CHAPTER IV. THINNINGS 



152. Thinning is the removal of some of the trees from 

 a stand for the benefit of the trees that remain. To under- 

 stand thinning it is necessary to review the development of 

 a stand. Suppose that a young stand is recently started, 

 and that the trees are 6 feet apart each way, or 1210 to the 

 acre. When the stand is about ten years old the side 

 branches of the trees will begin to touch, the ground will be 

 shaded; and the ^tand has become what the foresters call a 

 "closed stand." As soon as the stand is closed the trees be- 

 gin to crowd one another. The crowding results in the 

 dying of the lower side limbs and in an increased height 

 growth. Some of the trees get ahead of the others, and be- 

 fore many years they become separated into classes. These 

 classes are called (1) dominant, (2) intermediate, (3) sup- 

 pressed, and (4) dead. The names indicate the condition of 

 the trees in the classes to which they are applied. By the 

 time the stand is fifty years old probably not more than 500 

 out of the original 1210 trees will be alive. The others have 

 been shaded to death by their stronger neighbors; and some 

 of those that are still alive will succumb within a few years. 

 If, as often occurs in natural seeding, there are several 

 thousand trees at the start the crowding will be greater and 

 the results will be more marked. 



153. A moderate crowding is beneficial to the stand. 

 It causes the trees to grow up tall and straight and to shed 

 their side limbs. Long, clean, straight logs that saw out 

 clear lumber are the result of crowded stands. On the other 

 hand, the struggle in a closed stand may become too fierce; 

 and it may react in a harmful way on the stand. The stems 



