Groei en productie van zwarte els in Nederland

In the Netherlands growth and yield research on black alder was done on a limited scale from 1965 to 1990. This regards two studies by the Dorschkamp/IBN research institute; together with the permanent sample plots from the timber prognosis system HOSP, this comprises a dataset of 14 plots with 59 recordings. In addition, the information from 518 stands of the Fourth National Forest Inventory was used. For the development of top height htop with age t Jansen’s et al. polymorphic model with site index h50 and four additional parameters fitted best. The diameter at a height of 7 m (d7) was estimated from data of the Fourth National Forest Inven-tory. The diameter development 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 t, year of recording (yor), and the stand density of Hart (S %). For S% > 15.7 the basal area increment decreases non-linear with increasing S %. The model contains a correction factor for yor, although this was not significant, as the year of recording (yor), turned out to be not significant. The effect of thinning on the diameter 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.