Establishment and Tending of Timber Plantations 161 



distance of a few yards under the trees on either side of internal 

 belts or roads to prevent ground fires crossing. 



Burning operations should take place at the time of the day 

 when the vegetation is in its least inflammable condition, usually 

 after sunset or before sunrise, and when high winds are absent. 

 Burning should always proceed against the direction of the wind. 



Provided sufficient labour is available and there is an absence of 

 high velocity winds, most grass fires can be extinguished with the 

 aid of wet sacking or green branches of trees. 



A comprehensive system of good roads and paths is necessary 

 to facilitate rapid movement of men during an outbreak or when 

 one is threatened, but there always remains the danger that the 

 human element is liable to fail at the most critical moment. 



5. Thinning. 



Under the heading " Espacement " we saw how the struggle 

 for existence set in soon after the canopy had closed and that 

 thinning became necessary shortly thereafter. Mr. Carlson has 

 treated this very important forestal operation in such a clear 

 manner that I cannot do better than quote from him again. " Hav- 

 ing secured 'forest conditions', the forester's attention is next 

 concentrated on maintaining what is known as a ' normal stand ' 

 throughout the remainder of the rotation. By *normal stand'* 

 is understood that particular density which, without sacrificing 

 ' forest conditions ', will maintain normally vigorous growth in the 

 best stems. Everything depends on maintaining this density. A 

 too open stand is exposed to the dangers of understocking, and 

 if too dense, loss of increment takes place. As the stand de- 

 velops the correct density is maintained by a process of thinning 

 whereby espacement is constantly increased and the number of 

 stems to the acre reduced. This operation is of the utmost im- 

 portance and demands great skill and experience. The lungs and 



*The term is generally defined as a stand fully stocked for 

 the particular treatment which is being given to it. Mr. Carlson 

 here confines his definition to the subject he is dealing with riz., 

 '• The Growing of Mine Props on the High Veld ". 



