Modelling spiral grain angle variation in New Zealand-grown radiata pine

Background Spiral grain angle (SGA) is a wood property that has a strong influence on end-product quality, particularly for solid timber, and most commercial log and timber grading rules restrict the amount of visible surface sloping grain. The aim of this study was to develop parametric models that can be used to predict the intra- and inter-stem variation in SGA in radiata pine (Pinus radiata D.Don) trees growing in New Zealand.