Intra-tree models of basic density in Norway spruce as an input to simulation software

Basic density is said to influence aspects of conversion, properties, and e nd-use of forest products. Consequently, it is argued that accurate models of basic density variation, within and between trees, could be used to impr ove the utilisation of wood as an industrial raw material. The objective of the present study was to develop basic density models based on Norway spru ce trees, that could be used within a model system for conversion simulatio n studies. Nineteen stands of Norway spruce (Picea abies (L.) Karst.) were selected throughout Sweden. Based on dbh, two small, two moderate, and two large timber trees were taken from each stand. Dbh varied between 180-470 m m, tree height between 17-34 m, and total age between 51-152 years. Each se lected tree was cross-cut into logs; discs were prepared from the butt end of each log and from the top end of the top log. Computed tomography scanni ng and image analysis were used to determine basic density and growth ring development on sampled discs. Basic density development in 20-mm segments f rom pith outwards was modelled in models based on ring width, tree and grow th condition data. The resulting models had an adjusted R-2 Of 0.37-0.51 an d a RMSE of 37-41 kg/m(3).