124 THE THEORY AND PRACTICE OF WORKING PLANS 



(c) Value and Application. — This is an adaptation of Hartig's 

 volume — period method (see method No. 17, Var. II) but greatly 

 simplified. Some of the disadvantages of the period methods 

 adhere to it, but it has the following substantial advantages: 

 The commercial factors of demand and markets, as well as 

 the conditions of the stand, can be given full weight in fixing 

 the limits of the annual cut, actual increment is fully recog- 

 nized, and sustained yield is assured by recognition of the 

 amount and relation of the actual age classes. 



It is applicable to even-aged forests and to those uneven- 

 aged by groups of even age. It is not suited for the true selec- 

 tion forest unless a satisfactory yield table, based on age and 

 area, can be made. 



REVIEW OF THE METHODS OF DETERMINING THE CUT 



No single one of the methods described above will be 

 adapted to all varieties of conditions. The choice of method 

 depends: i, on the intensity of management possible; 2, the 

 kind of forest, and 3, the silvicultural method adopted. In the 

 light of these considerations, the methods may be valued as 

 follows : 



Method No. i is chiefly adapted to coppice and coppice 

 with standards. It is also useful as an area check on calculations 

 by volume alone. 



Methods Nos. 2 and 3 for provisional determination of the 

 cut under rough conditions, and as a check on other methods. 



Method No. 4 for selection forest. 



Methods Nos. 5-9 {" formula methods "): Of these all but 

 No. 9 are restricted to rough calculations in irregular stands 

 and as checks on other methods. No. 9 (Heyer's formula) 

 finds a wide application in uneven-aged, virgin stands when 

 supplemented by a careful cutting plan. 



Method No. 10 is adapted to high diameter limits and long 

 rotations. 



Method No. 11 is adapted to mixed tropical forests where 

 only one or two of the many species are merchantable. 



