Relationships between low-temperature fires, climate and vegetation during three late glacials and interglacials of the last 430 kyr in northeastern Siberia reconstructed from monosaccharide anhydrides in Lake El'gygytgyn sediments

Abstract

Abstract. Landscapes in high northern latitudes are assumed to be highly sensitive to future global change, but the rates and long-term trajectories of changes are rather uncertain. In the boreal zone, fires are an important factor in climate–vegetation interactions and biogeochemical cycles. Fire regimes are characterized by small, frequent, low-intensity fires within summergreen boreal forests dominated by larch, whereas evergreen boreal forests dominated by spruce and pine burn large areas less frequently but at higher intensities. Here, we explore the potential of the monosaccharide anhydrides (MA) levoglucosan, mannosan and galactosan to serve as proxies of low-intensity biomass burning in glacial-to-interglacial lake sediments from the high northern latitudes. We use sediments from Lake El'gygytgyn (cores PG 1351 and ICDP 5011-1), located in the far north-east of Russia, and study glacial and interglacial samples of the last 430 kyr (marine isotope stages 5e, 6, 7e, 8, 11c and 12) that had different climate and biome configurations. Combined with pollen and non-pollen palynomorph records from the same samples, we assess how far the modern relationships between fire, climate and vegetation persisted during the past, on orbital to centennial timescales. We find that MAs attached to particulates were well-preserved in up to 430 kyr old sediments with higher influxes from low-intensity biomass burning in interglacials compared to glacials. MA influxes significantly increase when summergreen boreal forest spreads closer to the lake, whereas they decrease when tundra-steppe environments and, especially, Sphagnum peatlands spread. This suggests that low-temperature fires are a typical characteristic of Siberian larch forests also on long timescales. The results also suggest that low-intensity fires would be reduced by vegetation shifts towards very dry environments due to reduced biomass availability, as well as by shifts towards peatlands, which limits fuel dryness. In addition, we observed very low MA ratios, which we interpret as high contributions of galactosan and mannosan from biomass sources other than those currently monitored, such as the moss–lichen mats in the understorey of the summergreen boreal forest. Overall, sedimentary MAs can provide a powerful proxy for fire regime reconstructions and extend our knowledge of long-term natural fire–climate–vegetation feedbacks in the high northern latitudes.

Wildfire history of the boreal forest of southwestern Yakutia (Siberia) over the last two millennia documented by a lake-sedimentary charcoal record

“…A principal component analysis (PCA; package "stats"; R Core Team, 2020) was used to assess relationships among the various centred log-ratio (clr) transformed (package "compositions"; van den Boogaart et al, 2020) relative distributions of charcoal particle classes. To evaluate potential associations between charcoal accumulation and vegetation we applied correlation tests using Kendall's τ (package "psych"; Revelle, 2020) to clr-transformed relative distributions of pollen types and charcoal classes following Dietze et al (2020).…”

“…The main fire regimes in the European and western Siberian evergreen boreal forest also differ markedly from those of its larch-dominated, deciduous counterpart in eastern Siberia. Many prevalent evergreen conifers (Pinus sibirica, Picea obovata, Abies sibirica) are commonly seen as fire avoiders and are more susceptible to crown fires 70 (Dietze et al, 2020;Isaev et al, 2010;Rogers et al, 2015). The predominant eastern Siberian larches (Larix gmelinii, L. cajanderi, L. sibirica), on the other hand, can resist fires with an insulating bark protecting the cambium from heat, while their deciduous and self-pruning nature restricts fires from reaching the crown (Wirth, 2005).…”

“…Moreover, larches are thought to benefit from occasional surface fires, leading to more saplings by clearing the lower vegetation layers of plant litter and mosses, although this might become a risk for young trees if fire 75 frequencies increase above a certain threshold (Sofronov and Volokitina, 2010). Surface fires in larch forest might also play a role in the long-term preservation of permafrost (Dietze et al, 2020;Herzschuh, 2020;Herzschuh et al, 2016). These different fire strategies within the Siberian boreal forest reinforce the need for fire reconstructions towards the eastern part to evaluate changes in fire regimes depending on the prevalent tree species and to obtain a biome-specific overview of fire regimes throughout time.…”

Wildfire history of the boreal forest of south-western Yakutia (Siberia) over the last two millennia documented by a lake-sediment charcoal record

“…When compared to the pastoralist societies that existed up to that point, anthropogenic influence on the fire regime likely increased at the end of phase 3 (ca. 1700 CE onwards) and throughout phase 4 after colonization and industrialization (Drobyshev et al, 2004). It has been shown that human livelihoods and the mentality towards fire use can often better explain shifts in fire regimes than population density alone (Bowman et al, 2011;Dietze et al, 2018).…”

Interaction of Fire, Vegetation, and Climate in Tropical Ecosystems: A Multiproxy Study Over the Past 22,000 Years

“…Levoglucosan may also be prone to post-depositional degradation, although the knowledge of its impact on levoglucosan concentrations over long time scales is limited (Suciu et al, 2019). Levoglucosan is detected in considerable concentrations in sediments dating back to 200 ka (Schreuder et al, 2019), 270 ka (Elias et al, 2001), and 430 ka (Dietze et al, 2020), suggesting its long lifetime in sedimentary environments after deposition, possibly related to the adsorption to biogenic particles proposed by Schreuder et al (2018). The postdepositional degradation of levoglucosan cannot be completely ruled out but is expected to have minor impact on the downcore variation in our record.…”