Predicting knot diameter of Pinus sylvestris in Sweden

Average diameter of the thickest knot of each whorl within a specific stem section of Scots pine (TK) was studied using functions based on growth ring widths, diameter of dry branches, site index, stand age, and latitude. Dat a from the Pine Stem Bank-a database of external and internal properties wh ere knots were detected by computerized tomography (CT) scanning-were used. A high value of the corrected coefficient of determination, R-2(adj) = 0.6 3, was found between TK and two independent variables, average width of gro wth rings 11-20 at stump height and latitude. It is argued that TK is a goo d parameter for describing timber quality, and that it now is predictable o n standing trees as well as on existing data from the National Forest Inven tory (NFI). An attempt was made to quantify the change in the TK-value by s ite index, tree class, age class, and region by applying functions to NFI d ata from 1988-92. In a second analysis, also based on NFI data, the TK-valu e had increased by 17% from 1966 to 1988-92. The authors believe that this is mainly a result of the silvicultural systems used and that it is possibl e to reverse the negative trend by changing silvicultural methods.