Except that it is more fastidious as to soil, white pine usually demands about the same treatment as that prescribed for Douglas fir, including clean cutting, slash burning and establishing a new even-aged stand by seed trees or artificial restocking. Under favorable conditions the stand is nearly even-aged, with little undergrowth except of undesirable species. What small pine may exist is seldom thrifty enough to be worth saving, so the best thing is to clean off the ground for the double purpose of removing weed trees and favoring valuable reproduction. Like that of fir, the natural rotation of white pine forests seems to have been accomplished often by the aid of fire, and where not given this aid it suffers from lack of suitable seed-bed and from the competition of other species already established.
Individual seed trees left in logging are not successful because of shallow root system and almost certain windfall. Replacement must be by seeding or planting, or by leaving small tracts of pine surrounded by cleared fire lines to protect them when the slashing is burned. The size and distance apart of these must be determined by their situation and exposure to wind, considering both the danger of windfall and the carrying of seed. Especially in younger growths, the quantity of merchantable material tied up in this way is not so great as is sometimes necessary in the case of red fir, where single seed trees may contain several thousand board feet. On the other hand, stumpage value may be high. For this reason artificial replacement may often be more profitable, especially where there is reasonable safety against recurring fire.
A thing to be borne in mind is that white pine seems to reach a healthier and better development when mixed with a small proportion of other species, such as cedar, tamarack, spruce, lodgepole pine and Douglas fir, so there is no object in trying to produce an absolutely pure stand. Some authorities think that 60 per cent of pine, with the rest helping to prune it, is an ideal mixture.
LODGEPOLE PINE (P. Murrayana)
Present interest in private reproduction of this species hardly warrants treating it at length in this publication, although unquestionably it will eventually occupy a higher place in the market than at present and its readiness to seize burned land in many regions will make it a factor whether desired or not. Where yellow pine will grow, the problem is most likely to be to discourage lodgepole competition.
In strictly lodgepole territory, however, it may be the only promise of a new forest. Generally speaking, an even-aged growth should be induced by clean cutting if the entire crop can be utilized. Slash burning in such cases is desirable. The chief difficulty is in providing seed supply, for either individual seed trees or small groups are almost certain to be blown down. Experiments so far indicate that heavy strips must be spared, chosen to afford the least present loss and safeguarded by fire lines.
In some lodgepole stands, especially where only certain sizes are marketable, the cutting practically amounts to thinning. Here obviously the effort should be to prevent over-thinning and to remove debris with the least damage to the remaining stand. Piling and burning is essential.
SUGAR PINE (P. Lambertiana)
This extremely valuable pine, commercially limited to the Oregon and California mountains, is fastidious in its choice of conditions. Not a frequent or prolific seed bearer, it still insists on a moist loose seed-bed and prefers the natural forest floor to burned-over land. It cannot stand drought when young and except on cool northern slopes seedlings may be killed or stunted by exposure to full sunlight. On the contrary it demands more and more light as it grows older and will be suppressed or killed if unable to secure it. Under natural conditions it perpetuates itself best by filling open places in the forest.
For the above reasons, sugar pine is naturally a component of mixed forests and it is doubtful whether it will be successfully grown as a pure stand. Unfortunately, also, logging methods which are both the simplest and most favorable to the reproduction of its associates may be discouraging to sugar pine reproduction. Nevertheless, its value warrants strong efforts to favor it and is an argument, where considerable young sugar pine exists, against either clean cutting or the use of fire.