This paper presents results of analyzing the second half of the 20th–early 21st century changes in lateral spatial structure of Larix sibirica Ledeb. population in the upper treeline ecotone located on the Rai-Iz massif (Polar Urals, Russia). The GIS layers characterizing distribution of Siberian larch trees and undergrowth together with their crowns was produced for a 7.32 square kilometer area based on aerial images recognition. Using statistical models, we assessed probabilities for assigning trees to age intervals of 1–10, 11–40, and 40+ years based on the average radius of tree crown projection. These maps and layer showing locations of trees that grew in the upper part of the ecotone, and died during the Little Ice Age, allow for assessing specifics of forest cover proliferation at different parts of upper treeline ecotone, and comparing current location of the trees with one from the past. The proposed method for probability-based recognition of Siberian larch tree generations in the upper treeline ecotone using average crown radius can be used to reconstruct time and spatial forest dynamics at the upper growth boundaries for time spans up to 100 years and more.

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The seasonal changes in a period of low temperatures and characteristic correlations of some antioxidant system (AOS) components in pine needles influenced by a gas flare are investigated in this study. The parameters taken are total water content (TWC) in needles, peroxidase activity (AP) and selected elements of the antioxidant system of needles, such as content of carotenoids (Car), ascorbic acid (AA), catechins (Cat) and flavanols (Fl). The needles come from Scots pine trees (Pinus sylvestris L.), which grow in a gradient of environmental conditions formed in the zone of thermal field of the gas flare impact (at various distances). The gas flare is situated on the territory of the Khanty-Mansiysk Autonomous Okrug (UGRA) of Russia. Three hypotheses were subject to verification: 1) the thermal field of the gas flare during the low temperature period affects the water exchange and the AOS state of needles; 2) increase in temperature of the environment in the flare impact zone during the autumn-winter period causes the decrease in amount of moisture in needles, which is a trait of oxidative stress in cells; 3) in the functioning of а needle’s AOS, there are correlations between its components, which values depend on distance from the gas flare and environment created by it. It was found that in the thermal field gradient of the flare, there is neither an additional reduction in TWC in needles compared to the background nor signs of change in the state of AOS corresponding to the oxidative stress in the cells. The greatest impact of the gas flare on characteristics of the physiological state of pine needles is observed in the section closest to the flare. It reveals in the higher values of AP, TWC, Car and decrease in concentration of Fl and AA. The seasonal dynamics of the studied traits values do not correlate with the temperature of the environment. It indicates the indirect effect on the regulation of needle’s AOS activity. The factor and correlation analysis of the data indicate a difference in physiological state of pine needles at different distances from the flare. There is no domination of any processes in the functioning of AOS components. The observed correlations between the studied properties change according to distance to the flare. The most stable is a negative AP relationship with ofter parameters, which rise with the increased distance from the flare. The consistency degree of separate AOS components functioning is maximal in background conditions and decreases when approaching the flare. This fact is explained by the modifying effect of the flare on physiological and biochemical processes of the needle’s adaptation to specific climatic conditions of the environment. For citation: Shavnin S.A., Yusupov I.A., Montile A.A., Golikov D.Yu., Marina N.V. Seasonal Dynamics of Content of Antioxidant System Components in Needles of Scots Pine (Pinus sylvestris L.) Trees Situated in the Local Warming Impact Zone. Lesnoy Zhurnal = Russian Forestry Journal, 2023, no. 2, pp. 38–57. (In Russ.). https://doi.org/10.37482/0536-1036-2023-2-38-57