268 THE PLAINS SHELTERBELT PROJECT 



mile of 640 acres. The width of shelterbelts will be at least 100 feet 

 if the planting is to be effective. A strip 8 rods or 132 feet wide will be 

 obtained by purchase or lease from the landowner and fenced against 

 stock of all kinds, the extra space being needed for extension of roads 

 and the overhanging branches of trees. Roadways will extend inside 

 the fences, and sandtraps will be used to protect the young trees. 



Planting strips will not always follow the same direction or plan. 

 Shelterbelts may also be planted along section lines where they will 

 not interfere with road development. A straight-line planting gives 

 protection in only one direction. In the northern part of the zone, 

 protection will be maintained from the northwesterly winds which 

 blow constantly during the winter and early spring. In the south, 

 however, south winds are much more prevalent, frequent, and de- 

 structive, and east-west belts will be established in that section. 



General Planting Arrangements and Trees to be Used. Trees are 

 planted close together in order to shade out grass and other sun-loving 

 plants. They are not planted, however, so close as to make cultiva- 

 tion in the early years of development difficult. 



The cost of fencing will be very large. Experience has indicated 

 that when shelterbelts or tree groves are open to stock, they quickly 

 deteriorate, owing to injuries, grazing, etc. The fencing of the shelter- 

 belts and the preparation of the ground prior to planting are the 

 largest sources of local employment. Many farmers are employed for 

 this work. Many variations from the general straight-line planting 

 are used, such as small clumps or groups of trees to furnish needed 

 shade for stock in pastures, larger groves or blocks where picnic 

 grounds or semi-parks are in demand and where the character of the 

 surface and topography indicate a need for protection from soil 

 erosion. The primary purpose, however, is to furnish protection from 

 wind to the largest possible areas. This will promote the conserva- 

 tion of the soil and will produce other economic benefits. Shelter and 

 food will be provided for many types of game and insectivorous birds 

 as well as other forms of animal life. 



The three principal requirements of the shelterbelt are sufficient 

 height, length, and density. The tallest growing trees are placed in the 

 center of the shelterbelts, and closely planted adjoining trees will force 

 them to attain the maximum height growth. The shorter growing 

 trees will be used along the sides, and shrubby growth on the edges. 

 This shape, similar to a hip roof, will tend to guide surface wind 

 currents upward. Evergreens can be used near the edges; retaining 

 their branches near the ground they give greater assurance for the 

 upward sweep of the winds and provide protection during both winter 



