-54 STATE BOARD OF FORESTRY 



necessarily of the locality where the forests are destroyed, but of the 

 drier regions into which the air currents flow. 



While they have a marked influence upon local precipitation, 

 the influence of forests in the mountains upon the humidity of regions 

 lying to the leeward on the whole is not very great. 



FORESTS AND STREAMFLOW. 



The effect of forests upon streamflow in level countries differs from 

 that of forests in hilly or mountainous regions. 



In a level country where there is no surface runoff, forests, in 

 common with other vegetation, act as drainers of the soil. Hence the 

 importance in draining the marshy lands and improving hygienic 

 conditions. In such countries the effect upon streams is unimportant. 



In the plains and in level country the forest : 



(1) Constitutes a-n effective means of draining and drying up 

 swampy lands, the breeding places of malaria, and swamp fevers. 

 The reforestation of the Landes, Sologne, the Pontine marshes, and a 

 hundred other examples prove this. 



(2) Draws moisture from a greater depth than does any other 

 plant organism, thus affecting the unutilized water of the lower 

 horizontal strata by bringing it again into the general circulation of 

 water in the atmosphere and making it available for vegetation. 



(3) Lowers to some extent the subterranean water level, but it 

 has no injurious effect upon springs, since these are practically 

 lacking in the level countries with horizontal geological strata, where 

 its lowering influence has been chiefly noted. 



(4) Refreshes the air above it and increases the condensation of 

 moisture carried by the winds, thus increasing the frequency of 

 rains during the vegetative season. 



In hilly and mountainous country forests are conservers of water 

 for streamflow. 



In the mountains the forests break the violence of rain, retard 

 the melting of snow, increase the absorptive capacity of the soil 



