Canadian Forestry Journal, June, 1920. 



281 



A cure for prairie baldness: An inviting bunimer home near Winnipeg, amply shaded with trees and 



protected against prairie winds. 



tection to building^s or crops may be 

 called a windbreak. This article has 

 to do, however, only with belts of trees 

 planted about fields and farm build- 

 ings, especially for the purpose of 

 breaking the force of the wind. The 

 typical windbreak is a belt consisting 

 of from six to eight rows of trees and 

 usually from a quarter of a mile to a 

 mile in length. 



CHECKING WIND MOVEMENT 

 The influence of a timber wind- 

 break upon air currents is purely me- 

 chanical. Its effectiveness depends, 

 therefore, upon how nearly impene- 

 trable it is. The ordinary windbreak 

 does not provide an absolute barrier to 

 the wind ; a certain amount of air for- 

 ces its way between the branches and 

 foliage of the trees, so that the move- 

 ment of the air on the leeward side 

 is not completely stopped but only 

 greatly reduced. When windbreaks 

 composed of such trees as cottonwood 

 become old, wide openings are left 

 between tlu- bare trunks and more 

 wind gets through near the ground 

 than higher uj). Such windbreaks can 

 be made efficient only by underplant- 

 ing the cottonwood with other trees 

 or shrubs. 



An ideal windbreak for checking 

 wind currents would have the con- 



tour of an earth dam. In the central 

 rows would be planted the tallest trees, 

 Such a windbreak would not be easily 

 penetrated, and its inclined surface 

 would divert the air currents upward 

 and relieve the horizontal wind pres- 

 sure. 



Breaking the mechanical force of 

 the wind benefits the farmer most 

 directly by protecting his grain crops 

 and his orchard. The value of the 

 windbreak in giving this protection is, 

 of course, difficult to measure in dol- 

 lars and cents, but where winds are 

 at all frequent such protection ah^ne 

 may be equal to the rental of the 

 grovmd occupied by the trees. In one 

 case in southern Minnesota a wind- 

 break, 80 rods long and abtuit 28 feet 

 high along the side ^U' a cornfield, 

 afforded complete i^rotection for a 

 strip about 10 rods wide during a wind 

 blowing at 50 miles an hour. On the 

 unprotected part o{ the field the wind 

 blew down half the corn and bent the 

 remainder halfway, the damage be- 

 ginning at the edge o{ tlie 10-rod strip 

 and increasing until it was greatest in 

 that part of the field farthest from the 

 windbreak. The corn was in the milk 

 stage at the time of the high wind 

 and did not produce more than a third 



