HOW WINDBREAKS ACT. 13 



The early settlers realized the value* of trees for protection and 

 attained success in tree planting under conditions which at first 

 seemed very unfavorable. First, small groves were planted about the 

 houses and barnyards. Gradually these were extended in the form of 

 belts or single rows to protect the larger areas of orchards and fields. 

 Where the soil was light it was necessary to prevent its drif ting. The 

 farmers soon found also that a windbreak was very useful in pre- 

 venting the drifting of snow. Railroad companies made many desul- 

 tory attempts to protect their tracks by planting belts of trees far 

 enough away to serve as snow traps, but more frequently loose fences 

 were used. 



Orchards must be protected from the mechanical effects of the 

 winds which strike the trees when they are laden with fruit; from 

 their drying effect; which blights the fruit and causes it to shrink; 

 and from the drying or " winterkilling " of the branches. This applies 

 not only to the prairie States but also to the lake States, the fruit 

 region of California, and the Columbia River Valley fruit region. In 

 many sections of Michigan, Wisconsin, Illinois, Maine, and New 

 York, where peach growing was formerly profitable, it is now impos- 

 sible to raise "consistent crops of this fruit because of the increased 

 exposure that has resulted from the removal of the original forests. 



It is necessary to consider also such winter crops as wheat and rye. 

 For the protection of these the windbreak serves the double purpose 

 of causing an even distribution of the protective snow cover and of 

 sheltering the tender plants from the wind itself, once the snow has 

 melted. The protection of all summer crops is important. 



The protection of stock is a matter of no small importance in many 

 of the Western States, where there are large ranches with no more 

 adequate shelter for the cattle than that afforded by a grove of trees. 

 Instances have been recorded where large herds of cattle have passed 

 through a severe winter in the shelter of a cottonwood grove. Such a 

 condition represents a low state of development in the economy of the 

 stock business, but the usefulness of a windbreak for the protection 

 of sheds and winter yards may always be considered. 



HOW WINDBREAKS ACT. 



A windbreak may affect crops or other objects near it only through 

 the agency of the atmosphere or soil. It may furnish protection to 

 man or beast or plant growth only by the interception of air currents 

 and the consequent effect upon wind velocities and air temperatures. 

 It may have both beneficial and detrimental effects upon field crops. 

 In the narrow zone adjacent to a row of trees or to the edge of a 

 grove, the effect of the trees upon field crops is that which results from 

 a vigorous competition between the two classes of plants for the essen- 

 tial elements of growth sunlight and soil moisture. By the inter- 



