THE NOKMAL FOREST. 49 



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 preponderance of certain age 

 classes. 



By a normal distribution of age classes is understood a series of 

 gradations, so arranged that at all times when cuttings are to be 

 made, woods of the required 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 mature age can be cut, and the returns 

 are equal, at any rate in quantity if not in value. 21 



It is a sine qua non of forestry that regeneration must follow the Normal 

 fellings and by normal regeneration is understood young growth regenera- 

 of sufficient quantity to ensure a normal series of age classes 

 and consequently a future normal yield. In a forest managed 

 under the system of clear felling and planting with a rotation 

 of 100 years jogth of the area is cut every year and immediately 

 planted up. In the shelterwood system it is essential that the 

 regeneration area be regenerated in the specified period and that 

 the progress of regeneration should keep pace with the progress of 

 the fellings, otherwise the whole structure of the working plan 

 falls to pieces. In selection forests regeneration is supposed 

 to be in progress everywhere and it is exceedingly difficult to 

 say whether normal regeneration is being obtained. It is only 

 by intensive management and frequent revisions of working 



!1 Manual of Forestry. Volume III. SCHLICH. 



4 



