Forest Influences 319 



windbreak and the physical obstacle presented would 

 counterbalance the superheating of the intervening 

 space. These same groves and shelter belts that prevent 

 evaporation and drying winds also perform several 

 other important functions. They prevent the drifting 

 of the sand and snow. This property of shelter belts 

 has been almost completely ignored in this country but 

 has been recognized in Europe for many years. In France, 

 plantations have been used to check and successfully keep 

 in place the enormous sand dunes which were and in some 

 places still are, traveling inland from the coast. The root 

 systems help to hold the sand in place and the upper parts 

 of the tree reduce the force of the wind. On the steppes 

 of Russia, where the tremendous sweep of the wind lays 

 bare the winter crops over large areas, and piles the snow in 

 great drifts where it is not wanted, low windbreaks have 

 been used very effectively to keep the snow in place. 

 It will not be long before such simple and natural devices 

 will take the place of the expensive snow breaks now built 

 by the railroads. 



Neither sand nor snow drifts in the forest and we should 

 learn our lesson from nature. Moreover, the absence of 

 strong winds in the interior of a forest makes it appear 

 very probable that the planting of breaks and groves at 

 short intervals would prevent the formation of tornadoes on 

 the opeii prairie, 7 for these violent windstorms soon lose 

 their force when they enter the forest. 



Another factor of forest influence well worth noticing 

 is the improvement of the soil on which trees grow. Large 

 amounts of soluble mineral salts are added to the surface 

 soil by the falling of leaves and small twigs, which decay 



