Forest Influences 317 



an appreciable influence for at least one rod for every 

 foot in height. 



It may not be necessary to state that the damage done 

 to crops by the cold, dry winter winds is mainly due to 

 rapid evaporation, and that plants are liable to suffer 

 as much by winter drought as by summer drought. 

 This is certain, that since summer and winter drought, 

 that is, rapid evaporation due to continuous dry winds, 

 is the bane of the farmer on the plains, rationally disposed 

 timber belts will do much to increase available water 

 supply by reducing evaporation. 



The exact difference in the rate of evaporation in the 

 forest and in the open country from all causes is not known 

 in this country, but experiments in Bavaria show the 

 rate in the open field to be six and one half times that in a 

 deciduous forest. In this connection we must consider 

 the hot winds that so often cause injury to farm crops 

 in Kansas, Nebraska and the Dakotas. These are often 

 ascribed to the " staked" plains, whence, taking a north- 

 easterly direction, they draw all the moisture from the 

 vegetation with which they come in contact. The view 

 has also been presented that they have their origin on the 

 Pacific coast, ascend the Rocky Mountains, lose their 

 moisture and descend on the eastern slopes. But all 

 theories that ascribe their origin to a distant source are 

 inadequate to explain their phenomena. For example, 

 all who are acquainted with these winds know that they 

 blow only during very dry weather, when the earth is 

 heated very hot, that a good rain speedily brings them 

 to an end, and that they blow only during the day time, 

 commencing about 9 A.M. and continuing until sundown. 



