Annotation of the results obtained in 2023
During the 2023, field work was carried out on lakes Shira, Uchum, Kiprino (North Minusinsk Basin), during which material from sediment traps and ice samples was obtained for the analysis of charcoal particles >100 мкм. The vertical distributions of the charcoal particles were analyzed in previously collected sediment cores of lakes Shira and Uchum, covering the period of about 1400 and 500 years ago, respectively. The resulting profiles were compared with the profiles of charcoal particles obtained at the first stage of the project in the upper part of bottom sediments, selected from both lakes using a freeze-corer and preserving the layered structure of the youngest semi-fluid layers. In addition, at the 2023 stage, the particle content in the material of sediment traps installed in the lake during 2022 was analyzed. The composition and annual integral fluxes of particles in the upper youngest layer of bottom sediments collected using a freeze-corer in March 2013, 2016, 2019, 2021, 2022 and 2023 were also analyzed. In all samples of bottom sediments, ice and sedimentary material of traps, carbonaceous particles were represented by three typical groups, differing in shape. The first group of particles had an elongated shape, which is interpreted as the remains of herbaceous plants, thin roots, etc.; these objects are conventionally called “blades of grass.” The second group had the appearance of thin flat “scales”, and was conventionally called “leaves”, since it is interpreted in the literature as the remains of leaves. The third group consisted of volumetric “3D particles”, presumably the remains of burning wood, coal and other combustible solid materials. In cores from lakes Shira and Uchum in layers corresponding to the last century, a sharp increase in the rate of accumulation of particles such as “leaves” and “3D particles” was revealed. The most likely reason for the increase in the rate of accumulation of charcoal particles of the second and third types in the modern period is human activity. On the shores of both lakes, the sources of such particles are the chimneys of boiler houses and private houses, as well as fires made by people on the shores during the summer holidays. The seasonal dynamics of the flow of charcoal particles into the sediments of Lake Shira, assessed using sediment traps, showed that these flows increase annually during the cold season, but this trend was not confirmed for 2023. In all seasons, “3D-particles” predominated in the traps, which indicates that their source was solid fuel (coal, firewood) burned in the surrounding villages. Indicators of natural fires are particles of the “blade of grass” type, and their flow has not increased in the modern period. It is likely that the intensity of steppe and forest fires in the ecosystems surrounding the lakes has not increased so noticeably compared to the past. The composition of particles on the ice surface generally confirmed the result revealed by sedimentation traps: in winter, mainly “3D particles” fall out. The smaller number of particles in Lake Kiprino confirms the assumption that the main source is the pipes of heated dwellings in the villages adjacent to lakes Shira and Uchum. A comparison of data from sediment traps with the results of analysis of charcoals on the ice surface and in the upper layer of bottom sediments confirmed that the content of particles in bottom sediments quantitatively adequately reflects their flow to the surface of the lake. The data obtained during this project on the content of charcoal particles in lakes Shira, Uchum, Cheko, Zapovednoye and Suzdalevo were entered into the Global Paleofire Database, https://www.paleofire.org) and expanded the world collection of knowledge in this area.

 

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Annotation of the results obtained in 2022
Forest and steppe fires pose a threat to natural ecosystems and significantly worsen the living conditions of people living in the surrounding areas. Analysis of the amount of charcoal macro-particles in lake sediments provides valuable information about the intensity of fires in the past for a particular region. In the bottom sediments of lakes Cheko and Zapovednoye, located in the southern part of the Evenk region (Krasnoyarsk Territory), the distributions of charcoal particles >100 microns have been analyzed. The background content of charcoal particles in sediments up to 1500 years ago was not less than in recent sediments. Thus, evidence was obtained that the intensity of fires in the vicinity of the studied lakes in the past was not less than at present, and during the 16-18 centuries it was possibly even higher. Therefore, a sharp increase in forest fires in recent times reported for other regions is not confirmed for this territory, which is probably due to the lack of economic activity due to the extremely low population density. In Lake Cheko, a local maximum of charcoal particles was revealed at the sediments corresponding to the year of 1908, presumably being the trace of an extensive forest fire resulted from Tunguska 1908 catastrophe. Studies of modern processes of formation of lake sediments by direct observation are quite rare, despite that only such studies make it possible to verify the adequacy of the interpretation of the content of ancient layers of bottom sediments. By cylindrical traps incubated in the depths of Lake Shira from 2012 to 2019, the seasonal dynamics of the sedimentation flow of charcoal particles larger than 100 microns into the bottom sediments of the lake was assessed for the first time. It is shown that the charcoal flux increases annually from October to May, which is explained by two factors: the burning of fuel by the inhabitants of the surrounding villages to heat their homes during the cold season and the spring steppe fires that occur in April-May. In the warm period of the year, the flow decreases significantly, therefore, campfires made by vacationers are a less significant source of carbon particles entering the lake. Our data show a significant contribution of anthropogenic factors to the sedimentation flow of charcoal particles, both from burning fuel and traces from fires. The annual flux of charcoal into traps coincides in order with the value estimated for recent bottom sediments of other lakes. The data obtained will be useful to more accurately interpret the distribution of charcoal particles in down-core studies and reconstruct the dynamics of fires in southern Siberia in the late Holocene. In upper part of bottom sediments of saline lakes Shira and Uchum located in steppe region of southern Siberia (Khakasia and Krasnoyarsk Region) we analyzed the distribution of charcoal particles >100 µm. The sediments aged up to 400 years BP were sampled by freeze-corer in order to avoid mixing of uppermost semi-liquid layers. Charcoal particles were divided into three classes according to their morphology. The first group of particles, arbitrarily named "grass", has an elongated shape, which is interpreted as the remains of herbaceous plants. The second group looks like thin flat plates (“leaves”) and is interpreted as the remains of leaves. The third group consists of volumetric "particles" of irregular shapes, presumably being the remains of the combustion of wood and coal. It is shown that in the last century the sedimentary flux of "particles" has increased significantly, which most likely reflects an increase in the amount of solid fuel (wood and coal) burned by people in settlements in the vicinity of lakes. The content of "grass" and "leaves", presumably being traces of natural fires, in the past was not less than in recent times. Consequently, the intensity of natural fires in the study region does not show a tendency to increase in the modern period. The information obtained will be useful for the reconstruction of fire regimes from longer cores covering a period of several millennia.

 

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