28 FORESTRY 



density of the timber crop, does not generally appear till 

 middle age is attained. In early youth all species, even 

 the most light-demanding, can tolerate a certain amount of 

 shade.. Plants in their first stages of growth are always 

 grateful for some protection against great heat, and the over- 

 rapid loss of warmth by radiation. Shade and shelter may 

 in this case be considered together. In the later life of our 

 forest trees there is no call for protection. A plentiful supply 

 of light then acts favourably upon the growth of all species. 

 The foliage becomes more luxuriant, the process of assimila- 

 tion is stimulated to greater activity, and an increased pro- 

 duction of wood results. With an accession of light, seed 

 production is encouraged, but takes place at the expense of 

 wood increment. 



Thus it is that man has it in his power to accelerate the 

 processes of timber or seed production as he will, and advan- 

 tage is taken of this fact in forest practice. 



The forester thins out the material which interferes with 

 the objects of his management. The result of his operations 

 is not equally marked with all species, nor, indeed, with all 

 trees of the same kind in one wood. Species like the Scots 

 Pine and Birch, which tend naturally to form thin, open 

 woods, when given more light and space, respond in growth 

 less quickly than do the shade-bearers. In all woods there 

 are found individual trees with their crowns so raised above 

 those of their neighbours that they are practically indepen- 

 dent of man's assistance. These are the so-called dominant 

 trees. On the other hand, there are stems already so hope- 

 lessly crippled and suppressed that interference on their 

 behalf would be useless. The class which really can take 

 advantage of a more free position is -that formed by actively 

 growing average trees. These have the power through 

 crown, root, and stem quickly and energetically to increase 

 in size. The behaviour in regard to light is to some 

 extent influenced by age, and the condition of the locality in 

 which the wood is situated. The better the situation the 

 more shade are the species able to bear. 



