Relationships between stem size and branch basal diameter variability in Norway spruce (Picea abies (L.)�Karsten) from two regions of France

Statistical relationships between branch basal diameter of living whorls, stem size (height and diameter at breast height) and stand parameters (stand age, site class) were analysed in Norway spruce. The first experimental sample used to calibrate a model consisted of 98 trees from young to old stands growing in Lorraine (Eastern part of France). Every second whorl branch basal diameter was measured and a regression model was established for the living branches. Basal diameter variance components were estimated by a non-linear mixed model analysis. Results confirmed the close statistical relationships between branch basal diameter, tree size and stand parameters, whereas covariance analysis revealed significant random fluctuations among whorls and trees. Every third whorl branch basal diameter of 36 Norway spruce trees growing naturally in Midi-Pyrnes was used for the second analysis. Applying the model to these trees showed a good stability of the statistical relationship between the two regions.