Efficiency of Thinning in Deciduous-Spruce Forest Stands in the Northern Taiga Forest Region of the European Part of the Russian Federation

Research on permanent sample plots (Arkhangelsk, Northern district forestry, Obozerskoye forestry) in birch and spruce stands with an understory layer of spruce was carried out. The sample plots were established since 1966 and differed in the intensity of thinning. The results were analyzed by correlating them with the data of 6 previously conducted surveys (in 1966, 1974, 1986, 2001, 2010, 2020) for permanent sample plots 1K and 2RU and 5 surveys (1974, 1986, 2001, 2010, 2020) for permanent sample plot 19. In the absence of maintenance in young stands aged 20-30 years (permanent sample plot 1K), further growth of spruce was inhibited, competition between trees increased, and growth tension increased. Birch had a biophysical impact on spruce. Carrying out thinning of various intensities made it possible to form the most productive forest stand on the permanent sample plot 2RU. The total stand stock here is maximum - 435 m3/ha, the average heights for the whole growth period is also maximum. In terms of stock, spruce prevails, however, it is still located in the understory forest level, but will eventually enter the canopy forest level. According to the results of the study, three stages of stand formation were identified. The first stage, the stage of emergence, is characterized by the predominance of birch and spruce over the area, spruce regeneration lasting 15–25 years. In the process of passing this stage, favorable conditions for spruce settlement and its survival are created. The second stage is accompanied by deterioration of spruce growth conditions, as the birch layer differentiation and birch growth are intensively going on. The duration of the stage is 70–90 years. As a result, a new mixed biogeocenosis is formed. The final third stage lasts until the formation of a pure spruce forest. Thinning in natural young forest stands should be considered as a measure providing reliable restoration of forests with coniferous species with costs and labor much less than in case of full artificial reforestation. Acknowledgements: The publication is based on the results of the research carried out within the framework of the state assignment of FBU "SevNIILKh" for applied scientific research. Subject registration number: AAAA-A20-120013090061-7, 121020500249-6. For citation: Surina E.A., Minin N.S. Efficiency of Thinning in Deciduous-Spruce Forest Stands in the Northern Taiga Forest Region of the European Part of the Russian Federation. Lesnoy Zhurnal = Russian Forestry Journal, 2023, no. 5, pp. 103–114. (In Russ.). https://doi.org/10.37482/0536-1036-2023-5-103-114