VARIATION OF GROWTH RING WIDTH IN MARITIME PINE (Pinus pinaster Ait.) WOOD

摘要

The variation of annual ring width, with height and radial distance from the pith, was measured in 83 year-old stems of maritime pine (Pinus pinaster Ait.) sampled in Portugal. The aim of this study was to incorporate ring width data into sawing yield studies through simulation and tree modelling techniques. Results on data analysis measuring annual growth variation contribute also to the raw material characterisation. Five wood discs were sampled at the tree bottom and at 5, 10, 15 and 20 meters of thee height. The discs were used to measure the ring growth in eight directions. Ring width was measured by image analysis. Growth ring variation was analyzed in vertical sequence in order to evaluate tree growth and its variation with the year, and oblique sequence in order to evaluate the behaviour of the last 13 years with the tree height. Data were evaluated with ANOVA analysis and principal components analysis to investigate the differences in trees, annual rings and radial and axial variation. Growth rings increased within the first 5-9 growth rings from the pith and then gradually decreased. Oblique variation of growth rate shows a clear tendency to decrease until 5 meter height then increase to the top of the tree for the earlywood. For latewood growth rate did not exhibit any clear tendency but was observed a small growth at the tree top. In the case of vertical variation, growth rate decreased gradually with the year of cambium formation. We found a great variability along the tree concerning the axial and radial positions. Variation between directions was not significant, and trees did not present a high eccentricity. It was not observed a good correlation between latewood and earlywood ring thickness. A 3D model of the measured rings was developed for each sampled stem that allowed visualization, in 3D and 2D, of the annual growth variation for any given stem height. This growth ring model is intended to be integrated with the 3D stem models including the internal knots and stem and heartwood shape, already developed for this species. These will be the virtual raw-material input for sawing simulation software.