Site index predictions by a model such as this will
only be reliable within the environmental ranges of the
original data: the results should not be extrapolated
outside the study area (Section 4.2). Furthermore, it
must be pointed out that the model is developed on a
selection of former agricultural sites under forest
conditions for the last decades. In the past, there
was no incentive to plant trees on agricultural land
of high quality. If there is a dramatic increase in
planting on deep, highly fertile agricultural soils at
low elevation in the future, the model will have to be
reassessed as this is not the typical site type of the
sample population in this study.