Raw material characteristics of maritime pine (Pinus pinaster Ait.) and their influence on simulated sawing yield

The objective of this work was to study maritime pine (Pinus pinaster Ait.) wood characteristics and their impact on the sawing yield using virtual stem models and sawing simulation procedures. In the first part of the work, a characterisation of maritime pine as raw material for the wood industry was performed. The stem shape, distribution of knots, and heartwood/sapwood contents were studied. In the second part of this work, the virtual stems provided the raw material for sawing-simulation studies. The stem reconstruction, bucking, and sawing simulation modules of WoodCIM® were used. WoodCIM® is an integrated optimising software system, developed at the Technical Research Centre of Finland (VTT), for the optimisation of the wood conversion chain. The software was adapted for maritime pine and validated. Thirty five maritime pine stems were randomly sampled from 4 sites in Portugal. These were mathematically reconstructed into virtual stems, based on image analysis of flitch surfaces. The 3D virtual stems included the description of external shape, internal knot architecture, and heartwood core. The reconstruction of the heartwood shape was a new feature added to the reconstruction module during this study. Input data concerning final products and process variables for sawing simulation were obtained directly from the wood-based industry. The average volume percentage of knots in 83 year-old maritime pine trees, varied from 0.07% for butt logs to 1.95% for top logs. Heartwood diameter either followed the stem profile or showed a maximum value at the height 3.8 m, on average, while sapwood width was higher at the stem base and after 3 m remained almost constant along the stem height. Production yields were higher for logs with origin of the first half of the stem as diameters were large and taper reduced when compared with top logs. Butt logs showed the highest value yields because of the knot core profile. When the target was to maximise the production of heartwood containing components, best yields were obtained with logs bucked between 3 and 9 m height. The results in this study increased the basic scientific knowledge about maritime pine concerning the variations of wood characteristics and their influence on sawing yield outputs. Also, these can contribute to further development of industrial applications of defect detection and sawing simulation tools.