VOLUME TABLES 209 



It is clearly established that trees of the same (a) species, (6) diameter, 

 (c) silvicultural system, and (d) height yield a greater volume as they 

 increase in age but the variation is usually disregarded in ordinary valua- 

 tion surveys, except so far as it is represented in local volume tables. 

 The wide variation between local volume tables for the same species and 

 diameter is merely a repetition of experience in all countries. But an- 

 other complication arises in working plan revisions. It is desired to esti- 

 mate the present stand accurately yet to-day's stand must be compared 

 with the stand at the last revision because the original stand plus the cut, 

 minus or plus the difference between the original stand and the present 

 stand, gives an accurate line on growth. It is, therefore, necessary to 

 compute the volumes to be compared by the same volume tables. In 

 fact, with hundred per cent estimates, each compartment or working 

 group is in reality a permanent sample plot which at each working plan 

 revision gives fairly exact data on growth and yield. 



The sample volume table which follows is for spruce and fir in the Jura. 

 To the figures given 10 per cent must be added if branches are included. 

 The volume tables supplied the local officers also give the volume by cir- 

 cumference and heights for one to nineteen trees (omitting the volumes 

 for ten and twenty trees) to facilitate multiplication when figuring results 

 of valuation surveys: 



