92 A MANUAL OF FORESTRY 



The first thinning should be deferred until the material taken 

 out is large enough for cordwood and the returns will at least 

 cover the cost of the operation. This will rarely occur before 

 the stand is twenty years old, and not later than the thirtieth 

 year. 



Thinnings should be repeated whenever needed. Unless the 

 thinning was very heavy this should be in five to ten years. 

 The time for making the next one can be judged by observing 

 the crowns. If the openings left by the previous cutting have 



Fig. 36. A (' grade thinning in a 38-year-old stand of mixed hardwoods containing oak, 

 chestnut, maple, black and yellow birches. Yield per acre 27 cords; actually cut 6j 

 cords per acre. 



been filled and the crowns of the trees are once more in close 

 contact, competition has again assumed serious proportions and 

 it i> time for another thinning. 



The best method is to make small openings in the crown cover 

 which will close together within a few years, necessitating an 

 early repetition of the operation. When only small gaps in the 

 cover are made there is no danger of the trees producing knotty 

 timber nor of the stand becoming insufficiently stocked with 

 trees. The soil is best protected by light thinnings, frequently 



