17 



first two rows on the south and west edges of the belts should consist 

 of Russian mulberry or Osage orange, the third and fourth rows of 

 Chinese arborvitsa, the fifth and sixth rows of black locust, the 

 seventh and eighth rows of green ash, the ninth and tenth rows of 

 white elm, and the remaining three rows of honey locust or common 

 Cottonwood. 



In southern California, where the damaging winds come from oppo- 

 site points of the compass (from both the southwest and northeast), 

 a good plan for a windbreak is one in which the tallest, most flexible 

 trees will be in the center rows, so that the species on either side will 

 slope downward toward the outside edges of the belt. For such a 

 windbreak 2J rods wide and consisting of 7 rows of trees, the follow- 

 ing arrangement may be suggested : The three rows in the middle of 

 the belt should be of blue gum {Eucdlyftua globulus) , the next row 

 toward the outside on each side should be of Monterey pine {Pinus 

 radiata), and the two rows occupying the two edges of the belt should 

 be of Monterey cypress ( Gupressus macrocarpa) . This same arrange- 

 ment may be used on a belt 5 rods wide by doubling the number of 

 rows of pine and cypress and increasing the gum to five rows. In 

 order to construct a windbreak in California that will be perfectly 

 effective, the belts should be placed on all four sides of the area which 

 is to be protected. This is illustrated by the farmstead on the north- 

 west quarter of the section shown in fig. 2. 



The belts advised in the model plan are of sufficient width to pro- 

 duce all the timber that will be needed on a farm of 160 acres, while 

 the fields are sufficiently narrow to be protected from winds by the 

 single lines of trees occupying the fence rows. Experiments have 

 demonstrated that a windbreak, on level land, will be effective for a 

 distance of at least ten times its height. For perfect px'otection on 

 the model farms herein described, the trees in the windbreak must 

 teach a height of at least 60 feet. 



An objection to growing trees along fence lines has been made by 

 farmers on the ground that such trees steal the soil nourishment from 

 the crops which are on the edges of the fields. It is true that healthy, 

 vigorous trees make great demands on the soil moisture in their imme- 

 diate vicinity, but wherever their influence is felt as windbreaks they 

 Conserve enough moisture, by preventing rapid evaporation, to more 

 than pay for all that they use. By planting a deep-rooted crop like 

 alfalfa under the shade of the fence-line trees, good returns from the 

 land may be secured in spite of the fact that the trees absorb a part of 

 its moisture. It is a great mistake to begrudge a useful tree the space 

 it occupies, and particularly so in the naturally treeless prairies of the 

 Middle West. 



228 



