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Infuences of silviculture, genetics and environment on radiata pine corewood properties: results from recent studies and a future direction

Authors: Euan Mason
Publication: New Zealand Journal of Forestry, Volume N.Z.J.For. 2008, Issue N.Z.J.For. 53(2) 2008, pp 26-31, Aug 2008
Publisher: New Zealand Institute of Forestry

Abstract: Marketing structural wood from radiata pine plantations is limited by the corewood zone of each log, a zone which lacks stiffness and is unstable during drying (Harris and Cown, 1991). While basic density is lower in the corewood zone, the key factor affecting wood properties in this zone is the angle of microfibrils of cellulose within the S2 layer relative to the tracheid axis (Walker & Butterfield 1996). Higher microfibril angle (MFA) is associated with lower stiffness (measured as dynamic modulus of elasticity, MOE) and with greater longitudinal shrinkage during drying (Pentoney 1953). Furthermore, high rates of change in MFA within this zone mean that different parts of boards shrink by different amounts, directly contributing to instability (Walker and Nakada, 1999). The corewood zone has been defined as the first 10 rings from the pith of a radiata pine log, but this is a rough approximation of a zone that varies in properties with silvicultural, climatic and genetic influences. “Outerwood” is wood beyond this zone.