A rapid method for estimating the median diameter of the stem profile of Norway spruce (Picea abies Karst) trees

The median diameter of a longitudinal section of the stem may be used to determine the stem volume. However, to calculate stem volume, many measurements of diameter at different heights along the stem are required. Therefore, this approach is not generally applied because time-consuming and expensive. Here, we propose a novel, more rapid method to obtain median diameter using the area of the stem profile. A total of 218 height/diameter classes from more than 5000 spruce trees (Picea abies Karst.) were used to compute the median diameter using the classical method. In parallel, a regression model to assess the median diameter was developed. The strongest predictor of the median diameter for the stem profile was the diameter at breast height (R2 = 0.9985). Statistical analysis revealed that the height of the median diameter on the stem profile was 0.3 × H (tree height). The model was verified on standing and felled trees, revealing that differences between classical computations and the proposed model were less than 2% in most cases (86.24% of trees). The median diameter of the stem profile provides valuable information on stand architecture that could help in advancing our understanding on the mechanical stability of Norway spruce trees (i.e., delineating breakage point), growth model predictions, and competition among trees