264 Studies in Forestry [CHAP. XIT. 



moist, they should either be drained or else planted up with 

 one of the genera of trees like Elm, Birch, and Larch, that 

 are at once hardy and capable of transpiring freely so as to 

 thrive on a moist soil. 



III. The Manner in which the Cohesiveness or Tenacity 

 of the Soil may be affected by the Methods of 

 Treatment of Woodland Crops. 



The productivity of any soil is dependent to no inconsider- 

 able extent on its cohesiveness. The whole relation towards 

 moisture and temperature is very directly and essentially influ- 

 enced by the fineness or coarseness of the individual particles 

 forming the soil. Whether the land be naturally binding and 

 tenacious, like heavy clays and argillaceous limes and loams, 

 or naturally light and porous, like many sandy soils, the main- 

 tenance of a good leaf-canopy throughout all the woodland 

 crops is of immense benefit in preventing the former class of 

 soils from becoming apt to get water-logged or else dried up 

 at different seasons, and the latter class from responding too 

 rapidly to changes in the atmospheric temperature, and from 

 running the risk of having portions of the soluble nutrient 

 salts washed out of the soil after heavy rainfall. Heavy soils, 

 that are insufficiently protected, are apt to become gradually 

 and imperceptibly caked in the upper layers, so that the 

 penetration, not only of the rootlets of seedlings, but also of 

 the atmospheric air, is rendered more difficult ; whilst sandy 

 soils rapidly sink below the freezing-point at night during the 

 cold seasons of the year, thereby exposing seedling crops to 

 late and early frosts, and become too easily heated during 

 summer days, thereby leading to excessive loss of moisture 

 through evaporation. 



The great importance attached to aeration, or circulation of 

 air within the soil, is very practically recognized in agriculture 



