20 ELEMENTARY. FORESTRY. 



colder than those received by the southern slope, but the few 

 winds which strike it during the growing season are not strong-, 

 hot or very dry. As the vegetation is a little delayed on a 

 northern slope there is less danger from late spring frosts, 

 than on a sunnier aspect and as the snow melts slowly there 

 is a better chance for its waters to soak into the ground. In 

 consequence of these facts trees are less liable to suffer from 

 drouth on the same kind of land with a northern than with a 

 southern exposure. The trees keep a more regular form and 

 growth is more uniform and certain. It will generally be 

 found that where timber is cut off from a northern slope 

 growth renews itself very quickly, for tree seeds are most likely 

 to grow under the conditions found there. 



An Eastern Slope receives the sun in the cool morning hours 

 when the temperature and light are moderate. It is not ex- 

 posed to our hot, dry winds nor to the intense heat of the sun. 

 The soil retains its moisture fairly well and trees make a 

 good growth. For trees it ranks next in value to a northern 

 slope. 



A Southern Slope receives the most direct rays of the sun, 

 and the full force of our hot, dry winds and beating rains 

 during the growing season. Consequently vegetation is more 

 liable to injury by late spring frosts because of starting 

 earlier in the spring than in any other location. The soil is 

 most liable to erosion from beating summer rains and dries 

 up most quickly after the spring rains. The trees grow irreg- 

 ular in form, the seeds seldom start well on southern or 

 western slopes and when once cleared tree growth is often dif- 

 ficult to renew. As proof of the importance of these con- 

 ditions as affecting tree growth we have the commonly ob- 

 served fact that the south and west sides of steep hills and 

 mountains are more likely to be bare than any others. This 

 can be very plainly seen on the bluffs along the Mississippi 

 River in Minnesota. 



A Western Slope receives the sun's rays obliquely, but in 

 the warmest part of the day and in this section gets the full 

 force of our hot dry southwest winds. The effect of such an ex- 

 posure on growth is about the same as the southern slope. 



