Models of height curves in fir-beech stands of the Eastern Carpathians

The models of height curves were derived from repeated measurements at six permanent research plots in the experimental object of Komarnik situated in the Eastern Carpathians. During more than 50 years of investigation, the heights of 1,346 beech and 1,208 fir trees were measured. Tree heights had a great variability, but the stage-shift of height curves was not confirmed. The non-linear regression models of height curves for beech and fir were derived, where tree height is a function of tree diameter and model height for a selected diameter class. They are based on the Korf growth curve with three parameters. The models explained 90% and 94% of beech and fir height variability, respectively. The models confirmed the actual knowledge that fir had higher tree height increment than beech especially for trees with greater diameters. The comparison of our models to those developed by other authors showed that the shape of height curves slightly differed. Beech curve was characterised by greater, while fir curve by lesser curvature in comparison with other published models. Our models have only local validity due to the limited scope of experimental data. They can be applied under the local conditions in order to perform valuation and simulation of growing stock development and increments of uneven-aged and multistoried fir-beech stands.