168 THE PRINCIPLES OF HANDLING WOODLANDS 



light or moderately light foliage, such as pine, oak, and 

 larch. When a given stand has reached its main height- 

 growth and the boles are well cleared by natural pruning, 

 a heavy thinning is made which removes from 40 to 60 

 per cent, of the trees. This thinning takes out the sup- 

 pressed, partially suppressed, and defective trees. Those 

 left standing are the best dominant trees in the stand. 

 Each tree is isolated, and will produce its greatest pos- 

 sible growth. Usually there is only one thinning, but if 

 the trees all tend to be slender and subject to possible 

 danger from windfall, two thinnings are made, the first a 

 light one and the second establishing just the conditions 

 desired. This thinning is made in pine stands at an age 

 of from 40 to 50 years, in oak at from 50 to 60 years, and 

 in larch at from 35 to 40 years. 



The stand is then underplanted with some tolerant 

 species like birch, hornbeam, spruce, or fir, according to 

 the requirements of site. This constitutes an under-story 

 which protects the soil from deterioration. The lower 

 crop is of tolerant species, and is able to live under the 

 open stand of the older trees. Usually the crowns of the 

 upper story spread rapidly, and it is necessary, about once 

 in ten years, to make a further thinning to sustain rapid 

 growth and prevent excessive injury to the under-story 

 by crowding. At the end of the rotation of the upper 

 story, the whole stand is cleared, including the lower 

 story, and restocked artificially to a stand of the species 

 composing the upper story. If the rotation is 120 

 years, the trees of the upper story contain material of 



