TENDING OP CROWDED WOODS. 215 



should the thinnings follow each other; hence the in- 

 tervals will be comparatively short during the first half 

 of life, and they become longer with advancing age. 

 For the rest, the length of the intervals depends on the 

 species and the soil. 



A frequent repetition of the thinning should not be 

 obviated by thinning too heavily at any particular time ; 

 such a measure would not secure the most favourable 

 development of the dominant .trees. 



In summing up it may be said that, where the object 

 is to produce quantity, the thinnings should commence 

 early, be heavy, and frequently repeated during the first 

 half of the life of a wood, and be more moderate and 

 repeated at longer intervals during the second half. 



b. Production of High-class Timber. 



Where the production of high-class timber is aimed 

 at, quantity must to some extent be sacrificed. Trees 

 fit to yield such timber must answer the following 

 description : 



(1.) The boles must be tall, straight, free of branches, 



and as little tapering as possible. 

 (2.) Differences in the breadth of the concentric rings 



must be slight. 

 (3.) The timber must have a high degree of density. 



Boles free from branches and non-tapering are not 

 produced, if heavy thinnings are made at an early 

 age of the wood ; at any rate not in the same degree 

 as if the wood were kept dense, when the lower 

 branches are more rapidly killed for want of light. 

 Pruning cannot make up for this, though it can do 

 something. 



