Predicting lumber volume and grade recovery from Scots pine stems using tree models and sawmill conversion simulation

Through application of tree models, stem shape and internal knot structure of Scots pine stems could be predicted using site, stand, and tree variables. Stem shape was described by stem taper and cross-sectional eccentricity. Knot properties included were knot diameter, sound knot length, loose knot length, number of knots per whorl, and longitudinal inclination. This model system was then integrated in a sawmill conversion simulation system (Saw2003) in order to evaluate lumber recovery in terms of lumber dimension distribution, volume, grade, and value. These applications showed that it was possible to predict the lumber grade recovery on the basis of stand and tree measurements. When comparing results of tree models against empirical data for 604 logs, the volume recovery of side boards was overestimated with the modeling approach, but the volume recovery of center boards and the grade recovery showed good agreement. For both methods, the recovery of the strictest grade decreased slightly with increasing diameter at breast height class, but increased with increasing lumber dimension. The results of this study illustrate how the Saw2003 system can be applied to estimate the lumber volume and grade recovery of standing Scots pine trees.

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