GROWTH OF TREES AND FORESTS 1 79 



2. Diameter Growth. 



The only accurate method of determining the diameter growth 

 of a stand is to measure carefully all the trees in a stand, mark 

 the points at which the measurements are taken, and remeasure 

 after a series of years. Usually, for accurate purposes of this 

 kind, the circumferences are measured and the diameter growth 

 calculated from the growth in circumference. This, of course, 

 is impracticable for immediate purposes. Fairly accurate data 

 may be obtained from the mean sample tree or tree of average 

 diameter. If the growth for the whole life of the stand is desired, 

 the sample tree is felled and the rings counted and measured; 

 but if the growth for the past few years only is required, a gash 

 can be cut in an inch or so and the radial growth measured. 

 The measurements from this sample tree are considered as 

 representing the diameter growth of the average tree in the 

 stand. Care must be taken that the average tree is normal in 

 other respects as well as diameter. 



3. Height Growth. 



The height growth of a second-growth pine forest can easily 

 be obtained by counting the whorls of branches of a few average 

 trees. With other species it is necessary to cut and measure 

 a few trees of average height. 



4. Volume Growth. 



One of the simplest methods of determining the volume growth 

 of a stand is to obtain the growth per cent of a mean sample 

 tree, that is, a tree of average size, and apply this per cent to the 

 total estimated volume of the stand. Thus, if the sample 

 tree is growing at the rate of 4 per cent and the total volume 

 of the stand per acre is 20 cords, the growth of the stand may be 

 considered as .8 of a cord per acre. 



Often the mean annual growth of a stand is found and used 

 as a basis for predicting the future growth. To secure this the 

 stand is carefully estimated, and the total volume divided by 



