Epsilon Archive for Student Projects

Abstract

The report compares the methods Site Index System (SIS), Upper Height Site Index (SIH),
and Elfving’s increment height development curves (E-SIH) for calculating site index (SI).
The aim was to investigate whether there were differences in estimated SI between the
methods within the same stands depending on geographic area, stand age, and different SI
classes.
For the analysis, inventory data from the National Forest Inventory for spruce (Picea Abies)
and pine (Pinus Sylvestris) in Sweden from the years 1983 to 2002 were used. The data
were divided into classes based on geographic area, age, and SI. Within these classes, SIS,
SIH, and E-SIH were compared with each other.
The results showed significant differences between the methods within all classes, with the
largest measured difference being one to one and a half meters. It also emerged that SIH
and E-SIH tend to give higher site indices in younger stands compared to SIS, than in older
stands. Depending on the geographic location, variations were also shown, with larger
differences between SIS, SIH, and E-SIH in northern Norrland than in other areas. Finally,
different SI classes were compared, where it was found that lower SI (between 10 and 21)
gave a larger difference than higher SI (between 28 and 32). Generally, for all classes, SIS,
SIH, and E-SIH gave a greater spread of SI in spruce stands than in pine stands.
All the differences mentioned above can create conflicts in forest planning. A one-meter
difference in site index makes little practical difference with today's methods, but further
research is needed to draw more precise conclusions and examine the practical implications
of the method differences.