172 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



" Thinnings from above," 



French (eclaircie par le haut). 

 German (hochdurch-forstung). 

 Swedish (krongalling). 



1. " Light crown thinning." 



Removal of tree-classes (/) and (g) in all groups, tree- 

 classes (d) to (e) in group II., and (c) to {e) of 

 group I. 



2. " Heavy crown thinning." 



Removal of tree-classes (i/) to (g) in groups I. and II. 



3. " Very heavy crown thinning." 



Removal of tree-classes (/) to (g) in groups I. and 

 II., and in addition a few trees of tree-class (a) 

 when the stand is dense. 



In " Thinning from above," it is also permissible to remove 

 all or a portion of the trees in tree-classes (^) to (e) in groups 

 III. and IV., so long as a sufficient number of well-formed 

 trees are left for the protection of the ground. 



In mixed coniferous forests where it is advisable to maintain 

 the undergrowth and perhaps the "understand" of suppressed 

 trees, the two systems, "Thinning from above" and "Thinning 

 from under," meet more or less. 



This classification is considered best adapted to thinnings in 

 pure pine or spruce forests. In mixed forests, Heck's system 

 (free thinning) is often the most practical one. 



According to Heck the thinning should cover all tree-classes, 

 each tree being yW^^^ as to its value in the stand. The object 

 of the system is to favour the best trees through their isolation 

 in the dominant stand. 



The system of classification described above may be, however, 

 used to great advantage in recording the removal of trees at the 

 thinning. 



The progress on the question of thinnings in Europe may be 

 summed up as follows : — 



Different main systems have been established and developed 

 independently of each other in various European countries. It 

 is only in later years that these systems have been made 

 generally known outside the boundaries of the country of their 

 origin, and more or less amalgamated with systems in use in 

 other countries. 



