SECTION XL— YIELD TABLE STUDIES 



Explanation. — Yield tables are tabular statements which show the average 

 stand of timber per acre. As in volume and growth studies separate tables 

 are made for stands growing under different conditions or having distinct 

 characters. »They are made both for even-aged stands and for uneven- 

 aged stands. Two forms are recognized for the even-aged stands : 1. The 

 Normal Yield Table, showing the stand per acre of normal or fully stocked 

 stands, and 2. The Empirical Yield Table, showing the average stand in 

 any locality irrespective of stocking. By a fully stocked stand is meant one 

 with the average maximum yield obtainable under the existing conditions. 



The construction of yield tables for even-aged stands does not present 

 any great difficulties. Yield tables for many-aged stands, however, offer a 

 number of serious difficulties. Up to the present time there has been no 

 general method devised for constructing these that is wholly satisfactory. 

 For this reason problems for many-aged stands have been omitted, but a list 

 of references to the various methods is included at the end of this section. 

 In dealing with yield tables the student should remember that he is dealing 

 with values per acre. 



PROBLEM 39. (Office.) The Construction of Yield Tables for Even- 

 aged Stands. 



Explanation. — In the foregoing problems the student has had practice in 

 nearly all the steps necessary for the construction of the different kinds of 

 yield tables for even-aged stands. The Method of Procedure in Problem 35 

 covers practically all of the points necessary for the collection of field data. 

 In fact in that exercise the student has virtually constructed an Emjyirical 

 Yield Table. All that is now necessary to further illustrate the work is to 

 take up the special problems that arise in connection with the construction 

 of Normal Yield Tables. 



Illustration. — To Construct a Normal Yield Table for IJuthinned Pure 

 Stands. 



Directions: 



A. Data Required. — The measurement of permanent sample plots would of 



course give the best results. However, when time is an important 



consideration these are out of the question, since it would take years to 



collect the necessary data by this means. To overcome the difficulty 



80 



