Functional Characteristics of Siberian Spruce Undergrowth Needles under the Canopy and in the Cutting of Bilberry Spruce Forest in the Middle Taiga Subzone

Currently, the coniferous undergrowth preservation in the cuttings of the boreal zone is of great importance for the accelerated restoration of coniferous forests. When assessing the natural regeneration of forests in clear cuttings of the North, it is important to know the basic life activity processes of the undergrowth that survived after logging. An attempt to consider these issues from a physiological point of view has been made. The pigment activity and carbon dioxide gas exchange of spruce undergrowth needles caused by industrial logging in the middle taiga subzone of the Komi Republic was studied. This article provides a comparative analysis of the photosynthetic apparatus physiological parameters of the 20-year-old spruce undergrowth under the canopy of the bilberry spruce forest and in the 8-10-year-old clear cutting. Changes in the undergrowth pigment pool due to spruce forest felling were revealed. In a damp spruce bilberry forest, the spruce undergrowth needles accumulate chlorophylls and carotenoids; 1.08–1.63 and 0.26–0.37 mg/g of dry weight, respectively. The concentration of green and yellow pigments in the spruce undergrowth needles is 18–25 and 18–35 % higher in the clear cutting than under the canopy. The undergrowth photosynthetic apparatus in the clear cutting adapts to environmental conditions at the pigment system level by activating the synthesis of chlorophylls and carotenoids. The seasonal rhythm of pigment content was the same in the spruce undergrowth in the clear cuttings and under the canopy of the bilberry spruce forest. The greatest amount of pigments was observed in autumn, which is an adaptive trait that ensures the resistance of the assimilation apparatus to the Northern conditions along with other mechanisms. We have found that the photosynthetic capacity (2.69 μmol CO2/(m2 ∙ s)) of the spruce undergrowth needles in the cutting is 1.5 times higher than in the bilberry spruce forest, which contributes to the assimilates accumulation and their use in growth processes. The spruce undergrowth needles in the cutting have a low respiratory capacity (0.20 μmol CO2/(m2 ∙ s)), which leads to an improved carbon balance. The obtained data provide the basis for modeling the behavior of natural regeneration of forests and can be used to address issues of improving the functioning of spruce forests during their intensive operation in the Komi Republic. Acknowledgements: The research was carried out within the framework of the state assignment of the Institute of Biology of Komi Scientific Centre of the Ural Branch of the Russian Academy of Sciences (state registration No. 1021051101417-8-1.6.19). For citation: Tuzhilkina V.V. Functional Characteristics of Siberian Spruce Undergrowth Needles under the Canopy and in the Cutting of Bilberry Spruce Forest in the Middle Taiga Subzone. Lesnoy Zhurnal = Russian Forestry Journal, 2022, no. 6, pp. 107–116. (In Russ.). https://doi.org/10.37482/0536-1036-2022-6-107-116