THE PROBLEM OF MAKING VOLUME TABLES 579 



and there is indication that in Service practice so-called standard tables 

 have been applied to too widespread and too variable types of timber. 

 District boundaries alone seem to have been the limit for standard 

 tables. Age classes and types should be the criterion of the application 

 of tables. It is too well known to need more than mention here that a 

 second-growth, 24-inch, 100-foot tree has a very different form from 

 an old-growth tree of the same dimension, or a tree on rich bottom 

 land from a tree of the same size and species on a rocky ridge. A 

 change of soil or of age may make more difference in tree form than 

 1,000 miles of geographic position. I do not believe that the Service 

 has taken sufficient account of this in making its standard volume 

 tables. It is necessary that Research should make a study of tree form, 

 probably by working out stem form factors from existing data so as to 

 determine what are the variables. To see, for example, how different 

 is the form factor for old-growth western yellow pine for a certain 

 class of site in Arizona from what it is in the Sierras or Black Hills or 

 Blue Mountains, to see whether the variation with age is material, to 

 see to what extent quahty of site affects the form factors and what the 

 law of the variation is. After a study of this kind has been made, it 

 may be decided that there should be six form classes for western 

 yellow pine; for example, one to include first quality old growth in 

 California and Oregon, another second quality in this region and first 

 quality in other regions, another young bull pine and black jacks for all 

 regions, etc. In Norway I understand that three site classes, or form 

 classes, are used for the spruce volume tables, besides height and 

 diameter classes. 



Shall Normal or Forest-run Trees Be the Basis for a Table? 



The selection of the trees to be measured has always been a matter 

 of discussion. Shall broken tops, "schoolma'ams," and the like be 

 included in the proportion in which they exist in the forest, or shall 

 only normal and regular trees be selected? This is a question which 

 must be worked out by the investigators and the administrative men 

 and some uniform policy decided upon and adhered to. This matter 

 of normal vs. forest-run trees is apart from the question of sound vs. 

 defective trees, which I shall take up next. 



Alloivance for Defect 



Some of the local volume tables have been constructed to allow for 

 defect and breakage. This may be all right for local volume tables to 



