132 forestry Quarterly. 



What we would call loc/s in German usage must be over 14 cm 

 (5.5 inch) measured at i ni from the smaller end; this we can 

 readily round off to 5 inch at the small end, and if it were stated 

 at 6 inch it would also not be egregiously wrong, and for East- 

 ern conditions at least we could accept either as standard. Un- 

 fortunately, few German yield tables contain this differentiation 

 into saw logs, the statement of generally useful wood production 

 satisfying the German forester. Even those yield tables which 

 make this differentiation, like Schwappach's, do not state them 

 in the simple board measure statement but, by percentage of the 

 stout wood product, in a classification which must be understood, 

 but is too complicated to elucidate here. 



The first thing that must be recognized is that it is absolutely 

 impossible to construct one conversion factor that is applicable 

 for tramlating a whole yield table into board measure, for th*e 

 simple reason that from decade to decade, from site to site, 

 from species to species the log per cent, varies. By using one 

 and the same conversion factor we come to the evidently absurd 

 result, that a lo-year-old, or 20- or ^o-year-old stand contains. 

 feet board measure, i. e. saw logs. It is not even possible 

 to secure a single conversion factor which can be used for the 

 same species at the same age, because different sites will vary 

 in their log production in a given time. We must then have 

 different conversion factors for given conditions, the variation 

 being due to a variable log content. 



Taking the Scotch Pine at 100 years, a usual rotation, the 

 percentages of log material run from site I to site V: 71, 60, 36, 

 18, none. These percentages may be increased by material taken 

 from thinnings and otherwise by a small amount. 



Taking Schwappach's yield table for Scotch Pine, we find that 



considering only the logs of the main stand on a first site no logs 



are found b. fore the 50th year. In the 50th year 9 per cent, of 



the stout wood produced are recorded and then from decade to 



decade the percentages are 20, 40, 53, 64, 71, 79, 84, 90, 90. 



That is to say after 130 years there is no change in log wood per 



14.3 

 cent. The corresponding conversion factors run ( x per 



cent.) : .02, .04, .06, .074, .081. .09, .097, .104. Who will average 

 these variables for translation of a whole yield table! We see 

 then that a direct translation from cubic meter per hectare to 



