328 



PRINCIPLES UNDERLYING THE STUDY OF GROWTH 



Volume-growth analysis of individual trees, although apparently 

 the most accurate and scientific basis of growth, is in reality the least 

 important and most inefficient when expense is compared with results. 

 It is invaluable to determine the laws of tree growth and the changes 

 which may take place in the form of individual trees as the result 

 of changed conditions, as for instance, on cutover lands, and as a pre- 

 caution against accepting general figures based on volume tables and 

 other short methods of growth study. But ordinarily, even where 

 volume of trees is desired, it will be obtained from diameter and height 

 growth supplemented by use of the form quotient rather than from 

 the stem analyses of trees. Many thousands of stem analyses have 

 been made in the past whose results were either not worked up at all 

 or since compilation have reposed in the archives of Government and 

 States while investigators vainly sought an answer to the pressing 

 problems as to what was the actual rate of growth per year on national, 

 state and private forests. 



The best possible basis for growth predictions is the actual records 

 of the growth in successive periods of specific forest stands whose 

 history is known and whose conditions of management are fixed. The 

 establishment of sample areas which are measured successively by 

 ten-year periods will give a firm basis for growth predictions superior 

 either to the method of comparison, based on past growth of older 



Chart of 



Purpose of growth study § 244 



I [Normal or index yields 



Productive capacity of different qualities of forest per acre for even-aged 



stands 

 , Pure stands — § 304 



Field measurements 



1, Diameters B.H. 

 § 309 

 2. Mixed stands— § 314 2. Heights, total 



3. Count of annual rings 

 on average trees — 

 §262 



Prediction -of 

 future 

 growth and 

 yiel d s on 



natural' For total age 

 forest areas or long per- 

 —§§247- iods— 

 248 §§249-250 



For even-aged stands 

 — §§ 256-262 



Comparison of stands 1. Timber estimate sepa- 

 with normal yields at rated by age classes — 

 same age — § 301 § 344 



2. Counts of annual rings 

 on average trees — 

 §262 



