42 PRACTICAL FORESTRY IN 



mercial form and does so only when deprived of side light hy 

 numerous neighbors. Then it sacrifices diameter growth to 

 height growth in reaching for the top light necessary for 

 its life. At the same time the lower branches are killed by 

 shade and drop off, the scars being healed and eventually 

 buried. The pin knots near the center of a big clear log are 

 the remains of branches which when living were at the top of 

 the young tree. 



This is why, if it is to produce good timber, any forest must 

 be dense enough to cover the ground throughout the early 

 part of its life at least. When we see an excellent clear stand 

 of mature Douglas fir, for example, we may know that it con- 

 sists of the comparatively few survivors of a close sapling 

 growth in which the weak were gradually killed out after 

 serving their office of pruning and forcing the vigorous. Had 

 only the trees we now see been on the ground they would 

 be worthless except for firewood. For the same reason artifi- 

 cial forest planting must be thick, although the fillers or 

 nurse trees may be of inferior species if not of so rapid 

 growth as to gain the mastery. 



Nature teaches many lessons which we must recognize in 

 artificial management or fail, but she is no more the best 

 grower of forest crops than she is of agricultural crops. We 

 have to study natural methods of forest perpetuation to see 

 how they may be improved upon as much as to adopt them as 

 models. As a rule the virgin forest is exceedingly wasteful of 

 ground. The possibilities under intelligent care are not in- 

 dicated by nature's average, but by her accidental best, and 

 usually they far exceed even this. A fair comparison is that 

 of scientific farming with unsystematic gleaning from wild 

 and untended fields. The foregoing general principles of 

 forest growth have been purposely outlined very briefly so as 

 to serve as a mere introduction to their application or modifi- 

 cation in concrete cases. 



