Efficiency of Interpolymer Complexes in Growing Scots Pine Seedlings During the Third Rotation

The study addresses the need to increase the production of high-quality Scots pine ( Pinus ylvestris L.) planting stock for forest restoration in the Irtysh ribbon pine forests. The aim was to assess whether standard containerized seedlings could be produced during a third growing rotation using biostimulants and interpolymer complexes based on chitosan and sodium carboxymethylcellulose. The study has been conducted since 2021 at the Forest Nursery and Forest Seed Station Complex of the Kanonersky branch of the State Forest Natural Reserve «Semey Ormany». Seed quality, emergence timing, seedling height, root development and the yield of standard planting stock were assessed. Laboratory germination reached 95%. During the first rotation, mass emergence occurred on days 4–5 in the interpolymer treatments compared with day 7 in the control; mean seedling height was 8.7–10.6 cm and the proportion of standard planting stock reached 83%. During the second rotation, mean height reached 9.4 cm and the yield of marketable planting stock was up to 70%. During the third rotation, seedling height did not exceed 3 cm, no standard planting stock was obtained, and the root plug failed to form. The results indicate that the effectiveness of biopolymer treatments depends substantially on nursery growing conditions. The practical significance of the study is related to optimizing the timing of the third rotation and greenhouse microclimate. Definitive quantitative attribution of the third-rotation failure to specific environmental factors requires additional instrumental measurements of temperature, light, substrate moisture and water–air conditions.

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