162 INTERMEDIATE CUTTINGS THINNINGS 



to be carried out from time to time may be indicated by the 

 total sectional area to be maintained on the ground , whereas 

 this could never be done by number of trees." 2 



Three distinct ideas in the method of making thinnings can 

 be recognized, each leading to a different selection of the trees 

 to be removed in a given stand. All three base the selection 

 of the trees upon their crown classifications. 



The three methods may be termed: 



1. The German or ordinary, 



2. The French, and 



3. Borggreve's method. 



Each will be discussed in turn. 



The German or Ordinary Method of Thinning. Sometimes 

 termed " thinning from below." 



In this method the principle used is to take out the poorest 

 crown class (suppressed trees) first and then to work upward 

 in consecutive order through the better crown classes in- 

 creasing the number of classes removed with the severity of 

 the thinning. The weakest trees and those which must be 

 utilized immediately to save them from death and decay are 

 cut and as many more of the intermediate, co-dominant, and 

 dominant as the desired heaviness of the thinning warrants. 

 All trees of the crown class next lowest would be cut before 

 trees from another crown class were taken. After the heavi- 

 est thinning some members of the dominant class will remain 

 but none of the other classes. Less severe thinnings leave 

 representatives of other crown classes. 



Based on the severity of the cutting, several grades of 

 thinnings are recognized under the ordinary method: (See 

 Appendix.) 



Grade A. Light. Removes suppressed trees. 



Grade B. Moderate. Removes in addition oppressed and 

 poorest intermediate trees. 



