280 



CLARENCE F. KORSTIAN 



direct light from above but none from the sides, usually 

 with small crowns considerably crowded on the sides. 

 S = Suppressed: Trees with crowns below the general level of the 

 forest canopy and receiving no direct light either from above 

 or from the sides; usually with small, poorly developed 

 crowns. 



Table 2 shows the average increment per tree for the different 

 crown classes on Sites I and II, only those trees being included 

 which were living and were measured in 1910 and 1915. The 

 greater apparent increment of the dominant crown class might 

 be explained by the fact that in the X class a greater amount of 



TABLE 2 



Periodic cubic increment of western yellow pine segregated by crown classes for 



Sites I and II 



limb-wood is produced, while in the dominant class, due to 

 their relative position in the forest, there is a stimulation in the 

 production of body-wood which is the portion of the tree meas- 

 ured to determine the increment. When the individual trees, 

 the component parts of an aggregate stand, are given separate 

 consideration it is evident that not only the effects of the physi- 

 cal site are revealed in the increment but also the effects of the 

 individual's associates, especially their influence on the amount 

 of light the individual receives or the amount of growing space 

 available for its use. Although the average increment per 

 tree varies directly with the favorableness of the conditions of 

 the site, the writer does not wish to leave the impression that 

 crown form may be regarded as an expression of site quality. 



