Accelerated formation of Siberian pine (Pinus sibirica Du Tour) stands: a case study from Siberia

Under natural conditions, Siberian pine Pinus sibirica begins to produce commercial cone yields of nuts relatively late (after more than 100 years). The aim of this study was to summarise the experience of the directed formation of Siberian pine forests in Siberia. Experimental objects included plots with traditional thinning of varying intensity and frequency as well as chemical treatment. We assessed the parameters of the stand and its seed production dynamics. Only stands with a minimum density (395-435 trees.ha(-1)) had a normal seed production energy (1.5 or more cones per shoot). Over-dense stands (830-930 trees.ha(-1)) were characterised by a low seed production energy (two times or more below the threshold value). In all plots, there were Siberian pine trees with absent or unacceptable seed production energy, which should be removed (DBH up to 28 cm). Seed production energy positively correlated with most tree parameters (age, height, diameter, volume, length and width of crown).