SYLVICULTURE. 



IJcech 18640 years. 



Chestnut 12920 years. 



Pine . : 48680 years. 



Sarvis 1330 to 2000 years. 



VL Structure of soil. 



Soil consists of natural rock; or of rock disintegrated under 

 the influence of water, frost, heat, oxygen, carbonic acid, lichens, 

 bacteria; or of washings deposited by water, wind or glaciers. 

 The components of soil are: 



a. Soil skeleton, large grains, principally quartz and stones. 



b. Soil flesh, minute semi-soluble particles, — the mud of tho 

 rivers. 



c. Soil fat, the humose particles giving the soil a dark color-. 



d. Soil blood, the air and water, filling the pores of the soil. 

 The size of the pores determines the capillary capacity. 



According to the resistance which soil offers to spade or plow, 

 we distinguish the following classes: 

 Light soil ; 

 Loose soil; 

 Binding soil; 

 Heavy soil; 

 Stiff soil. 



VII. Air in the soil. 



Roots require oxygen for breathing. Like fish, they die from 

 lack as well as from superabundance of oxygen. Subterranean air 

 is rich in carbonic acid exhaled by roots, fungi, bacteria, animals. 

 Swamp soil contains little air. Hence such species only find a 

 living in swamps which have large inner air ducts (Cypress knees, 

 Nyssa root, bamboo, cane breaks, sour grasses). 



Prairial soil is naturally so compact that it contains Jittle oxygen. 



VIII. Water in the soil. 

 It occurs: 



a. Chemically bound to minerals and salts. 



b. Absorbed by the hygroseopicity of soil. 



c. Raised by the capillary power of soil. 



d. As ground water — lakes, swamps, brooks being merely areas 



of open ground water. 

 The size of the pores and the presence of humus govern tho 

 intensity and rapidity of water obtention and retention. Sand, 

 for instance, allows water to enter its large pores quickly, but gives 

 it up rapidly as well. Wet, moist, fresh, dry and arid soil are 

 distinguished. 



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