PRINCIPAL FORMS OF TREATMENT. 303 



b. Prolongatiiiii of the Ratjeiipratioa Period under the 

 Shelter-wood Systems. 



Woods treated under artificial or natural regeneration under 

 a shelter-wood offer excellent opportunities for the realisation 

 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 increment ; 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. 

 The injurious effect of trees with crowns coming low down 

 upon the young growth must be mitigated by pruning away 

 their lower branches. 



c. lletention of Standards in Hiyh Forest. 



A limited number of the most suitable trees are, after the 

 wood has been regenerated, retained as standards for part or 

 the whole of the second rotation, and in some cases even for 

 a third rotation. Only wind firm species are thoroughly 

 suited for such treatment, and they should moreover be thin 

 crowned. The number of standards depends on the density 

 of their crown and the quality of the soil ; only perfectly 

 healthy well-formed trees should be chosen, especially those 

 which have cleared themselves of branches to some height, to 

 obviate the necessity of pruning. The tending of the proposed 

 standards may usefully be commenced some time before the 

 end of the first rotation, as indicated under a. 



d. Isolation of Trees in Conjunction a-ith an Underwood. 



A wood is uniformly thinned, and an underwood is formed 

 by sowing, planting, natural seeding, or by coppicing a portion 

 of the overwood. Thoroughly satisfactory results are obtained 

 only if the overwood consists of thin crowned and the 



