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Human-induced climate change during the 21^st century is expected to thaw large expanses of permafrost peatlands - one of Earth’s largest terrestrial carbon stores. Whilst frozen, peatland carbon fluxes are inhibited by cold temperatures, but emissions of carbon dioxide (CO₂) and methane (CH₄) are expected to substantially increase post-thaw. Peatland permafrost is often characterised by the presence of frost mounds, termed palsas/peat plateaus, or by ice-wedge polygons in more northerly regions. The spatio-temporal dynamics of future permafrost peatland thaw remain highly uncertain due to incomplete mapping of their modern distribution, the insulating properties of organic soils, and the variation in model projections of future climate.

Here, we present simulations of the modern and future climate envelopes of permafrost peatlands in Europe and Western Siberia. We collated > 2,000 site observations from across the northern hemisphere to quantify the modern distributions of palsas/peat plateaus and polygon mires. We fitted novel climate envelope models by relating landform distributions to modern climate data. We forced our climate envelope models with decadal projections of future climate under four Shared Socioeconomic Pathway (SSP) scenarios from 2020–2090, taken from an ensemble of 12 general circulation models included in the Coupled Model Intercomparison Project 6 (CMIP6). We then combined our simulations with recent soil organic carbon maps to estimate the total peat carbon stocks that may be at risk from future losses of suitable climate space.

Our simulations indicate that permafrost peatlands in Europe and Western Siberia will soon surpass a climatic tipping point under scenarios of moderate-to-high warming (SSP2-4.5, SSP3-7.0, and SSP5-8.5). We show that permafrost peatlands in Fennoscandia currently exist under warmer, wetter climates than those in Western Siberia. Our projections suggest that Fennoscandia will no longer be climatically suitable for peatland permafrost by 2040. Projected climate space losses by 2100 under these scenarios would affect peatlands containing 37.0–39.5 Gt carbon in Europe and Western Siberia (equivalent to twice the amount of carbon stored in European forests). Under a scenario with strong climate change mitigation (SSP1-2.6), our analyses show that permafrost peatlands storing 13.9 Gt carbon in the northernmost parts of Western Siberia would remain climatically supported by the 2090s. These results indicate that the rate and extent of 21st century permafrost peatland thaw will be determined by near-future socioeconomic developments.

How to cite: Fewster, R., Morris, P., Ivanovic, R., Swindles, G., Peregon, A., and Smith, C.: Future climatic suitability of permafrost peatlands in Europe and Western Siberia, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-86, https://doi.org/10.5194/egusphere-egu22-86, 2022.

Global change is expected to have adverse effects on the carbon (C) storage function of Sphagnum peat bogs. However, the consequences of the interaction of different aspects of global change for peatland C dynamics have not been systematically assessed yet.

The aim of this study is to examine how interactions between rising air temperatures, declining ground water levels (WL) and nitrogen eutrophication affect C exchange of both natural and degraded Sphagnum bog ecosystems.

A greenhouse experiment with Sphagnum papillosum planted on packed bog peat soil columns has been carried out in the vegetation period of 2021. Three different mean annual air temperature and WL treatments (ambient, + 1 °C, + 3 °C and 0 cm, 7 cm,15 cm below peat surface, respectively), three different amounts of nitrogen (N) input (5, 25 and 50 kg N/(ha*a)) and two different types of peat substrate (slightly and highly decomposed) were combined in a fully factorial design.

Three measurement campaigns with manual chambers were conducted over the course of the vegetation period to quantify CO₂ and CH₄ fluxes for each treatment combination. Soil temperature was measured continuously as explanatory variable. During each measurement campaign, three or more measurements using opaque chambers were conducted per soil column to assess the variation of ecosystem respiration (R_eco) and CH₄ exchange over the range of soil temperatures. To quantify the impact of the imposed environmental treatments on moss C-uptake capacity (GPP_sat), one measurement at an irradiation close to moss light saturation point (ca. 600-800 µmol/(s*m²); determined prior to the experiment) was conducted per column using a chamber illuminated by a LED grow light. Directly before each of these measurements, the mosses were light adapted to this irradiation intensity for 15 minutes.

Linear flux calculation and several steps of automated and manual filtering were applied to the data and a model describing the relationship between soil temperature and R_eco was fitted.

Preliminary results indicate that GPP_sat was affected negatively by higher air temperatures in summer, but positively in autumn. A negative response to a drop in WL was observed only after several weeks.

R_eco increased in columns with lower WL and at higher temperatures and showed a fast response to treatment variation (< two weeks). The effect of the lowered WL seemed to increase at higher temperatures.

WL strongly affected CH₄ fluxes with highest emissions observed in high WL treatments. In contrast, there seemed to be a net uptake of CH₄ in low temperature and low WL columns. No effect of diurnal air or soil temperature variations on CH₄ exchange could be observed, but emissions were higher in summer than in autumn. No short term effect of N eutrophication on any flux component could be detected.

The results of the study will provide insights into the effects of projected future environmental changes on Sphagnum bog peatlands. The findings can be used to optimize the management of natural, rewetted or commercially used Sphagnum peatlands with regard to the reduction of greenhouse gas emissions.

How to cite: Panitz, L., Hahn, S., and Tiemeyer, B.: Carbon Exchange Response Of Sphagnum Dominated Peatland To Multiple Aspects Of Global Change, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10353, https://doi.org/10.5194/egusphere-egu22-10353, 2022.

Worldwide, peatlands are estimated to store around 30% of soil organic carbon on only 3% of the land area. In Ireland, these numbers increase with peatlands covering ~20% of the land area and storing up to 75% of the terrestrial soil organic carbon. However, a large proportion (≥90%) of these ecosystems have been degraded through drainage for agriculture, forestry, horticulture and extraction for energy. With the increase in global initiatives for the conservation, rehabilitation and sustainable management of peatland, further investigation of the effect of drainage and rehabilitation is needed to better understand the carbon and greenhouse gas (GHG) dynamics of these ecosystems. Additionally, it is crucial to understand the natural adaptive capacity of the ecosystem to further inform effective rehabilitation strategies. This study investigated the carbon dioxide (CO₂) and methane (CH₄) fluxes from a former industrial peat extraction site in Ireland, prior to rehabilitation using static chamber techniques.  The site is an overall source of CO₂, releasing a cumulative annual flux of 9 g C-CO₂ m^-2 y^-1 for 2020-2021 and a small source of methane, releasing an average annual cumulative total of 1 g C-CH⁴ m^-2 y^-1.  

This research highlights the potential emissions savings that can be made through rehabilitation as water tables increase with rewetting and these sites become re-vegetated. However, long-term measurements to track the temporal dynamics of C/GHG emissions post-rehabilitation are required to fully assess the climate mitigation of this approach, particularly in light of a changing climate which might further influence the ecological, hydrological, and biogeochemical functions of these important ecosystems.

How to cite: Ingle, R. and Saunders, M.: Carbon and Greenhouse gas dynamics at an industrial cutaway peatland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9887, https://doi.org/10.5194/egusphere-egu22-9887, 2022.

Microbial breakdown of organic matter (OM) is slowed down by different environmental conditions in peatlands, such as low pH, low oxygen availability and presence of phenolic compounds, leading to their recognized carbon storage function (Freeman et al. 2001, Kang et al. 2018). Peatlands are worldwide distributed with environmental conditions and biogeographical legacy varying among regions, which determine different controlling factors of microbial OM degradation and affect carbon cycling and greenhouse gas (GHG) emissions from peat soils. Here, we present the results of a study aimed at investigating the structure and function of microbial communities involved in the OM decomposition in moss-dominated peatlands of tropical (Andes-Paramo, Colombia), temperate (Wales, UK), and arctic (Svalbard, Norway) regions. Prokaryote community, extracellular enzyme activity, and GHG (carbon dioxide, methane, and nitrous oxide) production were assessed in peat soil (first 10 cm depth) collected in one sampling campaign by region (summer north hemisphere). Results showed contrasting prokaryote communities among regions and a clear link between microbial composition and OM degrading metabolism. Arctic peatlands in Svalbard were shallow, circumneutral, with the highest prokaryote diversity (aerobic and anaerobic), an active lignin degradation, production of carbon dioxide, and nitrous oxide. In Wales, peatlands exhibited the lowest pH, an intermediate diversity of prokaryotes, with aerobic and anaerobic groups, and very low OM degrading activity and GHG production. Finally, in the Paramo’s peatlands, the oxygen level was the lowest and consequently prokaryote community was dominated by anaerobic groups with an active anaerobic OM degradation and methane production. Our study is the first, to the extent of our knowledge, giving a comparative view of microbial OM decomposition in peatlands from contrasting and remote regions. Our results highlight the great global diversity of prokaryotes and microbial metabolism and give new lights on the relationship between microbial composition and microbial carbon cycling in peatlands.

References

Freeman, C., Ostle, N., Kang, H. 2001. An enzymic “latch” on a global carbon store. Nature 409:149.

Kang, H., Kwon, M. J., Kim, S., Lee, S., Jones, T.G., Johncock, A. C., Haraguchi, A., Freeman, C. 2018. Biologically driven DOC release from peatlands during recovery from acidification. Nature Communications 9:1–7.

How to cite: Mora-Gomez, J., M. Alajmi, F. E., Jesus Orlando, J. O., Kang, H., and Freeman, C.: Peatlands in a latitudinal gradient: links between microbial composition and organic matter degradation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13469, https://doi.org/10.5194/egusphere-egu22-13469, 2022.

Northern peatlands are important long-term sinks of atmospheric carbon (C) due peat accumulation rates greater than rates of decomposition. Slow decomposition in northern peatlands is due to the presence of water saturated and low oxygen conditions, low temperatures, and decay resistant plant litter. The activity of extracellular enzymes produced by soil microbes is the first step in decomposition however, the relative importance of these abiotic and biotic variables in constraining extracellular enzyme activity remains poorly known. To address the multiple proposed mechanisms of what constrains peat enzyme activity, this study manipulates the biochemical controls associated with the inhibition and stimulation of enzyme activity. These biochemical constraints are regulated by abiotic (redox conditions and temperature) and biotic (organic matter source) factors. A 90-day incubation was carried out using peat from hummock and hollow microforms and peat was maintained under oxic and anoxic conditions at 20°C. Replicates of each microform and redox condition was amended as the following treatments: control, Fe addition, phenolics addition, oxidative enzyme addition, pH manipulation, nutrient addition, and pH manipulation and nutrient addition. Extracellular enzyme kinetics and temperature sensitivity (Q₁₀) of 6 hydrolytic and 2 oxidative enzymes was determined for each microform prior to treatment. Respiration rates of CO­₂­ and CH₄ were monitored throughout the incubation period. Following the termination of the incubation the enzyme kinetics and temperature sensitivity was determined for each treatment. This study provides the first comparison of multiple proposed mechanisms of what constrains peat enzyme activity within a single study. These results improve our understanding of what controls peat decomposition by assessing the relative importance of environmental, biological, and molecular resistance to enzymatic decay.

How to cite: Heffernan, L., Grasset, C., Kothawala, D., and Tranvik, L.: Assessing the influence of biogeochemical constraints on the enzymatic degradation and mineralization of peat, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2844, https://doi.org/10.5194/egusphere-egu22-2844, 2022.

Substantial peat deposits are known to exist across Amazonia. The peatlands of the Pastaza-Marañon Foreland Basin in Northern Peru have received increasing attention from researchers in the past decade, however, peatlands found in other Amazonian countries remain relatively unstudied. Most notably the peatlands of Brazil and Venezuela, which are predicted to cover 260,000 km² and 39,000 km², respectively. Peatlands are known to be the most carbon dense terrestrial ecosystem, once soil carbon is accounted for, and due to the remote and inaccessible location of many Amazonian peatlands most of them are believed to remain relatively intact. Thus, these ecosystems are likely to harbour large stocks of carbon, which need to be protected. We review the current state of knowledge of Amazonian peatlands to test the current predictions of peat distribution and extent, assess the ecological and social importance of these ecosystems, determine the potential threats to peatlands and evaluate the existing policy and regulatory frameworks and how they may help or hinder peatland protection. Finally, we highlight key areas where further research is needed and make recommendations for policy makers, to help improve our knowledge of this important ecosystem.

How to cite: Wheeler, C. and Hergoualc’h, K.: Peatlands of Amazonia, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8829, https://doi.org/10.5194/egusphere-egu22-8829, 2022.

We examined how changes in plant-fungal relationships induced by atmospheric nitrogen (N) deposition alter nutrient limitation and carbon sequestration in two main types of peatlands, bogs and fens. The study was carried out at three of the longest running nutrient addition experiments on peatlands: Whim Bog, United Kingdom, Mer Bleue Bog, Canada, and Degerö Stormyr Fen, Sweden. The treatments receive an additional load of 1.6-6.4 N g m^-2 y^-1 either as ammonium, nitrate, or ammonium nitrate with or without phosphorus (P) and potassium, alongside with unfertilized controls.

We determined the peak season aboveground biomass production and coverage of vascular plants using the point intercept method and measured fine roots production rates using the ingrowth core method. The ingrowth roots were also studied for amount of the root-associated fungi based on ergosterol and chitin concentrations (living and dead fungal mass indicators). In addition, we sampled fine roots from ericoid mycorrhizal shrubs and microscopically quantified them for abundance of fungal colonization as well as measured their potential to produce a set of hydrolytic enzymes degrading organic matter. The leaves of dominant vascular plants were analyzed their isotopic δ¹⁵N patterns and nutrient contents under different nutrient addition treatments.

Long-term nutrient addition increased foliar δ¹⁵N of shrubs, suggesting that ericoid mycorrhizal fungi were less important for plant N supply with increasing N load. Under high inorganic N availability, the plant biomass allocation shifted from belowground to aboveground at the two shrub-dominated bog sites: Mer Bleue and Whim, but not at the wet sedge dominated Degerö Stormyr. Unexpectedly, mycorrhizal colonization rates did not change significantly, but the presence of endophytic fungal mycelia in ericoid roots as well as ergosterol and chitin content in all fine roots generally increased under nutrient load. Interestingly, high doses of ammonium alleviated N deficiency in ericoid shrubs, whereas low doses of ammonium and nitrate improved plant P nutrition, indicated by the lowered foliar N:P ratios. Shrub root acid phosphatase activities correlated positively with foliar N:P ratios, suggesting enhanced P uptake as a result of improved N nutrition.

Collectively, altered biomass allocation to roots and fungi, altered functionality of root associated fungi and altered plant reliance on nutrient uptake systems as well as altered function of roots and their associated fungi in degrading organic matter suggest changes in the quantity and quality of carbon input to peat soils under nitrogen load. The study revealed that the responses depend on the dose and form of N added and interestingly may interact with uptake of other nutrients. The plant-fungal feedbacks also seem to differ between the two functionally and structurally distinct peatland types.

How to cite: Larmola, T., Adamczyk, S., Kiheri, H., Vesala, R., Straková, P., Bubier, J., van Dijk, N., Dise, N., Fritze, H., Juutinen, S., Laiho, R., Moore, T., Nilsson, M., and Pennanen, T.: Plant-fungal feedbacks of nitrogen deposition to peatland carbon sink potential, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3524, https://doi.org/10.5194/egusphere-egu22-3524, 2022.

Unlike carbon dynamics, nitrogen (N) dynamics in permafrost peatlands are not well-studied. For the prediction of permafrost N climate feedbacks, a better process-based understanding of the N cycle in permafrost peatlands is however urgently needed. Therefore, we characterized and quantified soil organic matter, soil gross microbial N turnover and soil-atmosphere exchange of nitrous oxide (N₂O) on the southern edge of the Eurasian permafrost area in situ (www.nifroclim.de). Specifically, we sampled a tree-free lowland peatland and a lowland peatland with an N₂-fixing alder forest in Northeast China.

Nuclear magnetic resonance spectroscopy revealed more recalcitrant organic matter at greater depth and more bioavailable organic matter substrates in upper peat horizons. In line with this result, gross ammonification and nitrification generally decreased with increasing sampling depth. Gross rates of mineral N turnover in the active layers of the tree-free peatland were comparable to those of temperate ecosystems. Despite substantial gross ammonification, the low nitrification:ammonification ratios and negligible soil N₂O emissions still depicted a closed N cycle characterized by N limitation in the tree-free peatland.

In strong contrast, the peatland underneath the alder forest showed an accelerated N turnover with very high gross rates of ammonification (3.1 g N m^-2 d^-1) and nitrification (0.6 g N m^-2 d^-1), exceeding those of the alder-free peatland by an order of magnitude. This was accompanied by substantial N₂O emissions. The increase in gross N turnover was most pronounced in the rooted soil layer, where N inputs from biological N fixation almost doubled total N concentrations and halved the ratios of soil organic carbon to total N. The frozen ground underneath alder trees contained strongly increased ammonium concentrations prone to be released upon thaw. This study shows that alder forests that further expand on permafrost-affected peatlands with global change create hot spots of soil mineral N turnover, thereby potentially enhancing permafrost N climate feedbacks.

How to cite: Ramm, E., Liu, C., Mueller, C. W., Gschwendtner, S., Yue, H., Wang, X., Bachmann, J., Bohnhoff, J. A., Ostler, U., Schloter, M., Rennenberg, H., and Dannenmann, M.: Alder-induced stimulation of soil gross nitrogen turnover in permafrost-affected peatlands of Northeast China, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9792, https://doi.org/10.5194/egusphere-egu22-9792, 2022.

This study considers how the stoichiometry and energy content of organic matter reservoirs and fluxes through and from a peatland enable the carbon fluxes and storage within a peatland to be constrained. The study considers the elemental composition of the above- and below-ground biomass, litter, the peat profile, dissolved and particulate organic matter within a blanket bog in northern England for which only the C budget had been measured. The study shows, based only the elemental composition and calculation of oxidation and energy contents, that:

• DOC in first-order streams is significantly more oxidised than that in peat pore water but that there is no significant difference in organic carbon oxidation state down the peat profile.
• The approach predicts the occurrence and speciation of N uptake and release in the peatland with N used and recycled.

• The relatively high oxidation state of DOC in stream water means that acts as an end point for reaction.
• Methanogenesis does not develop in deep peat as it requires too much energy to form.
• Sulphate reduction did result in the formation of deep peat but in this catchment this was inadequate to account for the rate of peat formation.

The formation of deep peat in this catchment could only be achieved if the DOM in the peat pore water was acting as an electron acceptor and energy source; however, it is unclear as to the flux of DOM up or down the peat profile.

How to cite: Worrall, F., Clay, G., Boothroyd, I., Moody, C., and Burt, T.: Constraining the carbon budget of peat ecosystems: application of stoichiometry and enthalpy balances., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1658, https://doi.org/10.5194/egusphere-egu22-1658, 2022.

As a result of limited decomposition under prevalent reducing conditions often over a timespan of thousands of years, organic soils store ±600 Gt of carbon. Currently, almost 14% of the global peat carbon storage is threatened by degradation, which was responsible for 2% of the anthropogenic greenhouse gas emissions in 2019. Decomposition of peat is the result of metabolic processes of the microbial community in the soil (also referred to as microbial respiration or oxidation). This microbial respiration activity strongly depends on biogeochemical conditions and especially to the availability of (alternative) electron acceptors in the soil profile. The redox potential is a reflection of the dominant electron acceptors present and the prevailing biogeochemical processes in the soil. Knowledge on the correlation between electron acceptor availability and redox conditions in peat soils remains however confined to laboratory studies, in which the sample is likely to be disturbed and boundary conditions are artificial. In this study we compared 2 years of continuous field measurements of redox potential with the chemical composition of over 1500 pore water samples, collected at different depths (20, 40 and 70 cm) in five agricultural peat soils throughout the Netherlands. The aim of this research is to identify the important metabolic processes for distinctive ranges in redox and pH under field conditions and compare these with known theoretical thermodynamic equilibria. We show that redox conditions are strongly correlated with products of anaerobic metabolism. Additionally, we present breakpoints for zones with distinct metabolic processes and biogeochemical states, which we use to interpret  time series of redox depth profiles. With these results we demonstrate the value of in-situ redox measurements to understand peat soil respiration rates and associated greenhouse gas emission from organic soils.

How to cite: van der Velde, Y., Boonman, J., Harpenslager, S. F., van Dijk, G., Smolders, F., van Huissteden, K., and Hefting, M.: Linking peatland redox conditions to pore water composition and greenhouse gas production, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7334, https://doi.org/10.5194/egusphere-egu22-7334, 2022.

Continuous in-situ measurement of reduction-oxidation (redox) potential is an emerging tool for analysing ecosystem biochemical status. Redox processes are intrinsically linked to methane (CH4) production and consumption in soils. Under highly reducing conditions, acetate and carbon dioxide (CO2) are reduced into CH4, while at less reducing conditions, CH4 is readily oxidised into CO2. These oxidation processes do not necessarily require oxygen; other electron acceptors such as nitrate (NO3-) and iron can also be used by microbes. The prevalence of different electron acceptors and donors is reflected in the redox potential of the soil solution which can be measured. Thus measurements of soil redox potential could in principle be used for predicting CH4 flux.

We measured soil redox potential continuously at 4 depths between 5 and 40 cm over one growing season on nine measurement plots on three different microsites (flark, lawn and string), in a north boreal flark fen, while concurrently measuring CO2 and CH4 flux of the same plots using the manual chamber method. Flux measurements were conducted five to seven times per week from late June to late September, 2019. Along with the redox potential, water table level (WTL), air and soil temperature (Tair, Tsoil) and several vegetation characteristics were measured.

Tsoil was found to be the major control of the momentary CH4 flux, but after standardizing the flux to 10 C using the Lloyd-Taylor equation, including the soil redox potential was found to significantly (p < 0.001) improve the prediction of the flux over a model incorporating only WTL and momentary Tsoil.

This is an initial step towards inclusion of redox potential as a continuous variable describing the processes active in the soil into CH4 production/consumption models.

How to cite: Koskinen, M., Finné, H., Virtanen, T., Lohila, A., Laiho, R., Laurila, T., and Aurela, M.: Predicting the methane flux from a north boreal fen using redox potential as an additional parameter, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-837, https://doi.org/10.5194/egusphere-egu22-837, 2022.

Ombrotrophic peat bogs are hydrologically isolated from the influence of local ground and surface waters and are fed exclusively by atmospheric deposition consisting of both solid particles and mineral substances dissolved in rain water. They have the advantage of widespread distribution and the physical and chemical properties of peat contribute to effective trapping and immobilization of atmospherically deposited solutes and particles. As a result, ombrotrophic peat can offer valuable opportunities to explore past atmospheric environmental conditions. Peatlands are widely distributed in China, including the Qingzang Plateau in the southwest and the mountains and plains in the northeast. However, the typical ombrotrophic peatlands with low ash content and rainfed characters are not common. The Motianling peatland in Aershan of Great Hinggan Mountains is in the most northern part of China that belongs to a moderate, cold climate with the domination of westerlies. This peatland has a well-established trophy status and its ombrotrophic character has been verified by multi-proxies. It has previously been studied to assess the levels of Pb and Hg pollution and dust deposition. To the best of our knowledge, Motianling peatland is one of the most typical ombrotrophic bog in China and its geochemical signatures document the anthropogenic impact history during the past centuries.

How to cite: Bao, K.: Motianling peatland, a typical ombrotrophic bog in China documents the anthropogenic impact history during the past centuries, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3490, https://doi.org/10.5194/egusphere-egu22-3490, 2022.