MANAGEMENT. 51 



the cubic volume. Thinnings of this kind result in many large open- 

 ings in the crown cover, and every effort should be made to leave 

 enough of the smaller trees and undergrowth to fill the openings and 

 protect the soil. The approximate amount of wood obtainable in 

 thinnings of a given degree of severity can easily be found for stands 

 of different ages and qualities by computing the required per cent 

 (20 to 40 per cent) of the cubic foot yields given in Tables 17 to 25. 

 It should be remembered that while more trees are removed in thin- 

 ning young stands than in thinning older ones, the actual volume of 

 wood secured is not as great, and hence the labor cost per cord is 

 greater. 



TREES REMOVED, 



In discussing thinnings it is convenient to classify the trees in a 

 stand as " dominant/' "codominant," "intermediate/' "overtopped/' 

 and "dead." These divisions are termed "crown classes, " and may 

 be readily observed in any unthinned woodlot. The dominant are 

 the conspicuously tallest and most thrifty trees. The codominant 

 trees may be as tall, but do not have such well-developed crowns. 

 Intermediate trees are those which form the lower part of the crown 

 cover; not as tall as the dominant or codominant, but whose crowns 

 still receive light from above. The overtopped trees are those which 

 are shaded from above by their neighbors. They may be either 

 flourishing trees of shade-enduring species, such as maple, black 

 birch, hickory, or hemlock, or else suppressed individuals of light- 

 needing species, like chestnut, which will soon die from lack of light. 

 Dead trees are always present in large numbers in the average uncared- 

 for woodlot. In this discussion, however, dead trees include only 

 those with a merchantable value for cordwood. 



Aside from dead trees, which may always be removed, no tree 

 should be cut merely because it belongs to a certain crown class. 

 Thus it may often be desirable to remove an unthrifty codominant 

 or even dominant tree in preference to one or more adjacent inter- 

 mediate trees of better promise. No definite rule will fit all cases, 

 and the removal of individual trees is largely a matter of judgment. 

 In general, all trees should be removed which are either unnecessary 

 or actually harmful to the stand by interfering with the develop- 

 ment of better trees, or by endangering the spread of disease. 



The trees should be favored in the order of the crown classes; that 

 is, there should be taken out first the merchantable dead trees, next 

 the overtopped, then some of the intermediate, while as many as 

 possible of the thrifty codominant and dominant trees should be left 

 standing. Since enough living trees must be left to shade the soil 

 and keep out weeds it may often be necessary to leave some of the 

 overtopped trees. Large openings in the stand should always be 

 avoided. 



