Evaluation of resin productivity of mature pure pine stands in the Leningrad region

The article considers the specific features of changes in resin productivity of pine (Pinus sylvestris L.) in a similar type of forest conditions with division into sections with different intensity of forest care. The object of the study was a 90-year-old lingonberry pine forest, and the resin productivity of 10 sections with different care was considered. Resin productivity was measured based on the intensity of oleoresin flow after applying uniform wounds on the tree trunk, then the length of oleoresin flow was measured after 10 hours. Experiments were conducted by month of summer, by four sides of the world and by stand thickness to study the effect of thickness on resin productivity. The obtained data were statistically processed and grouped where possible on the basis of homogeneity of indicators. It was found that resin production was not related to such factors as the month of summer period and the side of light. A positive effect of thinning treatments on productivity was revealed: the highest values were obtained in the section with 35 % intensity thinning and fertilizer application, as well as in the most sparse stand with 50 % intensity thinning. In these sections, the variability of resin productivity by thickness stages was much lower than in the others, with trees of 20−36 cm stages showing quite similar resin productivity. The stand density differed by site sections and amounted to 485−860 trees per hectare, in general, lower average resin productivity was observed in more dense control sections without thinning. However, no statistically significant influence of density on resin productivity was found at the 95 % confidence level. In the high resin-producing sections, analysis of variance revealed the effect of the tree size factor at a significance level of 90 %. Greater resin productivity is observed in the 28 cm thick stages, in the cases of more productive sections in the stages 28−32 cm.