530 JOURNAL OF FORKSTRV 



Investigations in Scotch Pine (Pinus silvestris) 



In his study of the stem form of Scotch pine, Jonson obtained the 

 following- results : 



As with spruce, a number of normal Scotch pine in different por- 

 tions of Sweden were selected as test trees. Care was of course taken 

 to exclude any trees which suffered from abnormities or irregularities 

 of any kind. 



While for all practical purposes the bark of Norway spruce can be 

 considered proportionate to the diameter at any point on the stem, and 

 consequently the stem form of spruce is the same over bark or inside 

 bark, this is not the case with Scotch pine. The thickness of bark 

 varies considerably, and the form of the tree with bark is, as a rule, 

 quite different from the form of the same tree inside bark. 



It was, therefore, necessary first to ascertain the normal form of the 

 stem exclusive of bark. If to this is added bark of normal thickness 

 a "normal" tree is obtained. 



The trees were measured and classified in the same manner as has 

 before been described for spruce, only the diameters were all measured 

 inside bark. 



After arranging the trees according to form class, it was again found 

 that trees with the same absolute form quotient zvere built after a 

 similar model, whether they zvere short or tall, small or large. 



Following is a comparison between the average series for Scotch 

 pine obtained from actual measurements and the series for Norway 

 spruce of the same absolute form quotient computed by the equation 



^=Clog^ 



Diam. at section 0(b.h.) I II III IV V VI VII VIII IX 



Pine, measured inside 



bark lOO 94.5 90.0 85.2 79.4 72.4 64.1 53.9 40.7 22.8 



Spruce, computed 100 95.6 90.8 85.8 79.4 72.4 64.3 54.7 42.6 26.0 



Variation in per cent — i.i — 0.8 — 0.6 ±0 — 0.2 — 0.8 — 1.9 — 3.2 



Ave. absolute form factor for pine = 0.502, for spruce = 0.509. 



The similarities in stem form between the two species are rather 

 striking. A still better result is obtained if we free the pine series from 

 the effect of a small root swelling. If we plot the series graphically we 

 find that the curve is inclined to go about i.i per cent inside the meas- 

 ured d. b. h. 



By multiplying all diameter quotients by -^ — the series is trans- 

 formed to a series where the d. b. h. has been corrected by i.i per cent. 

 \\'e then have the following two series : 



