86 



A MANUAL OF FORESTRY 



the stand is managed. Light and moderate thinnings favor the 

 production of high-grade timber free from knots. This is the 

 principal advantage of the competition between trees in a dense 

 stand, and thinnings of Grades A and B do not greatly lessen 

 the competition in a stand, since this is largely between trees 

 of the intermediate, codominant, and dominant classes. 



Heavy thinnings, by giving the trees ample growing space, 

 result in the production of shorter-boled and more knotty trees; 



By permission of the Connrrticul Stair Forr-.trr. 



\\. A white pine -land .; j years old sccurvd by artitkuil sordini;. 

 has just been made. 



AC grade thinning 



and, on account of the greater growing space, in more rapid 

 growth and higher yield in a given time. Where quantity with- 

 out regard to the highest quality is wanted heavier thinnings 

 are needed than where timber of high technical quality is the 

 primary consideration. 



In general, as the thinnings increase in severity, the diameter 

 and hence volume growth of the trees rises, but there always is a 



