YIELD TABLES 



321 



periods and to determine the probable yield of crops of timber, the 

 production of which is the purpose of forestry. This is accomplished 

 by the second general method of prediction which rests on the principle 

 of comparison. The past growth of existing stands is taken as an indi- 

 cation of the expected future growth of other younger stands whose 

 prediction is desired for a similar period. It is assumed that similar 

 stands will grow in a similar manner. The task consists of demon- 

 strating the relation between the stands whose past growth is measured 

 and those whose future growth is sought. 



249. Yield Tables. The most practical and useful expression of 

 growth is a yield table which shows the yields per acre for even-aged 

 stands at different ages by five- or ten-year periods separated into 

 different qualities of site. An example of such a yield table is shown 

 below: 



TABLE XLVIII 



Yield Table for White Pine * 

 Quality II f 



* Taken from Tables 4 and 6 in " White Pine under Forest Management,' 

 Bui. 13, Washington, 1914, pp. 22 and 23. 



f Similar tables are prepared for Qualities I and III. 



U. S. Dept. Agr., 



