MANAGEMENT. 49 



GREATEST INCOME. 



The greatest volume production of a stand does not necessarily 

 correspond with the highest net income. The accumulation at com- 

 pound interest of taxes, interest on the investment, and other outlays 

 may prevent a heavy average yearly production of material on a 

 long rotation from yielding as large a net return as a shorter rotation 

 and a smaller mean annual growth. The conditions with regard to 

 taxation and investment vary so widely that it is not practicable to 

 discuss them in this report. Every owner should consider them, 

 however, in the management of his woodland. 



THINNINGS. 



A stand of timber is much more valuable if its volume is contained 

 in a few large, well-formed trees than if it is distributed among many 

 small trees. The aim of thinning, therefore, is to throw the whole 

 volume of growth of the stand into only as many of the best trees as 

 will fully utilize the growing space. This is done by removing all 

 other trees that seriously interfere with them. Furthermore, if the 

 proper trees are selected for removal and the thinnings made at right 

 intervals they will not only yield a direct money return, but will 

 result in maintaining at the maximum the volume growth of the trees 

 left without interfering with the production of long, clear trunks. 



OBJECT OF THINNINGS. 



Since it is in the leaves that the food of the tree is manufactured, 

 any increase in the amount of foliage will increase the food supply, 

 and thereby the rate of growth. Leaves need a certain amount of 

 sunlight in order to manufacture food, and are not produced in those 

 portions of the tree which receive insufficient light. Thinnings, there- 

 fore, stimulate volume growth by opening up the stand and allowing 

 more leaves to be produced on the trees left than would be possible 

 if they were crowded by their neighbors. 



While the volume growth of stands is stimulated by opening them 

 up, their height growth is greatest if the trees are moderately 

 crowded. The period of most rapid height growth in oak and chest- 

 nut stands is during youth, and the rate of growth ordinarily begins 

 to decrease between the twentieth and thirtieth years. During this 

 period a moderate crown shade prevents the growth of lower branches, 

 and all the energy of the tree is directed toward its growth upward. 

 Occasionally, however, the crown shade during this period is so heavy 

 that the individual trees are unable to produce enough leaves even 

 for a rapid height growth. In such stands thinnings are especially 

 desirable. Since during youth the remaining crowns rapidly expand 

 23329°— Bull. 96—12 4 



