FORESTRY 1 2 99 



found for the " expectation value of the soil ". As valuation of the forest 

 and management should correspond in their results, the writer reconmiends 

 the abandonment of the theor}' of " expectation values " in favour of an- 

 other method of calculation. 



(3n the method here advocated only the present exchang'^ values (com- 

 mon values) of the plants have any influence on the result, and the method 

 is termed " method of the exchange values ". It gives much m.ore reliable 

 results, although the values are only approximate and depend on the laws 

 of supply and demand. 



The value of the soil on which the stands grow does not in an}' way form 

 a standard of guidance as regards the most judicious mode of working, and 

 consequently cannot be taken into account in this question. The value of 

 the initial material alone plaj's a decisive part in the installation of the fo- 

 rest management, because it is the fluctuations in this material which give 

 rise to those in the annual growth of the stand. Tabulation of the annual 

 increment (tables of return) is the best basis on which to decide as to the 

 method of working to adopt. These results ma}- serve as a reliable basis 

 with a \dew to the management of the forest. 



The science of forest management should furnish guidance as to 

 the course to be pursued in determining the initial material, and the average 

 annual growth. According to the writer, the determination of the \-alue 

 of the standing timber and growth should not be effected by measurement, 

 it being sufficient to calculate these values by the aid of properly compiled 

 tables. When the average figure representing the total annual growth of 

 workable wood, and also of secondary material and underwood, has been 

 determined by means of the tables of yield, and it has been ascertained that 

 this total growth can be utilised uninterruptedly without diminution in the 

 initial material, the task of practical management of the forest is solved. The 

 writer already demonstrated in 1888 and 1889, by means of an example of 

 average annual yield expressed in money, that the determination of this 

 value is practicable. It need hardly be said that the same mathematical 

 demonstration may be effected where yields by volume are in question in- 

 stead of money yields. 



The utilisation of the tables of yield by volume allows, by .simple 

 calculation, of determining the necessary bases for the management of 

 the forest. First there are calculated the total annual yields of workable 

 wood as well as secondary material and underwood then the material re- 

 quired for the durable working of these annual yields, and tinalK" the eco- 

 nomic age. 



If the period of rotation to be selected is designated by x, and if Zx de- 

 notes the total annual growth per acre of workable wood, secondary ma- 

 terial and underwood corresponding to such period, and Mx the normal nia- 



Zx X X 



terial of workable forest and underwood per acre, the equation Mx = 



is obtained. All the oldest plants in a class of management for which the 

 period x must be maintained, must be deemed workable in view of the fact 

 that their felling yield exceeds the mininuun amount ; all the youngest 



