CHAPTER XVII 

 WINTER INJURY TO THE ROOTS 



Root killing is very common in sections where winter precipitation 

 is light and it is rather common in humid sections where it is not always 

 recognized. It may occur, regardless of precipitation, at any point 

 where the soil freezes at all deeply (see Table 38) ; it is characteristically 

 associated with light and dry soils and with scanty snow cover. If 

 no part other than the roots is injured the tree may start growth in the 

 normal way, sending out vegetative shoots and blossoms and perhaps 

 even setting fruit; some time in the summer, usually with the first warm, 

 dry weather, it dies. Felled trees will sometimes start growth in a 

 comparable manner. If only a part of the roots have been injured, 

 the effect is quite likely to be a slowing in top growth. As the damage 

 is below ground, it escapes ordinary observation and the slow growth 

 of the tree may seem quite inexplicable. This condition may last for 

 several years or until the balance between root and top is more nearly 

 restored. 



Soil Temperatures in Winter. — For a thorough understanding of the 

 nature of root killing and of the conditions associated with it, some 

 knowledge of soil conditions during the winter and of the distribution 

 of roots in the soil is necessary. Table 39, taken from a report covering 

 12 years of soil temperature observations at Lincoln, Neb.,^^'' shows 

 quantitatively the effect of depth on soil temperatures. 



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