26 ELEMENTARY FORESTRY. 
EFFECT OF SLOPE AND ASPECT ON TREE GROWTH. 
The slope of the land affords drainage and so affects the 
growth oi trees, but trees will grow on any slope, even on 
precipices, if they can find room for their roots and the soil is 
somewhat moist. The direction of the slope usually has a very 
marked effect on the growth of vegetation. This is especially 
the case where high ranges of hills and other local conditions 
modify the climate. 
A Northern Slope receives no full sunlight; the sun’s rays 
fall obliquely in the morning or toward evening, according to 
the angle of elevation. The winds it receives in winter are 
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 con- 
sequence of these facts trees are less liable to suffer from drouth 
on the same kind of Jand 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 undei 
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 
exposed to our hot, dry winds nor to the intense heat of the 
sun. The soil retains its moisture fairly well and trees make a 
eood 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 irregular in 
form, the seeds seldom start well on southern or western slopes, 
