Models of knot properties for Norway spruce and Scots pine

Abstract

This thesis includes 4 published papers. Internal knot properties were studied for Norway spruce (Picea abies) and Scots pine (Pinus sylvestris). Knot diameter, sound-knot length, loose-knot length, knot frequency and vertical knot angle were obtained through computer tomography and image analysis for 114 Norway spruce stems and 198 Scots pine stems. Trees sampled from permanent research plots in Sweden were studied in terms of between-stand, between-tree and within-tree variation. Effects of site, silviculture, within-stand differentiation, height above ground and azimuth were considered. Using various tree and stand descriptors, statistical models were developed for each knot property. This involved the application of a variety of models such as linear, non-linear, mixed and generalized-linear models. In order to accommodate for different anticipated applications, several models were presented using different sets of independent variables. The resulting models are intended to be integrated in decision support systems for product recovery studies.