Practical Forestry in the Pacific Northwest Part 4

Compared with most important commercial trees, the Northwestern Douglas fir is remarkably easy to reproduce. It is an abundant seeder, grows very rapidly, and inhabits a region with every climatic advantage. In the typical fir districts of Oregon and Washington deforested land which escapes recurring fire is usually restocked naturally and with astonishing rapidity.

The exceptions to this rule are where the destruction of seed trees has been wide and absolute, where already established competing species are not removed with the original forest, and where the surviving fir is too old to seed. The two latter conditions are most prevalent near the coast, where the wet climate not only tends to protect slashings from fire and thus preserve the undergrowth of shade bearing species which escapes logging, but has also prevented the accidental destruction in the past of the original fir stand by fire.

In considering these natural results as they bear upon proposed methods, we find actual destruction of seed supply the easiest to avoid. If the original stand contains suitable seed trees we can protect a sufficient number of them. If not, or if it is less expensive, we can secure seed elsewhere. More frequent difficulty will lie in determining whether the reproduction of fir should be the sole effort, or whether it should not be sacrificed, if necessary, in order to utilize an existing start toward a second crop of other species. This is of peculiar and early importance, for it usually also decides the question of protecting the slashing from fire.

If the present stand is nearly pure fir, or if other species are represented almost wholly by merchantable trees, there will be no young growth worth saving. A new crop must be started from seed, and since fir is the quickest and easiest to grow, as well as probably the most valuable, it should be given every encouragement.

_Slash Burning and Its Exceptions._

In most cases this requires burning the ground after logging, not only to reduce the future fire risk but also to provide a suitable seedbed. Fir much prefers mineral soil to start in, as is easily seen from the far greater frequency of seedlings on road grades than on adjacent undisturbed ground covered with humus and rotten wood. Hemlock has no such fastidiousness, even preferring rotten wood as a seedbed. To protect the slashing from fire, therefore, both preserves the most unfavorable conditions for fir and subjects it to unnecessary compet.i.tion by its rival. Hemlock seedlings already established, seeds lying on the ground, and surrounding or surviving trees which may scatter more seed, are all encouraged to shade and stifle the struggling fir seedlings already handicapped by dislike for their situation.

On the other hand, a large proportion of what we now consider typically fir forest has a vigorous ground cover of hemlock and cedar which may become merchantable many years before an entirely new fir crop can be grown. The presumably greater value of the latter may be consumed by the heavier carrying charge before returns are available. Certainly if the promise of profit from other species and the difficulty of establishing fir both reach the extreme, protection of the growth already started is the best forestry if it is practicable. Moreover, there may be considerable young growth of other species under conditions which do not preclude satisfactory additional reseeding by fir.

When the owner is in position to plan far into the future, like the Government or State, he may seek a temporary compromise, although expecting eventually to secure pure fir. In such a case it may often be best to utilize a first new crop of hemlock, but on harvesting this a few decades hence to burn clean and start the next rotation with fir only.

_Conditions Vary Methods._

Between conditions clearly suggesting one course or another, all gradations will present themselves and no written rule can be given for determining the dividing line. Much depends upon future relative values of species, upon which the owner will have his own opinion.

More depends upon the character of existing young growth and consequent adaptability to changed conditions after logging. Even a very thick stand of young hemlock is unlikely to produce much if the overwood has been very dense, for much of it may be so old and stunted by shade that sudden advent of strong light will result merely in distorted worthless branch growth or in killing it outright. Occasional vigorous young trees just under present merchantable size are of doubtful value because they are likely to blow down. The most promising cla.s.s of undergrowth found in fir forests of the Northwest is where there has been sufficient light to produce a fairly thick stand of young hemlock or cedar from five to fifty feet high.

If the undergrowth from which any second crop may develop is insufficient to be worth much consideration, and reseeding must be depended upon entirely, there may still be a question as to species. If ample natural supply of fir seed can be expected, slash burning is indicated. But if not and the owner is not prepared to undertake the expense of artificial seeding, while at the same time there is a promising natural hemlock supply, burning has no object except the reduction of future fire risk. It may even r.e.t.a.r.d hemlock reproduction, both by destroying part of the seed supply and by encouraging the growth of brakes on the area. The question here is a really financial one. The cost of planting fir under these conditions may be more than reimbursed by the resultant more valuable and rapid growing crop. The owner must do his own conjecturing as to future comparative values of the species.

So far we have discussed slash burning only in its sylvicultural relation, finding that it encourages Douglas fir reproduction and is consequently advisable in Northwestern Douglas fir types unless there is an exceptionally promising second growth already started.

The balance will be further in its favor, in doubtful cases, because of the protective feature. This is discussed more fully in another chapter, but it is well to recall here that immunity from recurring fire is the first essential of profitable reforestation. To secure second growth by treatment which threatens its destruction later is bad management unless the original saving is ample to cover subsequent greater cost of protection. This is seldom the case.

_How to Reseed the Area._

Dismissing the exceptions noted, and returning to our rule that another crop of Douglas fir is usually the best secured by following nature--cutting practically clean, burning the ground and starting a new even-aged stand--we have still to consider means of getting this stand started. We may depend upon natural reseeding from trees preserved for the purpose or from the surrounding forest, or we may resort to planting. What are the comparative advantages of these two methods and the circ.u.mstances governing choice between them?

Hitherto, students of the subject have inclined to favor natural reproduction. The very general second growth on deforested land where no aid has been given indicates that excellent results will follow slight a.s.sistance. Red fir fruits frequently and profusely, and the seeds carry well in the wind. Burns have been known to restock fully from seed blown from forested hills a mile or more away. Moreover, while planting always involves initial expense, sometimes much may be done to insure natural seeding with little or no actual outlay.

There is danger, however, that in many instances this economy will be more apparent than real if it is effected by actually leaving much value in seed trees. Abroad and in the East there is comparatively little loss in leaving even a fourth or fifth of the original stand to furnish seed. The individual trees left may be good seeders, although small. Little capital is tied up in them and they may be utilized later to equal advantage. A mature fir forest of the Pacific coast may have no small fruiting trees at all, and if left such are likely to be knocked down in logging. To leave 20 per cent of the large trees standing would sometimes tie up 20,000 feet to the acre, worth $40 or $50. Age and windfall may cause loss equal to stumpage increase; moreover, they can never be utilized without the same expense for roads and machinery that is necessary in the original logging. The second crop will not be allowed to reach a size requiring such equipment. In considering possible windfall loss, not the normal wind but the possible maximum storm within the entire life of the second crop must be reckoned with.

It is probably safe to say of mature Pacific coast fir that leaving enough merchantable timber on a cutting area for adequate seeding costs more than to use it and restock. Restocking can be done for $2 to $10 an acre, which would leave a decided margin for profit on the seed trees. And if we undertake to reduce this balance by leaving very few seed trees, we decrease the certainty of successful reproduction and increase the danger of entire failure through windfall or accidental destruction when we burn the slashing. It cannot be denied, however, that fire after planting would result in complete loss, while seed trees might restock the area again and again after such accidents.

_Natural Reproduction._

On the other hand, natural reproduction does not always require the leaving of merchantable timber on the cutting area. Frequently there are enough crooked or conky trees to serve the purpose. These defects are not directly transmissible through seed to the offspring, although conk is infectious and the young crop should be protected by the removal of the diseased parents after it is well started.

Again, seeding from adjacent timber can often be relied upon. This is a question of economy in logging operations, lay of the ground, prevailing wind direction, fertility of the stand and other local considerations. A valley with healthy fir woods on either side is likely to seed up promptly even if a half mile wide. So is a flat at the leeward foot of a hill timbered on the summit where the wind strikes. A cutting on a ridge is correspondingly unlikely to restock. Theoretically if a tract of timber were large enough, it could be opened up by logging operations which, instead of proceeding steadily from one edge, might skip every other landing or so until the most remote portion was reached after a few years, and then work back again, cleaning up the neglected portions after they had seeded the first openings. The same effect sometimes results from actual accidental practice.

It is apparent that rules cannot be laid down for general application.

Generally speaking, a logger interested in fir reforestation should study his ground to see if naturally, or, with inexpensive aid, the cut-over area will not reseed from the sides and from the cull trees he will leave uncut. If not, he may leave a few merchantable seed bearing trees provided the soil is such as to make them deep-rooted and wind-firm. Groups are better than single trees because less likely to be blown down and easier to protect from the slashing fire. More should be left toward the windward edge. But before tieing up any considerable sum in merchantable trees he should consider the cost and safety of supplementing any shortage of natural supply by artificial seeding.

WESTERN HEMLOCK (_Tsuga heterophylla_)

Since hemlock is so frequently a.s.sociated with Douglas fir, the principles governing its reproduction and its relative promise as a second crop have necessarily been largely covered in the preceding discussion of fir. The following remarks are merely additional.

We have seen that the perpetuation of hemlock is advisable only where fir reproduction is difficult to obtain or will be at too great a sacrifice of valuable existing hemlock. The first of these conditions is confined chiefly to pure hemlock stands and to coast regions where the fir is often too old to seed well. The second may exist on the coast or in certain moist interior regions where there is a heavy hemlock undergrowth. In either case natural hemlock reproduction will be counted upon, both because it is practically certain to occur and because if it were not certain and artificial aid were necessary, we would abandon hemlock entirely and devote our efforts to fir. In short, discussion of hemlock as a second crop need not include systematic attempts to seed the ground but may be confined to protection of what we have to begin with.

In a straight hemlock proposition, the protection question may differ considerably from that involved by deciding between fir and hemlock. In the latter case, because of the a.s.sistance of fire to fir, the growth already on the ground must have considerable value to warrant foregoing the several advantages of slash burning.

In the former, slash burning has no object except to reduce future risk. The inference is that a much less promising stock of young growth is worth protecting.

While this is true, there is danger of overestimating its value, especially if care is not taken in logging. It has been remarked that suppressed misshapen hemlock is not apt to make a healthy growth, that windfall is a peril, and that if the previous shade has been heavy, sudden opening to sunlight may be fatal. It should also be remembered that even slightly injured young hemlock is worthless, for it is almost certain to be attacked by borers. Anything which deadens a small portion of the bark like axe blazes, fire scorch, or scars from strap leads, is dangerous. Hemlock is more liable than fir to general defects like black streak, borers, fungous disease and mistletoe, therefore investment in reforestation needs the maximum safeguard against them. In many instances better results may be obtained from a new healthy seedling stand following a purifying fire, even at some loss of time, than from well started young growth which is unhealthy and likely not only to fail itself but also to infect any seedlings which may come in among it. Consequently if the slashing is not large, and reproduction from the sides may be counted on, the above considerations, coupled with the reduction of future fire risk, may suggest slash burning just as in the case of fir. The remarks apply particularly if it is considered necessary to log as clean as possible.

With a good, healthy start toward a new forest, however, it will usually be best to keep fire out, for the material saved will warrant greater expense in protection during the growing period. Representative tracts, both on the coast and in the Cascades, have been studied which showed that, with care in lumbering, enough good young hemlock too small for logs or skids could be saved after present-day logging of a heavy mixed fir and hemlock stand to produce in fifty years 11,000 or 12,000 feet of timber over 14 inches in diameter. This would not be wholly additional to the second crop of seedlings which might be produced if these trees were not preserved, for the ground and light they use would be denied to the seedlings, but undoubtedly the yield would be greater than could be secured if they were destroyed.

This means that under similar conditions we may go still further and actually apply the selection system, especially if the original stand is nearly pure hemlock. So far we have discussed areas left by present-day logging methods. Suppose, however, the owner of a good tract of hemlock, having decided that conditions do not warrant trying to get fir, is willing to modify his methods for the sake of better hemlock returns at some future cutting. He would probably do best to take out only the mature trees, leaving everything which is still growing with fair rapidity. Greater light will stimulate these immensely as well as encourage further seeding of the ground.

The few merchantable trees he spares, together with those now unmerchantable, will, in perhaps twenty years, make another excellent crop. By leaving a fairly dense stand he prevents the windfall danger which threatens the survivors of too vigorous cutting, and also prevents them from a.s.suming the branchy form of trees which receive too much side light. The fire danger is much reduced by resultant shading of the ground and slightly by the lesser cover of debris. In short, he makes the most economical use of the ground, and the capital represented by the trees he spares is well invested.

To sum up, hemlock lends itself to almost every form of management.

Determination as to which is most advisable is governed by its extremely variable manner of occurrence and by the local promise offered by a.s.sociate species. The foregoing discussion can only serve as suggestive when considering given conditions.

WESTERN CEDAR (_Thuya plicata_)

Except for small swamp and river bottom areas, where the land is likely to be more valuable for agriculture than for forest culture, pure cedar stands are not common. Therefore it is as a component of mixed stands that cedar is likely to become a problem in conservative management. To some extent it presents a peculiar question by being taken out alone for special purposes, such as poles and bolts, independent of ordinary logging of sawtimber.

Western cedar is a typically shade-bearing tree and also endures much ground moisture. Its occurrence as an under story and in swamps does not indicate that it always requires such conditions, however, but more often means merely that they protected it from compet.i.tion or from destruction by fire. Charred remains of very large, fine cedar are often found on comparatively dry slopes where fire has resulted in complete occupation by fir at present. Cedar's failure to reappear there after removal is probably because its thin bark and shallow roots allowed its destruction by a fire which was survived by some better protected fir seed trees. Nevertheless, cedar must be cla.s.sified as a moisture-loving species and occupies dry soils only in coast or mountain localities where there is a compensating heavy rainfall.

Reproduction and management of western cedar have not been sufficiently studied to warrant very positive conclusions. This neglect is probably due to a wide belief that in spite of its present commercial importance, its place in the future forest will be small. It most commonly occurs with other trees in heavy stands, which make the preservation of any young cedar difficult because of the destructiveness of logging. Being of comparatively slow growth, also persistent in retaining branches when grown in the light, it is not as promising for artificial reproduction as Douglas fir or white pine. To let it become old enough for good shingle material will be too expensive to pay, for roofing is one of the wood products easiest to subst.i.tute for.

While cedar is adapted for poles, posts and other underground use, less decay-resisting species can be made equally durable by chemical treatment. In other words, as a second crop it is probably below other species in ease of establishment, rapidity and quant.i.ty, and will not have sufficient peculiar value to compensate for consequent less economical use of the ground.

There may be exceptions to this rule. Good young cedar in forests which are to be handled under the selection system should be carefully protected. It can always be utilized and may bring revenue before anything else can be cut. For the same reason it has been suggested for planting with fir and white pine, either simultaneously as a small proportion or later in blank s.p.a.ces where the others fail.

Under such conditions the main stand will not be modified and the cedar will afford a valuable adjunct.

SITKA SPRUCE (_Picea sitchensis_)

Although found in the moister mountain regions, this exceedingly valuable tree seldom occurs to a commercially important extent except along the coast, where it is common on swales and fertile benches and in river bottoms often forms pure stands of great density.

Yields of 100,000 feet an acre are not unusual and the trees are very large. It is also common, although of small size, in swamps.

This spruce reproduces readily in openings, whether made by fire or cutting. Unthrifty specimens may be found under shade, but considerable light is necessary for successful development. Even then, height growth in youth averages slower than that of fir or hemlock. The leader shoot is likely to die, so that hardly more than 25 per cent of the young trees establish a regular form of growth before a height of 20 or 30 feet is reached. After this stage spruce grows uniformly and rapidly, still somewhat slower than fir in height but exceeding it in diameter. The branches are slow to die, however, so that the tree remains bushy for most of its length until it reaches 60 or 80 feet in height, and even afterward a dense stand is required to clear it. In many pure spruce forests the larger trees have been able to withstand the pruning influences and remain limby, while the smaller ones, being pushed in height growth to reach sufficient light for survival, have cleared themselves with remarkable rapidity.

The natural occurrence of Sitka spruce, except in Alaska, is probably limited chiefly to situations where it escapes compet.i.tion, in youth at least, with the more hardy and rapid-growing species. It has the greatest advantage over these on river bottoms and flats where there is a dense growth of deciduous brush and where the soil is very wet in spring. In considering it as a possible second crop, the same compet.i.tion must be remembered. Whether seeding is natural or artificial, the extent to which it will hold its own with any considerable quant.i.ty of other species is doubtful. If such are present and the situation is adapted to them, any expensive effort to get spruce merely by modifying methods of logging or handling the slash is certainly likely to be disappointing. Under the conditions mentioned as peculiarly favorable for spruce, gradual natural restocking may be expected if some seed supply is preserved, but since the growth is rather slow and a thin stand will remain limby, it may pay to hasten returns by supplementary artificial planting. Some authorities question the financial practicability of this on the ground that since spruce is of slower growth it will pay better to use the ground for fir, but the latter is unlikely to be true of bottom land.

After summing all its advantages, the peculiar merits of spruce for certain purposes should be weighed, for sufficiently higher stumpage value will compensate for delay in harvesting the crop. Moreover, Sitka spruce has not been as thoroughly studied by foresters as the more prominent Western trees, and while the foregoing notes represent general present opinion, further figures on rate of height growth may be more encouraging. There is no doubt that diameter increase is rapid from the start. Most of the disadvantages mentioned also decrease toward the southern limit of the spruce range, the growth on the Oregon Coast being rapid.

WESTERN YELLOW PINE (_Pinus ponderosa_)

In this species we have the important western conifer which most often permits the selection system of management. With certain exceptions in which the entire stand is mature, the object of conservative logging should be to remove trees past the age of rapid growth and foster those that remain for a later cut. When comprising the entire stand, or at least clearly dominating it, with all ages fairly evenly represented, successful in reproduction, and not so dense as to present mechanical difficulties, it is ideally adapted to this form of management. The important underlying principle is that, since for a period of its life the normal individual tree increases in wood production and then declines, it is bad economy to cut it while it is still growing rapidly or to allow it, after slowing down, to occupy ground which might be used by a tree still in the vigor of production. For example, if at 100 years old it contains 500 board feet, it has averaged an addition of 5 feet, a year throughout its life. If at 125 years old it contains but 560 feet, the average increment will be but 4-1/2 feet a year.

It will not give equal return for the soil, moisture and light it monopolizes during these 25 years. At the same time, probably there are young trees nearby which hitherto have averaged below the maximum, but if released from its compet.i.tion will forge ahead for a period at the end of which they will give a greater annual return than if cut at present. It would be as bad economy to cut these today as to spare the over-mature tree. In short, the production of the forest is not only sustained, but actually increased, by removing the oldest trees at just the proper time; and is decreased by taking out young trees either not yet at the natural age of greatest mean annual increment or capable of artificial stimulation by thinning.

By studying the relation of age to production in the particular locality, the proportion of different age cla.s.ses, and also finding the approximate average diameter which corresponds to the age at which he desires to cut, the professional forester can make a very accurate selection of the trees which can be removed to best advantage at present and also fix the time and yield of the next cutting.

Fortunately, however, commercial and silvicultural considerations accidentally coincide so nearly under average yellow pine conditions as to make certain rough rules which can be laid down entirely consistent with logging methods now in practice. Diameter is far from exact indication of age, for the location of the forest and the situation of the individual tree, especially as it affects the relation between height and diameter growth, are potent factors, but as a rule merchantability for saw-material is not far from maturity.

In a great majority of cases the approximate minimum diameter for cutting which would be fixed by it forester would be somewhere between 16 and 30 inches, but say it were 18 inches, for example, it would not arbitrarily apply throughout the stand. Most trees with yellow, smooth bark and small heavy-limbed tops, perhaps partially dead, are mature regardless of their size. If small, they have been crowded or stunted and may as well be cut. Trees with large, healthy crowns composed of many comparatively small branches, and with rough dark bark showing no flat scaling, are sure to be growing rapidly, even if quite large. They are also less desired by the lumberman, who often calls them black pine or black jack, so may often be spared, without much sacrifice, for seed trees or in order to continue their rapid wood production.

The seed tree problem in such a pine forest and under such a system as has been described is comparatively simple, for there are likely to be enough young trees of fruiting age left to fill up the blanks between existing seedlings. The density of the latter determines to a large extent the number and location of seed trees necessary, but there should always be two to four to the acre, even if this requires leaving some that would otherwise be logged.

Under this system recurring cuts may be made at periods of perhaps 30 or 40 years, taking out each time the trees which have pa.s.sed the minimum diameter since the last previous cut. It is obvious, however, that if the process is to continue indefinitely, protection must be absolute. Destruction of young growth will stop the rotation at the time the surviving older material is harvested. At each cut the brush should be disposed of with this end in view. If the stand is very thin it may not add much to the danger of fire and, especially if reproduction is difficult and requires shelter, may best be left spread on the ground at some distance from remaining trees. Otherwise, and this is the rule, it should be piled and usually burned. In this process and in logging every effort should be made to protect existing young growth from injury. Ground fires should be prevented now and always hereafter.