Anyhow, stemanalyses aswell as temporaryplots have their
deficiencies when used as data for the development of site
index functions. In stem analysis it has to be assumed without
proof that the investigated trees have been belonging to the
stratum of dominant trees throughout their lifetime. The usual
method of using temporary plot data for site index functions
development is the guideline method, assuming – again
unproved – that the average height development found by
smoothing the dominant heights over age, represents the same
site quality throughout the range of data. Monserud (1985)
therefore noted that differences in the shape of site index
functions more often are the result of different methods in
gathering and smoothing data than to real site dependent height
growth differences.