36 BULLETIN 285, U. S. DEPARTMENT OF AGRICULTURE. 



other valuable intolerant species are available, these should be 

 favored. Together with ash they are best managed in small, exclusive 

 groups among the other species. 



SILVICULTURAL METHODS. 



It is impracticable to discuss in detail all the possible methods of 

 management. The method to be chosen depends not only upon the 

 kind of timber present, but also upon the kind of logging, the market 

 conditions, etc. Any method would probably have to conform to 

 local logging practice. In every case the management should follow 

 in general some definite, if elastic, plan prepared in advance. While 

 every stand presents its own problems, there are certain generally 

 applicable procedures which are dealt with in the f ollowing discussion 

 from a strictly silvicultural point of view, the many economic factors 

 being neglected. 



The most marked differences in silviculture are in the methods 

 employed in old-growth and " second-growth " forests. 



Old growth. — The aim of silviculture in old-growth stands, as has 

 already been pointed out, is to replace mature and unproducing with 

 immature, producing timber in such a way as to maintain a sustained 

 periodic (though not necessarily annual) yield, and, at the same time, 

 improve the composition of the stand in the direction indicated under 

 " Choice of species," page 35. This implies a more or less gradual 

 removal of the mature stand. For silvicultural as well as economic 

 reasons, however, the removal must often be accomplished in a single 

 cutting. The management will, therefore, approach two extremes: 

 Clear cutting, after which the management will be that applied to 

 second-growth stands; and the selection system, which is the nearest 

 to nature's method of general replacement in virgin stands. Between 

 these extremes are the seed tree and the shelterwood systems. 



Clear cutting is justified silviculturally when there is good promise 

 of seedling or sprout reproduction of desired species. The season in 

 which the cutting is done is, therefore, of importance. Thus by 

 cutting during a heavy seed year of a preferred and an "off" year 

 of an undesirable species it may be possible to control or modify 

 the character of the reproduction. This may also be done by cutting 

 early or late in the year, to avoid or take advantage of the season's 

 seed crop of a given species. Clear cutting may extend over a large 

 area in a single season, the stand supplying its own seed for repro- 

 duction, or be confined to a strip along the border of the stand, 

 whence the area is seeded down. In stands containing basswood, 

 clear cutting is usually followed by a vigorous growth of basswood 

 sprouts which far outstrip all other vegetation (PL IX). Since bass- 

 wood will sprout, and apparently with success, from very large stumps, 

 clear cutting seems well adapted to the perpetuation of basswood, 



