IMPACT OF PRUNING ON THE INCREMENT OF SCOTS PINE (Pinus sylvestris L.) FROM A SEEDLING SEED ORCHARD

Abstract

Research on the pruning of pine with thick branches from seedling seed orchards is not often presented in literature. The pruning of thick, living branches has come under criticism due to the increased potential for fungal infection or slower tree increment. The objective of the research was to analyse the increment reaction of pine after the pruning of thick, living branches. The research was carried out on a 26-year-old seedling seed orchard of Scots pine, established in 1983 in the Zdrojowa Góra Forest District (RDSF Piła). Pruning was applied up to 1.5 m on 25 April 1995, 14 July 1995 and 1 March 1996. In 2007, all the dbh measurements were taken and 16 sample trees were selected, from which short logs from the tree trunks were selected for further investigation of the knots after pruning. All the knots were opened by saw along the knot axis. After opening, 5 consecutive annual rings were measured (mm) before and after pruning. In addition, the time of knot occlusion was determined, as well as the number of annual increments after full knot occlusion. In addition the thickness of the inner bark was measured. After pruning, narrower annual rings (by 1.25 mm, 29%) were observed. However, smaller increments appearing directly after pruning were compensated for later, and 13 years after pruning the mean dbh of the pruned trees was larger (by 0.63 cm) than the mean dbh of the unpruned ones. It took 3 years and 8 months, on average, for full knot occlusion and 45% of the knots contained inner bark. All the knots, even those with large diameters, were sound knots. Therefore, the pruning of pine in seedling seed orchards may be recommended.