266 ASPECT, AND ITS EFFECTS UPON FOREST-GROWTH. 



Writers upon forestry adopt the following as a proper definition of 

 inclined surfaces : 



A gentle slope is from level to lO^ of elevation. 



A somewhat steep slope from 10° to 20*^. 



A steep slope from 20° to 34°. 



A very steep slope from 35'^ to 45°. 



An escarpment 45° and upwards. 



As a general rule, the climate of plains is more uniform than that of 

 mountains, but this depends upon elevation, i)revailing winds, and 

 proximity to large bodies of water. The latter have an equalizing 

 tendency, and the choicest fruit-regions of the country owe this excel- 

 lence to the protections thus afforded against premature blossoming. 



If such, we have examples iu the fruit-belt along the eastern shore of 

 Lake Michigan, the southern shores of Lakes Erie and Ontario, and the 

 region around the southern end of the interior lakes of central and 

 western New York. 



The influence of aspect upon the growth of trees, depends something 

 upon the prevailing winds and other causes. But soil, slope, and other 

 conditions being otherwise the same, we may state the effects of aspect 

 approximately as follows: 



The northern aspect receives no sun, or but obliquely, according to 

 the angle of elevation. The winds are colder and dryer, and generally 

 in the growing season not strong. The soil retains its moisture, and 

 the growth of vegetation is rapid. Tlie trees retain a more regular 

 shape, and their tissues are softer. The timber is therefore not as strong, 

 but it is very well adapted to manufacturing purposes. The later veg- 

 etation on a north slope delays the opening of buds, and reduces the 

 risk from late spring frosts; but from the late hardening of summer 

 growth, some injury may occur from freezing in winter. The snows 

 lie longest on this slope, which very materially favors forest growth. 

 The starting of a forest by seeding is more easily secured on a north 

 slope than any other. It was on a northern slope only, that forest 

 seeds sown upon the damp snows in the works of replanting the mount- 

 ain regions of the Alps, by the French Government, were found to 

 succeed. 



The eastern aspect receives the direct rays of the sun in the cool 

 morning hours, and the temperature and light are moderate. The 

 winds (in the United States) are often damp, especially in winter, and 

 the trees seldom become loaded with ice, except when the eastern winds 

 are blowing. The soil holds its moisture fairly, and the timber grows 

 well, and acquires medium qualities that adapt it to the greatest variety 

 of uses. 



The southern aspect receives the direct rays of the sun, and the light 

 and heat are both intense. It is liable to winds and storms, and to 

 erosion from rains, because from the heat, a protecting growth of herbage 

 is less liable to be found on the soil. The trees have, on the whole, a 

 slower growth and less regular form, but the timber is firm, heavy, and 

 strong, well adapted for building and manufacturing purposes. Seeding 

 can seldom be secured on an open exposure to the south in a warm climate, 

 and trees must usually be set and attended with greater care. 



On the western slope the sun shines obliquely, but in the hottest hours 

 of the day, and in our Western States, vegetation is most exposed to 

 drying southwesterly winds. The soil is liable to become dry, and tim- 



