Groei en productie van ruwe berk in Nederland

In the Netherlands growth and yield research on silver birch was done from 1982 to 1994. This includes studies by the Dorschkamp/IBN research institute and by Wageningen University. To-gether with the permanent sample plots from the timber prognosis system HOSP, this comprises a dataset of 43 plots with 132 recordings. For the development of top height htop with age t Cieszewski’s polymorphic model with site index h50 and three additional parameters fitted best.The diameter at a height of 7 m (d7) was estimated with the plot data and with the data of the Fourth National Forest Inventory, and the average of both estimates was chosen. The diameter develop-ment up to stand height of 7 m was described with a model of Jansen et al., a power function in htop and the estimated value for d7. From a stand height of 7 m upwards, the basal area increment (iG) was also described by Jansen’s et al. model based on a power function with h50, t, year of recording (yor), and the stand density of Hart (S %). For S% > 19.5 the basal area increment decreases non-lin-ear with increasing S %. The model contains a correction factor for yor, although this was not signifi-cant, as the year of recording (yor), turned out to be not significant. The effect of thinning on the di-ameter after thinning was modelled with the La Bastide-Faber model.The models were used to construct a yield table with five site classes and one thinning intensity.