Evaluation of height-diameter equations for predicting dominant height using data from Estonian forest research plots

The primary goal of forest modelling is to accurately describe various forest processes and estimate stand- or tree-level indicators through mathematical models. Developing an accurate height-diameter model is a critical step in the creation of forest growth and yield models. The height-diameter curve is a mathematical equation with tree diameter at breast height as an input value and tree height as an output value. The objective of this research was to assess 50 different height-diameter curves to identify the most suitable ones for predicting dominant height using individual tree data from the Estonian Network of Forest Research Plots (ENFRP). Dominant height is defined as the mean height of 100 largest trees per hectare. For the evaluation we used measurement data collected from ENFRP plots between the years 1995 and 2021. The evaluation of height-diameter curves was based on their mathematical properties and the prediction error of dominant height. Among the evaluated equations, a modified version of the Hossfeld IV equation, was identified as the most accurate for predicting dominant height. The same equation, with Artur Nilson’s parameterization, yielded similar results. The results of this study can be used for developing generalized height-diameter models.