36 WINDBREAKS. 



TABLE 6. Effect of competition on root extent of cottonwood. 



(7) Coppicing or cutting back $>f hedges. Coppicing does not 

 directly increase the length of roots, but leaves the new shoots to 

 grow with roots of the same length as those possessed by the 

 original trees. In the case of osage orange this is seen to have a 

 very important effect. 



TABLE 7. Effect of coppicing on proportionate root extent. 



The conditions stated above will, singly or collectively, account 

 for the unusual length of roots in almost every instance where they 

 are found to be longer in proportion to the height than is given in 

 Table 4. These conditions should be avoided as far as possible. 



EFFECTS OF SAPPING. 



As already stated, the effect of a lack of moisture in the zone next 

 to the trees will be felt most strongly by plants which begin life 

 anew each year; that is, by annual crops. Frequently seeds will 

 fail to germinate, or the young plants will die from lack of moisture 

 before their roots can be developed. It is believed that the ability 

 of perennial crops, like alfalfa and clover, to grow in the shade of 

 trees is in a large measure due to their extensive roots. 



Orchards. Fruit trees on the edge of the orchard where they 

 must compete with forest trees are usually small in size. Doubtless 

 this is partly due to shading. Even if the trees attain to good 

 bearing the fruit in dry years is likely to be small and of poor color. 

 In California trenches are dug to cut off the roots of eucalypts and 

 other large trees surrounding orchards in order to prevent their 

 taking moisture from the fruit trees. 



