176 PRINCIPLES OF WORKING PLANS. 



If a forest is to yield a return, either annually or periodi- 

 cally, it must be in a certain state. In order to determine 

 what this state should be under a given set of conditions, it is 

 useful to construct an ideal pattern in a simple form, which is 

 uninfluenced by external interfering circumstances. Such an 

 ideal state differs, of course, for every different method of 

 treatment, in accordance with the objects at which the manage- 

 ment aims. In all these cases a forest which corresponds in 

 every way to the objects of management is called a normal 

 forest. It enables the forester to study the laws which must 

 govern the management, and it serves as an ideal to be aimed 

 at, though it may never be altogether reached, and at any rate 

 not permanently maintained. 



The normal state of a forest, under a given set of conditions, 

 depends chiefly on the presence in it of : 



(1) A normal increment. 



(2) A normal distribution of the age classes. 

 (8) A normal growing stock. 



By normal increment is understood that which is possible, 

 given a certain locality, species and rotation. An abnormal 

 increment may be caused by faulty formation, faulty treatment, 

 injurious external influences, and also by a preponderance of 

 certain age classes. 



By a normal distribution of age classes is understood a 

 series of age gradations, so arranged that at all times when 

 cuttings are to be made, woods of the normal age are available 

 in such a position that no obstacles to their cutting exist. 



The normal growing stock is that which is present in a forest 

 in which the age gradations are arranged normally, and show 

 the normal increment. It can, however, also be present (in 

 quantity) in an abnormal forest, if the deficiency of some 

 woods is made good by a surplus in others. 



For the strictly annual working and the clear cutting system 

 a forest is, therefore, normal, if it consists of a series of 

 fully stocked woods equal in number to the number of years 

 in the rotation, so that each year a wood of the normal age 



