Studies of Trees Part 19

Another method of bracing limbs together consists in running a single bolt through them and fastening each end of the bolt with a washer and nut. This method is preferable to the first because it allows for the growth of the limbs in thickness.

[Ill.u.s.tration: FIG. 121.--Diagram Showing the Triple-bar Method of Fastening Limbs.]

A still better method, however, consists in using a bar composed of three parts as shown in Fig. 121. Each of the two branches has a short bolt pa.s.sed through it horizontally, and the two short bolts are then connected by a third bar. This arrangement will shift all the pressure caused by the swaying of the limbs to the middle connecting-bar. In case of a windstorm, the middle bar will be the one to bend, while the bolts which pa.s.s through the limbs will remain intact. The outer ends of the short bolts should have their washers and nuts slightly embedded in the wood of the tree, so that the living tissue of the tree may eventually grow over them in such a way as to hold the bars firmly in place and to exclude moisture and disease. The washers and nuts on the inner side of the limbs should also be embedded.

A chain is sometimes advantageously subst.i.tuted for the middle section of the bar and, in some cases, where more than two branches have to be joined together, a ring might take the place of the middle bar or chain.

Bolts on a tree detract considerably from its natural beauty and should, therefore, be used only where they are absolutely necessary for the safety of the tree. They should be placed as high up in the tree as possible without weakening the limbs.

CHAPTER VII

FORESTRY

STUDY I. WHAT FORESTRY IS AND WHAT IT DOES

Although Forestry is not a new idea but, as a science and an art, has been applied for nearly two thousand years, there are many persons who still need an explanation of its aims and principles.

Forestry deals with the establishment, protection and utilization of forests.

By establishment, is meant the planting of new forests and the cutting of mature forests, in such a way as to encourage a natural growth of new trees without artificial planting or seeding. The planting may consist of sowing seed, or of setting out young trees. The establishment of a forest by cutting may consist of the removal of all mature trees and dependence upon the remaining stumps to reproduce the forest from sprouts, or it may consist of the removal of only a portion of the mature trees, thus giving the young seedlings on the ground room in which to grow.

By protection, is meant the safeguarding of the forest from fire, wind, insects, disease and injury for which man is directly responsible. Here, the forester also prevents injury to the trees from the grazing and browsing of sheep and goats, and keeps his forest so well stocked that no wind can uproot the trees nor can the sun dry up the moist forest soil.

[Ill.u.s.tration: FIG. 122.--A Forest of Bull Pine Cut on Forestry Principles. (Photograph taken on the Black Hills National Forest, South Dakota.)]

By utilization, is meant the conservative and intelligent harvesting of the forest, with the aim of obtaining the greatest amount of product from a given area, with the least waste, in the quickest time, and without the slightest deterioration of the forest as a whole. The forester cuts his mature trees, only, and generally leaves a sufficient number on the ground to preserve the forest soil and to cast seed for the production of a new crop. In this way, he secures an annual output without hurting the forest itself. He studies the properties and values of the different woods and places them where they will be most useful.

He lays down principles for so harvesting the timber and the by-products of the forest that there will be the least waste and injury to the trees which remain standing. He utilizes the forest, but does not cut enough to interfere with the neighboring water-sheds, which the forests protect.

[Ill.u.s.tration: 123.--A White Pine Plantation, in Rhode Island, Where the Crowns of the Trees Have Met. The trees are fifteen years old and in many cases every other tree had to be removed.]

Forestry, therefore, deals with a vast and varied ma.s.s of information, comprising all the known facts relating to the life of a forest. It does not deal with the individual tree and its planting and care,--that would be arboriculture. Nor does it consider the grouping of trees for aesthetic effect,--that would be landscape gardening. It concerns itself with the forest as a community of trees and with the utilization of the forest on an economic basis.

Each one of these activities in Forestry is a study in itself and involves considerable detail, of which the reader may obtain a general knowledge in the following pages. For a more complete discussion, the reader is referred to any of the standard books on Forestry.

The life and nature of a forest: When we think of a forest we are apt to think of a large number of individual trees having no special relationship to each other. Closer observation, however, will reveal that the forest consists of a distinct group of trees, sufficiently dense to form an unbroken canopy of tops, and that, where trees grow so closely together, they become very interdependent. It is this interdependence that makes the forest different from a mere group of trees in a park or on a lawn. In this composite character, the forest enriches its own soil from year to year, changes the climate within its own bounds, controls the streams along its borders and supports a mult.i.tude of animals and plants peculiar to itself. This communal relationship in the life history of the forest furnishes a most interesting story of struggle and mutual aid. Different trees have different requirements with regard to water, food and light.

Some need more water and food than others, some will not endure much shade, and others will grow in the deepest shade. In the open, a tree, if once established, can meet its needs quite readily and, though it has to ward off a number of enemies, insects, disease and windstorm--its struggle for existence is comparatively easy. In the forest, the conditions are different. Here, the tree-enemies have to be battled with, just as in the open, and in addition, instead of there being only a few trees on a plot of ground, there are thousands growing on the same area, all demanding the same things out of a limited supply. The struggle for existence, therefore, becomes keen, many falling behind and but few surviving.

[Ill.u.s.tration: FIG. 124.--Measuring the Diameter of a Tree and Counting its Annual Rings.]

This struggle begins with the seed. At first there are thousands of seeds cast upon a given area by the neighboring trees or by the birds and the winds. Of these, only a few germinate; animals feed on some of them, frost nips some and excessive moisture and unfavorable soil conditions prevent others from starting. The few successful ones soon sprout into a number of young trees that grow thriftily until their crowns begin to meet. When the trees have thus met, the struggle is at its height. The side branches encroach upon each other (Fig. 123), shut out the light without which the branches cannot live, and finally kill each other off. The upper branches vie with one another for light, grow unusually fast, and the trees increase in height with special rapidity. This is nature's method of producing clear, straight trunks which are so desirable for poles and large timber. In this struggle for dominance, some survive and tower above the others, but many become stunted and fail to grow, while the majority become entirely overtopped and succ.u.mb in the struggle; see Fig. 139.

But in this strife there is also mutual aid. Each tree helps to protect its neighbors against the danger of being uprooted by the wind, and against the sun, which is liable to dry up the rich soil around the roots. This soil is different from the soil on the open lawn. It consists of an acc.u.mulation of decayed leaves mixed with inorganic matter, forming, together, a rich composition known as _humus_. The trees also aid each other in forming a close canopy that prevents the rapid evaporation of water from the ground.

The intensity of these conditions will vary a great deal with the composition of the forest and the nature and habits of the individual trees. By composition, or type of forest, is meant the proportion in which the various species of trees are grouped; i.e., whether a certain section of woodland is composed of one species or of a mixture of species. By habit is meant the requirements of the trees for light, water and food.

[Ill.u.s.tration: FIG. 125.--Mountain Slopes in North Carolina Well Covered with Forests.]

Some trees will grow in deep shade while others will demand the open. In the matter of water and food, the individual requirements of different trees are equally marked.

The natural rapidity of growth of different species is also important, and one caring for a forest must know this rate of growth, not only as to the individual species, but also with respect to the forest as a whole. If he knows how fast the trees in a forest grow, both in height and diameter, he will know how much wood, in cubic feet, the forest produces in a year, and he can then determine how much he may cut without decreasing the capital stock.

The rate of growth is determined in this way: A tree is cut and the rings on the cross-section surface are counted and measured; see Fig. 124. Each ring represents one year's growth. The total number of rings will show the age of the tree. By a study of the rings of the various species of trees on a given plot, the rate of growth of each species in that location can be ascertained and, by knowing the approximate number of trees of each species on the forest area, the rate of growth of the whole forest for any given year can be determined.

[Ill.u.s.tration: FIG. 126.--Bottom Lands Buried in Waste from Deforested Mountains. Wu-t'ai-shan, Shan-si Province, China.]

[Ill.u.s.tration: FIG. 127.--Eroded Slope in Western North Carolina.]

Forests prevent soil erosion and floods: Forests help to regulate the flow of streams and prevent floods. Most streams are bordered by vast tracts of forest growths. The rain that falls on these forest areas is absorbed and held by the forest soil, which is permeated with decayed leaves, decayed wood and root fibers. The forest floor is, moreover, covered with a heavy undergrowth and thus behaves like a sponge, absorbing the water that falls upon it and then permitting it to ooze out gradually to the valleys and rivers below. A forest soil will retain one-half of its own quant.i.ty of water; i.e., for every foot in depth of soil there can be six inches of water and, when thus saturated, the soil will act as a vast, underground reservoir from which the springs and streams are supplied (Fig.

125). Cut the forest down and the land becomes such a desert as is shown in Fig. 126. The soil, leaves, branches and fallen trees dry to dust, are carried off by the wind and, with the fall of rain, the soil begins to wash away and gullies, such as are shown in Fig. 127, are formed. Streams generally have their origins in mountain slopes and there, too, the forests, impeding the sudden run off of the water which is not immediately absorbed, prevent soil erosion.

[Ill.u.s.tration: FIG. 128.--Flood in Pittsburgh, Pa.]

Where the soil is allowed to wash off, frequent floods are inevitable. Rain which falls on bare slopes is not caught by the crowns of trees nor held by the forest floor. It does not sink into the ground as readily as in the forest. The result is that a great deal of water reaches the streams in a short time and thus hastens floods. At other periods the streams are low because the water which would have fed them for months has run off in a few days. The farms are the first to suffer from the drouths that follow and, during the period of floods, whole cities are often inundated. Fig. 128 shows such a scene. The history of Forestry is full of horrible incidents of the loss of life and property from floods which are directly traceable to the destruction of the local forests and, on the other hand, there are many cases on record where flood conditions have been entirely obviated by the planting of forests. France and Germany have suffered from inundations resulting from forest devastation and, more than a hundred years ago, both of these countries took steps to reforest their mountain slopes, and thereby to prevent many horrible disasters.

[Ill.u.s.tration: FIG. 129.--Planting a Forest with Seedling Trees on the Nebraska National Forest. The man on the right is placing the tree in a slit just made with the spade. The man on the left is shoveling the dry sand from the surface before making the slit for the tree.]

[Ill.u.s.tration: FIG. 130.--Diagrammatic Ill.u.s.tration of a Selection Forest.]

How forests are established: New forests may be started from seed or from shoots, or suckers. If from seed, the process may be carried on in one of three ways:

First, by sowing the seed directly on the land.

Second, by first raising young trees in nurseries and later setting them out in their permanent locations in the forest. This method is applicable where quick results are desired, where the area is not too large, or in treeless regions and large open gaps where there is little chance for new trees to spring up from seed furnished by the neighboring trees. It is a method extensively practiced abroad where some of the finest forests are the result. The U.S.

government, as well as many of the States, maintain forest-tree nurseries where millions of little trees are grown from seed and planted out on the National and State forests. Fig. 129 shows men engaged in this work. The fundamental principles of starting and maintaining a nursery have already been referred to in the chapter on "What Trees to Plant and How."

The third method of establishing a forest from seed is by cutting the trees in the existing forest so that the seed falling from the remaining trees will, with the addition of light and s.p.a.ce, readily take root and fill in the gaps with a vigorous growth of trees, without artificial seeding or planting. This gives rise to several methods of cutting or harvesting forests for the purpose of encouraging natural reproduction. The cutting may extend to single trees over the whole area or over only a part of the whole area.

Where the cutting is confined to single trees, the system is known as the "Selection System," because the trees are selected individually, with a view to retaining the best and most vigorous stock and removing the overcrowding specimens and those that are fully mature or infested with disease or insects.

Fig. 130 is a diagrammatic ill.u.s.tration of the operation of this system. In another system the cutting is done in groups, or in strips, and the number of areas of the groups or strips is extended from time to time until the whole forest is cleared. This system is ill.u.s.trated in Fig. 131. Still another method consists in encouraging trees which will thrive in the shade, such as the beech, spruce and hemlock, to grow under light-demanding trees like the pine. This system presents a "two-storied" forest and is known by that name. The under story often has to be established by planting.

[Ill.u.s.tration: FIG. 131.--Diagrammatic Ill.u.s.tration of the Group or Strip System.]

In the system of reproducing forests from shoots or suckers, all trees of a certain species on a given area are cut off and the old stumps and roots are depended upon to produce a new set of sprouts, the strongest of which will later develop into trees. The coniferous trees do not lend themselves at all to this system of treatment, and, among the broadleaf trees, the species vary in their ability to sprout. Some, like the chestnut and poplar, sprout profusely; others sprout very little.

How forests are protected: Forestry also tries to protect the forests from many destructive agencies. Wasteful lumbering and fire are the worst enemies of the forest. Fungi, insects, grazing, wind, snow and floods are the other enemies.

[Ill.u.s.tration: FIG. 132.--The Result of a Forest Fire. The trees, lodgepole pine and Englemann spruce, are all dead and down. Photograph taken in the Colorado National Forest, Colorado.]

By wasteful lumbering is meant that the forest is cut with no regard for the future and with considerable waste in the utilization of the product. Conservative lumbering, which is the term used by foresters to designate the opposite of wasteful lumbering, will be described more fully later in this study.

Protection from fire is no less important than protection from wasteful lumbering. Forest fires are very common in this country and cause incalculable destruction to life and property; see Fig. 132.

From ten to twelve million acres of forest-land are burnt over annually and the timber destroyed is estimated at fifty millions of dollars. The history of Forestry abounds in tales of destructive fires, where thousands of persons have been killed or left dest.i.tute, whole towns wiped out, and millions of dollars in property destroyed. In most cases, these uncontrollable fires started from small conflagrations that could readily, with proper fire-patrol, have been put out.

There are various ways of fighting fires, depending on the character of the fire,--whether it is a surface fire, burning along the surface layer of dry leaves and small ground vegetation, a ground fire, burning below the surface, through the layer of soil and vegetable matter that generally lines the forest floor, or a top fire, burning high up in the trees.