Photosynthetic Apparatus of Siberian Pine Needles During the Period of Emerging from the State of Winter Dormancy in the Conditions of the High-Altitude Zone of the Western Sayan

Due to climate change, many species of coniferous trees, which are the main forest formers of the forests of Western and Eastern Siberia, have shifts in both latitudinal and altitudinal boundaries of the range. This study is devoted to determining the features of photosynthetic activity and pigment composition of Siberian pine needles growing in the area of the Ergaki ridge of the Western Sayan, during the period of recovery from the state of winter dormancy. Young Siberian pine trees ( Pinus sibirica Du Tour) growing at different heights above sea level were taken as objects of research. In the area of Lake Oyskoe on the territory of the Ergaki Nature Park in the spring of 2023, a transect with four test areas was laid, crossing the timberline during the transition from the mountain taiga to the rocky-tundra area. Single specimens of Siberian pine , spread above the timberline, have a number of ecophysiological features that allow them to survive in fairly harsh conditions. Such features include a greater depth of winter dormancy, when trees in the phase of forced dormancy react more slowly to temperature increases, compared with trees growing below the timberline. For them, apparently, winter-spring thaws will not pose a danger. Strong insolation at low temperatures, characteristic of open mountain slopes in late winter and spring, is also not critically dangerous for the advancement of Siberian pine above the timberline, due to the predominance of carotenoids in the pigment complex of their needles during this period.