42 
should be windfirm. Those with large crowns and relatively thick 
trunks are least likely to be thrown. If, however, there is any ques- 
tion of windfirmness, it is usually best to leave the seed trees in 
groups of three or four for mutual protection. 
When a thrifty reproduction has been secured, seed trees should 
be removed if it is profitable to do so. If they are well formed and 
sound, however, they may be left until the land is again cut over. In 
this way the cost of their removal will be lessened and lumber of 
larger size and possibly of better quality secured. 
If seed trees are to be left, the stand may be logged before seed fall 
in a year of heavy production. This permits the logged area to be 
burned over lightly, should it be thought necessary to get rid of 
bushes and hardwood sprouts and seedlings. As in the other meth- 
ods, disengagement cuttings should be made if the pine seedlings are 
threatened by hardwoods. 
The seed-tree method has the advantage over the other methods 
described in that the area which can be cut over at any one time is 
unlimited. Since only one cutting is made in a rotation, there is no 
periodic income as in the strip method; but, on the other hand, the 
expense and trouble of logging come only once. 
SJielterwood method. — The shelterwood or "stand" method removes 
the trees by successive thinnings or partial clearings at intervals of a 
few years.* The object is to gradually establish thrifty reproduction 
under the best possible conditions and to preserve a seed supply in 
case of disaster to the young stand. In Germany, where the system 
originated, and where economic conditions allow of its intensive appli- 
cation, a large number of successive thinnings are made, classed as 
" preparatory," "seed," and "final" cuttings. The preparatory cut- 
tings aim to increase the air circulation in dense stands, and thus 
f acilitate decay of the humus and exposure of the mineral soil. They 
also stimulate seed production by admitting light to the tree crowns. 
From 25 to 40 per cent of the least desirable trees are removed, which 
reduces the density of the crown cover about one-fourth and leaves 
the dominant trees with their crowns separated by a space of from 
3 to 5 feet. A few years later, when the soil is in good condition and 
seed production assured, the seed cutting is made. This is done dur- 
ing a seed year, and reduces the crown cover to at least one-half its 
original density, in order that sufficient light may be admitted for the 
expected reproduction. When the latter is so large, thrifty, and 
uniformly distributed as to leave no doubt of its success, the shelter 
trees are removed. If the seedlings show need of increased light before 
the final cutting, as they may within 3 or 4 years after the seed cutting, 
some of the remaining trees must be removed in advance. The 
whole thinning process takes from 15 to 20 years. At its conclu- 
sion, should it prove successful, a thrifty stand of young trees, all of 
