250 



THE MEASUREMENT OF STANDING TREES 



is different from what the crown normally signifies. On this account special tables 

 have been made up for use with outside bark measurements, but, as the Scotch pine 

 shows many different types of bark, four tables have been compiled for trees whose 

 bark is thin, medium, thick and very thick. 



When judging the location of the form point, it should be remembered that it 

 is at the base of the branches where the acting forces of the wind are transferred 

 to the bole, for which reason deciduous trees with branches pointing up will have 

 the form point not in the center of the crown contour but as much lower as the 

 bases of the branches lie lower than the foliage on which the wind is acting. In 

 estimating trees which have quickly cleared themselves of branches, a better result 

 will be obtained, if the newly shed crown be imagined reconstructed before the 

 position of the form point is determined. 



Finally, should the butt sweUing extend so high as to influence the D.B.H., 

 and consequently make the final result inaccurate, it will be satisfactory for prac- 

 tical work either to rovmd the diameter off downward or measure the diameter 

 above the swelling; for scientific work, however, the form class should be lowered 

 as much as is made necessary by the butt swelling, which can be easily found through 

 a number of measurements taken above and below B.H. 



In extensive timber estimating the density is a good indication of the general 

 form which the trees ought to possess, as the tree grown up in dense stands will 

 have a clean bole and high crown, while on the contrary the tree grown in the open 

 will have a heavy, low crown and consequently a poor bole form. 



TABLE XL 



Table for Determination of Form Class of Trees by Means of Position of 



Form Point ^ 



Height 



of 

 tree 



in 

 feet 



Form Class 



0.50 



0.525 



0.55 



0.575 



0.60j0.625 



0.65 



;n 7nir 



0.675 0.7010.725 



0.7510.775 



0.80 



Form point height in per cent of height of tree 



37.5 

 1 35. 5 

 '34.5 



34 



34 

 34 

 34 

 34 



1 For spruce and fir in Norway, either inside or outside bark. Adapted from 

 Mas.satabeller for Traduppskatnung. Tor Jonson, Stockholm, 1918. 



The prevailing density of a stand causes the greater number of the trees to acquire 

 a certain similarity as to form, and only a very small number, usually the smallest 

 and largest trees, differ from this average form class. Accordingly it is often 



