224 A MANUAL OF FOKESTRY. 



a. Isolation of a few Selected Trees, without Underwood. 



A limited number of selected trees are placed in a 

 free position, by removing all surrounding trees which 

 threaten to interfere with them. The system should 

 only be applied in case the main part of the wood con- 

 sists .of a species with full crowns, and where the 

 selected trees are of quicker height-growth than the 

 rest. 



To avoid loss of height-growth and the retention of 

 low side branches, the operation should not be com- 

 menced until towards the end of the period of principal 

 height-growth. 



The treatment is specially adapted to mixed woods of 

 Beech, and light-demanding broad-leaved species, such 

 as Oak, Ash, and Elm. 



b. Prolongation of the Regeneration Period under the 

 Shelter-wood Systems. 



Woods treated under artificial or natural regeneration 

 under a shelter-wood offer excellent opportunities for 

 the realization of the extra increment due to an isolated 

 position of a limited number of trees. In the same 

 degree as the shelter-wood is thinned out by successive 

 cuttings, the remaining trees profit by accelerated incre- 

 ment ; the process can be further extended by retaining 

 a limited number of trees for an extra term of years, or 

 by prolonging the regeneration period. 



The method is specially adapted to thin-crowned, 

 wind-firm trees. Shallow-rooted trees are likely to be 

 thrown by wind, while the injurious effect of close- 



