Growth ring width of Pinus caribaea var. hondurensis and its relationship with wood proprieties

A striking feature of the genus Pinus are its growth rings, which originate from the seasonal activity of vascular change resulting in successive depositions on the stem. The technological properties of pine wood present variations related to the width of the growth rings, which is a conditioning factor in the physical-mechanical wood performance. The wood of Pinus caribaea var. hondurensis used in this research came from a 20 year old plantation in the region of Catalao - GO. Thirty-five specimens divided into three groups according to the width of the growth rings were analyzed: Group 1 (0.0 to 0.7 cm - higher percentage of late wood, fine and narrow rings); Group 2 (0.7 to 1.2 cm - the percentage of early and late wood is similar - rings of medium width); Group 3 (1.2 to 2.0 cm - higher percentage of early wood). The basic density, shrinking ability, modulus of elasticity and modulus of rupture were analyzed in static flexion tests, and dynamic elastic moduli determined by stress wave and ultrasound methods. The results indicate that Pinus caribaea var. hondurensis wood with narrower growth rings (greater percentage of late wood, corresponding to group 1) have higher values of density, shrinking ability and also higher stiffness. In this group, the correlations between the properties are higher. In general, the modulus of dynamic elasticity determined by stress wave showed a better correlation with the studied properties than that determined by ultrasound.