54 FORICST REGULATION 



a good tree throughout life, while the partial analysis does not give 

 this for any tree. The information applies usually to dominant tim- 

 ber, the kind composing the final crop. While, generally, a large 

 number of trees are called for, it is surprising how uniform and 

 how reliable is the information even from 100 trees. 



In all growth study work, only the valuable species are con- 

 sidered. The study of growth on different sites multiplies the task 

 and adds very materially to the cost. While apparently very simple 

 and mechanical, this kind of work requires a well prepared, 

 thoroughly interested and faithful worker.* 



b. Yield Tables. 



Present the volume of the Stand of trees per acre, at the age 

 of ten, twenty, thirty, etc., years. They are, therefore, not merely 

 tables of yield, but, also tables of growth, indicating the rate of 

 growth of the stand. 



For older stands (merchantable) it is desirable also to know 

 the amount of material in form of ties, poles, etc., i. e., in the usual 

 forms into which the particular timber is converted, and thus to 

 learn not only the volume, but also the value of the stand per acre. 



Yield tables are prepared for the different sites, and in their 

 final form usually include number of trees per acre and also height, 

 diameter and volume of the average tree.** 



These tables assume a pure stand and even aged stand; all 

 efforts to prepare satisfactory tables for mixed stands and for many 

 age stands have failed, so far, to produce satisfactory results. 



To secure the data for yield tables it is necessary to find pure 

 stands of different ages, get their volume and by means of curves 

 even up and complete the information so that it can be tabulated. 

 These stands should not only be pure stands and even aged, but also 

 fully stocked and in reasonably good condition. For these reasons 

 only good stands are of any use, and the selection of these stands 



* Ordinary Volume table work is done by two men crew ; doing 50 trees 

 per day ; office work adds 50% to cost ; 1000 trees for about $2CO-$3OO. Stem 

 Analyses by two men crew ; do about 10 trees per day ; office work adds 

 100% ; total cost about $i.oo-$2.co per tree. Varies greatly with timber, 

 locality, etc. 



** For models of completeness in Yield tables see the recent studies of 

 growth of Pine, Oak, and Spruce by Schwappach. 



