196 A MANUAL OF FORESTRY 



is cut over annually. A knowledge of the growth of the different 

 stands is essential for the Baden system. In our own country, 

 forestry which aims at a permanent income must rest on this 

 kind of knowledge. 



Just as we have considered the growth in diameter, height 

 and volume of individual trees, so the growth of whole stands 

 should be discussed under similar headings. 



i. Age of Stands. 



The age of a stand is usually considered to coincide with the 

 age of the tree of average size in the stand. Such a tree is 

 selected and its age ascertained as already described. This 

 result is taken as the average age of the stand. Such a figure 

 has more value in even-aged than in uneven-aged stands. 



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 



