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 

 b}^ 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," U. S. Dept. Agr. 

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



t Similar tables are prepared for Qualities I and III. 



