Graded quality of 30-year-old Norway spruce grown on agricultural and forest land

Noren, A. & Persson, A. 1997. Graded quality of 30-year-old Norway spruce grown on agricultural and forest land. Studia Forestalia Suecica 203. 19 pp. ISSN 0039-3150. ISBN 91-576-5553-7. Six 30-year-old, fast-grown Norway spruce (Picea abies (L.) Karst.) stands in Sweden, comprising a total of 700 stems, were examined. Four had been planted on agricultural land and two on very fertile forest land. The characteristics studied were branch properties, defects and basic density as well as the graded quality of timber, assessed by Swedish export grading, and the modulus of elasticity, assessed by machine strength grading (EJ. Our aim was to determine how the wood properties of Norway spruce grown on agricultural land differ from those of spruce grown on fertile forest land. The only differences found between the two sites concerned defects, especially spike knots. These were more common in the agricultural stands, where the frequency of logs with at least one spike knot was 33.7%, whereas the corresponding figure in the forest stands was 6.9%. The graded quality was low for boards from all stands according to both export and strength gradings. Only 7.1% of the boards were considered to be of highest export grade, u/s. Eighty-two per cent were approved for structural use, i.e., strength grade T18 or better. Basic density and annual ring width were the only characters that explained significant amounts of variation in EM. A model for predicting the EM of boards from a stand is presented. Wood properties could be improved silviculturally by thinning regimes and technically by cross-cutting and using the butt part of the tree for purposes other than sawing.