Size and localisation of knots in timber from mountain spruce stands in the Dolomites

The aim of the study was evaluation of knots in wood of 150-year-old Norway spruce [Picea abies (L.) Karst.] in stands situated at the altitude of 1450-1740 m above sea level in the Dolomites in Italian section of the Alps. In selected stands, spruce trees were cut down and their length, stem thickness, height to the crown base and stem diameters at every 1 m along the length of merchantable bole were measured. The diameter of knots was measured and they were classified according to their healthiness and the degree of their tightness with the surrounding wood. The relative knot diameters were calculated and the relative height of their location on stem was determined. In total on sample trees there were analysed 1070 knots, of which sound knots (close to 75%) and tight (more than 60%) prevailed. Sound and tight knots had largest diameters, relative diameters and relative heights of location on merchantable boles. The smallest diameters and relative diameters were indicated by rotten and not tight knots that were located at the lowest merchantable bole parts.