DAMAGE CAUSED BY AERIAL CUKRENTS. 37 



become an easier prey to the violence of the storm than is the 

 case with high forest in which close canopy is maintained till the 

 end of the period of rotation, and reproduction takes place only 

 after the annual total clearance of the mature crop.- 



Besides the density of the canopy formed, the general growth of 

 the trees is also of importance, as length of bole of course increases 

 the danger of being thrown, on account of the leverage afforded by 

 the stem, whilst this is diminished by shortness of bole. Sturdy 

 stems that have been allowed to develop in comparatively free 

 enjoyment of light and air are little exposed to danger, whilst 

 such as have been drawn up rapidly in close canopy, and then 

 suddenly admitted to the enjoyment of a greater amount of light 

 and air, are most liable to suffer. Sickly stems affected with red 

 rot, or perhaps damaged through former tapping of resin, or through 

 stripping of the bark by red-deer, are very apt to break at the 

 injured part. 



Soil and Situation are also factors of essential importance, as 

 localities exposed to storms suffer in a far greater degree than such 

 as are protected by hills, ridges, or other timber crops lying to 

 the windward. Shallow, light (sandy or marshy), damp soil in- 

 creases the danger, whilst deep, stiff, stony, and rocky soils diminish 

 it: when damage does however occur, it for obvious reasons 

 mostly takes the form of windfall on the former, and of breakage 

 on the latter. By soaking and softening the soil, rainfall increases 

 the danger, whilst frost lessens it ; and here again windfall will be 

 I the rule in the one case, and breakage in the other. 



24. Preventive Measures. 



Against very violent storms, hurricanes, and the much less 

 I frequent cyclones, no practical preventive measures can be adopted, 

 I as even in sheltered localities, and when forming good uninterrupted 

 : canopy, very great damage can be done to species, like the Beech 

 : for example, which are otherwise well capable of resisting the 

 ; action of strong winds. But, on the other hand, Sylviculture and 

 | the Management of Woodlands furnish us with a variety of practical 

 ! measures, by means of which the damage likely to be done by mode- 

 1 rately violent storms can to a not inconsiderable degree be obviated. 

 Such practical measures are included among the following : 



The Formation of Mixed Forests, in which the species most 



