BG3.24

When drained for e.g. agricultural use, natural peatlands turn from a net C sink to a net C source. It is therefore suggested that restoration of peatlands, despite of increasing CH₄ emissions, holds the potential to mitigate climate change by reducing their overall global warming potential. The time span required for this transition, however, is fairly unknown. Moreover, greenhouse gas emission measurements from peatlands are often limited to a couple of years only. This is problematic in so far, as most peatland ecosystems are in transitional stage due to restoration related disturbances (e.g. enhanced water table) and global climate change. This might affect GHG emissions in one way or another which emphasizes the necessity of longer-term observations to avoid misinterpretations and premature conclusions.       
Exemplary for that, we present 14 consecutive years of CH₄ flux measurements following restoration at a formerly long-term drained fen grassland within the Peene river catchment (near the town of Zarnekow: 53.52⁰N, 12.52⁰E). Restoration of peatland was done by simply opening the dike. Thus, no water table management was established and water table was strongly fluctuating.  CH₄ flux measurements were conducted at two sites (restored vs. non-restored) using non-flow-through non-steady-state (NFT-NSS) opaque chambers. 
Throughout the 14 years study period, distinct stages of an ecosystems transition, differing in their impact on measured CH₄ emissions, were observed. During the first two years of the measurement period directly following restoration in autumn 2004, an eutrophic shallow lake was formed. This development was accompanied by a fast vegetation shift from dying off cultivated grasses to submerged hydrophytes and helophytes and evidenced substantially increased CH₄ emissions. Since 2008, helophytes have gradually spread from the shore line into the established shallow lake especially during drying years. This process was only periodically delayed by exceptional inundation, such as in 2011, 2012 and 2015, and finally resulted in coverage of the measurement site in 2016 and 2017. While, especially the period between 2009 and 2015 showed exceptionally high CH₄ emissions, these decreased significantly after helophytes were established at the measurement site. Hence, CH₄ emissions only decreased after ten years transition following restoration and potentially reaching a new steady state.

How to cite: Antonijevic, D., Vaidya, S., Vincenz, C., Jurisch, N., Pehle, N., Albiac Borraz, E., Gusovius, B., Lück, M., Augustin, J., and Hoffmann, M.: Persistently high CH4 emissions 10 years after restoration: The necessity for long-term observations when measuring GHG emissions of transitional systems, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1211, https://doi.org/10.5194/egusphere-egu21-1211, 2021.

Ecosystems are increasingly exposed to climatic extremes, such as drought and extreme rainfall patterns. Recent studies evidenced the strong variability in ecosystem’s response to droughts, raising the issue of non-linear responses in ecosystem’s carbon (C) dynamic. The conundrum is what causes C fluxes to shift in response to drought, and most importantly, does such extreme events have lasting effects? Here, we will synthesize the results from three different studies testing the effect of droughts and/or extreme rainfall patterns on peatland CO₂ fluxes.

In a first experiment, we tested the resistance and resilience effects of extreme rainfall patterns on peatland C fluxes in a mesocosm experiment. We found that increasingly intense but less frequent rainfall, with longer intermediate dry periods, destabilises water table dynamic, with cascading effects on peatland C fluxes. Yet, peatland C dynamics might be more resilient than expected as vascular plants may fulfil a compensatory role by taking up more C. Moreover, CO₂ fluxes displayed lasting influence of extreme rainfall after restoration of the water table dynamics.

In a second experiment, we manipulated the water table depth in the field and generated a gradient spanning from -5 to -60 cm. We found that substantial changes in peatland CO₂ respiration occurred when the water level fell below a critical point of -24 cm. Around that apparently critical water level, we showed that plant and fungal communities were suddenly altered and raised CO₂ respiration rates.

In the last experiment, we tested the combined effect of prolonged drought and warming on the C uptake of two Sphagnum species. We found that the effect of climate warming on Sphagnum community photosynthesis toggles from positive to negative as the peatland goes from rainy to dry periods during summer. We further found that mechanisms of compensation among the dominant Sphagnum species stabilized the average C uptake of the Sphagnum community over the growing season.

As a corollary, our results show that extreme climatic events induce functional transitions in peatland C dynamics. These functional transitions further depends on the phenotypic plasticity among plant and microbial species as well as on the evenness of specific functional groups that modulate the effects of droughts on peatland C dynamic.

How to cite: Jassey, V. E. J., Barel, J. M., and Lamentowicz, M.: When water runs dry — peatland C dynamic under extreme droughts, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1058, https://doi.org/10.5194/egusphere-egu21-1058, 2021.

Abstract

Northern mires have sequestered substantial amounts of atmospheric carbon since the last glacial period forming one of the largest carbon pools in the biosphere (Hugelius et al., 2020). Current global warming is causing the subarctic and arctic regions warm rapidly, two to three times as fast as the rest of the world (Masson-Delmotte et al., 2018), which will affect the carbon balance of these mires.

In Kaamanen, northern Finland, we studied carbon dioxide (CO₂) and methane (CH₄) exchange between patterned mesotrophic fen and the atmosphere, both on ecosystem and plant community level. The ecosystem level measurements were conducted by utilizing eddy covariance method, while the fluxes on plant community scale were measured with flux chambers. The studied fen can be described as a mosaic of strings and flarks (or hummocks and hollows, respectively). The microtopography of the string-flark continuum form four main plant community types with varying water table conditions and vegetation composition. The measurements took place in 2017–2018. The two years in question were contrasting in their meteorological and environmental conditions. The 2017 growing season had average temperature, but high precipitation sum, while 2018 growing season was warm and dry. In July 2018 a north-western Europe-wide heatwave caused a month-long drought period at the site. Compared to 2017, the annual carbon balance of the Kaamanen fen was affected by earlier onset of photosynthesis in spring and the drought event during summer 2018.

We found that the annual carbon balance of the fen did not differ markedly between the studied years, even though the meteorological and environmental conditions did. The earlier onset of growing season in 2018 strengthened the CO₂ sink of the ecosystem, but this gain was counterbalanced by the later drought period. Additionally, we found strong spatial variation in CO₂ and CH₄ dynamics between the main plant communities. Most of the variation in ecosystem level carbon exchange could be explained by the variation in water table level, soil temperature and vegetation characteristics, which were also the environmental factors that varied between the plant community types.

References

Hugelius, G., Loisel, J., Chadburn, S., Jackson, R. B., Jones, M., MacDonald, G., Marushchak, M., Olefeldt, D., Packalen, M., Siewert, M. B., Treat, C., Turetsky, M., Voigt, C. and Yu, Z.: Large stocks of peatland carbon and nitrogen are vulnerable to permafrost thaw, Proceedings of the National Academy of Sciences - PNAS, 117, 20438–20446, doi:10.1073/pnas.1916387117, 2020.

Masson-Delmotte, V., Zhai, P., Pörtner, H.-O., Roberts, D., Skea, J., Shukla, P. R., Pirani, A., Moufouma-Okia, W., Péan, C., Pidcock, R., Connors, S., Matthews, J. B. R., Chen, Y., Zhou, X., Gomis, M. I., Lonnoy, E., Maycock, T., Tignor, M. and Waterfield T. (Eds.): Global Warming of 1.5°C. An IPCC Special Report on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty, World Meteorological Organization, Geneva, Switzerland, 2018.

How to cite: Heiskanen, L., Tuovinen, J.-P., Räsänen, A., Virtanen, T., Juutinen, S., Lohila, A., Penttilä, T., Linkosalmi, M., Mikola, J., Laurila, T., and Aurela, M.: Carbon dioxide and methane exchange of a patterned subarctic fen during two contrasting growing seasons, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2384, https://doi.org/10.5194/egusphere-egu21-2384, 2021.

Canada has extensive peat deposits in northern high latitude wetlands and permafrost ecosystems. Peat accumulation represents a natural long-term carbon sink attributed to the cumulative excess of growing season net ecosystem production over non-growing season net mineralization. However, near-surface peat deposits are vulnerable to climate change and permafrost landscape transition. One specific concern is a potential rapid increase in the non-growing season carbon loss through enhanced organic matter mineralization under a warming climate. Our experimental study explores the response of peat CO₂ exchanges to (1) temperature, using the conventional Q₁₀ parameter, and (2) moisture content. The observed responses are expected to reflect, at least in part, differential soil microbial adaptations to varying wetland conditions, across two northern ecoclimatic zones. Laboratory incubations were carried out with shallow peat samples from different depths collected at seven Canadian wetland sites and adjusted to five moisture levels. For each subsample (varying by site, depth and moisture content), CO₂ fluxes were measured at 12 sequential temperature settings from -10 to 35˚C. For each subsample, the data were fitted to an exponential equation to derive a Q₁₀ value. In general, boreal peat samples were more temperature sensitive than temperate peat. The optimum moisture level for CO₂ release was determined for all the subsamples and related to variations in wetland vegetation and landform types. As a general trend, increasing water saturation reduced the CO₂ release rate from a given subsample. We further tested a flexible curve-fitting equation, as recently proposed on a theoretical basis, to recompile the data by ecoclimatic peat type and to account for the non-growing season dynamics. These findings will contribute to Canada’s national carbon budget model by guiding the development and calibration of the peatland module.

How to cite: Byun, E., Rezanezhad, F., Fairbairn, L., Basiliko, N., Price, J., Quinton, W., Roy-Léveillée, P., Webster, K., and Van Cappellen, P.: Temperature and moisture controls on non-growing season CO2 emissions in laboratory incubations with soils from northern peatlands, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6281, https://doi.org/10.5194/egusphere-egu21-6281, 2021.

From a carbon sequestration perspective, peatland restoration projects could be considered successful when net primary productivity exceeds decomposition, resulting in net peat growth in the ecosystem. To demonstrate the effectiveness of peatland restoration projects with a carbon storage aim, analytical techniques are needed that can distinguish between natural/restored ecosystems undergoing (or transitioning to) net peat growth and degraded ecosystems experiencing increased rates of aerobic decomposition (carbon loss). Molecular analysis techniques able to relate changes in organic matter (OM) chemical composition to changes in degradation status occurring on the mechanistic level are especially needed.

This study combined a molecular biomarker and chemical compound class approach to conduct a depth-based molecular comparison of natural (ON) and drained (OD) ombrotrophic peatland sites in Lakkasuo Finland. To explore how changes in hydrology impacted peat OM chemical composition, the relative abundance of various molecular biomarkers (Sphagnum marker p-isopropenylphenol, lignin vascular plant markers) and chemical compound classes (phenolics, polysaccharides, aromatics, N-containing compounds, lipids) was determined with depth from three replicate cores per site using pyrolysis gas chromatography tandem mass spectrometry (Py-GCMS). Py-GCMS results were compared with onsite vegetative assemblages and bulk elemental analysis conducted on the same cores. ON and OD were matched by age using radiocarbon dating at three depths per core.

For OD relative to ON, significant reductions in average relative percent abundance were observed for p-isopropenylphenol, phenolics and polysaccharides, and corresponding increases in abundance were observed for lignin, aromatics, N-containing compounds, and lipid sterols. Differences in compound classes between sites were greatest in the drainage-affected upper acrotelm, and diminished with depth. Samples consistently below the depth of the water table (>20 cm) followed similar trends in both ON and OD, suggesting that deeper horizons remained unaffected by the onsite drainage activities. An increasing trend in the relative abundance of lignin-derived compounds was observed with depth - particularly in ON. As the plant macrofossil assessment did not suggest previous dominance of vascular plants, this trend was considered evidence for preservation of lignin in anaerobic conditions in organic soils. Overall, these findings indicate that differences in chemical composition between the two sites can be directly correlated to OM transformation occurring on a mechanistic level, and that observed shifts in chemical composition reflect the effect of altered hydrology in peatland ecosystems.

How to cite: Klein, K., Groβ-Schmölders, M., Alewell, C., and Leifeld, J.: Changes in peatland hydrology alter organic matter chemical composition in ombrotrophic Finnish mires: a comparative Py-GCMS depth profile study, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9922, https://doi.org/10.5194/egusphere-egu21-9922, 2021.

Peatland ecosystems are integral to the mitigation of climate change as they represent significant terrestrial carbon sinks. In Ireland, peatlands cover ~20% of the land area but hold up to 75% of the soil organic carbon stock however many of these ecosystems (~85% of the total area) have been degraded due to anthropogenic activities such as agriculture, forestry and extraction for horticulture or energy. Furthermore, the carbon stocks that remain in these systems are vulnerable to inter-annual variation in climate, such as changes in precipitation and temperature, which can alter the hydrological status of these systems leading to changes in key biogeochemical processes and carbon and greenhouse gas exchange.  During 2018 exceptional drought and heatwave conditions were reported across Northwestern Europe, where reductions in precipitation coupled with elevated temperatures were observed. Exceptional inter-annual climatic variability was also observed at Clara bog, a near natural raised bog in the Irish midlands when data from 2018 and 2019 were compared. Precipitation in 2018 was ~300 mm lower than 2019 while the average mean annual temperature was 0.5°C higher. The reduction in precipitation, particularly during the growing season in 2018, consistently lowered the water table where ~150 consecutive days where the water table was >5cm below the surface of the bog were observed at the central ecotope location. The differing hydrological conditions between years resulted in the study area, as determined by the flux footprint of the eddy covariance tower, acting as a net source of carbon of 53.5 g C m^-2 in 2018 and a net sink of 125.2 g C m^-2 in 2019. The differences in the carbon dynamics between years were primarily driven by enhanced ecosystem respiration (R_eco) and lower rates of Gross Primary Productivity (GPP) in the drier year, where the maximum monthly ratio of GPP:R_eco during the growing season was 0.96 g C m^-2 month in 2018 and 1.14 g C m^-2 month in 2019. This study highlights both the vulnerability and resilience of these ecosystems to exceptional inter-annual climatic variability and emphasises the need for long-term monitoring networks to enhance our understanding of the impacts of these events when they occur.

How to cite: Saunders, M., Ingle, R., and Regan, S.: Assessing the impact of exceptional inter-annual climatic variability on rates of net ecosystem carbon dioxide exchange at Clara bog., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13414, https://doi.org/10.5194/egusphere-egu21-13414, 2021.

Mapping the global peatland distribution is important for embedding peatland processes into Earth System Models. Peatland maps are typically compiled from nation-specific soil or ecosystem maps or based on machine learning tools trained on such data. Here, we evaluate the performance of a land surface model with two different peatland map inputs in providing critical land surface estimates (soil moisture, temperature) to a Radiative Transfer Model (RTM) for L-band brightness temperature (Tb). We hypothesize that an improved performance of the land surface model in Tb space indicates a better spatial peatland distribution input within the footprint of Tb observations (~40 km).

We employ the NASA Catchment Land Surface Model (CLSM) with a recently added module for peatland hydrology (PEATCLSM modules). We run this model at a 9-km EASEv2 resolution over the Northern Hemisphere for two soil maps that differ in their peatland distributions. The applied soil distributions are: (MAP1) a combination of the Harmonized World Soil Database and the State Soil Geographic Database, also used to generate the Soil Moisture Active Passive (SMAP) Level-4 soil moisture product, and (MAP2) a hybrid of HWSD-STATSGO and the ‘PEATMAP’ product, which is mainly compiled from national peatland maps. MAP2 indicates ~30 % more peatland area over the Northern Hemisphere. For both peat distributions, CLSM is run and parameters of the RTM are calibrated with 10 years of multi-angular L-band Tb observations from the Soil Moisture and Ocean Salinity SMOS mission. Afterwards, CLSM is run together with the calibrated RTM within a data assimilation system, with and without (open-loop) assimilating SMAP Tb observations, for the period 2015-2020. Our results demonstrate that Tb misfits (in both the open-loop and assimilation runs) are reduced in the areas with the largest differences in peat distribution, thus indicating a basic validity of assuming a peatland-like hydrological dynamics for the larger peat extent of MAP2. Results will be discussed in the context of how peatlands are defined in global peatland maps and the question of what is typically modeled as a peatland in Earth System Models. We propose the evaluation of future releases of peatland maps in Tb space as a tool to evaluate their suitability for implementation into Earth System Models.

How to cite: Bechtold, M., Mahanama, S. P., Reichle, R. H., Koster, R. D., and De Lannoy, G. J. M.: Where are the peatlands? Comparing two global peatland maps through L-band brightness temperature simulations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15134, https://doi.org/10.5194/egusphere-egu21-15134, 2021.

Microbial communities of methane producing methanogens and consuming methanotrophs play an important role for the earths atmospheric methane budget. Despite their global significance, the functional potential of these communities is poorly understood. To investigate this, we applied the molecular technique, captured metagenomics, to identify the variability in functional diversity of microorganisms involved in the metabolism of methanein an environmentally controlled laboratory study. Nine plant-peat mesocosms dominated by the sedge Eriophorum vaginatum, with varying coverage, were collected from a temperate natural wetland is Sweden and subjected to a simulated growing season. Samples for analysis of captured metagenomes were taken from the top, bottom and root adjacent zone at the end of the experiment. In addition, over the simulated season, measured gas fluxes of carbon dioxide (CO₂) and CH₄, δ¹³C of emitted CH₄ and the pore water concentration of dissolved methane and low molecular weight organic acids were recorded. The functional genes resulting from the captured metagenomes had a higher Shannon α-diversity in the root zone when compared to the bottom and top. Sequences coding for methane metabolism were significantly more diverse in the root and bottom zones when compared to the top. However, the frequency of Acetyl-CoA decarbonylase and methane monooxygenase subunit A were significantly higher in the high emitting methane flux category when compared to the medium and low emitting mesocosms. We conclude that captured metagenomic analyses of functional genes provides a good measure of the functional potential methanogenic and methanotrophic microbial communities. This technique can be used to investigate how methanogens and methanotrophs function in peatlands and thus, contribute to the concentration of atmospheric methane.

How to cite: White, J., Ström, L., Ahrén, D., Rinne, J., and Lehsten, V.: Captured metagenomics reveals high spatial variability in functional potential in CH4 producing and consuming microorganisms in a temperate Swedish peatland., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10861, https://doi.org/10.5194/egusphere-egu21-10861, 2021.

Besides water table depth, soil temperature is one of the main drivers of greenhouse gas (GHG) emissions in intact and managed peatlands. In this work, we evaluate the performance of remotely sensed land surface temperature (LST) as a proxy of greenhouse gas emissions in intact, drained and extracted peatlands. For this, we used chamber-measured carbon dioxide (CO₂) and methane (CH₄) data from seven peatlands in Estonia collected during vegetation season in 2017–2020. Additionally, we used temperature and water table depth data measured in situ. We studied relationships between CO₂, CH₄, in-situ parameters and remotely sensed LST from Landsat 7 and 8, and MODIS Terra. Results of our study suggest that LST has stronger relationships with surface and soil temperature as well as with ecosystem respiration (R_eco) over drained and extracted sites than over intact ones. Over the extracted cites the correlation between R_eco CO₂ and LST is 0.7, and over the drained sites correlation is 0.5. In natural sites, we revealed a moderate positive relationship between LST and CO₂ emitted in hollows (correlation is 0.6) while it is weak in hummocks (correlation is 0.3). Our study contributes to the better understanding of relationships between greenhouse gas emissions and their remotely sensed proxies over peatlands with different management status and enables better spatial assessment of GHG emissions in drainage affected northern temperate peatlands.

How to cite: Kull, A., Burdun, I., Veber, G., Karasov, O., Maddison, M., Sagris, V., and Mander, Ü.: Remotely sensed temperature is a proxy of greenhouse gas emissions in intact and managed peatlands, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4474, https://doi.org/10.5194/egusphere-egu21-4474, 2021.

Climate warming and permafrost thaw are exposing the large carbon (C) pools of northern wetlands to enhanced decomposition, potentially increasing the release of the greenhouse gases carbon dioxide (CO₂) and methane (CH₄). Permafrost thaw is usually associated with changes in hydrology and vegetation: Ground collapse leads to the formation of new, productive thermokarst wetlands, and active layer deepening allows plant roots to penetrate to deeper soil layers. These processes promote interaction between old permafrost carbon and recent plant-derived carbon, but the effect of this interaction on anaerobic decomposition processes is poorly known.

Here, we report the preliminary results of a 1+-year-long soil incubation experiment where we investigated the role of fresh organics on anaerobic decomposition in arctic wetlands. We sampled mineral subsoil of Greenlandic wetland sites and the active layer and permafrost peat in a Swedish palsa mire, and incubated them with and without repeated amendments of ¹³C enriched glucose and cellulose. We determined the rate and isotopic composition of CO₂ and CH₄ with an isotopic laser, and estimated the contribution of soil organic matter decomposition vs. added carbon to the total C gas release. These results represent new understanding on how plant-derived organics change the magnitude and composition of C gas, thus affecting the climatic feedbacks from permafrost wetland C pool.

How to cite: Marushchak, M. E., Nykänen, H., Pumpanen, J., Sannel, A. B. K., Ström, L., White, J., and Biasi, C.: Effects of labile carbon on anaerobic decomposition processes in permafrost wetlands, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9656, https://doi.org/10.5194/egusphere-egu21-9656, 2021.

The net methane emission of any mire ecosystem results from a combination of biological and physical processes, including methane production by archaea, methane consumption by bacteria, and transport of methane from peat to the atmosphere. The complexity of spatial and temporal behavior of methane emission is connected to these.

¹³C-signature of emitted methane offers us a further constraint to evaluate our hypothesis on the processes leading to the variation of methane emission rates. For example, assuming the spatial variation in methane emission rate at microtopographic scale is due to variation in trophic status or variation in methane consumption, will lead to differences in the relation of methane emission rate and its ¹³C-signature, expressed as δ¹³C.

We have measured the methane emission rates and δ¹³C of emitted methane by six automated chambers at a poor fen ecosystem over two growing seasons. The measurements were conducted at Mycklemossen mire (58°21'N 12°10'E, 80m a.s.l.), Sweden, during 2019-2020. In addition, we measured atmospheric surface layer methane mixing ratios and δ¹³C to obtain larger scale ¹³C-signatures by the nocturnal boundary-layer accumulation (NBL) approach. All δ¹³C-signatures were derived using the Keeling-plot approach.

The collected data shows spatial differences of up to 10-15 ‰ in 10-day averages of δ¹³C-signatures between different chamber locations. Temporal variations of 10-day average δ¹³C-signatures from most chamber locations reached over 5 ‰, while the temporal variation of NBL derived δ¹³C-signature was slightly lower.

The observed spatial variation in the δ¹³C-signature was somewhat systematic, indicating, especially in the middle of the summers, the main control of spatial variation of methane emission to be the trophic status. The temporal changes, measured at different locations, indicate spatial differences in the temporal dynamics at the microtopographic scale. The temporal behavior of larger scale NBL δ¹³C-signature does not fully correspond to the behavior of the chamber derived average δ¹³C-signature.

How to cite: Rinne, J., Łakomiec, P., Vestin, P., Weslien, P., Kelly, J., Liljebladh, B., Xie, X., Kljun, N., Ström, L., and Klemedtsson, L.: Spatial and temporal variation of 13C-signature of methane emitted by a temperate mire ecosystem, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12559, https://doi.org/10.5194/egusphere-egu21-12559, 2021.

Peatlands are a globally important carbon (C) store, although it is well understood that anthropogenic pressures including drainage can reduce potential for C sequestration, in part due to increased losses of C via the aquatic pathway. Superimposed onto land-use pressures on peatlands are those caused by extreme climate events. Following a drought in 2018 and a subsequent dry period in spring 2019, a large wildfire burnt approximately >60 km² of blanket bog and wet heath within the Flow Country peatlands, North Scotland in May 2019. The fire burned various peatland land types, including near-natural peatland and drained peatland areas. This event created an urgent opportunity to quantify the interacting effects of peat condition and wildfire on water quality, with a focus on dissolved organic matter (DOM) losses. An extensive water monitoring programme was established, covering 40 individual headwater stream sampling locations across the Flow Country, and monthly sampling ran from September 2019 to October 2020, with samples analysed for dissolved organic carbon (DOC), nutrients and UV-vis-based measurements to inform DOM composition. Initial data shows that samples from burned, drained areas are associated with higher DOC concentrations relative to both burned, near natural peatland areas, and unburned control sites. Furthermore the DOM from burned, drained sites is of a more aromatic nature, as indicated by elevated specific UV absorbance (SUVA), compared to unburned control sites. Such findings imply that wildfires may adversely affect water quality through changes DOM quantity and quality in areas of damaged (drained) peatland. However, more detailed compositional analyses are required to accurately predict changes in the ecological functioning of this peatland derived DOM as it enters the aquatic environment and, therefore, its likely end-fate.

How to cite: Pickard, A., Felgate, S., Fernandez Garcia, P., Gilbert, P., Mayor, D., Monteith, D., and Andersen, R.: How does wildfire impact carbon delivery to peatland drainage networks?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16046, https://doi.org/10.5194/egusphere-egu21-16046, 2021.

Despite being an important terrestrial carbon (C) reserve, tropical peatlands (TP) have been heavily degraded through extensive drainage and fire, to an extent where degraded TP occupies one-tenth of the total peatland area in Southeast Asia (as in 2015). Consequently, repeated fires along with frequent flooding can alter the microtopography, vegetation composition as well as higher diurnal temperature variation due to open canopy, where each is known to influence C dynamics. However, assessing the importance of all these variables on-site can be challenging due to difficult site conditions; hence an incubation experiment approach may provide more useful insights in disentangling the complex interplay of these important variables in regulating GHG (CO₂ and CH₄) production and emissions from fire-degraded tropical peatland areas. Therefore, we conducted an incubation study to investigate the interactions of microtopography (creating water-saturation conditions: mesic, flooded oxic, and anoxic), labile C inputs (in form of root exudate secretion from ferns and sedges), as well as on-site diurnal temperature variation in regulating CO₂ and CH₄ production from fire-degraded tropical peat.

            We found that CO₂ and CH₄ production significantly varied among treatments and were strongly regulated by microtopography, labile C inputs, and temperature variation. Mesic (oxic) treatments acted as a strong source of CO₂ (230.4 ± 29 µgCO₂ g^-1 hr^-1) and mild sink for CH₄ (-5.6 ± 0.2 ngCH₄ g^-1 hr^-1) compared to anoxic treatments acting as a mild source of CO₂ (61.3 ± 6.2 µgCO₂ g^-1 hr^-1) and strong source of CH₄ (591.9 ± 112.1 ngCH₄ g^-1 hr^-1). The addition of labile C enhanced both the CO₂ and CH₄ production irrespective of the treatment conditions, whereas the effect of diurnal temperature variation was clearly pronounced in mesic (for CO₂) and anoxic (for CH₄) conditions. Q₁₀ values for both CO₂ and CH₄ production varied significantly with higher values for CO₂ in mesic treatments (1.21 ± 0.28) and higher for CH₄ in anoxic treatments (1.56 ± 0.35). We also observed a gradient across conditions, where flooded oxic treatments showed in-between values both for CO₂ and CH₄ production and temperature sensitivity, further reflecting the importance of on-site peat water-saturation in regulating the GHG production and emission from the fire degraded tropical peatland areas.

            Overall, these findings highlight how the water-saturation conditions due to microtopographic variation in peat surface, quality, and quantity of labile C secreted from plant communities and temperature variation during a day can influence the GHGs production rates from the fire degraded tropical peat. More importantly, given the current state and extent of degraded tropical peatland areas and future climate and land-use changes as well as frequent fire episodes in the region, our results demonstrate the increasing trend in GHG production from the fire-degraded tropical peatlands in Southeast Asia.

How to cite: Akhtar, H., Lupascu, M., and Sukri, R. S.: Effects of microtopography, root exudates analogues and temperature variation on CO2 and CH4 production from fire-degraded tropical peat, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2665, https://doi.org/10.5194/egusphere-egu21-2665, 2021.

Permafrost peatlands are found in high-latitude regions and store globally-important amounts of soil organic carbon. These regions are warming at over twice the global average rate, causing permafrost thaw and exposing previously inert carbon to decomposition and emission to the atmosphere as greenhouse gases. However, it is unclear how peatland hydrological behaviour, vegetation structure and carbon balance, and the linkages between them, will respond to permafrost thaw in a warming climate. Here we show that permafrost peatlands follow divergent ecohydrological trajectories in response to recent climate change within the same rapidly warming region (northern Sweden). Whether a site becomes wetter or drier depends on local factors and the autogenic response of individual peatlands. We find that bryophyte-dominated vegetation demonstrates resistance, and in some cases resilience, to climatic and hydrological shifts. Drying at four sites is clearly associated with reduced carbon sequestration, while no clear relationship at wetting sites is observed. We highlight the complex dynamics of permafrost peatlands and warn against an overly-simple approach when considering their ecohydrological trajectories and role as C sinks under a warming climate.   

How to cite: Sim, T., Swindles, G., Morris, P., Baird, A., Cooper, C., Gallego-Sala, A., Charman, D., Roland, T., Borken, W., Mullan, D., Aquino-López, M., and Gałka, M.: Divergent responses of permafrost peatlands to recent climate change, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3220, https://doi.org/10.5194/egusphere-egu21-3220, 2021.

Northern peatlands are important terrestrial carbon (C) stores, but their ability to sequestrate C is at delicate balance affected by management and also by climate change. The climate change causes less snow pack and warmer winters with faster water table drop in spring and drier summers in most boreal areas. Due to those changes natural peatlands may become C source instead of sink.

This study presents ecosystem respiration (ER) over five-year period and the annual estimates of net ecosystem exchange (NEE) of CO₂ in Umbusi and Laukasoo in Estonia along disturbance gradient from drained to natural ombrotrophic bog. Both study sites locate next to the active cutaway peatlands. There were four CO₂ flux measurements plots with three measurements points at different distance from the drainage ditch (10, 50, 100 and 200 m in Umbusi; 3, 40, 50, 125 m in Laukasoo) to form a water table depth and soil moisture gradient on both study sites. ER was measured using opaque static chamber throughout of the year in period 2012-2016. A vented and thermostated transparent plastic chamber with removable opaque cover was used for CO₂ exchange measurements. NEE measurements occurred biweekly from April to December in 2015, totally were done 648 measurements. NEE was derived from modelling of ER and gross primary production with temperature, photosynthetically active radiation, water level and days of year (as phenological phase) as driving variables.

Annual mean NEE at four different distance from the ditch toward undisturbed area in Umbusi and Laukasoo were 0.37, 0.28, 0.15, 0.08 and 0.44, 0.34, 0.04, 0.21 kg C m^-2 y^-1, respectively. Although mean NEE was positive for all plots on both sites, there were also negative annual NEE values in some points in undisturbed plots (100 and 200 m from the ditch in Umbusi and 50 and 125 m in Laukasoo).

Average water level at four different distance from the ditch toward undisturbed area in Umbusi and Laukasoo during growing period (from the beginning of May to the end of October) in 2015 were -94, -45, -22, -22 and -124, -33, -21, -22 cm, respectively. Monthly mean air temperature and sum of precipitation were not different from the long-term measurements in studied growing period in 2015 while winter was significantly warmer.

Modelled ER remained high for cold period because of higher air temperature in 2015. Due to higher respiration rate from non-frozen peat layer in cold season, more CO₂ was released back to atmosphere and annually less C was accumulated. Monthly mean air temperature for cold period was 3.5 ºC warmer than the long-term average.

How to cite: Maddison, M., Veber, G., and Kull, A.: Net ecosystem exchange of CO2 and ecosystem respiration in two bogs in Estonia along disturbance gradient, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12999, https://doi.org/10.5194/egusphere-egu21-12999, 2021.

In the UK, peatlands are a significant provider of many ecosystem services including drinking water provision and carbon sequestration. However, a history of intense management and other environmental factors such as air pollution has led to large scale peatland degradation. In fact, a large proportion of UK peatland habitat, particularly upland blanket bog, is no longer being classified as ‘active’. Such degraded peatlands are characterised by lower water tables, causing increased peat decomposition and thus loss of carbon. Carbon is mainly lost via respiration (CO2 and CH4) and as dissolved organic carbon (DOC), the latter leading to a potential associated decline in water quality (affecting colour and taste); however, separating climatic from vegetation impacts and attributing negative impacts to management remains a challenge.

A particular issue in the UK is water quality from uplands containing blanket bog, as they provide most of the UK’s drinking water. Over recent decades drinking water quality has deteriorated as seen in increasing DOC concentrations. Whilst previous work has explored links between rising DOC and management practices, particularly grousemoor management involving rotational burning of vegetation to encourage red grouse populations on shooting estates, there continues to be a lack of understanding linkages in relation to alternative management/restoration, vegetation composition and, in particular, underpinning peat chemical processes. Understanding such linkages is becoming ever more important as many degraded peatlands are currently being restored by revegetation and rewetting as well as exploring alternative management such as mowing of vegetation.

Unravelling the underpinning peat chemistry and plant-soil processes regulating carbon cycling, and producing and/or altering DOC and its various constituent components, is key to understand impacts upon water treatment requirements. Of particular concern is that chemical (coagulant) water treatment has potential health implications via disinfectant by-product formation following chlorination of DOC rich water supply. Thus, ill-informed land management and/or restoration alongside climatic change may incur additional water treatment pressures and costs, putting increased pressure on an already strained system. Therefore, it is important to understand the role of catchment-scale peat plant-soil chemical processes and adapt best-practice land management options for supporting drinking water quality at the peatland source.

Here, insights into peat physical and chemical properties are presented, towards enabling management decisions based on ‘treatment at source’ rather than the conventional ‘end of pipe’ drinking water treatment. Field samples and monitoring of peat mesocosm cores taken from across a spectrum of ‘intact’ to degraded and restored UK blanket bogs (including conventionally burnt and alternatively mown grousemoors) are routinely monitored for gaseous carbon fluxes, DOC and water quality parameters relating DOC properties (e.g. UV-spectra) to vegetation, habitat condition and management. Mesocosms also included sampling from individual vegetated cores, each with two attached plant-free cores, either with or without roots. We compare findings from controlled mesocosms to samples from field sites, assess potential methodological aspects affecting DOC collection and characterisation, unravel potential links to specific vegetation types and management/habitat condition, and explore the characterisation of DOC compounds linked to colour, high coagulant demand and the formation of disinfectant by-products.

How to cite: Mycroft, A., Heinemeyer, A., Penkman, K., Banks, J., and Thom, T.: Towards unravelling the 'Black Box' of peatland carbon: Linking peatland habitat condition and management to water chemistry and quality, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15049, https://doi.org/10.5194/egusphere-egu21-15049, 2021.