An elliptical model for tree ring shape in transverse section. Methodologyand case study on Norway Spruce

The objective of this work was to built a model for describing the transver se section of Norway spruce (Picea abies Karst.) stems, i.e. the ring shape s and their variations within the trees. A set of 453 disks was sampled and more than 9500 ring's shapes were measured. Four different elliptical mode ls were analysed, and as a first result it was demonstrated that a single e lliptical model was well adapted to fit the data. On this base, the ring el lipticity variations were analysed from the pith to the bark and from the b ottom to the top of the tree. The rings are rather circular near the pith a nd at the top of the tree stem and rather elliptical close to the bark and at the bottom of the stem. As a second result we have built models describi ng these variations. These models could be further used on line by laser se nsors, for a better sawing pattern optimisation.