Groei en productie van Japanse lariks in Nederland

From 1934 to 1996 growth and yield research was done on Japanese larch in the Nether-lands. This includes studies by Becking and by the Dorschkamp/IBN research institute. Together with the permanent sample plots from the timber prognosis system HOSP, all this comprises a dataset of 151 plots with 835 recordings. For the development of top height htop with age t Cieszewski’s model with site index h50 and 3 additional parameters fitted best. The diameter development up to stand height of 7 m was best described with the model by Jansen et al. based on htop and initial density N0.From a stand height of 7 m and up, the basal area increment iG was best described by a power func-tion based on htop, calendar year yor, h50 and S%. For S% > 20.6 the basal area increment drops slightly with increasing S%. The model contains a correction factor for yor; for the period since 1981, this factor is 18 % above the level of the period 1934 till 1980. The effect of thinning on the diameter after thinning was modelled with a modified La Bastide-Faber model. With all models together, a stand projection model was constructed, which describes the measured stand development reasona-bly well. For several models, the parameters differ for the forest region North and South Nether-lands. The model was used to construct yield tables for both regions with five site classes and five thinning intensities.