Current issue: 53(4)
The most important characteristics for the quality of round timber is knottiness. Knots decrease the strength of the wood in sawn goods. Knots in pulpwood obstruct the production process of ground pulp and lower the quality. A qualitative classification of saw logs has been suggested, and the abundance of knots could also be used to determine the quality of pulpwood. In this study, visual observations on the preparation of pulpwood in pulp mill were made to observe the quality of the wood. Samples of the wood was collected, and they were divided in five quality classes. To study the influence of age, forest site type and stand on knots, 140 sample trees of Norway spruce (Picea abies (L.) H. Karst.) were analyzed. The article includes detailed analysis of the abundance and position of knots in the stems of spruce, anatomical structure of the knots, microscopic structure of the fibers, and mechanical properties of the branch and knot wood.
Healthy, straight, more or less free from branches and slowly tapering stems are good raw material for woodworking industry. The aim of the study was to investigate, from the stand point of forest management, the influence of stand and forest site type on the technical quality of the stems. Sample plots were measured in Norway spruce (Picea abies (L.) H. Karst.) stands in Eastern Finland. Norway spruce growing in a stand with closed crowns developed thin branches and self-pruned, if the stand was dense in the early stages. The decisive time for the stand is, therefore, when it is at seedling stage and young stand. The stems are more branchy if the stand has been planted. The adequate planting density is discussed based on earlier studies. The sufficient density seems to be achieved when the spacing is at maximum two meters. When the stems are branchless up to four meters, thinning of spruce stand does not affect knottiness or stem form. A sparsely stocked, knotty young stand does not produce good-quality timber even if the stand is later dense. Selective thinning from above can be used to improve the quality of the wood.
The PDF includes a summary in German.