Variability of Pinus sibirica Du Tour in the cones formation on a grafting hybrid-seed plantation over a 10-year period

Pinus sibirica Du Tour is one of the main forest-forming tree species of Siberia. It is distinguished not only by its high forestry characteristics, but also by the nutritional qualities of pine nuts. The aim of the study was to assess the productivity of clones of Siberian pine of different geographical origin over a 10-year period, the allocation of ramets, characterized by the greatest formation of cones on a tree and in a bunch, with an annual or short inter-crop period. The study object was the grafted trees of Pinus sibirica on a hybrid seed plantation created using cuttings of different geographical origin. The cuttings were cut from 21-22-year-old (mother) specimens of Siberian cedar, growing in the arboretum of the Siberian State University, grown from seeds collected in populations that differ in the place of growth. Sowing of seeds was conducted in the years 1961-1962 under the guidance of O.P. Olisova, Associate Professor, the Forest Cultures Department. The seedlings were grown and then transplanted to the geological school in the arboretum of the Siberian State University. In 1982, after a selection assessment, specimens were selected in each variant for harvesting cuttings and vaccinations on a hybrid-seed plantation (HSP) using 6–8 years old ordinary pine as stock. The vaccination was carried out by the method of "core to the cambium" according to E.P. Prokazin (1960). The placement of grafted plants was 5 × 5 m. The rest of the Scots pine undergrowth and other tree species was removed. We analyzed the variability of a 26-36-year-old scion of Siberian cedar according to the cones formation over a 10-year period, the number of cones on a tree and on a shoot “in a bundle” depending on geographical origin and clone affiliation. The number of cones was determined visually using binoculars. It has been established that the number of harvesting years and cones over a 10-year period in Pinus sibirica depends on the geographical origin of the mother trees. The shortest harvesting period had the trees of Sverdlovsk and Kemerovo origin. They also had the largest number of cones on the tree. It was established that the level of variability of ramets in terms of the number of harvesting years over a 10-year period was average (28.0%), and it was very high in the number of cones on a tree (52.2%). The number of trees that formed cones varied in some years from 58.3 to 100%. It should be noted that the variability in ramets yield is also manifested depending on the mother tree from which the cuttings were cut, i.e. a clone. Comparing the number of cones on grafted trees, it was found that abundant seed production occurred in 2009, 2013 and 2016. The smallest cone formation was observed in trees in 2014. The maximum number of cones (78 and 75 pcs.) was recorded in 2016 at the ramets of 15-8 Altai and 11-3 Sverdlovsk origin, respectively. The ramets that formed the largest number of cones during the study period and seed-bearing annually or with a minimum inter-crop period were selected. Multi-cone shaped ramets with 4-5 cones on the shoot “in a bundle” were identified.