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for the selection system. The method of culling onl\- 

 the largest trees and leaving the smaller ones is, however, 

 applicable only to stands having trees of different ages 

 mingled together. In handling a stand in which all, or 

 nearly all, the trees are mature, the design is to remove 

 the whole stand, and replace it with new growth in as 

 short a time as is feasible. This is accomplished either 

 by one of the clear-cutting or one of the shelterwood 

 systems. 



The conditions requiring a clear-cutting are the fol- 

 lowing: 



1. Where there is danger from windfall. Such a con- 

 dition is found in mature coniferous forests which are 

 growing on steep slopes and ridges in the mountains. 

 For example, the spruce stands growing on the exposed 

 slopes in the mountains of northern New England and 

 New York cannot, as a rule, be heavily thinned, because 

 the trees left standing would be almost certain to be up- 

 rooted by the wind. In most cases, however, a very light 

 thinning, such as could safely be made, would not pay, 

 so that some system of clear-cutting is necessary. 



Conspicuous examples of the same principle are found 

 in the mountains of the West. The lodgepole pine in 

 the Rocky Mountains grows at high elevations in exposed 

 situations. The stands are usually regular in form and 

 the trees long and slender, with shallow lateral roots. 

 Attempts to thin mature stands of lodgepole pine have, 

 in many cases, resulted in heavy windfall. 



2. Where all the trees are large and mature, and prac- 



