PETAWAWA EXPERIMENT FOREST STATION. 173 



The thinning from under is a German method. During the 

 eighteenth century and the first half of the nineteenth century, 

 cleanings and light thinning from under were the only methods 

 which were considered advisable, and only in the latter part of 

 the last century did advocates of "heavier thinnings" from 

 under appear. The protection of the ground by preserving 

 suppressed trees with healthy crowns was first advocated by 

 V. Salisc and Kraft. Kraft's system therefore approaches a 

 light crown thinning. 



In France, on the other hand, a system of light crown thinning 

 has been practised for a long time. As early as about 1550, 

 Tristan de Rostaing ordered thinnings among the dominating 

 tree-classes. 



The present French system of thinning from above {eclaircie 

 par le haut) was first mentioned by Varenne de Fenille in the 

 latter part of the eighteenth century. 



Independently of the two different French and German 

 methods, Denmark introduced a more free, economical and 

 ground-protecting method of thinning, which bore a certain 

 resemblance to the French method. 



The two main systems — " thinning from under or low thinning " 

 and thinning from above or "crown thinning" — were both included 

 in the programme of the International Federation of Forest 

 Experiment Stations in 1903. The system of heavy low thinning 

 was then made less rigid by permitting the removal of fast- 

 growing trees with large branches and "wolf trees." 



In Sweden a light low thinning was for many years considered 

 as the only satisfactory system. Only a few of the best-managed 

 private estates practised a heavy low thinning. Of late years, 

 however, an interest in heavier low thinning as well as crown 

 thinning has been awakened. This is especially due to the 

 efforts of Wallmo, Barthels, and Ernst Anderson. 



The crown thinnings are most suitable in mixed coniferous 

 stands and in uneven-aged stands, low thinnings give the best 

 results in pure and even-aged stands. 



