194- A MANUAL OF FORESTRY. 



lateral shelter for the young growth, while the old trees 

 give vertical shelter. 



In all these cases it is essential that the edges of the 

 wood towards the side whence cold winds blow should 

 always be kept as dense as possible. 



What has been said above applies not only to frost, 

 but also to drought, more especially in tropical climates, 

 where hot, dry winds may be even more disastrous than 

 cold winds are in higher latitudes. 



d. Weeds. 



In the case of the shelter-wood systems, under regular 

 and successful management, noxious weeds are kept suffi- 

 ciently in check to enable the young tree-growth to 

 make its way up through them. If this is not the case, 

 and in the cultivation of cleared areas, noxious weeds 

 must be removed wherever they threaten to choke the 

 young plants, until the latter have reached a sufficient 

 height to hold their own. Heather, Broom, Brambles, 

 climbing plants, etc., may become even more dangerous 

 than ordinary grasses and weeds. 



In considering the degree to which noxious plants 

 require to be cleared away, it must be remembered that 

 in moderation they may act beneficially, by sheltering 

 the very young trees ; hence interference is not called 

 for until they actually threaten tree growth. 



e. Insects and Fungi. 



These form standing dangers to woods throughout 

 life, especially where coniferous trees are grown over 

 extensive areas. The measures which should be adopted 



