Recent climate change in Siberia is increasing the probability of dangerous forest fires. The development of effective measures to mitigate and prevent fires is impossible without an understanding of long-term fire dynamics. This paper presents the first multi-site palaeo-fire reconstruction based on macroscopic charcoal data from peat and lake sediment cores located in different landscapes across the permafrost area of Central Siberia. The obtained results show similar temporal patterns of charcoal accumulation rates in the cores under study, and near synchronous changes in fire regimes. The paleo-fire record revealed moderate biomass burning between 3.4 and 2.6 ka BP, followed by the period of lower burning occurring from 2.6 to 1.7 ka BP that coincided with regional climate cooling and moistening. Minimal fire activity was also observed during the Little Ice Age (0.7 – 0.25 ka BP). Fire frequencies increased during the interval from 1.7 to 0.7 ka BP and appears to be partly synchronous with climate warming during the Medieval Climate Anomaly. Regional reconstructions of long-term fire history show that recent fires are unprecedented during the late Holocene, with modern high biomass burning lying outside millennial and centennial variability of the last 3400 years.
The peatlands in the northern hemisphere accumulated substantially more atmospheric carbon (C) during the Holocene than other terrestrial ecosystems. In this study we applied a multi-proxy record to distinguish variations in dynamics of two peatlands in the boreal belt (raised bog) and the forest-tundra ecotone (palsa mire) in Central Siberia. Carbon and nitrogen content in peatland soils and their stable isotope composition δ13C and δ15Μ) were used to trace likely changes of hydrothermal regimes, vegetation shifts and diagenetic alteration of accumulated peat. Several inter-related allogenic and autogenic forcings have influenced the changes in macroelement content and stable isotope composition of peat with depth. In particular, there were climate-induced and succession-driven vegetation community shifts in domination of plants characterized by specific nutrient requirements, nutrient stoichiometry and fractionation of stable isotope values. The climate and permafrost-mediated processes like hummock uplift affected 13C uptake by Sphagnum mosses in wet and dry periods and changing hydrothermal conditions in peat profiles resulted in perturbations of the nitrogen cycle inducing N loss and enrichment 15N abundance, as well as enhanced decomposition was responsible for enrichment of organic matter in the heavier isotopes. These findings confirm the hypothesis that combined use of elemental and stable isotope composition provide meaningful insights in tracing the hydrothermal conditions and the functional state of peatbogs for paleoecological and paleoclimate reconstructions.
The paper presents a new paleoecological evidence covering the last 6500 years based on detailed AMS radiocarbon dating, plant macrofossils, loss on ignition and macroscopic charcoal records from a 8 m long peat sequence, obtained from the palsa mire situated near Igarka (Yenisei Siberia). The obtained data show that the peatland initiation, development of the perennial frost mound and local vegetation history were strongly influenced by the Holocene climatic fluctuations and permafrost dynamics. The main stages of palsa uplift occurred at about 5360 cal yr BP and 2250 cal yr BP and coincided with the periods of cooling in the Russian Arctic region. According to the radiocarbon dating and plant macrofossil analysis of the upper part of peat sequences the peat accumulation rate in the palsa decreased significantly during the last 2000 years. Nevertheless, we consider that the rate of the peat vertical growth could be underestimated due to the disturbance of the frost mound, water erosion and wildfires.
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