Forest Mensuration 29 



The advantages of the Draudt-Urich method are: 



1. All sample trees can be worked up in a bunch. 



2. Not only the entire volume but as well the different grades of tim- 

 ber, fuel, ties, etc., composing the volume are found by one operation. 



A large number of sample trees are, however, required, and, since the 

 volumes of the various classes are unequal, a negative mistake made in 

 establishing the volume of one class is not apt to be counter-balanced by 

 a positive mistake made in finding the volume of another class* 



PARAGRAPH XLVI. 



ROBERT HARTIG METHOD. 



Robert Hartig's method forms tree classes containing equal sectional 

 areas not equal numbers of trees. An equal number of sample trees is 

 cut in each class and worked up separately for each class. The volume 

 of the forest is also obtained separately for each class. Otherwise, the 

 manner of proceeding is identical with that of Paragraph XLV. 



Preferable it would seem to cut in each class a number of sample trees 

 having, in the aggregate, the same sectional area. This scheme, how- 

 ever, would represent the big-diameter class by an absurdly small num- 

 ber of samples. 



PARAGRAPH XLVII. 



AVERAGE SAMPLE TREE METHOD. 



If average trees of the entire forest are taken as samples, then the 

 volume of the forest is obtained with smaller accuracy. 



The proportion which the different assortments of timber, wood, bark, 

 etc., form in the entire output is not clearly shown by such sampling. 



In a normal, even-aged wood the tree of average cubic volume is found 

 by deducting 40% from the total sectional area, beginning with the de- 

 duction at the biggest end. The largest tree then left is, or happens to 

 be, the average tree of the wood. 



PARAGRAPH XLVIII. 



EXACT MENSURATION WITHOUT CUTTING SAMPLE TREES. 



Frequently the cutting of sample trees for the purpose of a valuation 

 survey is not feasible. The volume of the forest in cubic feet but not 

 the assortments composing the volume may then be ascertained as fol- 

 lows : 



a. Take the total sectional area of the forest according to diameters 

 and species and, if necessary, according to height classes. 



b. Ascertain the bole volume of some available trees with the help of 

 Pressler's tube or by indirect measurement of heights and diameters. 



