Forest Mensuration 33 



Ascertain age and average height of the trees ; find the yield table 

 which gives a similar height for the same age; reduce the volume indi- 

 cated by this yield table and for this age, by estimating the deficiency of 

 the growing stock. 



Obviously, there is much room for guessing, since neither height nor 

 form figure nor sectional area in woodlots abnormally stocked can lay 

 claim to normality. 



Schuberg, denying a truism otherwise generally acknowledged, claims 

 that the height alone does not indicate the productiveness of the soil. 



At present, normal yield tables are of little use in American forestry. 



PARAGRAPH LIV. 



DISTANCE FIGURE. 



Under "distance figure," an invention of Koenig's, is understood the 

 quotient a formed by the side / of the average growing space of a tree 

 (considered as a square) and by the diameter of the average stem d. 



I 



The average distance from tree to tree and the average diameter of a 

 number of trees is obtained by a number of measurements in the forest. 

 If the area of the forest is F square feet, then the sectional area of the 

 forest is 



TT F 

 = X square feet 



The actual test proves the fallacy of Koenig's assumptions. The ex- 

 planation lies in the fact that the average diameter of a wood is not the 

 arithmetical mean of the diameters composing it. Further, the growing 

 space of a tree is not a square. 



The actual growing space per tree can be correctly ascertained by laying 

 a sample strip through the forest, counting at the same time the trees 

 within the strip. The sectional area of the forest is obtainable, however, 

 without greater trouble and with much greater accuracy, from the pro- 

 duct calipered sectional area of trees in the sample strip times area of the 

 forest over area of the sample strip. 



On an acre of average soil, there is on an average room for the fol- 

 lowing numbers of healthy trees, according to age : 



At 20 years 1,600 specimens. 



At 50 years 600 specimens. 



At 100 years 240 specimens. 



At 150 years 150 specimens. 



