200 THE PRINCIPLES OF HANDLING WOODLANDS 



of clear-holed trees; but excessive crowding in later life 

 results in a great reduction of growth. 



In a crowded stand left untouched, the struggle for 

 space sometimes results in injury to the form of good 

 trees. Most trees tend to grow straight, and the crook 

 or sweep in a stem is often due to its bending and reach- 

 ing for light, through being crowded on one side by 

 another tree. This is particularly true in coppice stands, 

 where a clump of sprouts all start straight, but through 

 mutual crowding may all develop crooked stems. 



Then, again, poor species will often take a dominant 

 place and crowd those of more value. 



Results of Thinnings. The practical results of thin- 

 nings are as follows: 



1. Rapid growth of individual trees. It is possible 

 to bring a stand to merchantable condition 10 or 20 

 years sooner than without thinnings. 



2. Increased total yield. In Europe, about 30 per 

 cent, of the total aggregate yield of a stand during the 

 rotation is from thinnings. This amount is really a sur- 

 plus, because the final yield is not less, and is sometimes 

 even more, than if there had been no thinnings. 



3. Improved quality of product. The forester has 

 the opportunity to develop trees of specially high quality, 

 clear stems, and even grain. By timely thinnings he can 

 prevent the distortion of valuable trees through side 

 crowding, and thus reduce the percentage of crook. 



4. If there is a cord wood market, decadent and de- 

 fective material can be utilized. 



