APPLICATION OF THINNINGS 187 



of growth on good soils. As the stand grows older the inter- 

 val between thinnings is apt to lengthen, because growth may 

 slow up and the openings in the canopy average larger due to 

 the larger crown spread of single older trees. 



FIG. 77. 



The same stand as shown in Fig. 68, but 10 years after the D grade thinning 

 was made. The crown canopy is almost complete. The stand is in need of a 

 second thinning. 



Thinnings should be carried on systematically from early 

 in the life of the stand until the period of regeneration, fol- 

 lowing a definite policy. What method of thinning should 

 be used and how severe the thinnings ought to be made, must 

 be determined separately for each case. All that can be 

 attempted here is to indicate the procedure in some of the 

 commoner cases. 



