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 assistance. 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 associated 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.