Studies in Forestry 



[CHAP. II. 



average density of crop is necessary for the formation of close 

 canopy : 



Although at first glance this almost looks as if it might be 

 argued that the Oak is more capable of bearing shade than 

 the Beech, which would be contrary to experience, it actually 

 proves nothing more than that the Oak takes considerably 

 longer than the Beech to develop in that locality, and that the 

 Beech finds lateral expansion of its crown a sine qua non of 

 existence at an earlier period of age than the Oak. 



Whilst the number of individual poles or trees forming 

 the crop is larger on poor than on good soils, yet the full 

 normal density of leaf-canopy is maintained longer on the 

 better classes of soil. But the actual extent to which the 

 ground is overshadowed varies also with the species of tree ; 

 for experiments and measurements have shown that in a Spruce 

 forest, of normal density for Spruce, the soil is overshadowed to 

 more than twice the extent that obtains in a Scots Pine forest, 

 of normal density for Pine. 



If what has been stated above be correct viz. that the pro- 

 ductive capacity of the soil can be best protected when close 

 canopy is maintained throughout woodland crops then it must 

 naturally follow that the greatest production of timber per acre 

 must take place in woods having a leaf-canopy of normal density. 

 And practical experience shows that such is the case. In general, 

 other things being equal as to the productive capacity of 

 the soil, the increment per individual stem is greater in trees 

 revelling in the full enjoyment of light, air, and warmth, than 



