THE MANAGEMENT OF PLANTATIONS. 



49 



combined. As the production of the greatest number of well- 

 formed boles is the aim in view, we must see that these have 

 sufficient head room necessary for crown formation, otherwise 

 the breadth of the wood-ring and the resulting increment of 

 timber will decrease. This may necessitate the removal of a 

 certain number of the smallest and least promising trees, for at 

 this, as at all previous stages, variations in the size of the trees 

 will occur. Now it has been proved by careful measurements 

 that thinning after height -growth has terminated does not 

 increase the total yield of timber at the final cutting, but affects 

 the size and quality of individual trees only. Therefore, if the 

 greatest number of cubic feet per acre is the main object, inde- 

 pendent of quality and size of timber, it makes little difference 

 whether we thin at this stage or not, as, although the trees will 

 be smaller, there will be a greater number of them to the acre, 

 and the balance will thus be restored. But in most cases we 

 shall find that the additional value possessed by the thinned 

 crop over that of the unthinned will make it worth our while to 

 produce the former. And another advantage in thinning lies in 

 the fact that we are able to realise a portion of the crop earlier 

 than by waiting until the whole is ripe. Under these circum- 

 stances, therefore, we should advise a judicious and moderate 

 thinning, to begin as soon as it becomes evident that the larger 

 trees no longer add appreciably to their height, as this is a sign 

 that permanent crown formation is ready to begin. This thin- 

 ning should be so regulated as to prevent sun and wind from 

 affecting the stems of the trees, or drying up and hardening the 

 soil surface, and should merely keep pace with the growth and 

 requirements of the trees until it is no longer required. It 

 should not, on the other hand, be delayed until the growth of 

 the trees has been checked, as when this has occurred they do 

 not in all cases recover when the cause has been removed. 



The effect of this thinning upon the remaining trees will be 

 to maintain the annual wood-ring at its proper breadth, instead of 

 allowing it to decrease too rapidly, as is usually the case where 

 the trees stand thickly together. This matter is still engaging 

 the attention of Prussian foresters, by whom investigations on 

 the growth of various forest-trees under sylvicultural treatment 

 have been carried on for more than twenty years. The princi- 

 pal conclusions arrived at with regard to those species already 



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