368 



GROWTH OF TREES IN HEIGHT 



(1) (2) (S) (4) (5> 



Rings Height Length Years to Years to' 



in of of Log Grow in Grow-to 



Section Section Feet height height of 



Feet for Log Section 



of 'he suppressed trees, but the maintenance of nearly the average 

 rate for all surviving trees. But the dotted lines indicate the greater 

 height of suppressed trees having a given diameter, when compared 

 with dominant trees. 



284. Measurement of Height Growth. For the juvenile period of 

 height growth of seedlings and saplings a practical method of measure- 

 ment is to determine the total 

 age and the total height of 

 dominant trees (§256 and §257). 

 Trees which will not survive 

 should not be measured for 

 height. For young conifers show- 

 ing annual whorls, the exact 

 height growth for each year may 

 })e determined by measuring the 

 length of the whorl. This method 

 is used in measuring the annual 

 height growth of coniferous plan- 

 tations (§258). 



On older trees height growth 

 should be measured by analyzing 

 the growth of individual trees. 

 Total height growth for a given 

 tree is obtained when its height 

 and total age are known, and a 

 composite growth ciuve may be 

 built up as suggested for seed- 

 lings, by obtaining these data for 

 a number of trees of different 

 ages on the same site quality, 

 plotting the heights on the basis 

 of age and drawing an average 

 curve of height on age. But a 

 more accurate method is possible 

 when each tree has been cut into 

 several sections, the age of which 

 can be determined from ring 

 counts. In this case as many 

 points for a curve of height 

 growth are found as there are 

 sections cut, and these points 

 form a true growth curve for the tree. Diameter growth begins, at 

 a given section, in the year in which the tree reaches the height of this 



Fig. 77. — Method of determining the 

 growth in height of a tree from the 

 ages of upper sections, or ring counts. 

 The difference in age between consecu- 

 tive sections indicates the period re- 

 quired to grow in height from the lower 

 to the upper section. 



