﻿42 BULLETIN 13, U. S. DEPABTMENT OF AUBICULTUBE. 



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 

 facilitate 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 



