30 BULLETIN 139, U. S. DEPARTMENT OF AGRICULTURE. 
that even forestation is made impossible through the prohibitive 
expense of clearing the soil. It is often practicable to assist repro- 
duction by partial sowing or planting within a few years after cut- 
ting, before the soil becomes choked with weeds. 
Group selection system. — Cutting Norway pine in irregular selected 
groups of from 2 to 10 trees may be advisable: (1) Where for aesthetic 
or protective purposes a mature stand must be maintained; or (2) 
where the fire danger is very acute and continuous areas of even-aged 
stands, such as would result from the shelter-wood system, must be 
avoided. The selection method of cutting is always more costly for 
the lumberman, and invariably results in considerable damage to the 
young growth. Theoretically not more than one-fourth to one-third 
of the stand should be cut at any one time, but in practice the lumber- 
man may be compelled to take out one-half or more and wait a longer 
time between cuttings. There will always be danger of weeds unless 
the cutting can be made closely to coincide with, good seed years, 
followed by favorable climatic conditions to insure immediate seeding. 
In a large operation, where cutting must be done every year, this 
would obviously be impracticable. 
Clear cutting. — Clear cutting in strips or blocks would reduce the 
cost of logging, but it has the danger of opening the soil to weeds, 
and hence should be tried only if it can be done during or immedi- 
ately following a good seed year; otherwise, planting may be neces- 
sary. The portion of the stand uncut should be north or west, as 
well as to the windward of the area to be restocked, in order that the 
ground may be kept as moist as possible. If there is not successful 
restocking within a few years, planting should be resorted to, where 
it can be done at a reasonable expense, before the ground has a chance 
to become choked with weeds and brush. 
Seed trees. — The plan of leaving scattered seed trees has on the 
whole proved unsatisfactory. This system is really a compromise; 
it is neither clear cutting nor partial cutting, for a few seed trees per 
acre are insufficient fully to seed up the ground. As generally prac- 
ticed, from 3 to 10 seed trees are left per acre, the more the better so 
far as the future reproduction is concerned. If logging can always 
be done at the time of a good seed crop satisfactory results-may be 
obtained, since the soil after being stirred up by hauling and skidding 
offers a good germinating bed. With a mature stand windfall and 
sun scald are likely. About one-fourth of the seed trees on the Minne- 
sota Forest have blown down. Yet owners may prefer to secure a 
very partial crop of the original species by this method on account 
of the small amount of merchantable timber which has to be left. 
The seed trees could be held over a rotation to yield lumber of large 
size as a provision against loss of the second growth by fire, or cut 
when no longer needed for purposes of seeding. 
