94 FORESTRY 



ing ought to be done in a thoroughly efficient manner, even 

 should apparently expensive methods have to be adopted. 



Protection Against Atmospheric Influences 



The forest is exposed to many dangers difficult to combat, 

 but in respect to none is it more defenceless than against the 

 natural phenomena of storm, snow, frost, and drought. Yet 

 even in resistance to these, man has devised certain precau- 

 tionary measures, which, while they are not able at all times 

 to prevent damage being done, can frequently obviate it to 

 a considerable extent. 



Storms. Windstorms may affect quite a limited area, 

 cutting out belts or strips of trees, very often only thirty or 

 forty yards in breadth, and leaving the rest of the forest 

 practically untouched ; or they may be of more general dis- 

 tribution. The former are erratic in the direction that they 

 take ; but the latter, in the west and centre of Europe, with 

 very few exceptions, come from the west, south-west, or 

 north-west. It is when gales follow immediately upon heavy 

 rains that have saturated the soil with water that they prove 

 most destructive, for the soft ground is then least able to 

 afford the roots support. The direct damage caused by high 

 wind consists in trees being " thrown," or uprooted, and in 

 stems being broken or snapped over at some height above the 

 surface of the ground. The latter form occasions the greater 

 loss, because the timber suffers more. 



Against winds of tornado force there is no protection, and 

 it is fortunate that these are of extremely rare occurrence in 

 temperate climes. But to mitigate or to avoid calamity from 

 strong winds and gales, some precautionary measures are 

 adopted. A forest can be made more storm-firm by mixing 

 shallow-rooted with deep-rooted species ; trees are better 

 able to resist wind if regular and fairly heavy thinnings be 

 made, or direct shelter may be provided. A belt of trees 

 the fringe of a previous wood may be left on the sides from 

 which there is most fear of damage by storm. Such trees 



