VOLUME I!s 7 CREMENT OF SINGLE TREES. 



83 



The breadth of n rings is ascertained at regular intervals, and 

 the difference between the present volume and that n years 

 ago calculated. 



The investigation of the progress of increment throughout 

 the life of a tree is called a stem analysis. It consists of a 

 combination of a height and a diameter analysis. 



The tree having been divided into a suitable number of 

 sections, each is cut through in the middle, the number of 

 concentric rings counted on the basal area, and the size of 

 the diameter at the several ages measured. The measurements 

 are best plotted, so that a representation of a longitudinal 

 section through the tree is obtained. For this purpose the 

 heights of the several cross sections from the ground are 

 marked on a vertical line, which represents the axis of the stem ; 

 also the heights which the tree had obtained at successive 

 periods of its life. Next the radii of each cross section are 

 marked on horizontal lines, and the points thus obtained con- 

 nected by a series of lines, which represent the stem curves of 

 the several stages during the life of the tree. From the data 

 thus obtained the increment throughout the several periods of 

 the life of the tree can be calculated. As the thickness of the 

 bark at former periods cannot be ascertained, these investiga- 

 tions can only refer to the increment in wood, exclusive of bark. 



The following example will explain the procedure : 



Analysis of a Scotch Pine Tree. 



The tree was cut up into nine pieces, which gave the 

 following cross sections : 



Section I. taken at foot of tree 



showing 97 concentric rings. 



G 2 



