SECTION IX. SAMPLE PLOT STUDIES 



Explanation. — Sample plot studies are useful for the determination of the 

 contents of stands, for solving certain problems in growth, and as a prelimi- 

 nary step in the construction of yield tables. In order that all of these 

 different problems may be worked out as laboratory exercises from the 

 same felled sample trees, and that unnecessary duplication of work may be 

 avoided, this section is placed immediately following the section on Growth 

 Studies. 



The underlying principle in all sample plot studies is to obtain the desired 

 information by the measurement of a few carefully selected average trees in 

 sample plots representing average conditions, and then to apply the com- 

 bined average results as obtained from the sample plots to an entire tract. 

 It should not be necessary to emphasize here that the greater the number of 

 plots used the greater will be the accuracy of the results. 



For a rough check in practical work, or where sample trees ^an not be 

 felled a standard volume table may be used to determine the volumes of 

 the sample trees. Do not do this where great accuracy is required. 



PROBLEM 33. (Field.) The Determination of the Contents of a Stant) 

 BY Means of Felled Sample Trees. 



ExPLitN ATiON . — The accompanying illustrations include three distinct 

 methods. With them as a foundation the student should have no difficulty 

 in understanding the underlying principles of any method. It is suggested 

 that this e.xercise be carried out in young, nearly even-aged stands. They 

 will serve the purpose of illustration fully as well as older stands, and, further, 

 will result in a considerable saving of time and unnecessary manual labor. 

 Each student should have a complete set of all the data and calculations 

 obtained by the other members of his party. These should be collected 

 from the other members immediately after each problem has been completed. 

 In each of the accompanying illustrations arrange the data and the results in 

 logical order so that each step will be indicated in the proper place. 



Illustration I. — The Mean Sample Tree Method. 



Principle. — The principle of this method is to base the contents of the sample 

 plot on the contents of one or more trees, each of which represents the 

 average of all the trees within the sample area. 



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