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JOURNAL OF FORESTRY 



be used only by the maker, but for standard volume tables this practice 

 is indefensible. Some allowance must be made anyway by the cruiser 

 for the variable amount of defect that occurs in all stands, and it is much 

 better that he should make it all. This view is generally accepted, I 

 believe. 



The Diameter Basis 



It has been Forest Service practice to base the tables on the diameter 

 at breast height outside the bark. This is unquestionably the easiest 

 measurement to take. With some species, however, the root swell 

 extends more than 4^ feet up the tree ; hence I would not recommend 

 holding universally to this height. With Sitka spruce, a very much 

 buttressed tree, District 6 based the table on the diameter at a point 

 1 foot above the pronounced root swell. Commercial cruisers com- 

 monly estimate the stump diameter ; some of them use the diameter 

 above the pronounced root swell. 



There is one important point of difference between private cruising 

 and Forest Service methods, and that is the former always considers 

 the diameter inside the bark and the latter that outside. With a species 

 such as Pacific Coast Douglas fir, that may have a bark 5 inches thick 

 or only 2 inches, depending on site, I am inclined to believe that a large 

 source of error is introduced in having standard volume tables based on 

 measurements outside the bark. Perhaps for some heavy-barked 

 species it would be best for the estimators to tally the diameter inside 

 the bark and have the tables constructed accordingly. 



Total z's. Merchantable Height 



There is a long-standing controversy as to whether the height 

 classes in a volume table should be expressed in total height or mer- 

 chantable height. I assume that all tables to be constructed hereafter 

 will be based on heights as well as diameters. Some of the districts 

 have settled this controversy by printing their volume tables both ways. 

 The advantages and disadvantages of each method about offset each 

 other. Personally, I feel that for most western conifers the top of 

 merchantability can be determined with the eye or with the hypsometer 

 about as accurately as the top of the tree, and that the moderately 

 careful estimator is as apt to get his trees in the proper merchantable 

 height class as in the proper total height class. The former — merchant- 

 able heights — is certainly the more convenient classification and more 



