HEIGHT AND DIAMETKR BASIS 557 



This is true, of course, only where the volume table is applicable to 

 the stand. If this is not the case, far greater errors are likely to occur. 

 The trees on which the above figures are based were (except in the 

 case of western white pine) in each case from a wide range of condi- 

 tions. They were collected from varying sites and include many dif- 

 ferent ages. They represent very fairly the sort of trees from which 

 the Forest Service has been preparing district volume tables. But 

 while significant, these figures are admittedly inconclusive. Other in- 

 formation is unfortunately meagre. Certain tables have been tested 

 and found to apply within 1 or 2 per cent in aggregate measurements 

 to practically the whole range of the species. In the case of other 

 tables, which have failed to give good results, there has sometimes been 

 reason to doubt whether the cause was not rather in the preparation of 

 the table itself, that is, whether the table would not have failed to 

 measure accurately even the very trees from which it was prepared. 

 In other cases the discrepancies were undoubtedly due to the use of a 

 different standard of top utilization. 



It is through lack of foresight on the part of the profession that this 

 ignorance still exists. Had a very little more care been put on volume 

 table preparation, had basis and form been standardized, had every 

 table made been checked against its basic data and the probable error 

 or average deviation been computed, and had slightly fuller data been 

 published in connection with each table on the range of site and age 

 conditions included, we would probably long since have arrived, almost 

 automatically, at some approximate standards of accuracy, and hence 

 today have some better conception of what limitations of conditions 

 must be observed to attain them. 



CONCLUSION 



In conclusion, it seems that for western conifers, at least, the proper 

 program is to prepare volume table on the basis of d.b.h. and either 

 total height or merchantable height to a fixed top cutting limit in ac- 

 cordance with the use to which they are to be put. omitting the addition 

 of the third factor of form until it has been proved needed. With a 

 little more attention to volume table preparation, the question of the 

 necessity of complicating further our tables should, in a few years, 

 answer itself. 



