40 



BULLETIN 308, U. S. DEPARTMENT OF AGRICULTURE. 



ways be avoided in order to prevent soil deterioration and the 

 entrance of weeds or undesirable hardwood species. In the absence 

 of other trees over a space larger than about two or more square 

 rods trees of all crown classes should be retained. The trees in a 

 well-stocked thinned stand of shortleaf should maintain a general 

 uniformity in height. 



Figure 4 shows graphically the actual appearance of the canopy of 

 a 30-year-old stand and the same after it was thinned by the removal 

 of 9 suppressed and 4 intermediate trees, equivalent to 46.4 per cent 

 of the number of trees, or about 8 per cent of the cubic volume. 



In this case thinning was badly needed because of the number of 

 trees in the lower crown classes and overcrowding in the main 



A B- 



Fig. 4. — Canopy of a crowded shortleaf pine stand 30 years old ; (A) before thinning ; 

 (B) after thinning. D dominant, C codominant, I intermediate, S suppressed. 



canopy. The expansion of the crowns of the remaining trees will 

 rapidly fill openings, making a second thinning necessary in about 

 five years. The selection of trees among the various crown classes 

 for thinning should always be preceded by the removal of unsound 

 and defective trees, such as those with crooked, forked, or short 

 knotty trunks. The presence of " punk," or the fruiting body of a 

 fungus, is certain evidence of a diseased tree. 



In mixed stands the pine should be favored at the expense of the 

 hardwoods practically always except on the least favorable situations 

 and extreme outer limits of its range. Artificial thinning will ac- 

 celerate growth, however, and make the tree successful on situations 

 formerly considered unfavorable. In proportion to the amount of 

 air and soil space occupied shortleaf pine produces more timber 



