Assessment of external wood quality in planted Silver birch stands of different genetic origin in Tönnersjöheden Experimental Forest

Abstract: The main objective of the thesis was to find out how the wood quality differed among Silverbirch provenances. The study was conducted in family, provenance and tree speciesexperiments in SW Sweden. External features like stem straightness, spike knots, doubleleader, diameter, tree height, leaning and other defects were measured and analyzed.Significant differences were found between birch families and provenances for a number ofmeasured parameters. In the family experiment, significant differences between families werefound for the parameters straight trees and diameter while no significant differences werefound for others measured parameters like spike knots, forking, leaning and tree height. Thelocal provenance “Tönnersjöheden” had the best overall quality and growth in the provenanceexperiment while Kulbäcksliden provenance (North Sweden) had a low overall quality. In thetree species experiment, significant differences between provenances were only found for thefrequency of straight and leaning trees. Asarum was suggested a good quality provenance withan overall high quality performance and a low percentage of leaning trees while Visingsö wasjudged a bad quality provenance with a high percentage of crooked stems and a many leaningtrees.