6 SEASIDE TREES AND SHRUBS 



ments conducted at various stations in this and 

 other countries, that both atmospheric and soil 

 temperatures have been raised when trees in 

 quantity have been planted in places which were 

 previously exposed. Even such shelter as that 

 afforded by a single hedge will often cause a 

 rise in temperature of 2 to 3 F. for some con- 

 siderable distance from it. 



Proof of the influence of the foliage of trees 

 upon the humidity of the soil may well be 

 given from the observations of various writers on 

 forestry and arboriculture in the New World. 

 The destruction of the great forests of North 

 America, owing to the onward march of the 

 settler, and the introduction upon a gigantic scale 

 of arable husbandry, have had the effect not only 

 of altering the character of the landscape, but 

 also of diminishing the annual rainfall in those 

 districts, to such an extent that in the drier 

 seasons conditions of drought arise approaching 

 those on the fringes of the great deserts. 



While the total annual transpiration from the 

 surface area exposed by the innumerable leaves 

 of these forests must have been enormous, and 

 the drain upon the soil water in consequence 

 very great, yet the other drying influences which 

 ordinarily come into play in causing the rapid 

 evaporation of water, such as the drying effects 

 of winds, evaporation of water due to direct solar 



