IntroductionPinus pinaster Ait. is one of the most important coniferous species used in the timber industry in Spain, especially in Galicia (NW Spain) where it covers around 587,000 ha of land and is the main forest industry resource. More than 2.8 million cubic meters of Pinus pinaster round wood are produced annually in Galicia, representing 72% of the total production of the species in Spain. Recent studies have demonstrated the good mechanical properties of Galician P. pinaster timber, which make it suitable for structural use (Riesco and Díaz González, 2007;Carballo et al., 2009).Forest management and climatic and soil factors have important effects on softwood properties (e.g. Lasserre et al., 2004;Moore et al., 2009;Roth et al., 2007;Watt et al., 2006;. Studies carried out in different regions have assessed the influence of these factors on the variation in wood properties in coniferous species (e.g. Lei et al., 2005;Liu et al., 2007, or Ikonen et al., 2008. The use of portable acoustic devices that estimate timber stiffness from measurements made on standing trees (e.g. Wang et al., 2001b;Merlo et al., 2008Merlo et al., , 2009Santaclara et al., 2011) is a key element of these studies. Stiffness (quantified by the modulus of elasticity, MOE) is an important mechanical property of timber and it is commonly measured in machine grading of timber strength. It is also the index parameter considered by
Abstract
Aim of study:Modelling the structural quality of Pinus pinaster Ait. wood on the basis of measurements made on standing trees is essential because of the importance of the species in the Galician forestry and timber industries and the good mechanical properties of its wood. In this study, we investigated how timber stiffness is affected by tree and stand properties, climatic and edaphic characteristics and competition.Area of study: The study was performed in Galicia, north-western Spain.
Material and methods:Ten pure and even-aged P. pinaster stands were selected and tree and stand variables and the stress wave velocity of 410 standing trees were measured. A sub-sample of 73 trees, representing the variability in acoustic velocity, were felled and sawed into structural timber pieces (224) which were subjected to a bending test to determine the modulus of elasticity (MOE).Main results: Linear models including wood properties explained more than 97%, 73% and 60% of the observed MOE variability at site, tree and board level, respectively, with acoustic velocity and wood density as the main regressors. Other linear models, which did not include wood density, explained more than 88%, 69% and 55% of the observed MOE variability at site, tree and board level, respectively, with acoustic velocity as the main regressor. Moreover, a classification tree for estimating the visual grade according to standard UNE 56544:2011 was developed.Research highlights: The results have demonstrated the usefulness of acoustic velocity for predicting MOE in standing trees. The use of the fitted equations together with existing d...
