METHODS OF CONSTRUCTING YIELD TABLES. 97 



preferable to the basal area. While two woods, of the same 

 species and equal basal areas, may have very different heights, 

 experience has shown, that two normal woods of the same 

 height have approximately equal basal areas. It follows, 

 that the height is, next to the volume itself, the best indi- 

 cator of the quality of the locality. Great height growth 

 means good quality, small height growth inferior quality of 

 locality. 



Neither the mean diameter nor the number of trees can be 

 used for the above purpose, as they are not in due proportion 

 to the volume. Nor can the product of number of trees 

 multiplied by the mean diameter be used. 



5. Methods of Constructing Yield Tables. 



The following methods have been proposed : — 



a. Annual or Periodical Measurement of the Grou'ing Stock of one 

 and the same Wood ; in the second case the Inteunediate Values 

 are found by Interjiolativn. 



The method gives absolute certainty, that all figures of the 

 yield table are derived from the same quality class, but as the 

 preparation of the table would take a century and more, 

 the method has only theoretical value. Moreover, accidents 

 may happen which would render the wood unfit for further 

 observation. 



l. Annual or Periodical MeasKremcnt of the Groicincj Stock of a 

 limited member of Woods of different Ages. 



In order to save time, it has been proposed to select several 

 woods differing in age by a certain number of years, say 20, 

 and to obtain from the measurements of each, extending over 

 20 years, part of the yield table. To make sure, that the 

 quality of the several woods is the same, it is necessary, that 

 they should have the same volume at the same age ; in other 

 words, the wood now 40 years old should have had, when 20 



F.M. H 



