times.
PROGRESS OF DEVELOPMENT.
Like the wheat or corn plant, the tree seed require as conditions for
sprouting sufficient moisture, warmth, and air. Tree seeds, however,
differ from grain in that most of the kinds lose their power of
germination easily; with few exceptions (locust, pine, spruce), they
can not be kept for any length of time.
The first leaves formed often differ essentially in shape from those
of the mature tree, which may cause their being confounded with other
plants, weeds, etc.
The little seedlings of many, especially the conifers, are quite
delicate, and remain very small the first season; they need, therefore,
the protecting shade of mother trees, or artificial shading, and also
protection against weeds. The amount of light or shade given requires
careful regulation for some of them; too much light and heat will kill
them, and so will too much shade. This accounts for the failure of many
seedlings that spring up in the virgin forest.
The planter, then, is required to know the nature and the needs of
the various kinds of seeds and seedlings, so as to provide favorable
conditions, when he will avoid sowing in the open field such as require
the care which it is impracticable to give outside of the nursery.
[Illustration: Fig. 2.--Bud development of beech. _B_, as it would be
if all formed buds were to live; _A_, as it is, many buds failing to
develop.]
GROWTH IN LENGTH AND RAMIFICATION.
While the stalk of wheat or corn grows for one season, exhausts
itself in seed production, and then dies, the tree continues to grow
from season to season, in length as well as in thickness. The growth
in length of shaft and branches proceeds from buds, made up of cell
tissues, which can subdivide and lengthen into shoots, as well as make
leaves. These buds are formed during summer, and when winter begins
contain embryo leaves, more or less developed, under the protecting
cover of scales (fig. 3). When spring stimulates the young plant to
new activity, the buds swell, shed their scales, distend their cells,
increasing their number by subdivision, and thus the leaves expand, and
the bud lengthens into a shoot and twig. During the season new buds are
formed, and the whole process repeats itself from year to year, giving
rise to the ramification and height growth of the tree. The end buds
being mostly stronger and better developed, the main axis of tree or
branch increases more rapidly than the rest. All these buds originate
from the youngest, central part of the shoot, the pith, and hence
when the tree grows in thickness, enveloping the base of the limbs,
their connection with the pith can always be traced. This is the usual
manner of bud formation; in addition, so-called "adventitious" buds
maybe formed from the young living wood in later life, which are not
connected with the pith. Such buds are those which develop into sprouts
from the stump when the tree is cut; also those which give rise to
what are known as "water sprouts." Many buds, although formed, are,
however, not developed at once, and perhaps not at all, especially as
the tree grows older; these either die or remain "dormant," often for a
hundred years, to spring into life when necessary (fig. 4).
[Illustration: Fig. 3.--Buds of maple. _A_, longitudinal section
through tip of a maple twig; _g_, end bud; _s_, lateral buds; _l_,
scars of leaves of last season. _B_, cross-section through end bud,
showing folded leaves in center and scales surrounding them.]
The fact that each ordinary limb starts as a bud from the pith is an
important one to the timber grower; it explains knotty timber and gives
him the hint that in order to obtain clear timber the branches first
formed must be soon removed, either by the knife or by proper shading,
which kills the branches and thus "clears" the shaft.
[Illustration: Fig. 4.--Dormant bud, _K_, on a 12-year old branch of
beech. The bud is still capable of development and is connected with
the pith, _mm_, of the stem by a line trace of pith, _S_.]
[Illustration: Fig. 5.--Section through a 12-year old stem of beech,
showing manner of bud and limb formation, _a_, dormant buds; _b_, their
trace of pith extending to the pith of the stem; _c_, a limb which
started two years ago from a dormant bud; _d_, normal limb; _e_, a limb
dead for four years; _f_, adventitious buds.]
The planter has it also in his power to influence the form development
of the tree by removing some of the buds, giving thereby better chance
to the remaining ones. This pruning of buds is, where practicable,
often better practice than the pruning of limbs.
Since the tree does not grow in length except by its buds it is evident
that a limb which started to grow at the height of 6 feet has its base
always 6 feet from the ground, and if allowed to grow to size, must be
surrounded by the wood which accumulates on the main stem or trunk. If
a limb is killed and broken off early, only a slender stub composed
entirely of rapidly decaying sapwood, is left, occasioning, therefore,
only a small defect in the heart of the tree; but if left to grow to
considerable age, the base of the limb is encased by the wood of the
stem, which, when the tree is cut into lumber, appears as a knot. The
longer the limb has been allowed to grow, the farther out is the timber
knotty and the thicker is the knot. If the limb remained alive, the
knot is "sound," closely grown together with the fibers of the tree.
If the limb died off, the remaining stub may behave in different ways.
In pines it will be largely composed of heartwood, very resinous and
durable; separated from the fibers of the overgrowing wood, it forms a
"loose" knot, which is apt to fall out of a board, leaving a hole.
In broad-leaved trees, where no resin assists in the process of
healing, the stub is apt to decay, and this decay, caused by the
growth of fungi, is apt to penetrate into the tree (fig. 6). In parks
and orchards, pruning is resorted to, and the cuts are painted or
tarred to avoid the decay. In well-managed forests and dense woods
in general, the light is cut off, the limb is killed when young and
breaks away, the shaft "clears itself," and the sound trunk furnishes
a good grade of material. The difference in development of the branch
system, whether in full enjoyment of light, in open stand, or with the
side light cut off, in dense position, is shown in the accompanying
illustration (fig. 7).
[Illustration: Fig. 6.--Section through partly decayed knot in
oak wood. _a_, wood of knot; _b_ and _c_, wood callus of the stem
covering the wound; shaded portion, decayed wood, black part, a cavity
remaining.]
Both trees start alike; the one retains its branches, the other loses
them gradually, the stubs being in time overgrown; finally the second
has a clear shaft, with a crown concentrated at the top, while the
first is beset with branches and branch stubs for its whole length
(fig. 8).
When ripped open lengthwise, the interior exhibits the condition shown
in figure 9, the dead parts of the knot being indicated in heavier
shading. Since the brandies grow in more or less regular whorls,
several knots, stumps, or limbs are met every 6 to 24 inches through
the entire stem.
Hence, in forest planting, trees are placed and kept for some time
close together, in order to decrease the branching in the lower part of
the tree and thus produce a clean bole and clear lumber.
GROWTH IN THICKNESS.
The young seedling and the young shoot of the older tree much resemble
in interior structure that of any herbaceous plant, being composed of a
large amount of pith, loose squarish cells, and a few bundles of long
fibers symmetrically distributed about the center, the whole covered
with a thin skin or epidermis. Each strand or bundle of fibers, called
fibro-vascular (fiber-vessel) bundles, consists of two kinds, namely,
wood fibers on the inner side and bast fibers of different structure
on the outer side. Between these two sets of fibers, the bast and the
wood, there is a row of cells which form the really active, growing
part of the plantlet, the cambium. The cambium cells are actively
subdividing and expanding, giving off wood cells to the interior and
bast cells to the exterior, and extending at the same time side-wise,
until at the end of the season not only are the wood and bast portions
increased in lines radiating from the center, but the cambium layer,
the wood cells, and the bast cells of all the bundles (scattered at
the beginning) join at the sides to form a complete ring, or rather
hollow cylinder, around the central pith. Only here and there the pith
cells remain, interrupting the wood cylinder and giving rise to the
system of cells known as medullary rays. The cross-section now shows a
comparatively small amount of pith and bast or bark and a larger body
of strong wood fibers. The new shoot at the end, to be sure, has the
same appearance and arrangement as the young plantlet had, the pith
preponderating, and the continuous cylinder of cambium, bast, and wood
being separated into strands or bundles.
[Illustration: Fig. 7.--Development in and out of the forest. _A_,
young tree alike. In both cases; _B_ and _C_, successive stages of tree
grown in the open; _B´_ and _C´_, corresponding stages of the tree
grown in the forest. Numbers refer to annual growth in height.]
During the season, through the activity of the cambial part of the
bundles, the same changes take place in the new shoot as did the
previous year in the young seedling, while at the same time the cambium
in the yearling part also actively subdivides, forming new wood and
bast cells, and thus a second ring, or rather cylinder, is formed. The
cambium of the young shoot is always a continuation of that of the ring
or cylinder formed the year before, and this cambium cylinder always
keeps moving outward, so that at the end of the season, when activity
ceases, it is always the last minute layer of cells on the outside of
the wood, between wood proper and bark. It is here, therefore, that
the life of the tree lies, and any injury to the cambium must interfere
with the growth and life of the tree.
[Illustration: Fig. 8.--Tree in and out of the forest. _D_, tree grown
in the open; _D´_, tree grown in the forest.]
The first wood cells which the cambium forms in the spring are usually
or always of a more open structure, thin-walled, and with a large
opening or "lumen," comparable to a blown-up paper bag; so large, in
fact, sometimes, is the "lumen" that the width of the cells can be
seen on a cross-section with the naked eye, as, for instance, in oak,
ash, elm, the so-called "pores" are this open wood formed in spring.
The cells, which are formed later in summer, have mostly thick walls,
are closely crowded and compressed, and show a very small opening or
"lumen," being comparable, perhaps, to a very thick wooden box. They
appear in the cross-section not only denser but of a deeper color, on
account of their crowded, compressed condition and thicker walls. Since
at the beginning of the next season again thin-walled cells with wide
openings or lumina are formed, this difference in the appearance of
"spring wood" and "summer wood" enables us to distinguish the layer of
wood formed each year. This "annual ring" is more conspicuous in Some
kinds than in others. In the so-called "ring porous" woods, like oak,
ash, elm, the rings are easily distinguished by the open spring wood;
in the conifers, especially pines, by the dark-colored summer wood;
while in maple, birch, tulip, etc., only a thin line of flattened,
hence darker and regularly aligned, summer cells, often hardly
recognizable, distinguishes The rings from each other. Cutting through
a tree, therefore, we can not only ascertain its age by counting its
annual layers in the cross-section, but also determine how much wood is
formed each year (fig. 10). We can, in fact, retrace the history of
its growth, the vicissitudes through which it has passed, by the record
preserved in its ring growth.
To ascertain the age of a tree correctly, however, we must cut so near
to the ground as to include the growth of the first year's little
plantlet; any section higher up shows as many years too few as it took
the tree to reach that height.
[Illustration: Fig. 9.--Sections of logs showing the relative
development of knots. _E_, from tree grown in the open; _E´_, from tree
grown in a dense forest; _a_ and _c_, whorls of knots; _b_, dead limb;
_sk_, "sound knot;" _dk_, "dead knot."]
This annual-ring formation is the rule in all countries which have
distinct seasons of summer and winter and temporary cessation of
growth. Only exceptionally a tree may fail to make its growth
throughout its whole length on account of loss of foliage or other
causes; and occasionally, when its growth has been disturbed during
the season, a "secondary" ring, resembling the annual ring, and
distinguishable only by the expert, may appear and mar the record.
To the forest planter this chapter on ring growth is of great
importance, because not only does this feature of tree life afford the
means of watching the progress of his crop, calculating the amount of
wood formed, and therefrom determining when it is most profitable for
him to harvest (namely, when the annual or periodic wood growth falls
below a certain amount), but since the proportion of summer wood and
spring wood determines largely the quality of the timber, and since he
has it in his power to influence the preponderance of the one or other
by adaptation of species to soils and by their management, ring growth
furnishes an index for regulating the quality of his crop.
FORM DEVELOPMENT.
If a tree is allowed to grow in the open, it has a tendency to branch,
and makes a low and spreading crown. In order to lengthen its shaft and
to reduce the number of branches it is necessary to narrow its growing
space, to shade its sides so that the lower branches and their foliage
do not receive light enough to perform their functions. When the side
shade is dense enough, these branches die and finally break off under
the influence of winds and fungous growth; wood then forms over the
scars and we get a clean shaft which carries a crown high up beyond the
reach of shade from neighbors.
[Illustration: Fig. 10.--Scheme to Illustrate the arrangement of annual
growth. 1, 2, 3, etc., represent the parts of the stem grown during the
first, second, third, etc., twenty years of the life of the tree, _k_,
knots; the shaded part of each is the "dead knot" of lumber.]
The branches being prevented from spreading out, the shaft is forced
to grow upward, and hence, when crowded by others, trees become taller
and more cylindrical in form, while in the open, where they can spread,
they remain lower and more conical in form (figs. 11, 12).
There are, to be sure, different natural types of development, some,
like the walnuts, oaks, beeches, and the broad-leaved trees generally,
having greater tendency to spread than others, like spruces, firs,
and conifers in general, which lengthen their shaft in preference
to spreading, even in the open. This tendency to spreading is also
influenced by soil conditions and climate, as well as by the age of the
tree. When the trees cease to grow in height, their crowns broaden, and
this takes place sooner in shallow soils than in deep, moist ones; but
the tendency can be checked and all can be made to develop the shaft at
the expense of the branches by proper shading from the sides.
It follows that the forest planter, who desires to produce long and
clean shafts and best working quality of timber, must secure and
maintain side shade by a close stand, while the landscape gardener,
who desires characteristic form, must maintain an open stand and full
enjoyment of light for his trees.
Now, as we have seen, different species afford different amounts of
shade, and in proportion to the shade which they afford can they
endure shade. The beech or sugar maple or spruce, which maintain a
large amount of foliage under the dense shade of their own crown, show
that their leaves can live and functionate with a small amount of
light. They are shade-enduring trees. On the other hand, the black
walnut, the locust, the catalpa, the poplars, and the larch show by the
manner in which their crowns thin out, the foliage being confined to
the ends of the branches, that their leaves require more light--they
are light-needing trees; so that the scale which arranges the trees
according to the amount of shade they exert serves also to measure
their shade endurance.
In making, therefore, mixed plantations, the different kinds must be so
grouped and managed that the shady trees will not outgrow and overtop
the light-needing; the latter must either have the start of the former
or must be quicker growers.
[Illustration: Fig. 11.--Oak tree grown in the open.]
[Illustration: Fig. 12.--Maple tree grown in the forest.]
RATE OF GROWTH.
Not only do different species grow more or less rapidly in height and
girth, but there is in each species a difference in the rate of growth
during different periods of life, and a difference in the persistence
of growth.
It stands to reason that trees grow differently in different soils and
situations, and hence we can not compare different species with respect
to their rate of growth except as they grow under the same conditions.
Thus the black walnut may grow as fast as or faster than the ash on
a rich, deep, moist, warm soil, but will soon fall to the rear in a
wetter, colder, and shallower soil.
Given the same conditions, some species will start on a rapid upward
growth at once, like the poplars, aspen, locust, and silver maple,
making rapid progress (the most rapid from their tenth to their
fifteenth year), but decreasing soon in rate and reaching their maximum
height early. Others, like the spruce, beech, and sugar maple, will
begin slowly, often occupying several, sometimes as many as 10 to
15, years before they appear to grow at all, their energy all going
into root growth. Then comes a period of more and more accelerated
growth, which reaches its maximum rate at 25 or 30 years; and when the
cottonwood or aspen has reached the end of its growth in height the
spruce or pine is still at its best rate, and continues to grow for a
long time at that rate; in later life the rate decreases, yet height
growth sometimes does not cease altogether for centuries. As a rule,
the light-needing species are the ones which show the rapid height
growth at the start, while the shade-enduring are slow at the start,
but persistent growers.
This fact is important in explaining the alternations of forest
growth in nature; the persistent shade-enduring species crowd out the
light-needing, and the latter rapidly take possession of any openings
that fire or storm has made. It is also important with reference to
the management of wood crops and starting of mixed plantations; the
light-needing species must be mixed only with such shade-enduring
species as are slower growers than themselves.
The diameter growth shows also periodic changes in its rate, and is,
of course, influenced in the same way by soil, climate, and light
conditions, as the height growth.
In the juvenile or brush stage, lasting 6 to 10 years in light-needing
and 20 to 40 years in shade-enduring species, the diameter grows
comparatively little, all energy being directed to height growth and
root growth. When the crown has been definitely formed, more food
material is available for wood formation, and the increase in foliage
is accompanied by a more rapid increase of trunk diameter; in favorable
situations, the highest rate occurs between the fortieth and sixtieth
years; in the poorer situations, between the fiftieth and eightieth
years, which rate continues for some time. Then comes a period of
slower rate, which finally in old age dwindles down almost to zero.
But neither the diameter growth nor the width of the annual rings alone
tells us directly what amount of wood is forming. The outer rings,
being laid over a larger circumference, although thinner than the
preceding rings, may yet have greater cubic contents. The statements
of diameter growth are, therefore, misleading if we are interested in
knowing how much wood is forming.
Accordingly the growth in volume must be considered separately, as
determined by the enlargement of the cross-section area and the height.
The growth in volume or mass accretion is quite small in young trees,
so that when wood is cut young the smallest amount of crop per year
is harvested, while, if it is allowed to grow, an increase more than
proportionate to the number of years may be obtained.
Only when the tree has a fully developed crown does it begin to make
much wood. Its volume growth progresses then at a uniform rate, and
continues to do so for decades, and sometimes for a century or more.
On poorer sites the rate is slower, but remains longer on the increase,
while on good sites the maximum rate is soon reached.
Of course, in a forest, where light conditions are not most favorable,
because form development and soil conditions require shade, the total
wood formation is less than in an isolated tree, favorably placed.
Just so the dominant trees in a forest--i. e., those which have their
crowns above all others--show, of course, the advantage they have
over the inferior trees which are suffering from the shade of their
neighbors.
Finally, if we would take into consideration an entire forest growth,
and determine, for instance, how much wood an acre of such forest
produces at different periods, we must not overlook the fact that the
number of trees per acre changes as the trees grow older. Some of them
are overshaded and crowded out by the others, so that a young growth of
spruce might start with 100,000 little seedlings to the acre, of which
in the twentieth year only 10,000 would be alive, while in the fortieth
year the number would be reduced to 1,200, and in the hundredth year to
280. Hence the rate of growth of any single tree gives no idea of what
the acre of forest will do.
Tims, while a single good white pine might grow the fastest in volume
when about one hundred years old, then making wood at the rate of,
say, 1.5 cubic feet per year, an acre of pine on good soil, containing
about 1,600 trees, may make the most wood in the thirtieth year, then
growing at the rate of 170 cubic feet per acre, while in the hundredth
year the rate would not exceed 70 cubic feet; and an acre of pine in a
poorer location, with about 1,400 trees, may make the most wood in the
fortieth year, at the rate of 100 cubic feet per acre.
From the consideration of the relation of light conditions to soil
conditions, to form development, and to rate of growth, we may make the
following deductions of interest to the forest planter:
In order to secure the best results in wood production, in quantity
and quality, at the same time preserving favorable soil conditions,
the forest should be composed of various species, a mixture of
light-needing and shade-enduring kinds. The light-needing ones should
be of quicker growth; the shady ones, in larger numbers, should
be slower growers. For the first fifteen to twenty-five years the
plantation should be kept as dense as possible, to secure clear shafts
and good growth in height; then it should be thinned, to increase crown
development and diameter growth; the thinning, however, is not to be so
severe that the crowns can not close up again in two or three years;
the thinning is to be repeated again and again, always favoring the
best developed trees.
REPRODUCTION.
All trees reproduce themselves naturally from seed. Man can secure
their reproduction also from cuttings or layers; and some kinds can
reproduce themselves by shoots from the stump when the parent tree has
been cut. This latter capacity is possessed in a varying degree by
different species; chestnuts, oaks, elms, maples, poplars, and willows
are most excellent sprouters; most conifers do not sprout at all, and
the shoots of those that do sprout soon die (Sequoia or California
redwood seems to be an exception). Sprouts of broad-leaved trees
develop differently from seedlings, growing very rapidly at first, but
soon lessening in the rate of growth and never attaining the height and
perhaps not the diameter of trees grown from the seed; they are also
shorter lived. With age the stumps lose their capacity for sprouting.
To secure best results, the parent tree should be cut close to the
ground in early spring, avoiding severe frost, and a sharp cut should
be made which will not sever the bark from the trunk.
Not all trees bear seed every year, and plentiful seed production,
especially in a forest, occurs, as a rule, periodically. The periods
differ with species, climate, and season.
Not all seeds can germinate, and in some species the number of seeds
that can germinate is very small, and they lose their power of
germination when kept a few hours, like the willows. Others, if kept
till they have become dry, will "lie over" in the soil a year or more
before germinating. The same thing will occur if they are covered too
deep in the soil, provided they germinate at all under such conditions.
In order to germinate, seeds must have warmth, air, and moisture.
The preparation of a seed bed is, therefore, necessary in order to
supply these conditions in most favorable combination. In the natural
forest millions of seeds rot or dry without sprouting, and millions
of seedlings sprout, but soon perish under the too dense shade of the
mother trees.
Man, desiring to reproduce a valuable wood crop, cannot afford to be
as lavish as nature, and must therefore improve upon nature's methods,
making more careful preparation for the production of his crop, either
by growing the seedlings in nurseries and transplanting them, or else
by cutting away the old growth in such a manner as to secure to the
young self-grown crop better chances for life and development.
2. HOW TO PLANT A FOREST.
Forest planting and tree planting are two different things. The
orchardist, who plants for fruit; the landscape gardener, who plants
for form; the roadside planter, who plants for shade, all have objects
in view different from that of the forest planter, and therefore
select and use their plant material differently. They deal with single
individual trees, each one by itself destined for a definite purpose.
The forester, on the other hand, plants a crop like the farmer; he
deals not with the single seed or plant, but with masses of trees; the
individual tree has value to him only as apart of the whole. It may
come to harvest for its timber, or it may not come to harvest, and yet
have answered its purpose as a part of the whole in shading the ground,
or acting as nurse or "forwarder" as long as it was necessary.
His object is not to grow trees, but to produce wood, the largest
amount of the best quality per acre, whether it be stored in one tree
or in many, and his methods must be directed to that end.
As far as the manner of setting out plants or sowing seeds is
concerned, the same general principles and the same care in
manipulation are applicable as in any other planting, except as the
coat of operating on so Large a scale may necessitate less careful
methods than the gardener or nurseryman can afford to apply; the
nearer, however, the performance of planting can be brought to the
careful manner of the gardener, the surer the success. The principles
underlying such methods have been discussed in the chapter "How trees
grow;" in the present chapter it is proposed to point out briefly
the special considerations which should guide the forest planter in
particular.
WHAT TREES TO PLANT.
_Adaptability to climate_ is the first requisite in the species to be
planted.
It is best to choose from the native growth of the region which is
known to be adapted to it. With regard to species not native, the
reliance must be placed upon the experience of neighboring planters
and upon experiment (at first on a small scale), after study of the
requirements of the kinds proposed for trial.
Adaptation must be studied, not only with reference to temperature
ranges and rainfall, but especially with reference to atmospheric
humidity and requirements of transpiration.
Many species have a wide range of natural distribution, and hence
of climatic adaptation. If such are to be used, it is important to
secure seeds from that part of the range of natural distribution where
the plants must be hardiest, i. e., the coldest and driest region in
which it occurs, which insures hardy qualities in the offspring. For
instance, the Douglas spruce from the humid and evenly tempered Pacific
Slope will not be as hardy as that grown from seed collected on the dry
and frigid slopes of the Rockies. Lack of attention to this requisite
accounts for many failures. It must also be kept in mind that, while
a species may be able to grow in another than its native climate, its
wood may not there have the same valuable qualities which it develops
in its native habitat.
_Adaptability to soil_ must be studied less with reference to mineral
constituents than to physical condition. Depth and moisture conditions,
and the structure of the soil, which influences the movement of water
in it, are the most important elements. While all trees thrive best
in a moist to "fresh" soil of moderate depth (from 2 to 4 feet) and
granular structure, some can adapt themselves to drier or wetter,
shallow, and compact soils. Fissures in rocks into which the roots can
penetrate often stand for depth of soil, and usually aid in maintaining
favorable moisture conditions. In soils of great depth (i. e., from the
surface to the impenetrable subsoil) and of coarse structure water may
drain away so fast as not to be available to the roots.
Soil moisture must always be studied in conjunction with atmospheric
moisture; for, while a species may thrive in an arid soil, when the
demands of transpiration are not great, it may not do so when aridity
of atmosphere is added. Trees of the swamp are apt to be indifferent to
soil moisture and to thrive quite well, if not better, in drier soils.
_Adaptability to site._--While a species may be well adapted to the
general climatic conditions of a region, and in general to the soil,
there still remains to be considered its adaptability to the particular
"site," under which term we may comprise the total effect of general
climate, local climate, and soil. The general climatic conditions are
locally influenced, especially by the slope, exposure, or aspect, and
the surroundings. Thus we know that eastern exposures are more liable
to frost, western exposures more liable to damage from winds, southern
more apt to be hot and to dry out, and northern to be cooler and
damper, having in consequence a shorter period of vegetation. Hollows
and lowlands are more exposed to frosts and more subject to variations
in soil moisture, etc.
Hence for these various situations it is advisable to select species
which can best withstand such local dangers.
_The use value, or utility_, of the species is next to be considered.
This must be done with reference to the commercial and domestic demand,
and the length of time it takes the species to attain its value. The
greater variety of purposes a wood may serve--i. e., the greater its
general utility--and the sooner it attains its use value the better.
White pine for the northeastern States as a wood is like the apple
among fruits, making an all-round useful material in large quantities
per acre in short time. Tulip poplar, applicable to a wider climatic
range, is almost as valuable, while oak, ash, and hickory are standard
woods in the market. Other woods are of limited application. Thus the
black locust, which grows most quickly into useful posts, has only a
limited market, much more limited than it should have; hickory soon
furnishes valuable hoop poles from the thinnings, and later the best
wagon material, not, however, large quantities in a short time; while
black walnut of good quality is very high in price, the market is also
limited, and the dark color of the heartwood, for which it is prized,
is attained only by old trees. The black cherry, used for similar
purposes, attains its value much sooner.
By planting various species together, variety of usefulness may be
secured and the certainty of a market increased.
_The forest value_ of the species is only in part expressed by its use
value. As has been shown in another place, the composition of the crop
must be such as to insure maintenance of favorable soil conditions,
as well as satisfactory development of the crop itself. Some species,
although of high use value, like ash, oak, etc, are poor preservers of
soil conditions, allowing grass and weeds to enter the plantation and
to deteriorate the soil under their thin foliage. Others, like beech,
sugar maple, box elder, etc., although of less use value, being dense
foliaged and preserving a shady crown for a long time, are of great
forest value as soil improvers.
Again, as the value of logs depends largely on their freedom from
knots, straightness, and length, it is of importance to secure these
qualities. Some valuable species, if grown by themselves, make crooked
trunks, do not clean their shafts of branches, and are apt to spread
rather than lengthen. If planted in close companionship with others,
they are forced by these "nurses or forwarders" to make better growths
and clean their shafts of branches.
Furthermore, from financial considerations, it is well to know that
some species develop more rapidly and produce larger quantities of
useful material per acre than others; thus the white pine is a "big
cropper," and, combining with this a tolerably good shading quality,
and being in addition capable of easy reproduction, it is of highest
"forest value."
Hence, as the object of forestry is to make money from continued wood
crops, use value and forest value must both be considered in The
selection of materials for forest planting.
_Mutual relationship of different species_, with reference especially
to their relative height growth and their relative light requirements,
must be considered in starting a mixed plantation.
Mixed forest plantations (made of several kinds) have so many
advantages over pure plantations (made of one kind) that they should
be preferred, except for very particular reasons. Mixed plantations
are capable of producing larger quantities of better and more varied
material, preserve soil conditions hotter, are less liable to damage
from winds, fires, and insects, and can be more readily reproduced.
The following general rules should guide in making up the composition
of a mixed plantation:
_a._ Shade-enduring kinds should form the bulk (five-eighths to
seven-eighths) of the plantation, except on specially favored
soils where no deterioration is to be feared from planting only
light-needing kinds, and in which case those may even be planted by
themselves.
_b._ The light-needing trees should be surrounded by shade-enduring
of slower growth, so that the former may not be overtopped, but have
the necessary light and be forced by side shade to straight growth.
_c._ Shade-enduring species may be grown in admixture with each
other when their rate of height growth is about equal, or when the
slower-growing kind can be protected against the quicker-growing (for
instance, by planting a larger proportion of the former in groups or
by cutting back the latter).
_d._ The more valuable timber trees which are to form the main crop
should be so disposed individually, and planted in such numbers among
the secondary crop or nurse crop, that the latter can be thinned out
first without disturbing the former.
Where a plantation of light-foliaged trees has been made (black walnut,
for instance), it can be greatly improved by "under-planting" densely
with a shade-enduring kind, which will choke out weed growth, improve
the soil, and thereby advance the growth of the plantation.
The selection and proper combination of species with reference to
this mutual relationship to each other and to the soil are the most
important elements of success.
_Availability_ of the species also still needs consideration in
this country; for, although a species may be very well adapted to
the purpose in hand, it may be too difficult to obtain material
for planting in quantity or at reasonable prices. While the beech
is one of the best species for shade endurance, and hence for soil
cover, seedlings can not be had as yet in quantity. Western conifers,
although promising good material for forest planting, are at present
too high priced for general use. Some eastern trees can be secured
readily--either their seed or seedlings--from the native woods; others
must be grown in nurseries before they can be placed in the field.
_Whether to procure seeds or plants_, and if the latter, what kind,
depends upon a number of considerations. The main crop, that which is
to furnish the better timber, had best be planted with nursery-grown
plants, if of slow-growing kinds, perhaps once transplanted, with
well-developed root systems, the plants in no case to be more than 2 to
3 years old. The secondary or nurse crop may then be sown or planted
with younger and less costly material taken from the woods or grown in
seed beds, or else cuttings may be used.
In some localities--for instance, the Western plains--the germinating
of seeds in the open field is so uncertain, and the life of the young
seedlings for the first year or two so precarious, that the use of
seeds in the field can not be recommended. In such locations careful
selection and treatment of the planting material according to the
hardships which it must encounter can alone insure success.
Seedlings from 6 to 12 inches high furnish the best material. The
planting of large-sized trees is not excluded, but is expensive and
hence often impracticable, besides being less sure of success, since
the larger-sized tree is apt to lose a greater proportion of its roots
in transplanting.
METHODS OF PLANTING.
_Preparation of soil_ is for the purpose of securing a favorable start
for the young crop; its effects are lost after the first few years.
Most land that is to be devoted to forest planting does not admit of
as careful preparation as for agricultural crops, nor is it necessary
where the climate is hot too severe and the soil not too compact to
prevent the young crop from establishing itself. Thousands of acres in
Germany are planted annually without any soil preparation, yearling
pine seedlings being set with a dibble in the unprepared ground. This
absence of preparation is even necessary in sandy soils, like that
encountered in the sand-hills of Nebraska, which may, if disturbed,
be blown out and shifted. In other cases a partial removal of a too
rank undergrowth or soil cover and a shallow scarifying or hoeing is
resorted to, or else furrows are thrown up and the trees set out in
them.
In land that has been tilled, deep plowing (10 to 12 inches) and
thorough pulverizing give the best chances for the young crop to
start. For special conditions, very dry or very moist situations,
special methods are required. The best methods for planting in the
semiarid regions of the far West have not yet been developed. Thorough
cultivation, as for agricultural crops, with subsequent culture, is
successful, but expensive. A plan which might be tried would consist in
breaking the raw prairie in June and turning over a shallow sod, sowing
a crop of oats or alfalfa, harvesting it with a high stubble, then
opening furrows for planting and leaving the ground between furrows
undisturbed, so as to secure the largest amount of drainage into the
furrows and a mulch between the rows.
_The time for planting_ depends on climatic and soil conditions and
the convenience of the planter. Spring planting is preferable except
in southern latitudes, especially in the West, where the winters are
severe and the fall apt to be dry, the soil therefore not in favorable
condition for planting.
The time for fall planting is after the leaves have fallen; for spring
planting, before or just when life begins anew. In order to be ready in
time for spring planting, it is a good practice to take up the plants
in the fall and "heel them in" over winter (covering them, closely
packed, in a dry trench of soil). Conifers can be planted later in
spring and earlier in fall than broad-leaved trees.
_The density_ of the trees is a matter in which most planters fail. The
advantages of close planting lie in the quicker shading of the soil,
hence the better preservation of its moisture and improved growth and
form development of the crop. These advantages must be balanced against
the increased cost of close planting. The closer the planting, the
sooner will the plantation be self-sustaining and the surer the success.
If planted in squares, or, better still, in quincunx order (the trees
in every other row alternating at equal distances), which is most
desirable on account of the more systematic work possible and the more
complete cover which it makes, the distance should not be more than 4
feet, unless for special reasons and conditions, while 2 feet apart is
not too close, and still closer planting is done by nature with the
best success.
The following numbers of trees per acre are required when planting at
distances as indicated:
1½ by 1½ feet 19,360 | 2 by 4 feet 6,445
1½ by 2 feet 14,520 | 3 by 3 feet 4,840
2 by 2 foot 10,890 | 3 by 4 feet 3,630
2 by 3 feet 7,260 | 4 by 4 feet 2,722
To decrease expense, the bulk of the plantation may be made of the
cheapest kinds of trees that may serve as soil cover and secondary or
nurse crop, the main crop of from 300 to 600 trees to consist of better
kinds, and with better planting material, mainly of light-needing
species. These should be evenly disposed through the plantation, each
closely surrounded by the nurse crop. It is, of course, understood that
not all trees grow up; a constant change in numbers by the death (or
else timely removal) of the overshaded takes place, so that the final
crop shows at 100 years a close cover, with hardly 300 trees to the
acre.
_After-culture_ is not entirely avoidable, especially under unfavorable
climatic conditions, and if the planting was not close enough. Shallow
cultivation between the rows is needed to prevent weed growth and to
keep the soil open, until it is shaded by the young trees, which may
take a year with close planting and two or three years with rows 4 by 4
feet apart, the time varying also with the species.
It is rare that a plantation succeeds in all its parts; gaps or fail
places occur, as a rule, and must be filled in by additional planting
as soon as possible, if of larger extent than can be closed up in a few
years by the neighboring growth.
When the soil is protected by a complete leaf canopy, the forest crop
may be considered as established, and the after-treatment will consist
of judicious thinning.
3. HOW TO TREAT THE WOOD LOT.
In the northeastern States it is the custom to have connected with
the farm apiece of virgin woodland, commonly called the wood lot. Its
object primarily is to supply the farmer with the firewood, fence
material, and such dimension timbers as he may need from time to time
for repairs on buildings, wagons, etc.
As a rule, the wood lot occupies, as it ought to, the poorer part of
the farm, the rocky or stony, the dry or the wet portions, which are
not well fitted for agricultural crops. As a rule, it is treated as
it ought not to be, if the intention is to have it serve its purpose
continuously; it is cut and culled without regard to its reproduction.
As far as firewood supplies go, the careful farmer will first use
the dead and dying trees, broken limbs, and leavings, which is quite
proper. The careless man avoids the extra labor which such material
requires, and takes whatever splits best, no matter whether the
material could be used for better purposes or not.
When it comes to the cutting of other material, fence rails, posts, or
dimension timber, the general rule is to go into the lot and select
the best trees of the best kind for the purpose. This looks at first
sight like the natural, most practical way of doing. It is the method
which the lumberman pursues when he "culls" the forest, and is, from
his point of view perhaps, justifiable, for he only desires to secure
at once what is most profitable in the forest. But for the farmer, who
proposes to use his wood lot continuously for supplies of this kind, it
is a method detrimental to his object, and in time it leaves him with a
lot of poor, useless timber which encumbers the ground and prevents the
growth of a better crop.
Our woods are mostly composed of many species of trees; they are mixed
woods. Some of the species are valuable for some special purposes,
others are applicable to a variety of purposes, and again others
furnish but poor material for anything but firewood, and even for that
use they may not be of the best.
Among the most valuable in the northeastern woods we should mention
the white pine--king of all--the white ash, white and chestnut oak,
hickories, tulip tree, black walnut, and black cherry, the last three
being now nearly exhausted; next, spruce and hemlock, red pine, sugar
maple, chestnut, various oaks of the black or red oak tribe, several
species of ash and birch, black locust; lastly, elms and soft maples,
basswood, poplars, and sycamore.
Now, by the common practice of culling the best it is evident that
gradually all the best trees of the best kinds are taken out, leaving
only inferior trees or inferior kinds--the weeds among trees, if one
may call them such--and thus the wood lot becomes well-nigh useless.
It does not supply that for which it was intended; the soil, which was
of little use for anything but a timber crop before, is still further
deteriorated under this treatment, and being compacted by the constant
running of cattle, the starting of a crop of seedlings is made nearly
impossible. It would not pay to turn it into tillage ground or pasture;
the farm has by so much lost in value. In other words, instead of using
the interest on his capital, interest and capital have been used up
together; the goose that laid the golden egg has been killed.
This is not necessary if only a little system is brought into the
management of the wood lot and the smallest care is taken to avoid
deterioration and secure reproduction.
IMPROVEMENT CUTTINGS.
The first care should be to improve the crop in its composition.
Instead of culling it of its best material, it should be culled of its
weeds, the poor kinds, which we do not care to reproduce, and which,
like all other weeds, propagate themselves only too readily. This
weeding must not, however, be done all sit once, as it could be in
a field crop, for in a full-grown piece of woodland each tree has a
value, even the weed trees, as soil cover.
The great secret of success in all crop production lies in the
regulating of water supplies; the manuring in part and the cultivating
entirely, as well as drainage and irrigation, are means to this end. In
forestry these means are usually not practicable, and hence other means
are resorted to. The principal of these is to keep the soil as much as
possible under cover, either by the shade which the foliage of the tall
trees furnishes, or by that from the underbrush, or by the litter which
accumulates and in decaying forms a humus cover, a most excellent mulch.
A combination of these three conditions, viz, a dense crown cover,
woody underbrush where the crown cover is interrupted, and a heavy
layer of well-decomposed humus, gives the best result. Under such
conditions, first of all, the rain, being intercepted by the foliage
and litter, reaches the ground only gradually, and therefore does not
compact the soil as it does in the open field, but leaves it granular
and open, so that the water can readily penetrate and move in the soil.
Secondly, the surface evaporation is considerably reduced by the shade
and lack of air circulation in the dense woods, be that more moisture
remains for the use of the trees. When the shade of the crowns overhead
(the so-called "crown cover," or "canopy,") is perfect, but little
undergrowth will be seen; but where the crown cover is interrupted
or imperfect, an undergrowth will appear. If this is composed of
young trees, or even shrubs, it is an advantage, but if of weeds, and
especially grass, it is a misfortune, because these transpire a great
deal more water than the woody plants and allow the soil to deteriorate
in structure and therefore in water capacity.
Some weeds and grasses, to be sure, are capable of existing where but
little light reaches the soil. When they appear it is a sign to the
forester that he must be careful not to thin out the crown cover any
more. When the more light-needing weeds and grasses appear it is a sign
that too much light reaches the ground, and that the soil is already
deteriorated. If this state continues, the heavy drain which the
transpiration of these weeds makes upon the soil moisture, without any
appreciable conservative action by their shade, will injure the soil
still further.
The overhead shade or crown cover may be imperfect because there are
not enough trees on the ground to close up the interspaces with their
crowns, or else because the kinds of trees which make up the forest do
not yield much shade; thus it can easily be observed that a beech, a
sugar maple, a hemlock, is so densely foliaged that but little light
reaches the soil through its crown canopy, while an ash, an oak, a
larch, when full grown, in the forest, allows a good deal of light to
penetrate.
Hence, in our weeding process for the improvement of the wood crop,
we must be careful not to interrupt the crown cover too much, and
thereby deteriorate the soil conditions. And for the same reason, in
the selection of the kinds that are to be left or to be taken out, we
shall not only consider their use value but also their shading value,
trying to bring about such a mixture of shady and less shady kinds as
will insure a continuously satisfactory crown cover, the shade-enduring
kinds to occupy the lower stratum in the crown canopy, and to be more
numerous than the light-needing.
The forester, therefore, watches first the conditions of his soil
cover, and his next care is for the condition of the overhead shade,
the "crown cover;" for a change in the condition of the latter brings
change into his soil conditions, and, inversely, from the changes
in the plant cover of the soil he judges whether he may or may not
change the light conditions. The changes of the soil cover teach him
more often when "to let alone" than when to go on with his operations
of thinning out; that is to say, he can rarely stop short of that
condition which is most favorable. Hence the improvement cuttings must
be made with caution and only very gradually, so that no deterioration
of the soil conditions be invited. We have repeated this injunction
again and again, because all success in the management of future wood
crops depends upon the care bestowed upon the maintenance of favorable
soil conditions.
As the object of this weeding is not only to remove the undesirable
kinds from the present crop, but to prevent as much as possible their
reappearance in subsequent crops, it maybe advisable to cut such kinds
as sprout readily from the stump in summer time--June or July--when the
stumps are, likely to die without sprouting.
It may take several years' cutting to bring the composition of the main
crop into such a condition as to satisfy us.
METHODS OF REPRODUCING THE WOOD CROP.
Then comes the period of utilizing the main crop. As we propose to keep
the wood lot as such, and desire to reproduce a satisfactory wood crop
in place of the old one, this latter must be cut always with a view to
that reproduction. There are various methods pursued for this purpose
in large forestry operations which are not practicable on small areas,
especially when these are expected to yield only small amounts of
timber, and these little by little as required. It is possible, to be
sure, to cut the entire crop and replant a new one, or else to use the
ax skillfully and bring about a natural reproduction in a few years;
but we want in the present case to lengthen out the period during which
the old crop is cut, and hence must resort to other methods. There are
three methods practicable.
We may clear narrow strips or bands entirely, expecting the neighboring
growth to furnish the seed for covering the strip with a new crop--"the
strip method;" or we can take out single trees here and there, relying
again on an after growth from seed shed by the surrounding trees--the
"selection method;" or, finally, instead of single trees, we may cut
entire groups of trees hero and there in the same manner, the gaps to
be filled, as in the other cases, with a young crop from the seed of
the surrounding trees, and this we may call the "group method."
In _the strip method_, in order to secure sufficient seeding of the
cleared strip, the latter must not be so broad that the seed from the
neighboring growth can not be carried over it by the wind. In order to
get the best results from the carrying power of the wind (as well as to
avoid windfalls when the old growth is suddenly opened on the windward
side) the strips should be located on the side opposite the prevailing
winds. Oaks, beech, hickory, and nut trees in general with heavy seeds
will not seed over any considerable breadth of strip, while with maple
and ash the breadth may be made twice as great as the height of the
timber, and the mother trees with lighter seeds, like spruce and pine,
or birch and elm, maybe able to cover strips of a breadth of 3 or 4 and
even 8 times their height. But such broad strips are hazardous, since
with insufficient seed fall, or fail years in the seed, the strip may
remain exposed to sun and wind for several years without a good cover
and deteriorate. It is safer, therefore, to make the strips no broader
than just the height of the neighboring timber, in which case not only
has the seed better chance of covering the ground, but the soil and
seedlings have more protection from the mother crop. In hilly country
the strips must not be made in the direction of the slope, for the
water would wash out soil and seed.
Every year, then, or from time to time, a new strip is to be cleared
and "regenerated." But if the first strip failed to cover itself
satisfactorily, the operation is stopped, for it would be unwise to
remove the seed trees further by an additional clearing. Accordingly,
this method should be used only where the kinds composing the mother
crop are frequent and abundant seeders and give assurance of reseeding
the strips quickly and successfully.
[Illustration: Fig. 13.--Showing plan of group system in regenerating
a forest crop. 1, 2, 3, 4, successive groups of young timber, 1 being
the oldest, 4 the youngest, 5 old timber; _a_, wind mantle, specially
managed to secure protection.]
The other two methods have greater chances of success in that they
preserve the soil conditions more surely, and there is more assurance
of seeding from the neighboring trees on all sides.
_The selection method_, by which single trees are taken out all over
the forest, is the same as has been practiced by the farmer and
lumberman hitherto, only they have forgotten to look after the young
crop. Millions of seed may fall to the ground and germinate, but
perish from the excessive shade of the mother trees. If we wish to be
successful in establishing a new crop, it will be necessary to be ready
with the ax all the time and give light as needed by the young crop.
The openings made by taking out single trees are so small that there is
great danger of the young crop being lost, or at least impeded in its
development, because it is impracticable to come in time to its relief
with the ax.
The best method, therefore, in all respects, is the "_group method_"
which not only secures continuous soil cover, chances for full seeding,
and more satisfactory light conditions, but requires loss careful
attention, or at least permits more freedom of movement and adaptation
to local conditions (fig. 13).
It is especially adapted to mixed woods, as it permits securing for
each species the most desirable light conditions by making the openings
larger or smaller, according as the species we wish to favor in a
particular group demand more or less shade. Further, when different
species are ripe for regeneration at different times, this plan makes
it possible to take them in hand as needed. Again, we can begin with
one group or we can take in hand several groups simultaneously, as may
be desirable and practicable.
We start our groups of new crop either where a young growth is already
on the ground, enlarging around it, or where old timber has reached
its highest usefulness and should be cut in order that we may not lose
the larger growth which young trees would make; or else we choose a
place which is but poorly stocked, where, if it is not regenerated,
the soil is likely to deteriorate further. The choice is affected
further by the consideration that dry situations should be taken in
hand earlier than those in which the soil and site are more favorable,
and that some species reach maturity and highest use value earlier
than others and should therefore be reproduced earlier. In short, we
begin the regeneration when and where the necessity for it exists, or
where the young crop has the best chance to start most satisfactorily
with the least artificial aid. Of course, advantage should betaken of
the occurrence of seed years, which come at different intervals with
different species.
If we begin with a group of young growth already on the ground, our
plan is to remove gradually the old trees standing over them when no
longer required for shade, and then to cut away the adjoining old
growth and enlarge the opening in successive narrow bands around the
young growth. When the first band has seeded itself satisfactorily, and
the young growth has come to require more light (which may take several
years), we remove another band around it, and thus the regeneration
progresses. Where no young growth already exists, of course the first
opening is made to afford a start, and afterwards the enlargement
follows as occasion requires.
SIZE OF OPENINGS.
The size of the openings and the rapidity with which they should be
enlarged vary, of course, with local conditions and the species which
is to 'be favored, the light-needing species requiring larger openings
and quicker light additions than the shade-enduring. It is difficult to
give any rules, since the modifications due to local conditions are so
manifold, requiring observation and judgment. Caution in not opening
too much at a time and too quickly may avoid failure in securing good
stands.
In general, the first openings may contain from one-fourth to one-half
an acre or more, and the gradual enlarging may progress by clearing
bands of a breadth not to exceed the height of the surrounding timber.
The time of the year when the cutting is to be done is naturally in
winter, when the farmer has the most leisure, and when the wood seasons
best after felling and is also most readily moved. Since it is expected
that the seed fallen in the autumn will sprout in the spring, all wood
should, of course, be removed from the seed ground.
The first opening, as well as the enlargement of the groups, should
not be made at once, but by gradual thinning out, if the soil is
not in good condition to receive and germinate the seed and it is
impracticable to put it in such condition by artificial means--hoeing
or plowing.
It is, of course, quite practicable--nay, sometimes very desirable--to
prepare the soil for the reception and germination of the seed. Where
undesirable undergrowth has started, it should be cut out, and where
the soil is deteriorated with weed growth or compacted by the tramping
of cattle, it should be hoed or otherwise scarified, so that the seed
may find favorable conditions. To let pigs do the plowing and the
covering of acorns is not an uncommon practice abroad.
It is also quite proper, if the reproduction from the seed of the
surrounding mother trees does not progress satisfactorily, to assist,
when an opportunity is afforded, by planting such desirable species as
were or were not in the composition of the original crop.
It may require ten, twenty, or forty years or more to secure the
reproduction of a wood lot in this way. A new growth, denser and better
than the old, with timber of varying age, will be the result. The
progress of the regeneration in groups is shown on the accompanying
plan, the different shadings showing the successive additions of young
crop, the darkest denoting the oldest parts, first regenerated. If we
should make a section through any one of the groups, this, ideally
represented, would be like figure 14, the old growth on the outside,
the youngest new crop adjoining it, and tiers of older growths of
varying height toward the center of the group.
WIND MANTLE.
On the plan there will be noted a strip specially shaded, surrounding
the entire plat (fig. 13, _a_), representing a strip of timber which
should surround the farmer's wood lot, and which he should keep as
dense as possible, especially favoring undergrowth. This part, if
practicable, should be kept reproduced as coppice or by the method of
selection, i. e., by taking out trees hero and there. When gaps are
made, they should be filled, if possible, by introducing shade-enduring
kinds, which, like the spruces and firs and beech, retain their
branches down to the foot for a long time. This mantle is intended to
protect the interior against the drying influence of winds, which are
bound to enter the small wood lot and deteriorate the soil. The smaller
the lot, the more necessary and desirable it is to maintain such a
protective cover or wind-break.
[Illustration: Fig. 14.--Appearance of regeneration by group method.]
COPPICE.
Besides reproducing a wood crop from the seed of mother trees or by
planting, there is another reproduction possible by sprouts from the
stump. This, to be sure, can be done only with broad-leaved species,
since conifers, with but few exceptions, do not sprout from the stump.
When a wood lot is cut over and over again, the reproduction taking
place by such sprouts we call coppice.
Most wooded areas in the Eastern States have been so cut that
reproduction from seed could not take place, and hence we have large
areas of coppice, with very few seedling trees interspersed. As we
have seen in the chapter on "How trees grow," the sprouts do not
develop into as good trees as the seedlings. They grow faster, to be
sure, in the beginning, but do not grow as tall and are apt to be
shorter lived.
For the production of firewood, fence, and post material, coppice
management may suffice, but not for dimension timber. And even to keep
the coppice in good reproductive condition, care should be taken to
secure a certain proportion of seedling trees, since the old stumps,
after repeated cutting, tail to sprout and die out.
Soil and climate influence the success of the coppice; shallow
soils produce weaker but more numerous sprouts and are more readily
deteriorated by the repeated laying bare of the soil; a mild climate is
most favorable to a continuance of the reproductive power of the stump.
Some species sprout more readily than others; hence the composition
of the crop will change, unless attention is paid to it. In the
coppice, as in any other management of a natural wood crop, a desirable
composition must first be secured, which is done by timely improvement
cuttings, as described in a previous section.
The best trees for coppice in the northeastern States are the chestnut,
various oaks, hickory, ash, elm, maples, basswood, and black locust,
which are all good sprouters.
When cutting is done for reproduction, the time and manner are the main
care. The best results are probably obtained, both financially and with
regard to satisfactory reproduction, when the coppice is cut between
the twentieth and thirtieth years. All cutting must be done in early
spring or in winter, avoiding, however, days of severe frost, which is
apt to sever the bark from the trunk and to kill the cambium. Cutting
in summer kills the stump, as a rule. The cut should be made slanting
downward, and as smooth as possible, to prevent collection of moisture
on the stump and the resulting decay, and as close as possible to
the ground, where the stump is less exposed to injuries, and the new
sprouts, starting close to the ground, may strike independent roots.
Fail places or gaps should be filled by planting. This can be readily
done by bending to the ground some of the neighboring sprouts, when 2
to 3 years old, notching, fastening them down with a wooden hook or a
stone, and covering them with soil a short distance (4 to 6 inches)
from the end. The sprout will then strike root, and after a year or so
may be severed from the mother stock by a sharp cut (fig. 15).
For the recuperation of the crop, it is desirable to maintain a supply
of seedling trees, which may be secured either by the natural seeding
of a few mother trees of the old crop which are left, or by planting.
This kind of management, coppice with seedling or standard trees
intermixed, if the latter are left regularly and well distributed over
the wood lot, leads to a management called "standard coppice." In this
it is attempted to avoid the drawbacks of the coppice, viz, failure to
produce dimension material and running out of the stocks. The former
object is, however, only partially accomplished, as the trees grown
without sufficient side shading are apt to produce branchy boles and
hence knotty timber, besides injuring the coppice by their shade.
PLAN OF MANAGEMENT.
In order to harmonize the requirements of the wood lot from a
sylvicultural point of view, and the needs of the farmer for wood
supplies, the cutting must follow some systematic plan.
The improvement cuttings need not, in point of time, have been made all
over the lot before beginning the cuttings for regeneration, provided
they have been made in those parts which are to be regenerated. Both
the cuttings may go on simultaneously, and this enables the farmer
to gauge the amount of cutting to his consumption. According to the
amount of wood needed, one or more groups may be started at the same
time. It is, however, desirable, for the sake of renewing the crop
systematically, to arrange the groups in a regular order over the lot.
[Illustration: Fig. 15.--Method of layering to produce new stocks in
coppice wood.]
4. HOW TO CULTIVATE THE WOOD CROP.
Where only firewood is desired, i. e., wood without special form, size,
or quality, no attention to the crop is necessary, except to insure
that it covers the ground completely. Nevertheless, even in such a
crop, which is usually managed as coppice,[2] some of the operations
described in this chapter may prove advantageous. Where, however, not
only quantity but useful quality of the crop is also to be secured,
the development of the wood crop may be advantageously influenced by
controlling the supply of light available to the individual trees.
[2] See page 35 for description of coppice.
It may be proper to repeat here briefly what has been explained in
previous pages regarding the influence of light on tree development.
EFFECT OF LIGHT ON WOOD PRODUCTION.
Dense shade preserves soil moisture, the most essential element for
wood production; a close stand of suitable kinds of trees secures this
shading and prevents the surface evaporation of soil moisture, making
it available for wood production. But a close stand also cuts off side
light and confines the lateral growing space, and hence prevents the
development of side branches and forces the growth energy of the soil
to expend itself in height growth; the crown is carried up, and long,
cylindrical shafts, clear of branches, are developed; a close stand
thus secures desirable form and quality. Yet, since the quality of
wood production or accretion (other things being equal) is in direct
proportion to the amount of foliage and the available light, and since
an open position promotes the development of a larger crown and of
more foliage, an open stand tends to secure a larger amount of wood
accretion on each tree. On the other hand, a tree grown in the open,
besides producing more branches, deposits a larger proportion of wood
at The base, so that the shape of the bole becomes more conical, a
form which in sawing proves unprofitable; whereas a tree grown in the
dense forest both lengthens its shaft at the expense of branch growth
and makes a more even deposit of wood over the whole trunk, thus
attaining a more cylindrical form. While, then, the total amount of
wood production per acre may be as large in a close stand of trees as
in an open one (within limits), the distribution of this amount among
a larger or smaller number of individual trees produces different
results in the quality of the crop. And since the size of a tree or log
is important in determining its usefulness and value, the sooner the
individual trees reach useful size, without suffering in other points
of quality, the more profitable the whole crop.
NUMBER OF TREES PER ACRE.
The care of the forester, then, should be to maintain the smallest
number of individuals on the ground which will secure the greatest
amount of wood growth in the most desirable form of which the soil and
climate are capable, without deteriorating the soil conditions. He
tries to secure the most advantageous individual development of single
trees without suffering the disadvantages resulting from too open
stand. The solution of this problem requires the greatest skill and
judgment, and rules can hardly be formulated with precision, since for
every species or combination of species and conditions these rules must
be modified.
In a well-established young crop the number of seedlings per acre
varies greatly, from 3,000 to 100,000, according to soil, species, and
the manner in which it originated, whether planted, sown, or seeded
naturally.[3] Left to themselves, the seedlings, as they develop, begin
to crowd each other. At first this crowding results only in increasing
the height growth and in preventing the spread and full development
of side branches; by and by the lower branches failing to receive
sufficient light finally die and break off--the shaft "clears itself."
Then a distinct development of definite crowns takes place, and after
some years a difference of height growth in different individuals
becomes marked. Not a few trees fail to reach the general upper crown
surface, and, being more or less overtopped, we can readily classify
them according to height and development of crown, the superior or
"dominating" ones growing more and more vigorously, the inferior or
"dominated" trees falling more and more behind, and finally dying for
lack of light, and thus a natural reduction in numbers, or thinning,
takes place. This natural thinning goes on with varying rates at
different ages continuing through the entire life of the crop, so
that, while only 4,000 trees per acre may be required in the tenth
year to make a dense crown cover or normally close stand, untouched by
man, in the fortieth year 1,200 would suffice to make the same dense
cover, in the eightieth year 350 would be a full stand, and in the one
hundredth not more than 250, according to soil and species, more or
less. As we can discern three stages in the development of a single
tree--the juvenile, adolescent, and mature--so, in the development
of a forest growth, we may distinguish three corresponding stages,
namely, the "thicket" or brushwood, the "pole-wood" or sapling, and
the "timber" stage. During The thicket stage, in which the trees have
a bushy appearance, allowing hardly any distinction of stem and crown,
the height growth is most rapid. This period may last, according to
conditions and species, from 5 or 10 to 30 and even 40 years--longer on
poor soils and with shade-enduring species, shorter with light-needing
species on good soils--and, while it lasts, it is in the interest of
the wood grower to maintain the close stand, which produces the long
shaft, clear of branches, on which at a later period the wood that
makes valuable, clear timber, may accumulate. Form development is now
most important. The lower branches are to die and break off before they
become too large. (See illustrations of the progress of "clearing,"
on pp. 15 and 16.) With light-needing species and with deciduous
trees generally this dying off is accomplished more easily than with
conifers. The spruces and even the white pine require very dense
shading to "clear" the shaft. During this period it is only necessary
to weed out the undesirable kinds, such as trees infested by insect
and fungus, shrubs, sickly, stunted, or bushy trees which are apt to
overtop and prevent the development of their better neighbors. In
short, our attention is now devoted mainly to improving the composition
of the crop.
[3] If the crop does not, at 3 to 5 years of age, shade the ground
well, with a complete crown cover, or canopy, it can not be said to be
well established and should be filled out by planting.
WEEDING AND CLEANING THE CROP.
This weeding or cleaning is easily done with shears when the crop is
from 3 to 5 years old. Later, mere cutting back of the undesirable
trees with a knife or hatchet maybe practiced. In well-made artificial
plantations this weeding is rarely needed until about the eighth or
tenth year. But in natural growths the young crop is sometimes so dense
as to inordinately interfere with the development of the individual
trees. The stems then remain so slender that there is danger of their
being bent or broken by storm or snow when the growth is thinned out
later. In such cases timely thinning is indicated to stimulate more
rapid development of the rest of the crop. This can be done most
cheaply by cutting swaths or lanes one yard wide and us far apart
through the crop, leaving strips standing. The outer trees of the
strip, at least, will then shoot ahead and become the main crop. These
weeding or improvement cuttings, which must be made gradually and be
repeated every two or three years, are best performed during the summer
months, or in August and September, when it is easy to judge what
should be taken out.
METHODS OF THINNING.
During the "thicket" stage, then, which may last from 10 to 25 and
more years, the crop is gradually brought into proper composition and
condition. When the "pole-wood" stage is reached, most of the saplings
being now from 3 to 6 inches in diameter and from 15 to 25 feet in
height, the variation in sizes and in appearance becomes more and more
marked. Some of the taller trees begin to show a long, clear shaft and
a definite crown. The trees can be more or less readily classified
into height and size classes. The rate at which the height growth has
progressed begins to fall off and diameter growth increases. Now comes
the time when attention must be given to increasing this diameter
growth by reducing the number of individuals and thus having all the
wood which the soil can produce deposited on fewer individuals. This
is done by judicious and often repeated thinning, taking out some of
the trees and thereby giving more light and increasing the foliage of
those remaining; and as the crowns expand, so do the trunks increase
their diameter in direct proportion. These thinnings must, however, be
made cautiously lest at the same time the soil is exposed too much, or
the branch growth of those trees which are to become timber wood is
too much stimulated. So varying are the conditions to be considered,
according to soil, site, species, and development of the crop, that it
is well-nigh impossible, without a long and detailed discussion, to
lay down rules for the proper procedure. In addition the opinions of
authorities differ largely both as to manner and degree of thinning,
the old school advising moderate, and the new school severer thinnings.
For the farmer, who can give personal attention to detail and whose
object is to grow a variety of sizes and kinds of wood, the following
general method may perhaps be most useful:
First determine which trees are to be treated as the main crop or
"final harvest" crop. For this 300 to 500 trees per acre of the
best grown and most useful kinds may be selected, which should be
distributed as uniformly as possible over the acre. These, then--or
as many as may live till the final harvest--are destined to grow into
timber and are to form the special favorites as much as possible. They
may at first be marked to insure recognition; later on they will be
readily distinguished by their superior development The rest, which we
will call the "subordinate" crop, is then to serve merely as filler,
nurse, and soil cover.
WHAT TREES TO REMOVE.
It is now necessary, by careful observation of the surroundings of
each of the "final harvest" crop trees, or "superiors," as we may call
them, to determine what trees of the "subordinate" crop trees, or
"inferiors," must be removed. All nurse trees that threaten to overtop
the superiors must either be cut out or cut back and topped, if that
is practicable, so that the crown of the superiors can develop freely.
Those that are only narrowing in the superiors from the side, without
preventing their free top development, need not be interfered with,
especially while they are still useful in preventing the formation and
spreading of side branches on the superiors. As soon as the latter
have fully cleared their shafts, these crowding inferiors must be
removed. Care must be taken, however, not to remove too many at a time,
thus opening the crown cover too severely and thereby exposing the
soil to the drying influence of the sun. Gradually, as the crowns of
inferiors standing farther away begin to interfere with those of the
superiors, the inferiors are removed, and thus the full effect of the
light is secured in the accretion of the main harvest crop; at the same
time the branch growth has been prevented and the soil has been kept
shaded. Meanwhile thinnings may also be made in the subordinate crop,
in order to secure also the most material from this part of the crop.
This is done by cutting out all trees that threaten to be killed by
their neighbors. In this way many a useful stick is saved and the dead
material, only good for firewood, lessened. It is evident that trees
which in the struggle for existence have fallen behind, so as to be
overtopped by their neighbors, can not, either by their presence or by
their removal, influence the remaining growth. They are removed only in
order to utilize their wood before it decays.
It may be well to remark again that an undergrowth of woody plants
interferes in no way with the development of the main crop, but, on
the contrary, aids by its shade in preserving favorable moisture
conditions. Its existence, however, shows in most cases that the crown
cover is not as dense as it should be, and hence that thinning is not
required. Grass and weed growth, on the other hand, is emphatically
disadvantageous and shows that the crown cover is dangerously open.
The answer to the three questions, When to begin the thinnings, How
severely to thin, and How often to repeat the operation, must always
depend upon the varying appearance of the growth and the necessities
in each case. The first necessity for interference may arise with
light-needing species as early as the twelfth or fifteenth year; with
shade-enduring, not before the twentieth or twenty-fifth year. The
necessary severity of the thinning and the repetition are somewhat
interdependent. It is better to thin carefully and repeat the operation
oftener than to open up so severely at once as to jeopardize the soil
conditions. Especially in younger growths and on poorer soil, it is
best never to open a continuous crown cover so that it could not close
up again within 3 to 5 years; rather repeat the operation oftener.
Later, when the trees have attained heights of 50 to 60 feet and clear
boles (which may be in 40 to 50 years, according to soil and kind) the
thinning may be more severe, so as to require repetition only every 6
to 10 years.
The condition of the crown cover, then, is the criterion which directs
the ax. As soon as the crowns again touch or interlace, the time has
arrived to thin again. In mixed growths it must not be overlooked that
light-needing species must be specially protected against shadier
neighbors. Shade-enduring trees, such as the spruces, beech, sugar
maple, and hickories, bear overtopping for a time and will then grow
vigorously when more light is given, while light-needing species, like
the pines, larch, oaks, and ash, when once suppressed, may never be
able to recover.
Particular attention is called to the necessity of leaving a rather
denser "wind mantle" all around small groves. In this part of the
grove the thinning must be less severe, unless coniferous trees on the
outside can be encouraged by severe thinning to hold their branches low
down, thus increasing their value as wind-breaks.
The thinnings, then, while giving to the "final harvest" crop all the
advantage of light for promoting its rapid development into serviceable
timber size, furnish also better material from the subordinate crop.
At 60 to 70 years of age the latter may have been entirely removed and
only the originally selected "superiors" remain on the ground, or as
many of them as have not died and been removed; 250 to 400 of these
per acre will make a perfect stand of most valuable form and size,
ready for the final harvest, which should be made as indicated in the
preceding chapter.
5.--THE RELATION OF FORESTS TO FARMS.
That all things in nature are related to each other and interdependent
is a common saying, a fact doubted by nobody, yet often forgotten or
neglected in practical life. The reason is partly indifference and
partly ignorance as to the actual nature of the relationship; hence we
suffer, deservedly or not.
The farmer's business, more than any other, perhaps, depends for
its success upon a true estimate of and careful regard for this
inter-relation, he adapts his crop to the nature of the soil, the
manner of its cultivation to the changes of the seasons, and altogether
he shapes conditions and places them in their proper relations to each
other and adapts himself to them.
Soil, moisture, and heat are the three factors which, if properly
related and utilized, combine to produce his crops. In some directions
he can control these factors more or less readily; in others they are
withdrawn from his immediate influence, and he is seemingly helpless.
He can maintain the fertility of the soil by manuring, by proper
rotation of crops, and by deep culture; he can remove surplus moisture
by ditching and draining; he can, by irrigation systems, bring water
to his crops, and by timely cultivation prevent excessive evaporation,
thereby rendering more water available to the crop; but he can not
control the rainfall nor the temperature changes of the seasons. Recent
attempts to control the rainfall by direct means exhibit one of the
greatest follies and misconceptions of natural forces we have witnessed
during this age. Nevertheless, by indirect means the farmer has it
in his power to exercise much greater control over these forces than
he has attempted hitherto. He can prevent or reduce the unfavorable
effects of temperature changes; he can increase the available water
supplies, and prevent the evil effects of excessive rainfall; he can so
manage the waters which fall as to get the most benefit from them and
avoid the harm which they are able to inflict.
Before attempting to control the rainfall itself by artifice, we should
study how to secure the best use of that which falls, as it comes
within reach of human agencies and becomes available by natural causes.
How poorly we understand the use of these water supplies is evidenced
yearly by destructive freshets and floods, with the accompanying
washing of soil, followed by droughts, low waters, and deterioration of
agricultural lands. It is claimed that annually in the United States
about 200 square miles of fertile soil are washed into brooks and
rivers, a loss of soil capital which can not be repaired for centuries.
At the same time millions of dollars are appropriated yearly in the
river and harbor bills to dig out the lost farms from the rivers,
and many thousands of dollars' worth of crops and other property are
destroyed by floods and overflows; not to count the large loss from
droughts which this country suffers yearly in one part or the other,
and which, undoubtedly, could be largely avoided, if we knew how to
manage the available water supplies.
The regulation, proper distribution, and utilization of the rain waters
in humid as well as in arid regions--water management--is to be the
great problem of successful-agriculture in the future.
One of the most powerful means for such water management lies in the
proper distribution and maintenance of forest areas. Nay, we can say
that the most successful water management is not possible without
forest management.
THE FOREST WATERS THE FARM.
Whether forests increase the amount of precipitation within or near
their limits is still an open question, although there are indications
that under certain conditions large, dense forest areas may have such
an effect. At any rate, the water transpired by the foliage is certain,
in some degree, to increase the relative humidity near the forest,
and thereby increase directly or indirectly the water supplies in its
neighborhood. This much we can assert, also, that while extended plains
and fields, heated by the sun, and hence giving rise to warm currents
of air, have the tendency to prevent condensation of the passing
moisture-bearing currents, forest areas, with their cooler, moister air
strata, do not have such a tendency, and local showers may therefore
become more frequent in their neighborhood. But, though no increase in
the amount of rainfall may be secured by forest areas, the availability
of whatever falls is increased for the locality by a well-kept and
properly located forest growth. The foliage, twigs, and branches break
the fall of the raindrops, and so does the litter of the forest floor,
hence the soil under this cover is not compacted as in the open field,
but kept loose and granular, so that the water can readily penetrate
and percolate; the water thus reaches the ground more slowly, dripping
gradually from the leaves, branches, and trunks, and allowing more time
for it to sink into the soil. This percolation is also made easier by
the channels along the many roots. Similarly, on account of the open
structure of the soil and the slower melting of the snow under a forest
cover in spring, where it lies a fortnight to a month longer than in
exposed positions and melts with less waste from evaporation, the snow
waters more fully penetrate the ground. Again, more snow is caught and
preserved under the forest cover than on the wind-swept fields and
prairies.
All these conditions operate together, with the result that larger
amounts of the water sink into the forest soil and to greater depths
than in open fields. This moisture is conserved because of the reduced
evaporation in the cool and still forest air, being protected from
the two great moisture-dissipating agents, sun and wind. By these
conditions alone the water supplies available in the soil are increased
from 50 to 60 per cent over those available on the open field.
Owing to those two causes, then--increased percolation and decreased
evaporation--larger amounts of moisture become available to feed the
springs and subsoil waters, and these become finally available to the
farm, if the forest is located at a higher elevation than the field.
The great importance of the subsoil water especially and the influence
of forest areas upon it has so far received too little attention and
appreciation. It is the subsoil water that is capable of supplying the
needed moisture in times of drought.
THE FOREST TEMPERS THE FARM.
Another method by which a forest belt becomes a conservator of moisture
lies in its wind-breaking capacity, by which both velocity and
temperature of winds are modified and evaporation from the fields to
the leeward is reduced.
On the prairie, wind-swept every day and every hour, the farmer has
learned to plant a wind-break around his buildings and orchards, often
only a single-row of trees, and finds even that a desirable shelter,
tempering both the hot winds of summer and the cold blasts of winter.
The fields he usually leaves unprotected; yet a wind-break around his
crops to the windward would bring him increased yield, and a timber
belt would act still more effectively. Says a farmer from Illinois:
My experience is that now in cold and stormy winters fields protected
by timber belts yield full crops, while fields not protected yield
only one-third of a crop. Twenty-five or thirty years ago we never
had any wheat killed by winter frost, and every year we had a full
crop of peaches, which is now very rare. At that time we had plenty
of timber around our fields and orchards, now cleared away.
Not only is the temperature of the winds modified by passing over
and through the shaded and cooler spaces of protecting timber bolts
disposed toward the windward and alternating with the fields, but their
velocity is broken and moderated, and since with reduced velocity the
evaporative power of the winds is very greatly reduced, so more water
is left available for crops. Every foot in height of a forest growth
will protect 1 rod in distance, and several bolts in succession would
probably greatly increase the effective distance. By preventing deep
freezing of the soil the winter cold is not so much prolonged, and
the frequent fogs and mists that hover near forest areas prevent many
frosts. That stock will thrive better where it can find protection from
the cold blasts of winter and from the heat of the sun in summer is a
well-established fact.
THE FOREST PROTECTS THE FARM.
On the sandy plains, where the winds are apt to blow the sand, shifting
it hither and thither, a forest belt to the windward is the only means
to keep the farm protected.
In the mountain and hill country the farms are apt to suffer from
heavy rains washing away the soil. Where the tops and slopes are
bared of their forest cover, the litter of the forest floor burnt up,
the soil trampled and compacted by cattle and by the patter of the
raindrops, the water can not penetrate the soil readily, but is earned
off superficially, especially when the soil is of, day and naturally
compact. As a result the waters, rushing over the surface down the
hill, run together in rivulets and streams and acquire such a force as
to be able to move loose particles and even stones; the ground becomes
furrowed with gullies and runs; the fertile soil is washed away; the
fields below are covered with silt; the roads are damaged; the water
courses tear their banks, and later run dry because the waters that
should feed them by subterranean channels have been carried away in the
flood.
The forest cover on the hilltops and steep hillsides which are not fit
for cultivation prevents this erosive action of the waters by the same
influence by which it increases available water supplies. The important
effects of a forest cover, then, are retention of larger quantities of
water and carrying them off under ground and giving them up gradually,
thus extending the time of their usefulness and preventing their
destructive action.
In order to be thoroughly effective, the forest growth must be
dense, and, especially, the forest floor must not be robbed of its
accumulations of foliage, surface mulch and litter, or its underbrush
by fire, nor must it be compacted by the trampling of cattle.
On the gentler slopes, which are devoted to cultivation, methods of
underdraining, such as horizontal ditches partly filled with stones and
covered with soil, terracing, and contour plowing, deep cultivation,
sodding, and proper rotation of crops, must be employed to prevent
damage from surface waters.
THE FOREST SUPPLIES THE FARM WITH USEFUL MATERIAL.
All the benefits derived from the favorable influence of forest bolts
upon water conditions can be had without losing any of the useful
material that the forest produces. The forest grows to be cut and to be
utilized; it is a crop to be harvested. It is a crop which, if properly
managed, does not need to be replanted; it reproduces itself.
When once established, the ax, if properly guided by skillful hands, is
the only tool necessary to cultivate it and to reproduce it. There is
no necessity of planting unless the wood lot has been mismanaged.
The wood lot, then, if properly managed, is not only the guardian of
the farm, but it is the savings bank from which fair interest can be
annually drawn, utilizing for the purpose the poorest part of the farm.
Nor does the wood lot require much attention; it is to the farm what
the workbasket is to the good housewife--a means with which improve
the odds and ends of time, especially during the winter, when other
farm business is at a standstill.
It may be added that the material which the farmer can secure from the
wood lot, besides the other advantages recited above, is of far greater
importance and value than is generally admitted.
On a well-regulated farm of 160 acres, with its 4 miles and more
of fencing and with its wood fires in range and stove, at least 25
cords of wood are required annually, besides material for repair of
buildings, or altogether the annual product of probably 40 to 50 acres
of well-stocked forest is needed. The product may represent, according
to location, an actual stumpage value of from $1 to $3 per acre, a sure
crop coming every year without regard to weather, without trouble and
work, and raised on the poorest part of the farm. It is questionable
whether such net results could be secured with the same steadiness from
any other crop. Nor must it be overlooked that the work in harvesting
this crop falls into a time when little else could be done.
Wire fences and coal fires are, no doubt, good substitutes, but they
require ready cash, and often the distance of haulage makes them
rather expensive. Presently, too, when the virgin woods have been
still further culled of their valuable stores, the farmer who has
preserved a sufficiently large and well-tended wood lot will be able
to derive a comfortable money revenue from it by supplying the market
with wood of various kinds and sizes. The German State forests, with
their complicated administrations, which eat up 4 per cent of the gross
income, yield, with prices of wood about the same as in our country,
an annual net revenue of from $1 to $4 and more per acre. Why should
not the farmer, who does not pay salaries to managers, overseers, and
forest guards, make at least as much money out of this crop when he is
within reach of a market?
With varying conditions the methods would of course vary. In a general
way, if he happens to have a virgin growth of mixed woods, the first
care would be to improve the composition of the wood lot by cutting
out the less desirable kinds, the weeds of tree growth, and the poorly
grown trees which impede the development of more deserving neighbors.
The wood thus cut he will use as firewood or in any other way, and,
even if he could not use it at all, and had to burn it up, the
operation would pay indirectly by leaving him a better crop. Then he
may use the rest of the crop, gradually cutting the trees as needed,
but he must take care that the openings are not made too large, so
that they can readily fill out with young growth from the seed of
the remaining trees, and he must also pay attention to the young
aftergrowth, giving it light as needed. Thus without ever resorting to
planting he may harvest the old timber and have a now crop taking its
place and perpetuate the wood lot without in any way curtailing his use
of the same.
FARMERS' BULLETINS.
These bulletins are sent free of charge to any address upon application
to the Secretary of Agriculture. Washington, D. C. Only the following
are available for distribution:
No. 15. Some Destructive Potato Diseases: What They Are and How to
Prevent Thorn. Pp. 8.
No. 16. Leguminous Plants for Green Manuring and for Feeding. Pp. 24.
No. 18. Forage Plants for the South. Pp. 30.
No. 19. Important Insecticides: Directions For Their Preparation
and Use. Pp. 20.
No. 21. Barnyard Manure. Pp. 32.
No. 22. Feeding Farm Animals. Pp. 32.
No. 23. Foods: Nutritive Value and Cost. Pp. 32.
No. 24. Hog Cholera and Swine Plague. Pp. 16.
No. 25. Peanuts: Culture and Uses. Pp. 24.
No. 26. Sweet Potatoes: Culture and Uses. Pp. 30.
No. 27. Flax for Seed and Fiber. Pp. 16.
No. 28. Weeds; and How to Kill Them. Pp. 30.
No. 29. Souring of Milk, and Other Changes in Milk Products. Pp. 28.
No. 30. Grape Diseases on the Pacific Coast. Pp. 16.
No. 31. Alfalfa, or Lucern. Pp. 23.
No. 32. Silos and Silage. Pp. 31.
No. 33. Peach Growing for Market. Pp. 24.
No. 34. Meats: Composition and Cooking. Pp. 29.
No. 35. Potato Culture. Pp. 23.
No. 36. Cotton Seed and Its Products. Pp. 10.
No. 37. Katir Corn: Characteristics, Culture, and Uses. Pp. 12.
No. 38. Spraying for Fruit Diseases. Pp. 12.
No. 39. Onion Culture. Pp. 31.
No. 40. Farm Drainage. Pp. 24.
No. 41. Fowls: Care and Feeding. Pp. 24.
No. 42. Facts About Milk. Pp. 29.
No. 43. Sewage Disposal on the Farm. Pp. 22.
No. 44. Commercial Fertilizers. Pp. 24.
No. 45. Some Insects Injurious to Stored Grain. Pp. 32.
No. 46. Irrigation in Humid Climates. Pp. 27.
No. 47. Insects Affecting the Cotton Plant. Pp. 32.
No. 48. The Manuring of Cotton. Pp. 10.
No. 49. Sheep Feeding. Pp. 24.
No. 50. Sorghum as a Forage Crop. Pp. 24.
No. 51. Standard Varieties of Chickens. Pp. 48.
No. 52. The Sugar Beet. Pp. 48.
No. 53. How to Grow Mushrooms. Pp. 20.
No. 54. Some Common Birds in Their Relation to Agriculture. Pp. 40.
No. 55. The Dairy Herd: Its Formation and Management. Pp. 24.
No. 56. Experiment Station Work--I. Pp. 30.
No. 57. Butter Making on the Farm. Pp. 15.
No. 58. The Soy Bean as a Forage Crop. Pp. 24.
No. 59. Bee Keeping. Pp. 32.
No. 60. Methods of Curing Tobacco. Pp. 10.
No. 61. Asparagus Culture. Pp. 40.
No. 62. Marketing Farm Produce. Pp. 28.
No. 63. Care of Milk on the Farm. Pp. 40.
No. 64. Ducks and Geese. Pp. 48.
No. 65. Experiment Station Work--II. Pp. 32.
No. 66. Meadows and Pastures. Pp. 24.
No. 67. Forestry for Farmers. Pp. 48.
No. 68. The Black Rot of the Cabbage. Pp. 22.
No. 69. Experiment Station Work--III. Pp. 32.
No. 70. The Principal Insect Enemies of the Grape. Pp. 24.
No. 71. Some Essentials of Beef Production. Pp. 24.
No. 72. Cattle Ranges of the Southwest. Pp. 32.
No. 73. Experiment Station Work--IV. Pp. 32.
No. 74. Milk as Food. Pp. 39.
No. 75. The Grain Smuts. Pp. 20.
No. 76. Tomato Growing. Pp. 30.
No. 77. The Liming of Soils. Pp. 19.
No. 78. Experiment Station Work--V. Pp. 32.
No. 79. Experiment Station Work--VI. Pp. 28.
No. 80. The Peach Twig-borer--an Important Enemy of Stone Fruits. Pp. 10.
No. 81. Corn Culture in the South. Pp. 24.
No. 82. The Culture of Tobacco. Pp. 23.
No. 83. Tobacco Soils. Pp. 23.
No. 84. Experiment Station Work--VII. Pp. 82.
No. 85. Fish as Food. Pp. 30.
No. 86. Thirty Poisonous Plants. Pp. 32.
No. 87. Experiment Station Work--VIII. (In press.)
No. 88. Alkali Lands. Pp. 23.
No. 89. Cowpeas. (In press.)
* * * * *
Transcriber Note
Illustrations were move so a to prevent splitting paragraphs. Minor
typos corrected. Illustrations were obtained from the The Internet
Archive and the University of North Texas' USDA Farmers' Bulletins
Digital Library.
*** End of this LibraryBlog Digital Book "USDA Farmers' Bulletin No. 67 - Forestry For Farmers" ***
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