556 JOURNAL OF FORESTRY 



of timber the site may ibe the same. A windfall or an insect attack may- 

 remove half the timber on an area in a year, and this would accordingly 

 halve the site quality. A fully stocked stand would give one volume, 

 and hence determine a site ; whereas an understocked stand would give 

 less volume, and hence be determined as a poorer site. 



Again, the yield in volume is applied to an even-aged stand, and 

 how can this be applied to the forest which is often composed of 

 irregular sized patches of even-aged and uneven-aged material and 

 every possible combination of ages and stocking possible? 



Finally, how could this method be used in a mixed forest, where 

 the site may be firj^t class for one species but second class for another 

 species ? 



A single tree in the stand may be selected for the determination of 

 site. It has the advantage that it does not depend upon any definite 

 unit of area, is equally good in pure or in mixed forest, in wild woods, 

 or in artificial woods, in even- or in uneven-aged stands, and is prob- 

 ably as sensitive to site changes as is any measure. 



The form of a tree is generally expressed by either its height, its 

 diameter, its form factor, or a combination of these three into its 

 volume. The results of site on a tree may therefore be expressed 

 either by any one of the above or any of their combinations. 



The diameter of a tree as an expression of site is not satisfactory, 

 for the reason that it does not respond strongly to site in actual meas- 

 urable amounts. The form factor of a tree does vary somewhat with 

 the site upon which the tree is growing, but its use as an expression of 

 site cannot be recommended, due to the uncertainty of the value of the 

 expression and to the laboriousness of the work entailed in deter- 

 mining it. 



The height of a tree is often used to determine site. The height is 

 affected to some extent and in some cases by density of stocking; for 

 if the stand is so densely stocked that more or less stagnation of 

 growth results, then, of course, the height growth of the tree is reduced 

 appreciably. But this does not often occur so severely that the height 

 cannot be used. 



It is said, in general, that a tree which is grown in the open is not 

 so tall at the same age as a tree which is grown in the forest. In the 

 forest, it is argued, the tree is forced to climb for light through com- 

 petition, and is thus forced into a more rapid height growth. This may 

 be true to a slight extent, but given the same site it is doubtful. 



