530 Forestry Quarterly 



more rapid, but the difference between two age classes is found 

 greater than on medium and poor sites. The relative progress of 

 value increment does, however, not stand in direct relation to the 

 site class, but special features of the site, e.g., looseness and depth, 

 temperature and light, rather than the total productivity upon 

 which site classes are based, are influential. 



A few examples of data collected in certain localities for pine 

 have, of course, absolute values (mark per cubic meter) only for 

 the locality and the time of collection, but, nevertheless, show the 

 general tendency which would be of influence everywhere and at 

 any time. 



Site II 



Age: 20 40 60 80 100 120 140 



Good Stands 



Favorable Market 1 4 7 10 13 16 19 



Unfavorable Market . . A 1.4 2.4 3 .Z 5.4 7.4 10.4 



Branchy Stands 



Favorable Market 2.5 6 9 11 12 



Unfavorable Market . . .7 1.6 2.4 3 3.6 



Site IV 



Good Stands 



Favorable 2 4 6 8 10 12 



Unfavorable 7 1.3 1.9 2.9 4.4 6.4 



Branchy Stands 



Favorable 1.5 6 8.5 9 



Unfavorable 9 1.3 1.5 



These are values for wood cut, lying in the forest. Good stands 

 show on good as well as on poor soils a very steady continuous 

 rise in value, while poorly managed branchy stands decline 

 rapidly in old age. 



The difficulties in properly collecting and interpreting such 

 data are then discussed. They lie in the facts, that imiform 

 stands of great age variation are not often cut; that most stands 

 which are cut have been subject to some influence which make 

 them abnormal, Hke damage by rot; lack of satisfactory grading 

 of logs. 



The author then develops a method of arriving at value incre- 

 ment. In using sample trees for determining value increment 

 either the mean tree of the stand may be used or preferably sample 



