Formation of crown for Siberian cedar over a 12-year period after decapi-tation (suburban area of Krasnoyarsk)

Trees are decapitated to form a low-topped crown to improve cuttings and cone harvesting conditions. To do this, offer different methods of crowns decapi-tation with an intensity of 55-75%. The stimulating effect of pruning on the productivity of trees, the crowns growth, and the formation of multi-tops esti-mated. The plantations of Siberian cedar Pinus sibirica Du Tour are established to obtain valuable seeds and improve the environmental conditions in the subur-ban area of large industrial centers of Siberia. The Siberian cedar is distinguished not only by its high silvicultural characteristics, but also by the nutritional quali-ty of its pine "nuts". The aim of the research was to establish the peculiarities of crown formation for Siberian cedar on the plantation "Meteostation" over a 12-year period after decapitation. The plantation was established under the supervi-sion of R.N. Matveeva. Planting scheme 5 × 5 m applied. The object of the re-search was 54-year-old Siberian cedar grown from seeds harvested in 1964 in Leninogorsk Forestry of the Republic of Kazakhstan. The decapitation was per-formed for trees of 42 years old in 2005 at the height of 1.4-1.7 m. The height of the trees before decapitation varied from 3.3 to 4.5 m, the trunk diameter – from 9.5 to 23.6 cm. The average crown diameter was 3.8-4.3 m. The upper part of the crown is removed by 50.0-66.7%. The trees were measured for height, growth of the leading shoots replacing the central shoot, and trunk diameter at the soil sur-face. The level of variability was assessed according to S.A. Mamaev scale. By 2017, the trees had reached the height of 5.6-9.1 m; the number of leading shoots replacing the central one was 3-7. Trees with a trunk diameter of 12-18 cm had 3-4 leading shoots replacing the central one; those with a diameter of 20-26 cm had 6-7 shoots each. Linear growth of branches replacing the central shoot for the 12-year period was 4.0-7.6 m. The maximum growth was noted in tree 4-98: 7.0-90.0 % more than the others. Trees 4-33, 4-46, 4-73, 4-117 had the largest trunk diameter. It was found that the level of variability of tree height is low; growth, trunk diameter - medium, the number of leading shoots - high. The highest height (9.1 m) had the tree number 4-98, exceeding the others by 8.3-62.5 %. The aver-age number of lateral branches formed during the 5-year period on the leading shoots was compared. Between 2013 and 2017, the average growth was between 23.6 and 45.5 cm. The highest value of average growth over the 5-year period (45.5 cm) was in tree number 4-73, which was 12.1-71.0% higher than the others. Trees 4-117 and 4-33 were distinguished by weak growth, where the average growth was 23.6-29.9 cm. The average number of lateral branches formed during the 5-year period on the leading shoots was compared: by 4.4-7.9 branches of 3.6 to 2.0 m in length. The greatest length of lateral branches was on tree No. 4-85. Weak branch formation in whorls was observed in tree 4-117. A close direct cor-relation was established between the diameter of the trunk and the number of leading shoots; the number of leading shoots and the total number of lateral branches on the shoots; the trunk diameter during pruning, and the height of trees after 12 years of decapitation. The decapitation has resulted in the formation of a multi-trunk crown in Siberian cedar trees. When decapitating Siberian cedar trees, it is necessary to give preference to the specimens that have the largest number of developed lateral branches in the lower whorls, the trunk diameter is larger. It is recommended to leave at least 6-7 leading shoots during decapitation.