170 THE FOUNDATIONS OF FOREST MANAGEMENT. 



The major produce of forests, wood, is one of the mdispens- 

 able articles of life, but it is bulky and not adapted for a long 

 transport by land. Hence, it must in many cases be produced 

 locally. To this must be added, that long periods of time 

 elapse between the planting and harvesting of woods. Both 

 these matters make it desirable, that the yield of forests should 

 be continuous and brought into the market in annually equal 

 or approximately equal quantities, necessitating a management 

 based upon the principle of a sustained yield. 



Generally speaking, a " sustained yield " is secured, if 

 all areas, which have been cleared, are re-stocked within a 

 reasonable time and the young woods, which spring up, 

 properly tended, so that the soil continues to produce crops 

 of wood. At the same time, a distinction must be made 

 between — 



(1.) The intermittent working, if the successive final returns 

 are separated by a varying number of years. 



(2.) The annual working, if final cuttings occur in each year. 

 If the latter are approximately equal in quantity year 

 by year, the method is called the " equalised annual 

 working." 



The regulation of the yield of forests worked intermittently 

 is very simple. It is only necessary to ascertain the most 

 suitable rotation, taking into consideration the objects of 

 management and to make the intermediate cuttings, whenever 

 they are necessary. The matter becomes more difficult, 

 when an annually equal yield is expected. 



Although the method of annual working, and especially of 

 the equalised annual working, is not an absolute necessity, 

 still it is in the majority of cases highly desirable, more espe- 

 cially where extensive areas are under treatment, or where a 

 steady market has to be regularly satisfied. Moreover, it has 

 considerable advantages, of which the following may be 

 mentioned : — 



(1.) It is best adapted to meet the requirements of the market 

 and therefore favours the development of a regular 



