Soils in Karst Sinkholes Record the Holocene History of Local Forest Fires at the North of European Russia

Abstract

Despite the abundance of charcoal material entrapped in soils, they remain relatively less studied pyrogenic archives in comparison to the sedimentary paleofire records (e.g., lacustrine and peat deposits), and that is especially the case in most of Russia’s territory. We report here on the deep soil archives of the Holocene forest fires from the Pinega District of the Arkhangelsk region (64.747° N, 43.387° E). Series of buried soil profiles separated by charcoal layers and clusters were revealed in specific geomorphological traps represented by the active and paleokarst subsidence sinkholes on sulfate rocks overlaid by glacial and fluvial deposits. We combine the study of soil morphology and stratigraphy with a set of radiocarbon data on charcoal and soil organic matter, as well as the anthracomass analysis, to extract a set of paleoenvironmental data. A total of 45 radiocarbon dates were obtained for the macrocharcoal material and the soil organic matter. The maximum temporal “depth” of archives estimated from the radiocarbon dating of macrocharcoal reached 10,260 ± 35 cal yr BP. Soil formation with Podzols established at the inter-pyrogenic stages repeatedly reproduced within the period of ten thousand years, while the dominant tree species was Pinus sp. According to the macrocharcoal data, the intervals between fires have shortened in the last thousand years. Dendrochronological estimates suggest the occurrence of fires in almost every decade of the 20th and early 21st centuries. This is the first study of the millennia-scale soil record of forest fires in this particular region of Russia.

Fire Impact on Carbon Pools and Basic Properties of Retisols in Native Spruce Forests of the European North and Central Siberia of Russia

“…It was found that well-defined coal inclusions occur in the upper horizons of the studied soils in the lower part of the organic and upper part of the mineral horizons, which is the result of old ground fires. Coal particles are an integral part of soils after a fire [44], which is consistent with our results and the data from the literature [45][46][47].…”

Polyarenes Distribution in the Soil-Plant System of Reindeer Pastures in the Polar Urals

“…In the lower horizon at a depth of 25-35 cm, the content of large carbonaceous particles increases significantly (from 3-5 mm to 10-12 mm). According to a number of authors [21,24,27], this indicates a local type of fire. The presence of a powerful buried layer of coals (with dimensions up to 5-6 mm or more) in karst craters (located lower down the slope from plots 6 and 5) at a depth of 35-50 cm demonstrates the profile of buried soil with a distinct differentiation into genetic horizons that are formed as a result of erosion-decomposition processes after fires.…”

“…However, forest fires of both modern and past geological epochs are recognised as the main natural source of polycyclic aromatic hydrocarbons in soils. Factual information about the role of paleofires on this issue is fragmentary [17][18][19][20][21].…”

Dendrochronology in European Russia in the Early 21st Century: State of the Art

“…Aakala et al (2011) identified droughts and bark beetles to be driving the forest dynamics in the past 200 years in the Arkhangelsk region. Several studies were focused on the forest fire reconstructions (Drobyshev and Niklasson, 2004;Kharitonova and Novenko, 2019;Mergelov et al, 2020;Ryzhkova et al, 2020). Lange et al (2018) found that in Scots pine ring-width and density chronologies at northern sites microsite differences affect the absolute tree growth, but play a minor role for the summer temperature signal.…”