CR5.2

CR5
Thawing permafrost - stabilization versus decomposition of organic matter? 

About 800 Pg soil carbon has been frozen for centuries to millennia. A large fraction of it is assumed to be thawed due to climate change in the near future. A rapid mineralization of this carbon to carbon dioxide or methane will directly alter the global carbon cycle resulting in positive feedback mechanisms that even accelerate climate change. However, permafrost-affected soils and the organic matter stored within are distributed heterogeneously with depth and across ecosystems. Is such thawing organic matter accessible to microorganisms and vulnerable to microbial decay, and hence will it be decomposed fast? Will a large part of it be stabilized at mineral surfaces or in soil aggregates, or will stabilization processes known from temperate soils be rather ineffective? Furthermore, what is the effect of hydrological changes to carbon mineralization or stabilization, particularly with respect to energy constraints of microorganisms? What will be effects of changing vegetation functions to soil organic matter dynamics? This session invites papers that investigate decomposition versus stabilization of thawing permafrost or active layer-organic matter. Contributions may be based on laboratory experiments, field observations, or modelling from the process level to the global scale.

Co-organized by BG3
Convener: Christian Beer | Co-conveners: Georg Guggenberger, Carsten W. Mueller
Presentations
| Tue, 24 May, 08:30–10:40 (CEST)
 
Room 1.15/16

Presentations: Tue, 24 May | Room 1.15/16

Chairperson: Christian Beer
08:30–08:40
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EGU22-6418
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ECS
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solicited
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On-site presentation
Prachi Joshi, Monique Patzner, Ankita Chauhan, Eva Voggenreiter, Katrin Wunsch, Casey Bryce, and Andreas Kappler

As permafrost thaws, vast stocks of organic carbon previously accumulated within these systems are vulnerable to microbial decomposition and may be released as the greenhouse gases CO2 and CH4. The release of carbon from permafrost systems is expected to lead to runaway positive feedbacks. The timescale and magnitude of the permafrost-climate feedback is highly uncertain as knowledge gaps remain regarding the rate of decomposition of permafrost organic carbon. These knowledge gaps stem, in part, from poor understanding of the association between organic carbon (in the form of organic matter) and minerals, especially high surface area iron minerals. In this work, we investigated the coupling of iron and carbon cycles in permafrost peatlands and its effect on greenhouse gas release. We first showed that up to 20% of the organic carbon in intact permafrost sites may be associated with iron(III) (oxyhydr)oxides and thereby protected from microbial decomposition. At the onset of thaw, this association is broken down, likely due to the microbial reduction of iron(III), and previously protected carbon is thus released. Using microbiological and molecular biological tools, we linked this breakdown to an increase in the abundance of methanogenic microorganisms and concentrations of methane. Preliminary work also suggests that part of the released organic carbon may re-associate with dissolved iron in thaw ponds to form flocs. Currently, we are investigating the molecular composition of organic matter as it undergoes these redox processes with the goal of linking bioavailability to composition. We complement this work with enrichment experiments and microbial community analyses to determine the microbial key players controlling iron(III) reduction and the potential for subsequent microbial Fe(II) oxidation. Collectively, the results of this project suggest that upon thawing, organic matter previously associated with minerals is mobilized and is likely susceptible to microbially-mediated release as CO2 and CH4.

How to cite: Joshi, P., Patzner, M., Chauhan, A., Voggenreiter, E., Wunsch, K., Bryce, C., and Kappler, A.: Role of iron-carbon interactions in the release of greenhouse gases from permafrost systems, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6418, https://doi.org/10.5194/egusphere-egu22-6418, 2022.

08:40–08:45
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EGU22-10683
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Virtual presentation
Christian Knoblauch, Janet Rethemeyer, Carsten W. Mueller, Pavel A. Barsukov, and Christian Beer

Thawing of permafrost like the wide spread  ice-rich Yedoma deposits in northern Siberia release large quantities of organic matter that may be decomposed to the greenhouse gases (GHG) CO2 and CH4. Since Yedoma deposits store up to 130 Pg of organic carbon (OC), the release of GHG from these thawing deposits might be of global relevance. The degradability of released organic matter is unclear. Current estimates on how fast the organic matter from thawing Yedoma may be transferred into CO2 range between 66% in one summer thaw season and 15% in 100 years. To reduce uncertainties about the degradability of Yedoma organic matter and to quantify the carbon pool that rapidly may be released a CO2, we incubated samples from different thermokarst affected soils and fractionated the organic matter by density fractionation. One set of soils originated from a vegetated thermokarst depression, the second set from a retrogressive thaw slump without vegetation. The total release of CO2 after 500 days at 4°C was significantly higher from soils of the vegetated thermokarst depression (4.0 ± 4.1% of OC) than from the retrogressive thaw slump (2.1 ± 0.9 % of OC), likely due to the input of fresh organic matter by the vegetation. Most of the organic carbon was bound to the mineral fraction (45 ± 24%), while the free particulate organic matter (fPOM) and the occluded organic matter (oPOM) contributed almost equally (26.8 ± 20.9% and 27.8 ± 12.0% of OC, respectively). The amount of carbon in the mineral fraction did not correlate with the CO2 formation, indicating stabilization of organic matter. Surprisingly, the oPOM fraction was stronger correlated with released CO2 than the fPOM fraction. However, the strongest correlation was found between CO2 production and the C/N ratio of total OC.

How to cite: Knoblauch, C., Rethemeyer, J., Mueller, C. W., Barsukov, P. A., and Beer, C.: Organic matter decomposition and stabilization in Siberian tundra soils affected by thermokarst processes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10683, https://doi.org/10.5194/egusphere-egu22-10683, 2022.

08:45–08:50
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EGU22-4211
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Presentation form not yet defined
Hanna Lee, Casper Christiansen, Inge Althuizen, Anders Michelsen, Peter Dörsch, Sebastian Westermann, and David Risk

Abrupt permafrost thawing is expected to release large amounts of greenhouse gasses to the atmosphere, creating a positive feedback to climate warming. There is, however, still large uncertainty in the timing, duration, magnitude, and mechanisms controlling this process, which hampers accurate quantification of permafrost carbon climate feedback cycles. The current understanding supports that abrupt permafrost thaw will lead to surface inundation and create anaerobic landscapes, which dominantly produce methane during the decomposition process. Over time, natural succession and vegetation growth may decrease methane release and increase net carbon uptake. We investigated how rapid permafrost thawing and subsequent natural succession over time affect CO2, CH4, and N2O release at a field site in northern Norway (69ᵒN), where recent abrupt degradation of permafrost created thaw ponds in palsa peat plateau-mire ecosystems. The site exhibits a natural gradient of permafrost thaw, which also corresponds to a strong hydrological gradient (i.e. dry peat plateau underlain by intact permafrost, seasonally inundated thaw slumps, thaw ponds, and natural succession ponds covered by sphagnum and sedges). Since 2017, we used a range of manual and automated techniques to measure changes in vegetation, soil and water microclimate, biogeochemistry, and soil CO2, CH4, and N2O concentrations and fluxes across the permafrost thaw gradient. In the three-year observations, we show that abrupt permafrost thaw and land surface subsidence – both intermediate slumping and pond formation – increase net annual carbon loss. Permafrost thaw accelerated CO2 release greatly in thaw slumps (177.5 gCO2 m-2) compared to intact permafrost peat plateau (59.0 gCO2 m-2). During the growing season, peat plateau was a small sink of atmospheric CH4 (-2.5 gCH4 m-2), whereas permafrost thaw slumping and pond formation increased CH4 release dramatically (ranging from 9.7 to 36.1 gCH4 m-2). Furthermore, CH4 release continues to increase even in natural succession pond likely due to aerenchyma transport of CH4 from deeper soil. The overall N2O release was negligeable except in the bare soil peat plateau. The net radiative forcing of ecosystem carbon balance will depend on the carbon uptake from the natural succession of vegetation, but we show that greenhouse gas emissions continue to increase beyond abrupt permafrost thaw event towards natural succession.

How to cite: Lee, H., Christiansen, C., Althuizen, I., Michelsen, A., Dörsch, P., Westermann, S., and Risk, D.: Long lasting greenhouse gas emissions beyond abrupt permafrost thaw event in permafrost peatlands, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4211, https://doi.org/10.5194/egusphere-egu22-4211, 2022.

08:50–08:55
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EGU22-7837
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ECS
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On-site presentation
Cosima Schröer, Christian Knoblauch, and Christian Beer

Permafrost thaw may stimulate microbial degradation of large soil organic carbon (SOC) stocks, releasing greenhouse gases into the atmosphere. Projecting this feedback to the global carbon (C) balance is urgent, but remains highly uncertain, because complex interactions between soil and microbes make it difficult to capture C dynamics accurately in models. How much CO2 will be respired is to a high degree dependent on C stabilization and persistence in the soil. SOC may be adsorbed to minerals and thereby unavailable to microbes. Common land surface models ignore this process, potentially overestimating C release from thawing permafrost.

This study investigates the effect of this stabilization mechanism on the decomposition process by applying a process-orientated model approach. We fit a microbial-explicit model, which includes mineral adsorption, to a four-year dataset of aerobic incubations of soils from the Lena River Delta, Siberia. We compare this model to a more conceptual first-order decay model, and to a version without mineral adsorption.

Preliminary results suggest that the mechanistic representation of mineral adsorption is crucial for extrapolations into the future, to avoid depletion of organic C pools or the introduction of artificially long C residence times.  We further emphasize the importance of long-term incubation studies.

How to cite: Schröer, C., Knoblauch, C., and Beer, C.: Stabilization in the fate of destabilization: Improving the representation of C stabilization when modeling C decomposition in permafrost-affected soils , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7837, https://doi.org/10.5194/egusphere-egu22-7837, 2022.

08:55–09:00
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EGU22-429
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ECS
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Virtual presentation
Stanislav Chuvanov, George Matyshak, Victoria Trifonova, and Maria Timofeeva

Peatlands comprise 19% of the permafrost area in the subarctic zone, they store 277 Pg of organic carbon. Peatlands in that area are represented by palsa mire. The palsa mire consists of frozen peat mounds (palsa), thermokarst depression and the wet bog without permafrost.

Climate change and thawing of permafrost leads to a change in soil moisture, both drying and wetting. This can lead to a change in the carbon balance of the ecosystem and increase or decrease the emission of greenhouse gases (CO2 and CH4).

The aim of the work was to study the effect of changes in soil moisture on the biological activity of palsa mire peat soils in the north of Western Siberia (65°18'52"N, 72°52'32"E). The studies were conducted in 2018-2021 in the northern taiga in the discontinuous permafrost zone.

The two palsas (Cryic Histosol) and the surrounding bog (Fibric Histosol) were examined. Palsa soils were characterized by high variability of the studied parameters; active layer thickness was 0.66±0.07 m, soil moisture - 30.98±2.49%, soil temperature - 8.31±0.45°C. The soils of the bog were characterized by the absence of permafrost, a higher soil temperature - 13.58±0.26°C and soil moisture - 74.59±0.26%. Despite the difference in the studied parameters of these ecosystems, no significant differences in biological activity were found (185.97±30.51 mgCO2/m2/h).

Based on field measurements, 3 plots were identified with the same type of vegetation and soil temperature, but significantly differ in soil moisture. Depending on soil moisture, the plots were named “Dry” (25.73±1.89%), “Wet” (38.44±0.70%) and “Moist” (53.09±1.06%). Biological activity did not vary significantly between the studied sites but had a multidirectional dynamic in different years. This shows the complexity of palsa, their multifactorial nature and an ambiguous response to changes in moisture.

An added experiment was set up to change soil moisture - transplantation. Measured of CO2 emissions from undisturbed peat soil of a large volume transferred from dry palsa to a wetting bog. And vice versa. The biological activity of the soils did not differ considerable both during wetting and draining. In different years, there was a vary dynamics in CO2 emissions.

According to the results of the study, with climate change, thawing of permafrost and palsa degradation, there will be no significant CO2 flux. This may be due to the multifactorial nature of ecosystems, a wide optimum of soil moisture for peat soils. The influence of additional factors is also significant: the size of the methanotrophic barrier, the transport of CO2 with solutions over the surface of the palsa permafrost.

How to cite: Chuvanov, S., Matyshak, G., Trifonova, V., and Timofeeva, M.: Permafrost thawing and changes on peat biological activity of palsa mire in Western Siberia , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-429, https://doi.org/10.5194/egusphere-egu22-429, 2022.

09:00–09:05
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EGU22-431
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ECS
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Virtual presentation
Viktoriia Trifonova, Irina Ryzhova, George Matyshak, Stanislav Chuvanov, and Matvey Tarkhov

Wetland ecosystems play a significant role in organic carbon conservation; one meter layer of peat soils store over 30 percent of terrestrial organic carbon (Lal, 2008). Ecosystems have different sensitivity to climate change in different nature zones (IPCC, 2014) due to various moisture and temperature regime.

The aim in this work is to define effect of temperature and moisture on mineralization rate in peat soils in Northern and Southern taiga.

The samples of Cryic Histosol (WRB, 2014) were taken from Northern Taiga (65°18'52" N, 72°52'32" E). The samples of Fibric Histosol (WRB, 2014) were taken from Southern Taiga (55°40'04" N 36°42'49" E). In laboratory conditions, samples were brought to certain soil moisture (SM): 30, 60, 80, 100 % (Gritsch, 2015), temperature of incubation was ranging from 5 to 25 ◦C (equal-time method).

In all the cases basal respiration (BR) was growing with increasing of temperature. Samples of Cryic Histosol are more sensitive to changes both in temperature and moisture. BR varies from 0.58 ±0.26 (30% SM and 5 ◦C) to 13.53±0.22 mg C-CO2/g/h (100% SM and 25 ◦C). Q10 coefficient varies from 4.64 to 2.82 respectively (this coefficient demonstrates differences in the temperature sensitivity of soil respiration (Kirschbaum, 1995)). For samples of Fibric Histosol BR varies from 0.75±0.01 (30% SM and 5 ◦C) to 6.14±0.26 mg C-CO2/g/h (100% SM and 25 ◦C). Q10 coefficient varies from 2.70 to 2.18 respectively.

Influence of moisture and temperature on biological activity in all of the cases was statistically confirmed, but interaction of factors is significant only for Cryic Histosol. According to the results, Cryic Histosol is more sensitive to temperature and moisture change, than Fibric Histosol. Peat soils in the northern area are subjected to more rapid organic carbon mineralization after a change of hydrothermal regime, than southern peat soils. In conclusion, Q10 coefficient variation indicates that soils with low soil moisture are more sensitive to temperature changes.

How to cite: Trifonova, V., Ryzhova, I., Matyshak, G., Chuvanov, S., and Tarkhov, M.: Effects of temperature and moisture manipulation on biological activity of Northern and Southern taiga peat soils , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-431, https://doi.org/10.5194/egusphere-egu22-431, 2022.

09:05–09:10
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EGU22-2251
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ECS
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On-site presentation
Alexandra Hamm and Andrew Frampton

Subsurface hydrology in regions dominated by permafrost is expected to change as a response to global climate change. Groundwater transports energy as well as dissolved solutes such as contaminants and carbon. To investigate the changes in advected energy as well as potential implications for solute transport, we created a permafrost hillslope modeling study that simulates current day active layer hydrology as well as future conditions based on climate projections.

Simulations are conducted with a state-of-the-art physically based numerical model (ATS) and combine a generic modeling approach with site-specific boundary conditions representative of the Adventdalen valley in Svalbard. We find that in the current climate, the subsurface hydrothermal state of the active layer along the hillslope transect is affected by lateral groundwater flow through differences in moisture distribution up- and downhill. Although lateral heat advection along the transect was found to be negligible, we show that the moisture distribution by gravitationally-driven seepage flow along the hillslope leads to unexpected temperature differences between the uphill and downhill parts of the transect. A non-negligible warming effect is observed uphill, resulting in deeper active layer depths than downhill.

Additionally, preliminary results based on transport modeling indicate that solute migration is mostly longitudinal and slow due to low liquid saturation of the active layer in summer. Under warmer conditions (increased air temperatures), lateral heat advection is expected to increase with more available energy, but solute migration may be partially counteracted by a greater volume of unfrozen soil in summer caused by less saturated conditions closer to the surface.

Furthermore, we discuss the potential implications this has for subsurface transport of solutes and dissolved constituents, and highlight challenges for numerical modeling of these systems.

How to cite: Hamm, A. and Frampton, A.: Modeling groundwater flow and solute transport in the active layer of hillslope system in permafrost environments, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2251, https://doi.org/10.5194/egusphere-egu22-2251, 2022.

09:10–09:15
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EGU22-2539
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Presentation form not yet defined
Andrew H. MacDougall

Zero Emissions Commitment (ZEC), the expected change in global temperature following the cessation of anthropogenic greenhouse gas emissions has recently been assessed by the Zero Emissions Commitment Model Intercomparison Project (ZECMIP). ZECMIP concluded that the component of ZEC from CO2 emissions will likely be close to zero in the decades following the cessation of emissions. However, of the 18 Earth system models that participated in ZECMIP only two included a representation of the permafrost carbon feedback to climate change. To better assess the potential impact of permafrost carbon decay on ZEC a series of perturbed parameter experiments were conducted with an Earth system model of intermediate complexity. The experiment suggest that the permafrost carbon cycle feedback will directly add 0.06 [0.02 to 0.14]oC to the benchmark ZEC value assesses 50 years after 1000 PgC of CO2 has been emitted to the atmosphere. An additional 0.04 [0 to 0.06]oC is likely to been added relative to the benchmark ZEC value from the thaw-lag effect unaccounted for in the ZECMIP experiment design. Overall we assess that the permafrost carbon feedback is unlikely to change the assessment that ZEC is close to zero on decadal timescales, however the feedback is expected to become more important over the coming centuries.

How to cite: MacDougall, A. H.: Estimated effect of the permafrost carbon stability on the zero emissions commitment to climate change, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2539, https://doi.org/10.5194/egusphere-egu22-2539, 2022.

09:15–09:20
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EGU22-2733
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ECS
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On-site presentation
Marcus Schiedung, Severin-Luca Bellè, and Samuel Abiven

Permafrost-affected mineral soils store large amounts of the soil organic matter (SOM) in high-latitude regions. These regions are large terrestrial carbon reservoirs and highly vulnerable to the global climate change. Global warming will cause rapid permafrost thaw and potentially accelerate decomposition of SOM. High-latitude regions, such as boreal and arctic ecozones, are regularly affected by wildfires with increasing intensity and frequency caused by global climate change. Wildfires produce pyrogenic organic matter (PyOM) during incomplete combustion of the fuel biomass. Little is known about the cycling of SOM and especially PyOM in permafrost-affected mineral soils, which limits our understanding of potential shifts in cycling and interaction with the soil mineral phase over time.

Here we study the fate of highly 13C-labelled (2-3 atm%) ryegrass organic matter and PyOM from the same feedstock (pyrolyzed at 400°C for 4h) during two years of in-situ incubation in boreal forest mineral soils. Soil cores (10 cm length and 6 cm diameter) were buried in the upper 10 cm of mineral soils under continuous and discontinuous to sporadic permafrost conditions at eleven forest locations (with six replicates) in Northern Canada. At the same locations, litter bags (green and rooibos teabags) were buried and soil temperatures were recorded. The soils cores were separated in three depth (0-3, 3-6 and 6-10 cm) to trace the vertical allocation of the applied organic matter. Density and particle fractionations are applied to identify mineral interactions of the ryegrass and pyrolyzed organic matter.

Preliminary δ13C results from the soil cores show a more extensive vertical allocation of ryegrass organic matter and PyOM in continuous permafrost-affected soils within the cores. This can be associated to the importance of freeze and thaw cycles for the carbon dynamics of permafrost-affected mineral soils. Tracing the labelled ryegrass organic matter and PyOM offers not only the opportunity to quantify the translocated fraction but also the decomposed proportion of the freshly added organic matter and thus understand short-term carbon dynamics. Preliminary results from the litter bags indicate a larger mass loss of slow cycling woody organic matter (rooibos tea) in discontinuous to sporadic permafrost-affected mineral soils, while larger mass losses of fast cycling organic matter (green tea) were observed in continuous permafrost-affected soils. These initial results indicate a complex cycling of organic matter in soils under different permafrost conditions.

How to cite: Schiedung, M., Bellè, S.-L., and Abiven, S.: Fate of pyrogenic and organic matter in permafrost-affected soils: A two years in-situ incubation , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2733, https://doi.org/10.5194/egusphere-egu22-2733, 2022.

09:20–09:25
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EGU22-3437
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ECS
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Virtual presentation
Hansu Park, Na-Yeon Ko, JeongEun Kim, Thomas Opel, Hanno Meyer, Sebastian Wetterich, Alexander Fedorov, Andrei Shepelev, and Jinho Ahn

Permafrost has a huge potential as a source for greenhouse gas release under global warming. In this context, it is very important to understand biogeochemical mechanisms of permafrost-related greenhouse gas formation and capacity. As ice wedges are an essential component of ice-rich permafrost and often occupy a large volume fraction of permafrost deposits, it is necessary to study the their gas chemistry. The Batagay megaslump (Yana Uplands, Northeast Siberia) exposes ice-rich permafrost deposits (Ice Complex) that have formed in the Middle and Late Pleistocene. Previous studies suggest the ages of these deposits as MIS 4-2 and at least MIS 16 for the Upper and Lower Ice Complexes, respectively. In this study, we analyzed mixing ratios of gas in air bubbles occluded in ice wedges of both ice complexes. We extracted gas by both, wet and dry extraction methods that connected with a gas chromatography system to analyze CO2, N2O, and CH4 concentrations. We observe CO2 concentrations of 1.9–10.3%, N2O of 0.1–8 ppm, and CH4 of 30–170 ppm for the Lower Ice Complex, and CO2 of 0.03–8.89%, N2O of 0.3–70 ppm, and CH4 of 5–980 ppm for the Upper Ice Complex. Greenhouse gas mixing ratios higher than atmospheric level indicate active microbial activity. This is supported by the δ(O2/Ar) values, which range from –89.01 to –67.43% and from –98.07 to –47.06% for the Lower and Upper Ice Complexes, respectively. The highly depleted δ(O2/Ar) values may indicate strong oxidation reactions by microbial activity and/or non-biological oxidation reactions. Even though there is no significant correlation between CO2 and CH4, abiotic CH4 formation might be negligible because it is unlikely to occur under permanently frozen conditions. Interestingly, CH4 and N2O show a weak negative correlation in both ice complexes, which can be explained by the nitrogen compounds’ inhibitory effect for methanogenesis. The δ(N2/Ar) values range from –8.06% to 33.86% for the Lower Ice Complex and from –5.49% to 30.64% for the Upper Ice Complex. Since nitrogen is more soluble in water than argon, this might indicate that ice wedges may have formed without a major contribution of snowmelt but mainly by dry snow compaction, which is also supported by the spherical shape of gas bubbles within the wedge ice. Furthermore, in ice the argon permeation coefficient is higher than that of nitrogen. Thus, high δ(N2/Ar) values (>10%) are due to argon’s diffusion through ice. Our future research will focus on deciphering the biogeochemical process of greenhouse gas formation for both ice complexes by comparison with ice wedges from other Siberian locations which have experienced different biogeochemical conditions in the past.

How to cite: Park, H., Ko, N.-Y., Kim, J., Opel, T., Meyer, H., Wetterich, S., Fedorov, A., Shepelev, A., and Ahn, J.: Compositions and origins of greenhouse gas species in permafrost ice wedges at the Batagay megaslump, Yana Uplands, Northeast Siberia, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3437, https://doi.org/10.5194/egusphere-egu22-3437, 2022.

09:25–09:30
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EGU22-3779
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Presentation form not yet defined
Anatoly Prokushkin, Elena Novenko, Sergey Serikov, and Daria Polosukhina

In northern palsa mires stable isotopes of C and N of peat organic matter (OM) and O and H of segregated ice may serve as an important conduit of information about variability of environment conditions and OM turnover in the past millennia and modern time. In our study we applied the multi-isotopic record to distinguish variation in the development of palsa peatlands located in forest-tundra ecotone of Central Siberia.

The study sites are located in vicinity of Igarka settlement (67o31’ N, 86o38’E) within the area underlain discontinuous permafrost. The peat cores were obtained in the central intact parts of perennial frost hummocks located in basins of the Gravijka and Little Gravijka rivers (depth 8.6 and 2.7 m, respectively). Thawed and frozen peat samples were collected at 1.0-5.0 cm step depending on the amount of peat and ice material. Peat (solid) samples were analyzed for C and N content and stable isotopic composition (δ13C and δ15N) by TOC Macro cube (Elementar, Germany) paralleled with Isoprime 100 IRMS (UK). Water stable isotope composition (δ18O and δ2H) of segregated ice samples (melted) were obtained by Picarro L-2120-i (Picarro Inc. USA).

The age of studied peatlands ranged between about 6200 cal yr BP (Gravijka site) and 4300 cal yr BP (Little Gravijka site). Meanwhile, there was the large loss of organic matter in the upper active layer of peat deposits as at 15 cm depth the age of OM was ca. 1800 cal yr BP. These findings suggest OM removal during wildfires and likely erosion processes following fires, and specific isotopic composition mirrors an enhanced OM decomposition in active layer. The large variations in composition of analyzed stable isotopes in frozen peat core captured the changes occurred during the past epochs in an input of OM (changes in vegetation and productivity), peat decomposition rates, nitrogen cycle perturbations as well as hydrothermal regimes and permafrost processes like aggradation (e.g. hummock uplift and cryoturbation) and degradation (e.g. hummock collapse, shifts from minerotrophic to ombrotrophic conditions and vice versa).

This work was supported by the Russian Science Foundation, project № 20-17-00043.

How to cite: Prokushkin, A., Novenko, E., Serikov, S., and Polosukhina, D.: A multi-isotopic approach to the reconstruction of palsa hummock formation: the case study from the Central Siberia, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3779, https://doi.org/10.5194/egusphere-egu22-3779, 2022.

09:30–09:35
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EGU22-4024
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ECS
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Virtual presentation
Maëlle Villani, Elisabeth Mauclet, Yannick Agnan, Arsène Druel, Briana Jasinski, Meghan Taylor, Edward A.G. Schuur, and Sophie Opfergelt

Climate change affects the Arctic and Subarctic regions by exposing previously frozen permafrost to thaw, unlocking nutrients, changing hydrological processes, and boosting plant growth. As a result, Arctic tundra is subject to a shrub expansion, called “shrubification” at the expense of sedge species. Depending on intrinsic foliar properties of these plant species, changes in foliar fluxes with shrubification in the context of permafrost degradation may influence topsoil mineral element composition. Despite the potential implications for the fate of organic carbon in the topsoil, this remains poorly quantified. Here, we investigate vegetation foliar and topsoil mineral element composition (mineral elements that influence organic carbon decomposition: Si, K, Ca, P, Mn, Zn, Cu, Mo and V) from a typical Arctic tundra at Eight Mile Lake (Alaska, USA) across a natural gradient of permafrost degradation. Results show that foliar element concentrations are higher (up to 9 times; Si, K, Mo, and for some species Zn) or lower (up to 2 times; Ca, P, Mn, Cu, V, and for some species Zn) in sedge than in shrub species. This induces different foliar flux with permafrost degradation and shrubification. As a result, a vegetation shift over ~40 years from sedges to shrubs has resulted in lower topsoil concentrations in Si, K, Zn and Mo (respectively of 52, 24, 20 and 51%) in poorly degraded permafrost sites compared to highly degraded permafrost sites. For other mineral elements (Ca, P, Mn, Cu and V), the vegetation shift has not induced a marked changed in topsoil concentrations at this stage of permafrost degradation. This observed change in topsoil composition involving beneficial or toxic elements for decomposers is likely to influence organic carbon decomposition. These data can serve as a first estimate to assess the influence of other shifts in vegetation in Arctic tundra such as sedge expansion with wildfires.

How to cite: Villani, M., Mauclet, E., Agnan, Y., Druel, A., Jasinski, B., Taylor, M., Schuur, E. A. G., and Opfergelt, S.: Does vegetation shift in Arctic tundra upon permafrost degradation influence mineral element recycling in the topsoil?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4024, https://doi.org/10.5194/egusphere-egu22-4024, 2022.

09:35–09:40
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EGU22-4672
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Virtual presentation
Huiru Jiang, Yonghong Yi, Wenjiang Zhang, Deliang Chen, and Rongxing Li

Permafrost degradation caused by climate warming has potentially large impact on the hydro-eco environment in the Tibetan Plateau (TP) through affecting soil water redistribution, and it is critical to investigate the soil moisture changes and estimate their response to future climate conditions. In this study, we first analyzed the in-situ soil temperature and moisture data to examine the impact of active layer thickening on soil moisture redistribution. There is generally a “water-rich zone” around the bottom of the active layer at sites with the active layer thickness (ALT) greater than ~2 m, and a relative low soil moisture zone occurs approximately between the bottom of the root zone (~ 0.4 m) and the bottom of the active layer. However, at shallower-ALT sites (e.g., ALT< 2 m), a “soil water rich zone” occurs at the upper active layer rather than at the bottom of the active layer, and soil moisture at the deeper active layer generally shows a decreasing trend along soil depth. We used a process-based permafrost hydrology model to represent the above effects of active layer thickening on soil moisture redistribution through modifying the soil hydraulic profile. Model sensitivity runs indicate that soil moisture redistribution with active layer thickening is largely due to dramatic changes of hydraulic conductivity between the root zone and deeper layers (>~ 1m). The saturated hydraulic conductivity tends to increase a little in the root zoon and then show a sharp exponential decline along soil depth, while the pedo-transfer functions that are commonly used in models cannot reproduce this process well.

Our results indicate that shallower ALT helps to retain soil moisture in the soil root zone; however, when ALT increases to a certain depth, the root-zone soil layer tends to lose water because of little recharge from deeper (>~1m) soils due to the dramatical decreases in soil hydraulic conductivity. Therefore, active layer thickening may exacerbate soil drying in the root-zone, which will have negative impacts on the vegetation growth and performances of ecosystem functioning. We will further investigate the soil moisture changes under different climate scenarios in order to better project the future hydro-eco response in the TP permafrost region.

How to cite: Jiang, H., Yi, Y., Zhang, W., Chen, D., and Li, R.: Investigating the impact of active layer thickening on vertical soil moisture distribution in the Tibetan Plateau, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4672, https://doi.org/10.5194/egusphere-egu22-4672, 2022.

09:40–09:45
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EGU22-5760
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ECS
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Presentation form not yet defined
Quantifying Arctic methane emissions from Alaska’s North Slope and Northeast Siberia from 2010-2020 using high-frequency atmospheric measurements
(withdrawn)
Rebecca Ward, Anita Ganesan, Colm Sweeney, John Miller, and Mathias Goeckede
09:45–09:50
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EGU22-6825
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ECS
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Presentation form not yet defined
Mitsuaki Ota, Amanda Muller, Gurbir Dhilon, and Steven Siciliano

High Arctic polar deserts cover 26% of the Arctic and are predicted to transform dramatically with rapidly rising temperatures. Previous studies found that polar deserts store larger amounts of soil organic carbon (SOC) in the permafrost than previously expected and can emit greenhouse gases (GHGs) at rate comparable to mesic Arctic ecosystems. However, the mechanism of the GHG production is not clear, which contributes to a great source of uncertainty regarding ecological feedbacks to the warming climate. Extreme climate conditions thaw the uppermost part of the permafrost, and the accumulated soil nutrients are ejected into the overlying soil layers where the subsurface nutrient patches (diapirs) form to increase carbon and nitrogen (N) contents by 7% and 20%, respectively. Previous mechanical models suggest that the ejection is facilitated by the increase in soil viscosity in the overlying soil layer. We previously found that diapirs developed about 30% of sorted circles in our study site and that the dominant vascular plant (Salix arctica) increased root biomass and nitrogen uptake from diapirs. To understand a GHG-feedback to the warming climate, we collected 40 soil samples with diapirs and 40 without diapirs during July and August 2013 to investigate gross N transformation rates and GHG emissions associated with diapirs in laboratory. Our study site encompasses two Canadian High Arctic polar deserts and is located near Alexandra Fjord (78°51′N, 75°54′W), Ellesmere Island, Nunavut, Canada. To deal with small amounts of nitrous oxide (N2O) emissions near or below the detection limit, we employed the hurdle models including (1) a Bernoulli component that models whether the data cross the detection limit based on covariates and (2) generalized linear model component that models the data above the detection limit. Our results showed that diapirs decreased gross N mineralization up to 48% and slowed carbon dioxide and methane emissions. Consistently, we found that diapirs contained more recalcitrant SOC using attenuated total reflectance Fourier transformed mid-infrared (ATR-FTIR) spectroscopy. ATR-FTIR also showed higher amounts of polysaccharides known to raise soil viscosity. The hurdle model approach showed that diapirs increased the estimated N2O emissions by up to 49% under wet conditions and suggested that the increase links to the increase in the probability of N2O emissions. On the other hand, under dry conditions, the hurdle models suggested that the increase in the estimated N2O emissions from diapirs links to the increase in the magnitude of the N2O emissions. The higher abundance of polysaccharides and recalcitrant SOC may indicate that biological factors are involved in forming diapirs and that diapirs supply vascular plants with nutrients as a result of a mutualistic relationship. Our study showed that diapirs altered GHG emissions and suggest that future research should include plant-microbe relationship in diapirs and other factors such as occlusion in soil aggregates for a more robust evaluation of diaper-GHG production. Furthermore, we suggest that the hurdle model may be a useful tool for evaluating N2O emissions that are locally small but could be critical in total in the Arctic.

How to cite: Ota, M., Muller, A., Dhilon, G., and Siciliano, S.: Biogeochemical and Ecological Responses to Warming Climate in High Arctic Polar Deserts, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6825, https://doi.org/10.5194/egusphere-egu22-6825, 2022.

09:50–09:55
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EGU22-7559
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ECS
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Virtual presentation
Lara Kaiser, Christian Knoblauch, and Christian Beer

The release of CH4 and CO2 from thawing permafrost soils will substantially impact the global carbon budget. During anaerobic conditions, these emissions are caused by a complex web of microbes. Depending on their interactions, differing ratios of CH4 to CO2 are produced. In order to predict these emissions, mechanistic modeling of microbial processes is essential but is largely omitted in current climate models. 

We present a new, process-based model for CH4 and CO2 production in anaerobic permafrost soils after thaw, incorporating key microbial functional types. Each microbial functional type is represented by a specific chemical pathway, allowing the calculation of substance utilization and production stoichiometrically for each time step. To the best of our knowledge, this is the first model incorporating a microbial type utilizing alternative electron acceptors, specifically Fe3+. These microbes out-compete acetoclastic methanogens for acetate as long as Fe3+ is sufficiently abundant, thereby suppressing CH4 production via this pathway. In addition, fermentation can be inhibited by the accumulation of its end product acetate, as has been observed in experiments.  We optimize the model parameters against data from an anaerobic permafrost soil incubation experiment over seven years.   

How to cite: Kaiser, L., Knoblauch, C., and Beer, C.: Who dealt it? Mechanistic modeling of microbial functional types in anaerobic permafrost soils., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7559, https://doi.org/10.5194/egusphere-egu22-7559, 2022.

09:55–10:00
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EGU22-9286
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ECS
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On-site presentation
Tianpeng Li, Lichao Fan, Rinat Manasypov, Yakov Kuzyakov, Klaus-Holger Knorr, and Maxim Dorodnikov

Thermokarst lakes formed form permafrost thawing under the global warming are an important source of greenhouse gases (GHG). However, the driving mechanisms and temperature sensitivity (Q10) of GHG emissions from the sediments of thermokarst lakes require deeper understanding. From existing studies of organic matter (OM) turnover and thermodynamic theory, it is known that more refractory OM has a higher temperature sensitivity of decomposition. To test the relevance of such effects in thermokarst lakes, sediments of two differently sized lakes (small = young, DOC rich; large = mature, DOC poor) from Western Siberia were anoxically incubated under three temperatures (4, 10, 16°C) for 49 days. We hypothesized that the Q10 of CO2, CH4 and N2O production increases with lake size as OM becomes increasingly refractory. Rates of CO2 production increased exponentially with temperature in sediments from lakes of both sizes, whereas the highest rates were observed for sediments of the small lake (4.2-9.7 μg C g-1 day-1), as expected for the more labile OM. However, the Q10 of CO2 production (1.8-2.2) was unexpectedly similar between two lakes. The small lake sediment emitted 2-3 orders of magnitude larger amount of CH4 (20-583 ng C g-1 day-1) as compared with large lake. The Q10 values and activation energy (Ea) of CH4 production in small lake sediment significantly decreased from 4-10°C (Q10 = 6.7; Ea = 124 kJ mol-1) to 10-16°C (Q10 = 3.1; Ea = 76 kJ mol-1). This suggests that methanogenesis is a strongly temperature-dependent process that is more sensitive in the low-temperature range. However, Q10 of CH4 production in the large lake did not reveal a sensitivity to temperature probably due to too low CH4 concentrations. In contrast to low CH4 production, the N2O emission rates were dramatically high (0.1-1.3 μg N g-1 day-1) in the sediment of the large lake. Interestingly, there was no N2O detected in the small lake sediment. Presumably, intensive denitrification in the large lake sediment outcompeted methanogenesis for substrate and energy, or enhanced CH4 oxidation occurred with NO3- as the electron acceptor. In summary, the temperature sensitivity of GHG production in thermokarst lake sediments depended more on gas species than on lake size. Nevertheless, the size of thermokarst lakes can serve as an indicator of biogeochemical processes in the sediments, as the small lakes are hotspots of CH4 and the large lakes are hotspots of N2O production.

How to cite: Li, T., Fan, L., Manasypov, R., Kuzyakov, Y., Knorr, K.-H., and Dorodnikov, M.: Thermokarst lake size controls greenhouse gases production but not its temperature sensitivity, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9286, https://doi.org/10.5194/egusphere-egu22-9286, 2022.

Coffee break
Chairperson: Christian Beer
10:20–10:25
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EGU22-9369
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Presentation form not yet defined
Oriol Grau, Olga Margalef, Joosten Hans, Richter Andreas, Canarini Alberto, Dorrepaal Ellen, Keuper Frida, Sardans Jordi, Peñuelas Josep, and Janssens Ivan

Permafrost peatlands are particularly sensitive to climate warming. The thawing of permafrost in these ecosystems accelerates the decomposition of old organic matter in deep soil layers and re-activates the cycling of carbon (C) and nutrients. Several studies showed that the thawing of permafrost in subarctic peatlands increases nitrogen (N) availability, ecosystem productivity as well as methane (CH4) and C dioxide (CO2) emissions. The mobilisation of other nutrients like phosphorus (P) or potassium (K) and the stoichiometric changes occurring in plants, soils and microbes in these fragile ecosystems are nevertheless poorly understood. In June 2018 we collected plant and soil samples across several permafrost thaw gradients in a palsa mire complex at Stordalen (Abisko, 68°N, Sweden). We selected three contrasting situations across the gradients: a) peat mounds with an intact permafrost core (‘palsa’ areas), b) semi-degraded palsas (‘transition’ area), and c) completely degraded palsas with no permafrost (‘collapsed’ area). For each situation we collected samples of the aboveground vegetation and soil samples at 5-10, 40-45, 70-75 and 95-100 cm (layers A-D), encompassing peat (A and B) and mineral soil layers (C and D). We determined total C, N, P and K, extractable organic C (EOC), total extractable N (TEN), extractable organic N (EON), ammonium (NH4+), nitrate (NO3-), extractable organic and inorganic P (EOP and EIP), microbial enzymatic activity, microbial C, N and P and pH in soil samples at each of the four depths across the gradient. We also determined total C, N, P and K in aboveground vegetation samples. The uppermost soil layer A showed the most statistically significant changes across the gradient of permafrost thaw, namely a 2-fold increase of total N and total P, 3- fold increase of EIP, 4-fold increase of EOP and 5-fold increase of NH4+, along with an increase of potential extracellular enzymatic activity. The fraction of total P immobilised by microbes was highest in the uppermost soil layer of palsas, where microbial P reached 33% of total P. In layer B, there were also several significant changes, such as a 4-fold increase of EOC and TEN and 12-fold increase of NH4+ in transition areas, and a 4-fold increase of EOP in collapsed areas. In addition, foliar chemistry changed significatively across the gradient of permafrost thaw, with a generalised increase of N, P and K, and a decrease of the CN and NP ratios. Along with these changes in foliar chemistry there was an increase of the stocks of N, P and K in biomass across the gradient. The biogeochemical and stoichiometric changes observed in plants, soil and microbes at different soil layers and across the gradient of permafrost thaw evidence that ongoing and future environmental changes will have a major impact on the functioning of these fragile ecosystems in the Subarctic.

How to cite: Grau, O., Margalef, O., Hans, J., Andreas, R., Alberto, C., Ellen, D., Frida, K., Jordi, S., Josep, P., and Ivan, J.: Biogeochemical responses of plants, soils and microbes to permafrost degradation in a subarctic peatland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9369, https://doi.org/10.5194/egusphere-egu22-9369, 2022.

10:25–10:30
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EGU22-9891
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ECS
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On-site presentation
Cornelia Rottensteiner, Victoria Martin, Hannes Schmidt, Leila Hadžiabdić, Julia Horak, Moritz Mohrlok, Carolina Urbina Malo, Julia Wagner, Willeke A'Campo, Luca Durstewitz, Rachele Lodi, Niek Jesse Speetjens, George Tanski, Michael Fritz, Hugues Lantuit, Gustaf Hugelius, and Andreas Richter

Climate change threatens the Earth’s biggest terrestrial organic carbon reservoir: permafrost soils. With climate warming, frozen soil organic matter may thaw and become available for microbial decomposition and subsequent greenhouse gas emissions. Permafrost soils are extremely heterogenous within the soil profile and between landforms. This heterogeneity in environmental conditions, carbon content and soil organic matter composition, potentially leads to different microbial communities with different responses to warming. The aim of the present study is to (1) elucidate these differences in microbial community compositions and (2) investigate how these communities react to warming.

We performed short-term warming experiments with permafrost soil organic matter from northwestern Canada. We compared two sites characterized by different glacial histories (Laurentide Ice Sheet cover during LGM and without glaciation), three landscape types (low-center, flat-center, high-center polygons) and four different soil horizons (organic topsoil layer, mineral topsoil layer, cryoturbated soil layer, and the upper permanently frozen soil layer). We incubated aliquots of all soil samples at 4 °C and at 14 °C for 8 weeks and analyzed microbial community compositions (amplicon sequencing of 16S rRNA gene and ITS1 region) before and after the incubation, comparing them to microbial growth, microbial respiration, microbial biomass and soil organic matter composition.

We found distinct bacterial, archaeal and fungal communities for soils of different glaciation history, polygon types and for different soil layers. Communities of low-center polygons differ from high-center and flat-center polygons in bacterial, archaeal and fungal community compositions, while communities of organic soil layers are significantly different from all other horizons. Interestingly, permanently frozen soil layers differ from all other horizons in bacterial and archaeal, but not fungal community composition.

The 8-week incubations led to minor shifts in bacterial and archaeal community composition between initial soils and those subjected to 14 °C warming. We also found a strong warming effect on the community compositions in some of the extreme habitats: microbial community compositions of (i) the upper permanently frozen layer and of (ii) low-center polygons differ significantly for incubations at 4 °C and 14 °C. Yet, the lack of a community change in horizons of the active layer suggests that microbes are adapted to fluctuating temperatures due to seasonal thaw events.

Our results suggest that warming responses of permafrost soil organic matter, if not frozen or water-saturated, may be predictable by current models. Process changes induced by short-term warming can be rather attributed to changes in microbial physiology than community composition.

This work is part of the EU H2020 project “Nunataryuk”.

How to cite: Rottensteiner, C., Martin, V., Schmidt, H., Hadžiabdić, L., Horak, J., Mohrlok, M., Urbina Malo, C., Wagner, J., A'Campo, W., Durstewitz, L., Lodi, R., Speetjens, N. J., Tanski, G., Fritz, M., Lantuit, H., Hugelius, G., and Richter, A.: Spatial variability shapes microbial communities of permafrost soils and their reaction to warming, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9891, https://doi.org/10.5194/egusphere-egu22-9891, 2022.

10:30–10:35
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EGU22-11774
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ECS
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Virtual presentation
Geert Hensgens, Jorien Vonk, Roman Petrov, Sergey Karsanaev, Torifm Maximov, and Han Dolman

The arctic is warming at double the average global rate. This raises the concern that permafrost is beginning to thaw and could release large amounts of stored carbon, parts of which can be centuries old. If the total carbon release exceeds the carbon uptake the net ecosystem exchange (NEE) shifts from carbon sink to source, amplifying global warming. Here we present long-term eddy covariance (EC) data of a tundra ecosystem in northeast Siberia, showing the current NEE and its drivers in one of the most remote and coldest EC sites of the northern hemisphere. During the growing season the site is an overall carbon sink. The start of the carbon uptake quickly follows snowmelt and total growing season uptake is positively correlated with an earlier timing of the carbon uptake. While snowfall and the timing of snowmelt is highly variable no discernible trend can be seen in long-term data. In general, increased temperatures yield higher net carbon uptake during the growing season, although this effect levels off at roughly 20°C, likely due to the steadily decreasing solar radiation throughout the growing season. Because of the remoteness and extremely low temperatures, no winter measurements exist. However, machine learning gap filling suggests the site is a small net carbon source during most of the winter. This is in accordance with some of the recent findings at other sites and potentially offsets large parts of the growing season uptake. Thus, while the growing season initially might see increased terrestrial carbon uptake at higher regional temperatures, constraining yearly budgets with winter measurements is indispensable to get a full picture of changes in the total carbon budget of arctic tundra sites in Siberia.

How to cite: Hensgens, G., Vonk, J., Petrov, R., Karsanaev, S., Maximov, T., and Dolman, H.: The long-term Net Ecosystem Exchange of a remote Siberian high arctic site, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11774, https://doi.org/10.5194/egusphere-egu22-11774, 2022.

10:35–10:40
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EGU22-11958
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Virtual presentation
Kathleen Stoof-Leichsenring, Amedea Perfumo, Sichao Huang, Lars Harms, Luidmila Pestryakova, Boris Biskaborn, and Ulrike Herzschuh

Dynamics of litter decomposition in Arctic terrestrial environments control about carbon storage in permafrost soils and release of CO2 into the atmosphere. Climate warming can accelerate litter decomposition because degradational processes increase, due to shifts in types of labile organic matter available and the composition of decomposing taxa. How litter decomposition changed in former interglacial and glacial periods is rarely studied, because time-series data is lacking, but highly needed to foresee consequences of decomposition and carbon cycling for warming Arctic ecosystems. Innovative shotgun ancient DNA sequencing on sediment core samples provide a snapshot of entire components of past biotic ecosystems and deliver qualitative data on organismal and functional compositional shifts. Our study, for the first time, investigates sedimentary ancient DNA shotgun data in a 52ka sediment core from Far North-Eastern Russia, Lake Ilirney, that recovers former glacial and interglacial periods with pronounced shifts in taxonomic composition in terrestrial vegetation, microbial and fungal diversity. At the same time, the ancient DNA data provides information on gene functions, like degrading enzymes that support variation in functional composition through time. With this data, we aim to understand how litter quality, based on vegetational composition, alters the taxonomic (bacteria, fungi) and functional (enzymes involved in decomposition) community of decomposers. Our result show that glacial times are characterized by tundra vegetation, mainly herbs, accompanied with a dominance of cryophilic soil degraders and relatively lower abundance of enzymes degrading plant organic material. Interglacial periods (like late Holocene) are typified by shrub-tree and heath dominated vegetation with microbes more specialized to degrade plant material, which is supported by an increase of the relative abundance of cellulose and ligninolytic enzymes. Our preliminary results support that under future warming the expansion of shrubs and trees and the increase of specified degraders in Arctic terrestrial environments might lead to enhanced degradation of plant litter resulting in a potential increase of CO2 emissions.

How to cite: Stoof-Leichsenring, K., Perfumo, A., Huang, S., Harms, L., Pestryakova, L., Biskaborn, B., and Herzschuh, U.: Past decomposition dynamics in Arctic terrestrial environments revealed by shotgun sedaDNA, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11958, https://doi.org/10.5194/egusphere-egu22-11958, 2022.