CM JOURNAI, OF FORESTRY 



at the base of the tree and in the roots, action of boring insects on 

 trees weakened by exposure and final overthrow by wind. 



Annual loss can be determined only by annual survey and this extra 

 cost is not justified on extensive areas. The determination of loss in 

 successive decades will serve every purpose, and will very probably 

 decrease as more care is used in disposing of slash, since this will 

 reduce tlie l)ree(ling places for insects. The loss will also decrease 

 as the timber grows more rapidly by virtue of increased growing 

 space, and overcomes the influence of decay. 



Diameter Grozvth. — Diameter increment measurements can be best 

 taken by boring at breast height in soft woods up to 14 inches in 

 diameter, and should be made systematically in conjunction with the 

 caliper record, using the same distribution of types and tree classes. 

 Borings should be made on at least 100 trees for each inch class in a 

 given species to give good averages. Classification of trees within a 

 species is only made necessary by severe suppression or injury to 

 some individuals. If the stand left after logging is open, the effect of 

 ten years' growth is to render identification of suppressed trees diffi- 

 cult. This causes lack of uniformity lietween the stand table and 

 borings, and makes the separation of free and suppressed trees 

 inadvisable. 



Measurement may l)e made of the number of rings in the last inch, 

 or half-inch of radius, or the width in inches of the growth of a given 

 period of years may be taken. After a series of measurements have 

 been collected to show the trend of growth, determination can be made 

 as to the most useful measurement for a given purpose. A measure- 

 ment of diameter increment on any inch class, which includes two 

 rates of growth, will not be useful for prediction of future growth, 

 since it does not give a representative average. The field form at- 

 tached shows the range of possible measurements on cut-over types 

 where acceleration has taken place. 



The error due to oblique boring can be made negligible for measure- 

 ments of the outer inch or half-inch, by care in alignment of the in- 

 strument. Borings made at breast height will avoid the root swelling 

 on trees up to 14 inches, while larger spruce and balsam trees which 

 survive a pulpwood logging operation are usually defective and are 

 not making appreciable net growth. 



The relation of height to diameter can be determined on bored 

 trees by hypsometer measurement. Position of the crown with its 



