176 



FORESTRY IN NEW ENGLAND 



The height growth of individual trees can be obtained by- 

 counting the rings at the various sections into which the tree 

 is cut. The number of rings on the stump represents the total 

 age of the portion of the tree above the stump cut. Obviously 

 a tree two hundred years old would have that number of rings 

 at its base, but it would have only one ring at the very tip for 

 the growth made the last year. Since the first ring is made by 

 the leader, the number of rings in any section of the tree 

 represents the number of years since the leader reached that 

 point. Each section cut from the base up has, therefore, a 

 diminishing number of rings. This difference in age at various 

 sections is the number of years required by the tree to grow 

 the distance between the sections. By cutting felled trees into 

 sections it is possible to read the record of their height growth. 



4. Volume Growth. 



To compute the mean annual growth of a tree after the volume 

 and age are obtained, one divides the volume by the total age. 

 The figures below, which are actual measurements of a few 

 trees of different species, illustrate this method. 



Species. 



Total 

 volume, 

 cubic feet. 



Total 



volume, 



board feet. 



Age, 

 years. 



Mean annual growth. 



cubic feet, board feet 



White pine 

 White pine 

 White pine 

 Hemlock. . 

 Hemlock. . 

 Hemlock. . 

 Beech 



48 

 32 

 72 

 370 

 552 

 480 

 225 



40 



44 



314 



294 



255 



1. 14 

 .80 

 1.60 

 1. 16 

 1.90 

 I 5° 

 1. 00 



In the life of most trees, there are periods of slow growth due 

 to suppression by neighboring trees, or to other causes. For 

 this reason the mean annual growth is always low. Foresters 

 sometimes speak of the economic age of a tree as referring to 

 that part of the tree's life during which it made a normal 

 growth. 



