218 SVEN PETRINI [54] 



time to fell sample trees or whether to use local or general empirical figures. 

 The form point method has been shown to give a systematic error with 

 estimates of form class values, which goes up to about — 2 E (7,9). — A 

 combination of accessible material of Lappland pine shows that the systematic 

 error can become remarkably larger (see table V). The best method may 

 therefore be to use experience figures. Table VI gives a similar general 

 average series for Lappland pine showing average form classes in stånds of 

 difterent ages. The variation from the average series is rather small, and 

 for forests över 80 years old, the average lies between 0,715 and 0,74. Mate- 

 rial for the series is taken from 25 stånds and the standard variation from the 

 average series is for the individual stånd + or — 1,86 E. For general estimating 

 the series in table VI may well be used. It is best however that every forest 

 management procure for itself local empirical figures as to how the form 

 class varies in the district. An investigation that sets forth a nev/ function 

 between the formpoint and the form class is demonstrated in fig. 1 2 and 

 table VIII. Here have been compared empirical series, concerning average 

 form points in stånds of different ages, with the series in table VI. The new 

 function should apply only to Lappland pine. Meanwhile one may reach a 

 similar safe result by keeping only to the series for average form class and 

 age in table VI. 



Yield estimating. 



In table IX are given the results of a valutation of a stånd of 100 blazed 

 trees. Here two different calipers have been verified, Karsbergs caliper and 

 Arvidsjaur caliper. Two different persons did the caliper estimating. These 

 persons are called A and B in the table. This showed that the difiference 

 between the two persons' value determinations was slight, the same is the 

 case with the difterence between the two types of calipers. With investi- 

 gation the stems have subsequently been felled and the actual logs measure- 

 raents taken. All estimation has given somewhat lower results. With the 

 formclass method — with the use of the real form class value — good re- 

 sults were obtained but this demands a very careful log division of the diffe- 

 rent diameter classes average trees. Here an average form class for the entire 

 blazed stånd was used and log division carried out partly in diameter classes 

 of 5 cm interval and partly in classes of i" interval. One may get a clear 

 difference which is merely dependent on the diameter class interval. If we 

 increase the class interval the resultant value will be higher. This depends 

 on the circumstance that both the largest and smallest dimensions are more 

 uncommon than the average size. Within every diameter class the average 

 is somewhat displaced from the center, that is to say the average numbers 

 in classes lie somewhat displaced against the average stem in the stånd 

 so that in the largest diameter classes the average diameter lies somewhat 

 lower than the middle point and for small dimensions the opposite holds true. 

 The greater the interval the greater the error becomes. In the lowest I have 

 found a value too low while in the highest classes a value too high. In as 

 much as the larger trees show the most for yield value the error is found 

 to be in the positive direction. 



A valuation with the use of the form point method for estimating the form 



