ADVANTAGES OF THINNINGS 157 



The productive energy of the site is thus utilized by a smaller 

 number of trees which are thereby enabled to attain a given 

 size more quickly. It should be emphasized that not only is 

 diameter growth increased but also to a lesser extent growth 

 in height. The popular idea that height growth is directly 

 dependent upon, and increases with the density of the stand 

 is unsound. Height growth will be greatest when the trees 

 are kept in the vigorous condition found in the properly 

 thinned stand.^ 



The actual crown surface exposed to direct sunlight is 

 greater in the thinned than in the unthinned stand, making 

 possible faster growth. In the latter the crowns of the trees 

 interlace with a relatively level top surface exposed to the 

 sun with only occasional dominant trees raising a portion of 

 their crown above the general level. After a thinning cup- 

 like depressions exist between the individual trees allowing 

 direct light to reach the sides as well as the tops of the 

 crowns. Thus the crown area receiving direct light is greater. 

 (See Fig. 60.) 



Profile of Crowns on a 

 Section through aa 

 Unthinned Stand 



Exoffle of Crowns on a 

 Section through a 

 Thinned Stand 



Fig. 60. 

 Profiles of tree crowns on sections through unthinned and thinned stands. 



2. Thinnings raise the quaHty of the product composing 

 the final crop. Trees of poor form, those containing defects 

 or of relatively inferior species can be taken out and the few 

 best trees left upon which growth will be concentrated. 



