60 GENERAL GROWTH OF STUDIES 



5. Draw a smooth curve and read off a table showing the average 



diameters at the end of each ten-year period. 



6. Label. 



PROBLEM 27. (Office.) The Determination of Growth in Uneven-aged 

 Stands. 



Explanation. — Growth in uneven- or many-aged stands differs from growth 

 in even-aged stands in that the individual trees grow more nearly like the 

 trees of a certain diameter than they do like trees of a certain age. Hence, 

 except when it is desired to determine the mean annual growth of trees, 

 growth studies in uneven aged stands are usually based on diameters (D.B.H.) 

 instead of ages. This holds true and, as described below, is applicable to all 

 kinds of growth in uneven-aged stands. The object, then, is to determine 

 how fast a tree of a certain diameter is growing, either in diameter, height, 

 volume, or other dimensions. This immediately makes it evident that 

 when a tree of one diameter class has grown to the next higher diameter 

 class it has a different rate of growth. Our problem then becomes one of 

 determining first of all the periodic annual growth for each diameter class 

 and from this the number of years required to grow one unit; i.e., in diam- 

 eter, one inch. 



The independent variables, then, will be diameters breast high, and the 

 dependent variables, periodic growth as determined in 5- or 10-year periods. 

 Unless there is some special reason for determining the mean annual growth 

 use periodic growth on D.B.H. for all problems in mamj- (or uneven-) aged 

 stands. 



Illustration. — To Construct a Table of Diameter Growth at the Stump for 

 Uneven-aged Stands, Based on D.B.H. 



Directions: 



A. Data Required. — The D.B.H. and measurements of the last 10 rings at 



the stump, or at D.B.H. 



Note. — The data for this problem can be obtained at D.B.H. from standing trees with 

 the increment borer, but usually more satisfactory work can be done on felled trees in con- 

 nection with a logging operation. The data supplied for this exercise were obtained in the 

 latter manner. Use Scries II. The data in this series are somewhat limited for the 

 purpose but show admirably what a small variation enters into the final results even with 

 limited data. Compare the results obtained under " D " of this problem as worked out by 

 different members of the class. The problem also illustrates the need for a large number 

 of data for absolute accuracy in all problems dealing with averages. 



B. Method. — Averaging before plotting. 



C. Method of Procedure. 



1. Group all trees into 1-inch D.B.H. classes {e.g. 8-inch class 7.6-8.5, 

 inclusive) , 



