METHOD OF USING YIELD TABLES IN THE FIELD 83 



tically, it will be necessary to i)lace in their hands a yield table applicable to 

 the section of the country in which they are working. A yield table for 

 Second Growth Douglas Fir will be found in the Appendix. Others can 

 sometimes be obtained in Forest Service publications dealing with the 

 particular region in question, or they may in some cases be obtainable from 

 the Forester at Washington, D. C. The illustrations given below are out- 

 lined with reference to Normal Yield Tables. If these are not available 

 Empirical Tables will do, but in that case provision should be made in the 

 directions for the discrepancy that will arise in connection with the question 

 of normality of stocking. 



Choose for the purpose of illustrating this exercise young, even-aged 

 stands, preferably under 50 years old, and as fully stocked as possible. 

 Illustration I. — To Estimate the Contents of a Stand. 



A. Parties. — 3 men in each. 



B. Equipment. — To be determined by chief of party. 



C. Method of Procedure. — Lay out a representative plot of ^ acre in the 



tract to which the table is to be applied and by means of the Mean 

 Sample Tree IMethod determine the following: 



1. The average age of the stand as the age index. When the age is not 



an even multiple of 10, all calculations will need to be reduced by 

 proportion to the nearest 10-year period in the table. 



2. The average height * of the stand as an index to the site quality. 



3. The total basal area (in acre terms) as in index to the normality of 



stocking. This should be stated in terms of the per cent of the 

 total basal area indicated in the table. 



4. The ijield. Reduce the yield indicated in the table by the per cent 



of stocking. 

 Illustration II. — To determine what the Volume of the Stand will be when 

 it is 100 years old. 



A. Method of Procedure. — With the information obtained in Illustration I 



it is now only necessary to refer to the table to obtain the future yield. 

 The yield indicated for the 100-year-old stand should be reduced by 

 the per cent of stocking. 



B. References. — Number 68. 



C. Discussion. — In the two illustrations given above no use was made of: 



(a) The number of trees i)er acre; (b) The average diameter at the 

 different ages; (c) The form factor. What is the object of including 

 these in a yield table? 



Uneven-aged Stands 



The following references may be helpful in understanding the question 

 of yield tables for uneven-aged stands: Numbers 69, 70, 75, 77, 78 and 79. 



* If the site factor has been established for the region it may be used. 



