198 THE PRINCIPLES OF HANDLING WOODLANDS 



The term has, however, come to have a restricted techni- 

 cal meaning, both in British and American practise, and 

 for that reason the author has chosen to retain it rather 

 than to undertake the establishment of a new and unfa- 

 miliar expression. 



Thinnings are made chiefly in even-aged stands. 

 When used in even-aged groups in irregular stands, 

 the principles are the same as where the whole stand 

 is even-aged. Therefore the discussion in the follow- 

 ing pages will be confined chiefly to the application of 

 thinnings in stands which are even-aged or approxi- 

 mately so. 



Need of Thinnings. — For the purposes of forestry it 

 is desirable for trees to grow in crowded stands. The 

 mutual crowding results in the natural pruning of the 

 stems and the production of high-grade lumber. In 

 planting forests the trees are set from 4 to 6 feet apart, or 

 from 1,200 to 2,800 trees per acre, and successful natural 

 reproduction often results in an even greater density of 

 stocking. As soon as the crowns of the trees meet, and 

 their growth is consequently restricted, the struggle for 

 light, space, moisture, and nourishment begins. One 

 of the first manifestations of this competition between 

 the trees is their difference in crown development. 

 Some trees forge ahead and take their place as leaders, 

 with strong, dominant crowns; others fall behind, with 

 crowded crowns, and take an intermediate place, while 

 the weak trees are suppressed and overtopped. As the 

 stand grows older and the trees must have more space 



