In a stand of trees, an acre of forest growth, the progress of wood production is, to be sure, different from that in the individual tree, for here the amount of wood to the acre at any time depends on the number of trees as well as their volume. And this number, as we have seen, rapidly decreases as the trees grow older and crowd each other, when some are killed and eliminated from taking part in the total wood production, while the remaining, with the increase in light and food supplies, increase their production. This increase in the rate of volume growth per acre is very rapid in young woods and on good soil; it reaches a maximum and then declines more or less rapidly according to species and site, very much according to the diameter growth of the individual.

The question as to the number of trees which should be allowed to grow per acre, so as to produce not only the largest amount of wood, but of useful sizes and best quality, which means freedom from knots and technically most serviceable in form and grain, is one of the foremost problems of both the technicist and the manager.

The capacity of our unmanaged virgin forests in this respect is no criterion of the possibilities, and on the other hand the experience of other countries is only partially applicable to our conditions. But as an example of what our white pine forests, for instance, may eventually produce, we may cite the experience with spruce in Germany, which on good soil is capable of producing at the rate of 40 cubic feet per acre each year during the first decade, as much as 120 cubic feet in the second decade, and at the rate of 200 cubic feet at the age of 40, while at one hundred and fifty it shows only an average of 80 cubic feet per acre annually; having declined from about the seventieth year on.

On poorer soils about one-half of this production may be expected, and if we inquire into the total quantity per acre we may find at thirty years 4,200 cubic feet of wood, more than twice that amount at sixty years, and 14,000 cubic feet at one hundred years, which appears an enormous yield compared to those of our virgin forests, whose yield is depressed by the presence of much valueless material and lack of density, and which would in double the time hardly have produced such amount. With other species, to be sure, entirely different aggregate amounts would result, but in general the march of progress would be in a similar proportion.

If, however, we have to deal not with seedling trees, but with coppice growth like the sprout lands of our New England States, the progress is entirely different. There are several million acres of hard-wood coppice in these States, which, when fairly stocked, produce annually for the first twenty-five to thirty years at the rate of a cord or a little less (i. e., about 100 cubic feet solid) per acre, but after that time very rapidly decline in production without an equivalent value increase, and hence must be cut when the maximum amount of wood production has been attained; this is also necessary from silvicultural reasons, as the stocks, if left too long, are impaired in reproductive power.

To be sure, such woods yield hardly any other material than firewood and fence rails. There are many trees to the acre, 1,500 to 2,000 at least, but each one is small, not more than 10 to 12 inches in diameter at best, hence the supply of firewood is in excess of the home demand and the price obtained hardly covers the expense of getting the material to market.

To produce materials of size and quality such as we now require in the lumber market, nature has taken from one hundred and fifty to five hundred years, and for the giants of the Pacific, two thousand years and more. Even with the best skill in managing the crop, not less than seventyfive to one hundred years from the seed will be required to produce logs fit for the mill, such as are now considered hardly worth sawing.

From such measurements and considerations of the quantitative and qualitative development of the crop, the economist will learn that the time at which a forest growth is utilized has an important bearing on the more or less intensive and profitable use of the resource.

When the crop, accumulated during a longer or shorter period, is ripe for the ax depends not only upon silvicultural and forest-technical considerations influenced by soil and climatic conditions and the species composing the forest, but, from a business point of view, upon market conditions and financial considerations. The material would hardly be useful for anything but firewood or small posts and fencing material at best before twenty years, and again for lumber or purposes of construction it may be considered fit for use not before one hundred and more years.

Market conditions may be such that the small demand for the first-mentioned class of products would make it unprofitable to cut the growth, and again while, other things being equal, the larger dimensions are not only more valuable and in greater demand, but permit a greater and greater intensity of exploitation,' yet the long time during which the capital represented in the standing timber is tied up, and must therefore produce at compound interest, may have a disadvantageous influence upon the balance sheet.

The determination, therefore, of the length of time during which the growth is to be allowed to accumulate, which is called rotation, requires not only consideration by the technicist, but very close and complicated calculations by the manager. According to the point of view from which this period of rotation is determined, we can distinguish and designate these time periods by various names which explain themselves, namely, as silvicultural 10tation, rotation of greatest material production, financial rotation of highest harvest value, rotation of highest forest revenue, etc.2

Now, if an owner of land should stock it all with forest growth at the same time, he would have to wait twenty, forty, sixty, one hundred years or more, according to the rotation which he has recognized as most desirable, before he would have any returns, or else, if he should have a tract of virgin growth, all ripe for the ax, and cut it all, he would again have to wait many decades. without income until the new growth can be profitably cut.

Such an intermittent revenue is not only undesirable for private enterprise, but also impracti cable, since the cost of caring for the property would have to be provided for without any direct income during a long period.

For small holdings, such as the wood lot of a farmer, attached to the farm and readily supervised by him while attending to his regular business, the objection to the intermission of revenue is not serious altogether he manages his wood lot mainly for his own use. But in growing wood crops for the market as a business it is necessary to change the intermittent into an annual revenue, or at least one returning in short periods.

This is done by gradually bringing the forest into such condition that each year, or at least during each short period of the rotation, a portion or parcel, as nearly as possible producing the same amount of material or revenue, becomes ready for the harvest, until finally the whole forest area assumes the condition of what may be called the normal forest, or at least a regulated forest

Ideally such a forest when so regulated would yield every year or short period of years the same amount of material and approximately the same money revenue, the amount to be cut annually or periodically being as nearly as possible the amount annually growing.

If, for instance, we have a pine forest which we propose to manage under a rotation of one hundred years, which means that we expect to return for a new crop within one hundred years to the same acre we have just cut, and finding from our measurements that all our acres are of a uniformly producing capacity, we would have it divided into 100 equally large compartments, each stocked with trees just one year older than the preceding, and successfully representing 100 age classes, so that we could cut each year one compartment with the same amount of wood just one hundred years old.

How, with the increase in the size of the log, the amount of lumber that can be obtained from it increases or the necessary waste decreases disproportionately may be seen from the subjoined table of output, based upon the results of the average sawmill practice:

1

The total amount of wood standing in such a forest at the time of entering upon the work would represent the normal stock-the wood capital which must be maintained in order to insure an equal annual yield. The average difference of the amounts of wood standing in any two compartments would represent the normal annual accretion-the amount of wood which we are entitled to harvest if we desire to secure a continuous revenue in equal annual amounts.

If, for example, on our 100 acres managed with a 100-year rotation we found the average annual accretion per acre to be 50 cubic feet, the normal stock-the wood capital-which must be maintained on the acre would be found by the addition of the contents of all compartments, 100 × 50 × 100 = 250,000 cubic feet. The total normal yield which we are entitled to harvest 2 would be represented by the oldest 100 year-old compartment, containing, naturally, 50 x 100 = 5,000 cubic feet, or 2 per cent of the normal stock.

as

If we were to cut more than this normal yield in any year, we would be trenching on the capital stock and disturb the attempted equalization of income. If we were to cut less, we would unnecessarily accumulate capital in the wood, which would be lying idle and be for the time unremunerative.

The conception of a normal forest, with normal stock, normal accretion, normal distribution of age classes, and normal yield, first taught in 1788, is a most useful one, representing an ideal or standard which, although in practice never attained and hardly fully attempted, serves nevertheless as a guide in calculation and working plans.

In practice the growths of different age may be distributed in compartments of separate areas or they may be distributed in single trees over the entire area or in groups of trees, and thus many variations of the method may occur, but they are all based on the same principle of maintaining a wood capital distributed over a number of age classes in such amounts that the oldest classes always represent what may be cut as the annual or periodic revenue which has accumulated on the entire capital.

Before even an approach to such ideal and systematic condition can be secured in our virgin woods a long time must elapse-the period during which the regulation is gradually perfected, the length of which depends upon the condition of the forest area. If begun with a well stocked virgin forest composed of old and young timber of varying age, the conditions are most favorable, and a systematic management can be instituted in a comparatively short time and with a revenue from the start.

In any case it requires a strong mind and persistent effort on the part of the owner to accumulate the wood capital, to forego, if need be, present revenue for future profits and to keep capital and interest account in the growing crop clearly separate, and to abstain from cutting into the wood capital before it has done its full duty when tempting opportunity arises for liquidating it.

This fact, namely, that a differentiation into fixed capital and interest as represented in the growing timber and the harvest is not readily recognizable-that the choice of when to harvest the growth is not based on natural conditions so much as on the opinion and pecuniary interest of the owner, and in addition that there is a long time during which he could if he chose turn the accumulated fixed capital into cash-may sometimes, to be sure, appear as an advantage from the standpoint of private industry, but from that of national economy it is fraught with danger, as it is apt to lead to uneconomical use of the forest resource whenever the owner finds himself in difficulties or sees a temporary advantage in reducing this capital, which can be restituted only by the expenditure of a long time.

If a farmer sells his cattle, horses, plows, etc., and leaves the ground to fallow, he may suffer loss individually, but the community does not, or at least only to a slight degree; for while, to be sure, the land does not produce, it accumulates in the fallow conditions the elements of fertility, and as a rule is not long allowed to remain unused and can in a season's time be made to produce again.

On the other hand, if a forest growth is removed without reference to the requirements of a regulated management, namely, without leaving a wood capital of useful kinds upon which a new growth can accumulate, not only is the area of wood production reduced, but in the new spontaneous growth of undesirable kinds which, as a rule, come in, an impediment to useful occupation

of the soil is invited, while by the sudden excessive offer of material followed by corresponding decrease of supplies the market and prices are disturbed and the rational management (if existing) of neighboring forest areas unfavorably influenced.

Such disturbances leading to trade depressions, while in the end they are equalized by trade booms, are never desirable, and especially not in an industry which requires such a long time to gain an equilibrium.

To be sure, the growing of wood crops, as in agriculture may be carried on in a small way with a small wood capital, or else in a large way with a large wood capital, but it will be readily seen that since the most useful, most necessary, and most valuable sizes of timber upon which the lumber industry of the country is based requires not less than a century for their production, this industry must finally be carried on by large capital, preferably by corporations, which have in them the elements of perpetuity, and eventually by the Government.

The present consumption, for instance, of the lumber industry in the United States may be set at 40,000,000,000 feet B. M. annually, which corresponds to about 5,000,000,000 cubic feet of log timber in the woods; the normal wood reserve, which under first-class management could be expected to furnish such amounts continuously, would figure up to at least 1,000 billion cubic feet, which would require 400,000,000 acres fully stocked in good condition to be constantly kept in wood.

Figuring the stumpage value somewhat like the present average rates at 2 cents per cubic foot it appears that a capital of at least $20,000,000,000 would have to be tied up in the wood capital which is capable of furnishing continuously the present requirements of our lumber market. In this calculation we assume that our requirements for firewood and other forest products, not lumber and timber, can be satisfied by the inferior material remaining over after the log timber has been taken out, which is not now the case.

The experience of European nations has amply demonstrated that the small forest owner soon tires of the burden of maintaining the wood capital; he reduces it by shortening the rotation more and more, confining himself finally to the production of firewood and inferior sizes, and being unable to acquire or employ the skill necessary to carry on a systematic forestry business, his wood lots deteriorate more and more and play no rôle in the supplies for the lumber market which are furnished by the State forests and the large landed proprietors, who can keep up well-stocked areas of large enough size to pay for the employment of competent managers and skilled labor and the maintenance of a business organization; who can leave the large wood capital intact, which with the long rotation is necessary to produce sizable material, and who are satisfied with the low but steady and safe interest which their capital produces.

H. Doc. 181-20

H. FOREST INFLUENCES.

[Condensed from Bulletin 7, Forest Influences, pp. 191, 1893, with additional notes.]

One of the arguments upon which a change of policy in regard to our forests, and especially on the part of the National Government, is demanded, refers to the influence which it is claimed forest areas exert upon climate and water flow. It is argued that the wholesale removal and devastation of forests affects climate and water flow unfavorably.

Popular writers on forestry, friends of forestry reform, and the public mind have readily taken hold of this proposition, enlarged upon it, and generalized without sufficient and relevant premises, and before it was possible for science and systematic observations to furnish grounds or sound deductions; hence we have had only presumptions supported by superficial reasoning and occasional experiences. Even scientific writers have discussed the question without proper bases, and have sought to reason out the existence or absence of such an influence upon general premises and such evidence as the history of the world seemed to furnish, or else upon observations which were either of too short duration to allow elimination of other disturbing factors or else were otherwise unreliable.

From the complication of causes which produce climatic conditions it has always been difficult to prove, when changes of these conditions in a given region were observed, that they are perma nent and not due merely to the general periodic variations which have been noted in all climates of the earth, or that they are due to a change of forest conditions and to no other causes; hence some climatologists have thought proper to deny such influences entirely. On the other hand there are as trustworthy and careful observers who maintain the existence of such influences; but only of late has the question been removed from the battlefield of opinions, scientific and unscientific, to the field of experiment and scientific research, and from the field of mere speculation to that of exact deduction. But the crop of incontrovertible facts is still scanty, and further cultivation will be necessary to gather a fuller harvest and then to set clear the many complicated questions connected with this inquiry.

Meanwhile a thorough beginning with a view to settle the question by scientific methods and careful systematic measurements and observations has been made in Europe, where the existence of well-established forest administrations, manned with trained observers, has rendered practicable the institution of such work on an extensive scale-the only one which can yield adequate results.. Nevertheless, the results of these experiments, cited below, have so far failed to advance materially our positive knowledge regarding the relation of forest growth and meteorological phenomena.

The reason for this failure is to be sought, first, in the complexity of the problem, which renders any experimentation difficult, and, secondly, in the deficiency in appliances and methods of meteorological observations.

Not only is it difficult to analyze or control the various causes that may influence climatic variations from year to year, but we are not yet prepared to determine the uniformity of the local distribution of meteorological phenomena or of the measurements of the same by our instruments.

Hence some of the small, though well defined differences in rainfall and temperature observed over forest and open country in earlier experiments may be attributed to the nonconformity of the natural local distribution of these phenomena or to lack of uniformity in instruments and methods. It may be proper to call attention to and accentuate the fact that the question of practical importance is not so much as to the effects upon the general climate, but as to the local modification of climatic conditions which a forest area may produce.