Boreal peatlands are a major source of global wetland methane emissions. With ongoing climate change, these emissions could rise sharply in future, further enhancing climate change. Yet, long-term studies evaluating the impact of climate change on boreal peatlands are scarce. We have monitored methane emissions at a boreal fen in Lompolojänkkä, Northern Finland (ICOS ecosystem class II site) for 13 years (2007-2019) using the eddy covariance technique, accompanied by measurements of abiotic and biotic variables, such as peat temperature, water level, and vegetation parameters. Peat temperatures strongly drove methane emissions, that is, methane emissions increased significantly with peat temperature. Year-to-year variation in CH₄ emissions was correlated to year-to-year variation in peat temperatures. Annual variation in water levels had no significant impact. Our results confirm that peat temperature explains CH₄ variation to a large extent. In this presentation, we will further evaluate the role of snow cover and melt on CH₄ emissions in spring.

How to cite: Kübert, A., Aurela, M., Hatakka, J., Laurila, T., Rainne, J., Tuovinen, J.-P., Vekuri, H., and Lohila, A.: Peatland methane emissions in a changing climate: A 13-year time series of a boreal fen in Northern Finland, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8556, https://doi.org/10.5194/egusphere-egu23-8556, 2023.

Clear-cutting of drained peatland forests, as a part of the conventional even-aged rotation forestry, significantly disturbs peat soil biogeochemistry due to changes in soil physical characteristics and microbial activity. Achieving spatially representative estimates of GHG emissions from such a complex area is a challenging task. Accurate estimates of GHG fluxes following clear-cutting are sorely needed for national greenhouse gas reporting and devising more climate-friendly forestry practices for these production ecosystems, abundant in the Nordic countries.

In December 2021 we initiated continuous eddy covariance (EC) measurements of carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) fluxes on a nutrient-rich drained boreal peatland forest (ca. 6.1 ha) in southern Finland. The mature tree stand dominated by Norway spruce (Picea abies) was clear cut in March 2021. The measurements are part of a larger research effort aimed at understanding climatic impacts of forest management practices on drained peatlands. Here we focus on interpreting the spatiotemporal variability of GHG fluxes from the clear-cut site using the EC measurements.

The clear-cut area was emitting N₂O to the atmosphere throughout the measurement period, including the winter period. The emissions increased after snow melt and peaked during late July 2022. Despite CO₂ uptake offsetting approximately one third of ecosystem respiration, the clear-cut area was a strong source of CO₂ to the atmosphere during the year 2022 (2.0 kg(CO₂) m^-2 yr^-1). CH₄ emissions were small, yet clearly positive. The observed GHG fluxes showed clear wind-direction dependency indicative of spatial variability of GHG fluxes within the clear-cut. The spatial variability will be analysed based on detailed mapping of the clear-cut surface and footprint (i.e. source area) modelling, in combination with further scrutiny of the EC fluxes. Overall, these results provide the much-needed information on the GHG fluxes from such ecosystems and serve as a baseline for this site in the future.

How to cite: Peltola, O., Tikkasalo, O.-P., Alekseychik, P., Launiainen, S., Lehtonen, A., Li, Q., Peltoniemi, M., Rinne, J., Rissanen, A., Sarkkola, S., and Mäkipää, R.: Eddy covariance observations of CO2, CH4 and N2O fluxes of a drained boreal peatland forest after clear-cutting, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3889, https://doi.org/10.5194/egusphere-egu23-3889, 2023.

Greenhouse gas (GHG) emissions from peatland forest soils are associated with ground water table (WT) level, which controls the vertical distribution of aerobic and anaerobic processes in soil. It has been suggested that transition from rotation forestry with ditch network maintenance (DNM) to selection harvesting would be a feasible alternative to reduce negative GHG and water impacts of peatland forestry as it raises WT and reduces aerobic decomposition of deep peat compared to mature forests. Transpiration from remaining trees would keep WT low enough for stand growth and natural regeneration without DNM. We measured vertical CO₂, CH₄, N₂O and O₂ concentration profiles in two peatland forests to provide insights on the controls of processes producing and consuming gases in the soil after harvest-induced hydrological change. The sites located on nutrient-rich peatland soils in Southern Finland, were dominated by Norway spruce, and parts of the sites were selection harvested. Selection harvesting raised WT by 14 cm relative to non-harvested controls, on average. All soil gas concentrations were associated with the proximity to the WT, but their patterns and in-soil fluxes were decoupled. CH₄ and CO₂ showed remarkable vertical concentration gradients, with very high values in the deepest layer due to low gas permeability of wet peat. However, CH₄ was efficiently consumed in the peat layers above the WT where it reached sub-atmospheric concentrations, indicating oxidation of CH₄ from both atmospheric and deeper origins. Soils maintained these functions after selection harvest. Surface peat contributed the most to soil-atmosphere CO₂ flux, but harvest treatment also modestly increased the source in deeper soil. No consistent differences were observed in N₂O emissions, which were the least associated with other gases. Based on our results, selection harvesting in drained nutrient-rich peatland forests without other hydrological measures limitedly reduces soil net emissions compared to non-harvested mature stands.

How to cite: Peltoniemi, M., Li, Q., Turunen, P., Tupek, B., Mäkiranta, P., Leppä, K., Müller, M., Rissanen, A. J., Laiho, R., Anttila, J., Koskinen, M., Lehtonen, A., Ojanen, P., Pihlatie, M., Sarkkola, S., Vainio, E., and Mäkipää, R.: Soil CO2, CH4 and N2O concentrations and fluxes in peatland forests are associated with water table level - implications of selection harvesting on soil emissions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7536, https://doi.org/10.5194/egusphere-egu23-7536, 2023.

Planning of peatland management under contrasting economic and environmental targets requires application of ecosystem models that can account for complex interactions and feedbacks between biogeochemical, hydrological and forest-related processes. Here we present a further developed version of Peatland simulator SUSI (Lauren et al. 2021) that calculates formation, transport and biodegradation of dissolved organic carbon (DOC). We tested the new model structure against laboratory incubation results containing peat columns from Finland, Estonia, Sweden and Ireland. The drainage strategy (distance between ditches and ditch depth) is considerably different in all these countries: In Finland the ditch network forms a dense fish-bone pattern with an average ditch distance of 40 m, in Estonia the ditch distance is longer but the ditches are arranged to square blocks, in Sweden the network is often irregular, and in Ireland shallow ditches are spaced densely. Then we applied SUSI and assessed the impacts of changing ditch depth and distance on stand and soil C balance, lateral C flux and forest growth. We found that DOC export originated mainly from the close proximity of the ditches because the rate of decomposition is highest and the transport time is shortest. Further from the ditches, water residence time can be several months or even longer enabling biodegradation of a large part of DOC during the transport. The results revealed that even small slopes had a remarkable impact on WT, residence time and DOC export; and that the effect of the slope could exceed that of drainage dimensions per se. Overall results indicated that drainage strategy in Finland was particularly sensitive to changes in ditch depth and distance. In contrast, changes in irregular, sparse ditch network in Sweden caused only minor effects on forest growth, C balance and lateral C fluxes. 

How to cite: Laurén, A., Kiuru, P., Könönen, M., Peltomaa, E., Pumpanen, J., Ojala, A., Hasselquist, E., Laudon, H., Ostonen, I., Renou-Wilson, F., Petty, A., and Palviainen, M.: Effect of drainage intensity on lateral carbon fluxes in forested peatlands, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6364, https://doi.org/10.5194/egusphere-egu23-6364, 2023.

Lateral carbon (C) flux results from complex interplay of formation, transport and biodegradation of dissolved organic carbon (DOC), and is an important but rather scarcely studied component of the C balance in peatlands. Temperature and water table (WT) are the primary factors regulating peat CO₂ emissions and the release of DOC. DOC dynamics in soil is complicated because the DOC storage is continuously increased by the decomposition of solid organic matter, but simultaneously decreased by biodegradation. Any upscaling of lateral C fluxes requires understanding these coinciding processes. We studied the effect of temperature and WT on CO₂ emission and DOC concentration in pore water while incubating peat columns (diameter 0.2 m height 0.5 m) in laboratory conditions for eight months. Peat columns were extracted from drained forested peatlands in Finland, Estonia, Sweden and Ireland. WT was set to -0.2 m and -0.4 m distance from the column upper end. During the incubation, the temperature ranged between 18  and 34 ⁰C. DOC samples were extracted in monthly intervals from the columns using Rhizon soil water samplers. At the same time CO₂ emission was measured from the headspace of the column. DOC biodegradation to CO₂ and its temperature sensitivity was studied by incubating soil water samples in controlled conditions. The quality (aromaticity) of DOC was investigated with a UV-VIS spectrophotometer. The effect of temperature on DOC concentration was not straightforward unlike in the case of CO₂ emission. DOC concentration increased steepest when the temperature exceeded 25  ⁰C, whereas with lower temperatures DOC was unchanged or slightly decreased. This can be due to different temperature sensitivities of DOC release and its biodegradation. Low WT resulted in high CO₂ emissions and DOC concentrations. These results are important in developing ecosystem models accounting for lateral C fluxes and the effects of forest management, drainage and climate change in managed peatlands.

How to cite: Palviainen, M., Könönen, M., Peltomaa, E., Pumpanen, J., Ojala, A., Hasselquist, E., Laudon, H., Ostonen, I., Renou-Wilson, F., Kull, A., Veber, G., Mosquera, V., and Laurén, A.: Processes affecting lateral carbon fluxes from drained forested peatlands, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6367, https://doi.org/10.5194/egusphere-egu23-6367, 2023.

Continuous cover forestry (CCF) has been promoted as an environmentally sustainable option for drained peatlands. The CCF management has been challenged due to potentially lower tree growth compared to traditional even-aged management, especially with suppressed trees that are released during a selection harvesting under CCF management.

Our objective was to quantify the time lag of stem diameter growth response of suppressed Norway spruce trees (Picea abies Karst.) after a selection harvesting compared to that of dominant trees. We also tested if the carbon assimilation of the trees increased immediately after selection harvesting. We used radial increment cores from suppressed Norway spruce trees to estimate the impact of selection harvesting on the diameter growth and intrinsic water use efficiency (iWUE). We measured carbon isotope composition (δ¹³C) of wood, to quantify how the reduced competition between trees altered iWUE and its components, the photosynthetic rate (A) and stomatal conductance (g).

The study was conducted in the Lettosuo experimental site on fertile forestry drained peatland area in southern Finland. Approximately 70 % of the initial stand area (18.5 ha) was harvested according to CCF principles by applying selection harvesting, and the rest of the area was divided to intact control area and to clear-cut area. In the study site, by selection harvest, trees were removed from multiple age classes, but especially mature trees individually or in a small groups were taken away to maintain uneven-aged structure of the forest. All the target trees grew in the similar competitive position before selection harvesting.

Our results show that there was a delay with the diameter growth of the suppressed trees to selection harvesting, whereas the most significant growth-enhancing effect occurred three-four years after selection harvesting. In contrast to the delay in the increment, the photosynthetic rate relative to stomatal conductance increased immediately after selection harvesting, as shown by the instant 2.5‰ increase in δ¹³C to a post-harvest level.

Our results show that carbon uptake increased immediately for suppressed Norway spruce trees after selection harvesting, but the harvest did not induce a clear increase in stem diameter growth during the first years after the harvest.

How to cite: Lehtonen, A., Leppä, K., Rinne-Garmston, K., Sahlstedt, E., Schiestl-Aalto, P., Heikkinen, J., Young, G., Korkiakoski, M., Peltoniemi, M., Sarkkola, S., Lohila, A., and Mäkipää, R.: Fast recovery of suppressed Norway spruce trees after selection harvesting on a drained peatland forest site, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2639, https://doi.org/10.5194/egusphere-egu23-2639, 2023.

Freezing and thawing are common phenomena and potential sources of N2O emissions in ecosystems at high latitudes. Earlier it was hypothesized that the frozen soil layer might trap the underlying production of N2O and release this as the top layer is thawed. However, newer research has found other factors playing role in the de novo emissions such as fluctuating availability of organic matter, nitrates, and ammonia, microbial activity, and changing oxic conditions of the soil. But, the variation in the abundance of genes involved in the nitrogen cycle during these events is rarely explained thus, a generally accepted theory of the impact of freeze-thaw on N2O fluxes is still missing.
To further investigate the relationships between physical, chemical, and microbial parameters with N2O emissions, we conducted a two-week experiment of three thaw-freeze events in March 2022 using artificial heating with electrical cables installed in collars of greenhouse gas sampling chambers conducted in a drained Downy birch peatland forest. Gas and soil samples were obtained on three non-consecutive days from these collars. Soil temperature, soil water content (SWC), NH4-N, and NO3-N were measured in the soil. Also, the abundances of functional genes involved in the nitrification (bacterial, archaeal, and comammox (complete ammonia oxidation) amoA) and denitrification (nirS, nirK, nosZI, and nosZII) were known using qPCR.
Our results show that artificial heating induced the thawing of the frozen top layer of soil during our experiment. The increase in soil surface temperature positively correlated with the soil water content in the top layer (R=0.58, p<0.01). N2O emissions also increased with heating and correlated with SWC (R=0.38, p<0.01). Ammonia in soil decreased and was negatively associated with N2O emissions (R=−0.28, p<0.05), suggesting active nitrification as the amount of nitrates also increased during heating. The abundance of all functional genes significantly increased during the heating except for those responsible for the consumption of N2O (nosZ genes) during
denitrification. Although we found evidence of both active nitrification and denitrification, the multiple regressions between N2O emissions and the proportion of different functional genes suggest that the nirK-type denitrifiers dominated in the denitrification as well as in the overall production of the N2O (p<0.001). Meanwhile, the inactivation of N2O consumers (nosZ) at thawing temperatures resulted in the emission of N2O during the thawing events in the drained peatland’s nitrogen-rich soil.

How to cite: Kazmi, F. A., Espenberg, M., Masta, M., Gadegaonkar, S. S., Thayamkottu, S., Ranniku, R., Parn, J., and Mander, Ü.: Impact of soil moisture changes on nitrogen cycle microbiome during the experiment of thaw-freeze cycle in a drained peatland forest, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5712, https://doi.org/10.5194/egusphere-egu23-5712, 2023.

In drained peatland forests, drainage ditches cover ca. 3% of the area, but contribute to up to 100% of methane (CH₄) emission. The drained peat soils, in contrast, can act as a CH₄ sink especially under efficient drainage. Therefore, emissions from ditches will impact whether drained peatland is a net CH₄ sink or source. The net CH₄ flux is likely to be impacted by the conditions in the ditches such as the extent and type of plant cover and the time since drainage. In order to provide more accurate ditch CH₄ emission factors for national greenhouse gas (GHG) inventory, we examined the fluxes and the underlying CH₄ cycling processes in a nutrient rich peatland forest in Ränskälänkorpi, Southern Finland during May-October 2021. We compared the ecosystem-atmosphere CH₄ fluxes and their δ¹³C values from moss dominated and open water ditches. We determined CH₄ and CO₂ mixing ratios and their δ¹³C values in water and in sediment by gas chromatography and cavity ring-down spectroscopy (Picarro G2201-i), respectively. We also assessed the role of CH₄ as a carbon source for Sphagnum mosses growing in ditches by analyzing δ¹³C values in submerged and partly submerged Sphagnum using elemental analysis - isotope ratio mass spectrometry. We found that mean seasonal CH₄ emissions from moss dominated ditches were 90% lower than from open water surfaces. In this dry summer, moss-dominated ditches were occasionally net sinks of atmospheric CH₄. These results can be explained by CH₄ consuming microbes inhabiting surface water, moss layer or sediment below the moss layer and using CH₄ as a source of carbon and energy. Isotopic mass balance calculations accounting for the measured δ¹³C values of Sphagnum moss, dissolved CO₂ and CH₄ as well as fractionation against ¹³C during (mass-transfer-limited) moss CO₂ fixation indicated that 10-28% of carbon in ditch Sphagnum mosses potentially originated from oxidized CH₄. Ditch network maintenance, including removing mosses, is likely to decrease along with changing peatland forest management, e.g., continuous cover forestry. Our results suggest that ditches overgrown by mosses have potential to reduce CH₄ emissions from drained peatland forests and could serve as an additional GHG mitigation measure to management practices that maintain a continuous forest cover, attenuate the changes in water table level and thus reduce CH₄ emissions from peat soils.

How to cite: Larmola, T., Rissanen, A. J., Ojanen, P., Stenberg, L., Kohl, L., and Mäkipää, R.: Mosses as biofilters for ditch methane emissions from forestry drained peatlands, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1382, https://doi.org/10.5194/egusphere-egu23-1382, 2023.

Definitions of peatlands based on peat thickness often exclude areas of shallow peat such as those found across Bodmin Moor, southwest UK.  Although thin, in areas, these peats support Sphagnum rich vegetation communities. 

We are continuously (every 30 minutes) measuring net ecosystem exchange and methane fluxes, using automated chambers, in four vegetation communities along a wetness gradient.  We hypothesis despite the thin peat, these communities are carbon sequestering, and therefore require protection and/or restoration.

These peatlands are heterogeneous on meter spatial scales, chamber measurements enable us to capture that variability and quantify the difference between the vegetation communities present.  The temporal resolution of the data gives us certainty in the carbon budgets not previously possible using survey techniques.

How to cite: Goodger, L., Gatis, N., Benaud, P., Anderson, K., and Brazier, R.: Can thin peats sequester carbon?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5809, https://doi.org/10.5194/egusphere-egu23-5809, 2023.

Norway has the third greatest extent of peatlands in Europe, after Finland and Sweden. Norwegian peatlands cover nearly 30 000 km² or 7.7 percent of Norway’s land area. However, 6500 km² of these peatlands have been drained for forestry or agriculture and are estimated to emit approximately 6 Mton CO₂ annually, accounting for 11 percent of Norway’s total carbon emissions. In 2016, the Norwegian Environment Agency and the Norwegian Directorate of Agriculture embarked on a peatland restoration plan to reduce greenhouse gas emissions and improve the ecological conditions of drained and degraded peatlands in Norway. Since then, over 100 peatland sites have been restored. However, only one of these sites is being actively monitored to determine the effect of restoration on carbon fluxes, making this site critical to understanding carbon dynamics of restored peatlands in Norway. The site, located in the Regnåsen and Hisåsen Nature Reserve (Trysil Municipality, Innlandet county) consists of two study areas that are sub-catchments of the same watershed, cover approximately 0.5 km², and are separated by 0.5 km. Both areas were drained in the 1960s, with a network of drainage ditches totaling approximately 4000m. One of the areas was restored in 2021 by constructing 318 dams in the drainage ditches, while the other area remains drained as a control. In 2019 eddy covariance towers were installed to track vertical CO₂ and CH₄ fluxes on each site. In addition, DOC, DIC and water discharge measurements were taken to estimate lateral carbon transport, and soil samples were taken to estimate carbon stocks. Preliminary results indicate that CO₂ fluxes have decreased and CH₄ fluxes have increased in the restored site as compared to the drained site, and that vertical carbon fluxes account for over 90% of carbon transport on both sites. This project is coordinated by the LATICE (Land-ATmosphere Interactions in Cold Environments) project at University of Oslo. The results of this study will assist the Norwegian Environment Agency in shaping the next phase of the peatland restoration work in Norway.

How to cite: Bekken, M., Pirk, N., Vatne, A., Tallaksen, L., Westermann, S., Larsen, P., Ibrom, A., Steenberg Larsen, K., Knutson, J., and Dörsch, P.: Carbon dynamics of a controlled peatland restoration experiment in Norway, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15754, https://doi.org/10.5194/egusphere-egu23-15754, 2023.

Rewetting drained peatlands is recognized as a leading and effective natural climate solution to curbing greenhouse gas (GHG) emissions. However, CO₂ source-to-sink transition is not necessarily detected in years immediately following rewetting and temporal dynamics in carbon budgets can be seen in rewetted systems. Here, we investigate long-term (2008 & 2013 - present) ecosystem flux measurements using the eddy covariance technique, revealing the temporal patterns of annual carbon dioxide (CO₂) and methane (CH₄) fluxes, in a rewetted peatland site in northeastern Germany. We show that site-level annual emissions presented in this study are only approaching the IPCC default Tier 1 emission factors (EFs) and those suggested for the German national inventory report after 13-16 years of rewetting when the optimum range of water level (close to the soil surface) is reached during the vegetation period. Overall, our results indicate that in addition to annual variation in soil temperature, vegetation development (post-rewetting successional vegetation dynamics) along with water table depth have the greatest effect on the carbon sink function. We further observe a transitional change into a new phase in the ecosystem carbon status throughout the study period that includes a source-to-sink transition of annual CO₂ fluxes in 2020. The decreasing trend for CO₂ fluxes is estimated at -0.37 t CO₂-C ha^-1 yr^-1 and -44 kg CH₄ ha^-1 yr^-1 for CH₄ emissions for the period until 2021.  While we found a strong reduction in CH₄ emissions in 2019 (following a severe drought), the negative trend in CH₄ emissions in the years before the drought event is still statistically significant (-17 kg CH₄ ha^-1 yr^-1). Accordingly, a considerable reduction of the 100-year annual global warming potential (GWP) and sustained-flux global warming potential (SGWP) was observed during the course of the study and potentially approaching a new steady-state phase within the last few years. In Germany, the published long-term datasets from rewetted peatlands only cover a period of ≤10 years after rewetting, thus, the duration of potential phases and development of future emissions are still unclear. This outlines the need for more long-term datasets to cover the source-to-sink transition in rewetted peatlands that also capture the impacts of likely future climate extremes. Here, we aim to establish a baseline to contribute a better understanding of the transitioning, complexity, and climate sensitivity of rewetted systems by analyzing the dynamics within the site and the inter-annual variability via their respective drivers. The introduction, monitoring, and targeted management of an ensemble of site characteristics (coverage/type of dominant vegetation, average water level along with microclimate and microtopographic conditions) is necessary in understanding the transient nature of such systems and further refine the existing static default EFs.

How to cite: Kalhori, A., Wille, C., Gottschalk, P., and Sachs, T.: Temporal phases of GHG emissions in rewetted fen sites using multiyear ecosystem carbon flux measurements, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5930, https://doi.org/10.5194/egusphere-egu23-5930, 2023.

Natural peatlands represent 1/3 of the world C soils and contribute significantly to sequestration of atmospheric CO₂ by assimilation and storage of non-well decomposed organic C, due to their specific predominant vegetation such as Sphagnum species. However, they are encountering anthropogenic-induced pressures that disturb their structure (implying shift of vegetation), with potential consequences on their carbon sink function. In an attempt to mitigate this effect, restoration experiments were undertaken at La Guette peatland, a hydrologically disturbed temperate Sphagnum-peatland invaded by vascular plants, which is now a carbon source. Hydrological restoration was performed by blocking drains with dams and vegetation restoration was undertaken by either i) removing first 5 cm of peat (bare plots) or ii) removing first 5 cm of peat and transferring Sphagnum mosses (Sphagnum plots). To study the effect of these experiments, CO₂ and CH₄ fluxes together with environmental variables and vegetation indices were monitored from 2014 to 2017 in 24 2mx2m plots. The annual carbon budget for each plot was estimated using empirical models. Preliminary results show that the hydrological restored site presented lower annual mean CO₂ emissions than the undisturbed site. In addition, Sphagnum plots had the lowest annual mean CO₂ emissions followed by bare peat plots then by intact plots. Hence, the results of these models provide evidence that hydrological and vegetation restorations favour the return to the C sink function of the peatland. However, there is still a need for larger-scale studies to better estimate the effect of restoration activities on peatland greenhouse carbon budgets.

How to cite: Bou Melhem, R., Jourdain, L., Gogo, S., Leroy, F., Jacotot, A., D'Angelo, B., Laggoun-Défarge, F., and Guimbaud, C.: Effect of hydrological and vegetation restorations on the C sink function of the disturbed La Guette peatland., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7044, https://doi.org/10.5194/egusphere-egu23-7044, 2023.

Rewetting of drained peatlands reduces the emissions of carbon dioxide (CO₂) and nitrous oxide (N₂O) substantially. However, elevated methane (CH₄) emissions can occur, at least in the short-term. The impact of rewetting coastal peatlands with brackish water remains yet unclear, although beneficial effects such as lower CH₄ emissions seem likely, due to high sulfate availability. Here, we compare pre- and post-rewetting greenhouse gas fluxes, biogeochemical parameters and the abundance of specific microbial groups in a coastal peatland at the German Baltic Sea coast that was formerly drained and used as an agricultural grassland and recently rewetted with brackish water. 

We hypothesized that flooding with brackish seawater reduces CO₂ emissions despite favoring sulfate-reducers. It should also limit CH₄ production and favor anaerobic methane and thus keep CH₄ emissions low although aerobic methane oxidation may decrease. We measured CH₄ and CO₂ fluxes along a soil wetness gradient before rewetting and along a water level gradient after rewetting with brackish seawater and estimated cumulative CH₄, CO₂ net ecosystem exchange (NEE), and ecosystem respiration (R_eco). Soil cores for biogeochemical and microbial analyses were taken at seven locations along the transect pre- and post-rewetting. We used quantitative polymerase chain reaction (qPCR) on 16S rRNA, mcrA, pmoA and dsrB genes to quantify the abundances of total prokaryotes, methanogens, aerobic methanotrophs and sulfate-reducing bacteria.

After rewetting, cumulative CH₄ net fluxes and NEE increased at locations that were previously dry, while R_eco halved compared to before rewetting. This correlated with the absolute abundances of specific microbial groups and the surface/pore water biogeochemistry. Under the newly created water-logged conditions, the abundances of methanogenic as well as of sulfate-reducing bacteria (SRB) increased at previously dry sampling locations, but remained constant at the former ditch location. At the same time, the abundance of the aerobic methanotroph community on previously dry locations decreased, which indicates lower aerobic methane oxidation potentials. Pore water CH₄ and CO₂ concentrations suggest that gas production most likely increased at the former terrestrial locations and stable carbon isotope measurements support an increase of methanogenesis in the peat at some locations. Isotopic analyses also provide some support for persistent methane oxidation either through anaerobic or aerobic taxa at one location.

Brackish water rewetting strongly modified the dominant methane-cycling processes but resulted in higher greenhouse gas emissions of both CO₂ and CH₄ in the first year after rewetting. As expected, CH₄ emissions after rewetting were lower than in freshwater rewetted fens, while NEE was unexpectedly high. Since R_eco strongly decreased, we assume that peat mineralization was successfully prevented and that ongoing CO₂ emissions rather derived from strongly reduced CO₂ uptake, supply of terminal electron acceptors (especially sulfate), and excess substrate availability from decaying vegetation. There is great potential for reduction of both, CH₄ and CO₂ emissions after the initial boost when readily available substrate is depleted. However, our study also reveals the complexity of peatland restoration and the possibility of transient effects upon rewetting, and therefore the value of undrained, pristine peatlands as well as their importance in sequestering carbon.

How to cite: Jurasinski, G., Gutekunst, C. N., Liebner, S., Jenner, A.-K., Racasa, E. D., Knorr, K.-H., Anthony, S. E., Pönisch, D. L., Böttcher, M. E., Janssen, M., Kallmeyer, J., Koebsch, F., and Rehder, G.: Changes of greenhouse gas fluxes and corresponding microbial communities upon rewetting of a coastal peatland with brackish seawater, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15114, https://doi.org/10.5194/egusphere-egu23-15114, 2023.

Peatlands represent 2.5% of all agricultural land in the EU, yet they account for ~ 25% of agricultural greenhouse gas (GHG) emissions, and ~ 5% of total EU-wide GHG emissions. Several studies have shown that peatland rewetting can reduce, or even reverse, the net GHG emissions from previously drained peatlands. We investigated GHG emissions from 14 different European peatland sites (Germany [6], Poland [4] and Netherlands [4]) across a landuse (3 levels) and water table (2 levels) gradient during a 2 year period (July 2021 – June 2023). GHG flux measurements utilizing closed, non-flow-through, dark, non-steady-state chambers were implemented to estimate ecosystem respiration from the study sites. Ecosystem respiration represents the largest share of carbon export to the atmosphere from terrestrial ecosystems. Within the study, landuse gradient was represented by the level of paludiculture (harvest frequency/ soil nitrogen levels), and water table level indicated by Typha- and Carex- dominated vegetation. Initial study results indicate that overall, CO₂ fluxes varied across seasons (ANOVA, p<0.001, n = 1738, F = 14.08), with the highest fluxes occurring in summer (0.402 ± 0.342 g CO₂ m^-2h^-1), and lowest in winter (0.233 ± 0.368 g CO₂ m^-2h^-1). Similarly, CH₄ fluxes varied seasonally, with the highest CH₄ fluxes in summer (6.95 ± 8.07 mg CH₄ m^-2h^-1) and lowest in winter (1.98 ± 4.07 mg CH₄ m^-2h^-1). Average CO₂ fluxes decreased with the increasing level of paludiculture intensity for both Typha and Carex dominated sites, while CH₄ fluxes typically increased with increasing harvest frequency/ soil nitrogen levels. While CO₂ and CH₄ fluxes were generally higher in the early morning (as compared to afternoons), particularly during summer and autumn, we could not show an overall significant diurnal difference in GHG fluxes. Seasonal variability in CO₂ and CH₄ was likely an indicator of the effect of temperature and water table level on GHG fluxes. GHG fluxes at the Typha dominated sites were consistently higher than those of complimentary Carex dominated sites for each landuse class, highlighting the importance of water table and vegetation species on GHG emissions. This research was conducted as part of the Peatland Rewetting In Nitrogen-Contaminated Environments: Synergies and trade-offs between biodiversity, climate, water quality & Society (PRINCESS) project, investigating rewetting of drained, nitrogen contaminated peatlands and their potential role in reducing EU-wide greenhouse gas emissions and improving wetland biodiversity.

How to cite: Boodoo, K., Niese, J., Herbst, E., Fischer, K., and Glatzel, S.: Seasonal and diurnal patterns in Greenhouse Gas fluxes from re-wetted European peatlands, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13951, https://doi.org/10.5194/egusphere-egu23-13951, 2023.

Peatlands are a vast and vulnerable carbon stock. Although they cover only 3% of the land area, globally the organic matter stored in peat accounts for 20% of soil carbon. In peat-rich countries, peat soils contribute much to the carbon dioxide (CO₂) emissions from croplands and grasslands in the national greenhouse gas (GHG) budgets. This may seriously diminish any possible net carbon sink of the land use sector. Owing to their high emission reduction potential per area, cultivated peat soils are often considered as a very effective target for GHG mitigation measures in the agriculture and land use sector. This goal can be achieved by rewetting. Rewetting often comes with synergies such as water protection, as peat soils are also high sources of dissolved organic matter and nutrient efflux. In wet soil transformation is driven by anaerobic processes and the resulting methane emissions can be considered a tradeoff of CO₂ savings by wet management. How groundwater table raise influences GHG emissions depends e.g. on peat properties, environmental conditions and site management. The goal of the EU project EJP Soil INSURE, to which our research project belongs, is to evaluate the significance of different factors regulating the GHG balance of wet cultivated peat soils at different European sites and to seek for indicators of successful GHG mitigation. We contribute to this goal by analyzing the organic matter of peat profiles. We study the molecular composition of the different peats using analytical pyrolysis GC-MS, in conjunction with organic matter stoichiometry. Our aim is to better understand the role of peat properties for the biogeochemical cycles in rewetted peatlands and their GHG balance. By using different classes of compounds, we were able to distinguish between transformed organic matter and peat that is relatively rich in undecomposed plant material. We identified marker compounds that were highly specific for fresh plants, transformed plant material or microbial abundance. For example, the abundance of undecomposed plants can be linked to levosugars, decomposed plant material is pictured by low weight polysaccharides such as 5-methyl-2-furalaldehyde and microbial matter is displayed by specific nitrogen compounds, as pyridines, pyrroles and indene’s, such as 1H-indene, 3-methyl. In addition, we studied the correlation between peat stoichiometry, compound abundance and the degree of transformation. We find that for example a high C/N ratio is negatively correlated with a high amount of low weight polysaccharides and compounds indicative for microbial abundance. We conclude that our method gives a detailed insight of peat composition. Further, it enhances our knowledge of peat quality and could therefore help to gain insights into the dependency of GHG emissions on peat quality.

How to cite: Groß-Schmölders, M. and Leifeld, J.: Analyzing the degree of organic matter transformation of rewetted European peatlands in the context of their greenhouse gas emission potential, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2244, https://doi.org/10.5194/egusphere-egu23-2244, 2023.

The major objective behind peatland restoration is to improve ecosystem services, such as increased biodiversity, increased carbon sequestration, increased groundwater storage, and improved surface water quality. However, a century or more of drained conditions has drastically changed the soil properties in relation to natural wetlands and this is likely to profoundly influence the potential for various biogeochemical peat processes. Thus, peatland restoration may result in undesired impacts and potential environmental threats. Two such undesired effects are increased methane production and increased mercury methylation.

In this study, we investigated how nine boreal peatlands across a latitudinal gradient in Sweden have been affected by rewetting after up to a century of drained conditions. Each peatland was sampled for three 50 cm deep peat cores that were analyzed for carbon, nitrogen, δ¹³C, δ¹⁵N, bulk density, and organic matter proportion. Adjacent to each restored peatland, we sampled a corresponding pristine (natural) peatland to facilitate a comparison of how the peat properties have been affected by drainage and subsequent rewetting of the peatlands. Groundwater depth was monitored at all peatland locations to confirm restored conditions at the rewetted peatlands.

The results indicate that a long period of drained conditions and subsequent rewetting have changed the peat properties, with differences shown in C/N ratio, dry bulk density, and organic matter content. Rewetting will thus not regenerate a pristine environment. Instead, it creates new conditions to which various biogeochemical processes will respond and these do not necessarily represent conditions prior to disturbance. Our study will provide background information to understand the biogeochemical dynamics in peatlands after restoration, especially since the study covers a large span of nutrient conditions and catchment settings. This understanding will be fundamental for the development of strategies to minimize undesired biogeochemical responses following peatland restoration.

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How to cite: Smeds, J., Nilsson, M., Skyllberg, U., Björn, E., Bertilsson, S., Bishop, K., and Öquist, M.: Biogeochemistry and Peat Properties of Restored Wetlands, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15213, https://doi.org/10.5194/egusphere-egu23-15213, 2023.

In the new demonstrator project, Greenhouse Gas Removals – Peat, we aim to improve the greenhouse gas balance of peatland restoration projects so that net-negative carbon projects can be achieved. To do this, we are trialling a suite of methods including gully blocking, Sphagnum planting, biomass harvesting coupled with biochar production, and methane suppression via gypsum dosing. Through these methods, we hope to increase the input of recalcitrant carbon whilst minimising methane emissions.

We present the results of a survey of 17 peatland pools across four sites in the south Pennines, UK. The pools were created via different restoration methods and have either been colonised naturally by Sphagnum or have been planted with commercially available mixes. Our data show that floating Sphagnum mats create a poorly mixed zone in the restoration pools where temperature and dissolved oxygen levels are elevated, resulting in lower dissolved methane concentrations beneath the Sphagnum mats compared to the rest of the pool. When accounting for higher methane emission rates due to the elevated temperature, our results suggest an overall ~40% lowering of diffusive methane flux in areas colonised by Sphagnum.

Modelling of water quality parameters from the pools suggest methane flux is controlled via different mechanisms in the two areas of the pools. In the clearwater areas, redox potential and nitrogen availability are the dominant controls on methane flux, whereas under Sphagnum, dissolved oxygen concentration was the only significant driver. We interpret this as a switch in relative activity between methanogens and methanotrophs in the two areas. Taken together, our results provide real world evidence of the role of Sphagnum in creating a habitat niche favourable for methanotrophs and thereby lowering methane flux from peatland restoration projects.

In this presentation we will also discuss preliminary findings from the other treatments being trialled at our sites.

How to cite: Ritson, J., Self, R., Evans, C., and Evans, M.: Floating Sphagnum moss mats as a tool to lower methane emissions in restored peatlands, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5553, https://doi.org/10.5194/egusphere-egu23-5553, 2023.

Peatlands are valuable ecosystems that hold a high biodiversity and provide many ecosystem services such as carbon sequestration, water storage and water purification. However, a large part of the peatlands are drained, often for agricultural purposes, resulting in CO₂ emissions, soil subsidence and biodiversity loss. To combat these negative effects, various rewetting measures are being installed which can be combined with varying land-uses such as intensive dairy farming, extensive agriculture, semi-natural grasslands, paludiculture (farming on moist/wet soils) and nature restoration. This broad applicability implies that the extent by which the groundwater level is raised can be fine-tuned to the intended land use. In our study, we conducted a mesocosm experiment in which we exposed intact fen peat cores (80cm, 20cm Ø) to five different water levels (0, 20, 40, 60 cm and variable - surface), two nutrient application levels and two water qualities. For an eight-month period, monthly samples from each peat core were taken at two depths and chemically analyzed. Further, the vegetation in the cores was cut five times throughout the growing season. Above-ground biomass was measured as well as nutrient concentrations in the vegetation. Our results show increased phosphate and ammonium availability upon fully rewetting (0 cm – surface), in contrast to partially rewetted circumstances (20cm – surface) where nutrient availability was lowest. Above-ground biomass was strongly affected by nutrient application and, except for early spring growth, less by water levels. Nitrogen concentrations in the vegetation decreased with increasing water levels indicating stronger nitrogen limitation. This is likely the result of increased denitrification rates under wet circumstances. We conclude that in order to achieve nature restoration under fully rewetted conditions, additional steps must be taken to remove nutrients, particularly phosphorus, from the system. Further, we conclude that partial rewetting can be a solution to slow down the adverse effects of drainage, although agricultural production will decrease. 

How to cite: van der Laan, A., van Dijk, J., Rebel, K., and Wassen, M.: Nutrient dynamics in fen peat in relation to water level management: a mesocosm experiment, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12066, https://doi.org/10.5194/egusphere-egu23-12066, 2023.

Canada is a leading producer, and exporter of peat used for horticultural purposes. Nevertheless, in that context, peat extraction requires the removal of vegetation and the drainage of Sphagnum-dominated peatlands causing disturbances of hydrological regimes and the disappearance of biodiversity as well as most ecosystems services. Moreover, when peat extraction is over, the formerly extracted peatlands become a source of greenhouse gases due to the oxidation of residual peat. Without human intervention, horticultural post-extracted peatlands will almost never return to their original pre-disturbance state. In order to solve this ecological problem, the Peatland Ecology Research Group (PERG) developed in the late 1990s an active ecological restoration method better known as the Moss Layer Transfer Technique (MLTT). Thus, the MLTT allows not only to restore the specific hydrology, but also to restore the Sphagnum carpet as well as typical peatland vegetation communities. Given the effectiveness of the MLTT to restore Sphagnum-dominated peatlands in a short period of time, it is now necessary to clarify and define the notion of a successful peatland restoration work. To achieve this, the present research project uses a fundamental tool of the science of ecological restoration embodied by the reference ecosystem. Consequently, the use of a reference set perform by natural peatlands makes it possible, through the intermediary of the vegetation communities, to appreciate the similarity or the ecological distance of the restored peatlands according to the time up since the restoration. This research work thus underlines the capacity of the MLTT to restore functional peatlands ecosystems on the basis of certain foundations taught by ecological restoration in the context of global climate change and erosion of biodiversity.

How to cite: Breton, G., Guêné-Nanchen, M., and Rochefort, L.: Ecological restoration of post-extracted peatland in Canada. A comparative approach of the vegetation community between restored and natural peatland, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17384, https://doi.org/10.5194/egusphere-egu23-17384, 2023.

Draining temperate fen peatlands created multiple problems such as greenhouse gas emissions, eutrophication and subsidence due to peat mineralization, but also loss of highly specialized biodiversity. Based on recent own publications and (not yet published) studies, we here explore the potential of paludiculture, i.e. the wet use of peatlands, in tackling the multiple challenges mentioned above. Rewetting effectively curbs carbon losses (Tanneberger et al. 2020, 2021), but rewetted fens are more enriched in nutrients and differ in vegetation composition compared to natural fens (Kreyling et al. 2021). Brown mosses, for instance, are outcompeted by tall helophytes (Jaszczuk et al. 2022). Harvesting aboveground plant biomass can effectively reduce nutrient loads (Hinzke et al. 2021a), while belowground production leading to peat formation is even enhanced by high nutrient loads (Hinzke 2021b). Paludiculture with productive species such as Typha, however, is possible even with low nutrient availability (Haldan et al. 2022). If productive species such as Phragmites are actively introduced for paludiculture, genotypes should carefully be selected as they differ strongly in performance (Haldan et al. unpublished). Paludiculture has the potential to foster conservation targets across multiple taxa such as plants, arthropods, and birds (Martens et al. unpublished). Drought events occur with increasing intensity and frequency idue to climate change. High decomposition under these circumstances, however, is balanced by increased root production (Schwieger et al. 2020) due to an elongated belowground growing season (Schwieger et al. 2022). We conclude that paludiculture is a viable management option for rewetted fens that can curb multiple environmental challenges such as greenhouse gas emissions, eutrophication and biodiversity loss.

Haldan K, et al. (2022) Typha for paludiculture—Suitable water table and nutrient conditions for potential biomass utilization explored in mesocosm gradient experiments. Ecology and Evolution 12: e9191. https://doi.org/10.1002/ece3.9191

Hinzke T, et al. (2021a) Can nutrient uptake by Carex counteract eutrophication in fen peatlands? Science of the Total Environment 785: 147276.

Hinzke T, et al. (2021) Potentially peat-forming biomass of fen sedges increases with increasing nutrient levels. Functional Ecology 35, 1579-1595. I

Jaszczuk I, et al. (2022) Physiological responses of fen mosses along a nitrogen gradient point to competition restricting their fundamental niches. Oikos DOI: 10.1111/oik.09336

Kreyling J, et al. (2021) Rewetting does not return drained fen peatlands to their old selves. Nature Communications 12: 5693.

Schwieger S, et al. (2020) Wetter is better: rewetting of minerotrophic peatlands increases plant production and moves them towards carbon sinks in a dry year. Ecosystems 24: 1093–1109.

Schwieger S, et al. (2022) Rewetting prolongs belowground growing season in minerotrophic peatlands and mitigates negative drought effects. Journal of Applied Ecology DOI 10.1111/1365-2664.14222.

Tanneberger F., et al. (2020) The power of nature-based solutions: how peatlands can help us to achieve key EU sustainability objectives. Advanced Sustainable Systems 20000146, DOI 10.1002/adsu.202000146

Tanneberger F., et al. (2021) Towards net zero CO₂ in 2050: An emission reduction pathway for organic soils in Germany. Mires and Peat 27, Article 05, doi: 10.19189/MaP.2020.SNPG.StA.1951.

How to cite: Kreyling, J. and Tanneberger, F.: Paludiculture in temperate fens to combat eutrophication, biodiversity loss, and climate change, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11048, https://doi.org/10.5194/egusphere-egu23-11048, 2023.

The concept of paludicultures is growing in importance as a promising climate mitigation measure and a sustainable alternative to current agricultural use of organic soils. Besides agricultural and economic viability, quantifying the climatic effects of paludicultures is essential to give reliable policy advice and facilitate sustainable management decisions with regard to climate change. Emission factors (EFs) of the relevant greenhouse gases (GHG) carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) for a variety of potential paludiculture plants are still rare, especially from comparable treatments and site conditions.

Five different temperate fen plant species (Carex acutiformis, Phragmites australis, Phalaris arundinacea, Typha latifolia and T. angustifolia) were established as paludicultures with one or two-cut harvest frequencies at three former grassland or arable sites on fen peatland in southern Germany. Ground water levels (gwl) were manipulated to generate a water table gradient spanning annual mean gwl between +4 to −22 cm to derive an optimum gwl for GHG mitigation. One to five years after plant establishment, we measured fluxes of CO₂, CH₄ and N₂O to obtain annual budgets (n=81 / 43 rewetted: gwl +4 to −10 cm, 38 moderately rewetted: gwl −11 to −22 cm) using manual and automatic closed chambers. Besides gas flux measurements, we observed vegetation growth parameters (LAI, NDVI) and biomass yield from harvests. The resulting mean global warming potentials are −13.0 ± 13.9 t CO₂-eq ha⁻¹ yr⁻¹ under rewetted conditions (annual mean gwl ≥ −10 cm) and −1.0 ± 9.8 t CO₂-eq ha⁻¹ yr⁻¹ under moderately rewetted conditions (annual mean gwl < −10 cm). Our dataset revealed that a maximum mitigation potential of paludicultures is achieved at a gwl of −7 cm. These values represent the first EFs of paludicultures for potential integration into the German national GHG inventory.

How to cite: Bockermann, C., Eickenscheidt, T., and Drösler, M.: Greenhouse gas emissions and global warming potentials of five paludiculture plants in fen peatlands in southern Germany, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14397, https://doi.org/10.5194/egusphere-egu23-14397, 2023.

With the increasing demand to reduce greenhouse gas (GHG) emissions to meet the climate goals, rewetting of peatlands has gained attention as a promising measure. To reduce or stop peat oxidation, peat should be brought in anoxic conditions again by elevating the groundwater table. With this action, land becomes less suitable for traditional agriculture. Paludiculture would be a form in which wetland plants are grown and biomass is commercially used.
In a field experiment, we studied the effect on GHG emissions from three different paludiculture species: Typha latifolia, Typha angustifolia and Azolla filiculoides. In this presentation we will focus on the following research questions: 1) Can CO₂ emission reduction compensate increased CH₄ emission when peatland is rewetted for paludiculture purposes? 2) What is contribution of ebullition and diffusive fluxes to the total CH₄ flux of the different crop types? 3) What is the contribution of CO₂ and CH₄ to the total GHG balance with different crop types?

From our results we show that all paludiculture crops reduce GHG emission compared to a drained peat meadow, with highest reduction for Azolla and lowest for Typha latifolia. CH₄ emission in CO₂-eq is as high or higher than the CO₂ emission from drained peatland, but is compensated by net CO₂ uptake. Typha roots in the sediment (resulting in plant mediated gas transport), which leads to lower contribution of ebullition to the total CH₄ flux. Azolla had the highest ebullition rate, but has nevertheless the lowest total CH₄ emission. Most probably because Azolla is a floating plant without roots in the soil. This means that less easily degradable carbon is brought into the soil by e.g. root exudates, and that there is also no CH₄ transport through the plants.

How to cite: van den Berg, M., Vroom, R., Gremmen, T., van Huissteden, J., Boonman, J., and van de Riet, B.: Comparing greenhouse gas balances from three paludiculture crops after rewetting peat: Typha latifolia, Typha angustifolia and Azolla filiculoides, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15534, https://doi.org/10.5194/egusphere-egu23-15534, 2023.

Peatlands, drained for agriculture and peat extraction, are carbon sources contributing 5% to global greenhouse gas emissions. In order to combat climate change and to meet carbon neutrality, peatlands need to be rewetted right away. Sustainable land-use alternatives such as paludiculture are needed for these rewetted sites. Paludiculture enables the production of biomass on rewetted peatlands while lowering emissions and further enhancing ecosystem services. Still, the applicability of paludiculture needs to be investigated in pilot schemes. To track the effectiveness of rewetting and crop growth, monitoring concepts are required. Data from Unmanned Aerial Systems (UAS) can help in predicting biomass by contributing information on spatial patterns of crop growth while keeping the workload of harvesting samples realistic. Here, the ability of optical UAS systems to provide both, spectral and structural information appears especially promising.

On a test site of 8 ha in Mecklenburg-Western Pomerania, Germany, a pilot scheme was established in 2019 (Paludi-PRIMA project) using Typha latifolia and T. angustifolia as target species. We monitored biomass production of Typha sp. using multispectral imagery (Blue, Green, Red, Red Edge, Near Infrared) and a Digital Surface Model (DSM), obtained from the UAS data with structure for motion.

We predicted Typha biomass for three different months (Jul, Aug, Sep), to evaluate the influence of phenology on prediction accuracy. In order to make best use of the different data properties, we combined a Typha mask from the multispectral imagery from all three dates (Random Forest classification with 82.5% overall accuracy and above) with structural information from the DSM.

Biomass was predicted by regression models using training data from in-situ harvests of Typha in 1-m² square plots. For these plots, spatial metrics were derived for selected UAS data derivates, e.g. the median of vegetation height from the DSM or of the NDVI. The resulting regression models were then applied to rasters representing the same metrics for the full study area. Results were validated using R², RMSE and MAE and reference information that was independently predicted from field measurements (height and shoots) for the respective observation dates.

Biomass prediction worked best with the DSM max throughout the months, with highest accuracies in August (R²=0.68 and above, RMSE<150 g/m²). The application of the Typha mask improved results for all regression models, not only for Typha-free but also surfaces with mixed vegetation cover.

We conclude that UAS data contributes essentially to biomass monitoring on experimental paludiculture sites. The combination of structural and spectral information, e.g. in the form of structural metrics and a spectral-based species mask, uses the advantages of UAS data. For larger areas the present findings need to be integrated with spaceborne data, e.g. hyperspectral satellites that add further information to the modelling.

How to cite: Hellmann, C., Bobertz, B., Hübner, F., Köhn, N., Kreyling, J., and van der Linden, S.: Predicting biomass production of Typha spec. on a rewetted paludiculture site over time using multitemporal and multispectral UAS data, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13705, https://doi.org/10.5194/egusphere-egu23-13705, 2023.

Undisturbed peatlands constitute relevant carbon sinks. However, drained or degraded peatlands cause carbon emissions and more than 90 % of the peatlands in Mecklenburg-Western Pomerania, Germany, have been drained. In order to achieve the goals for climate change mitigation, several initiatives have been taken to restore drained and degraded peatlands by rewetting. Previously, drained peatlands were used for agricultural and grassland production, which led to significant carbon emissions. The Paludiculture scheme was introduced to allow sustainable and climate-friendly agricultural production under permanently wet conditions, which allow carbon sequestration of the soil. Phragmites australis (Reed) and Typha spp. (Cattail) are key plants for paludicluture in rewetted areas of north-east Germany.

It is necessary to regularly monitor the plant communities in rewetted areas, as this can be an indicator of rewetting success. Distinguishing peatland vegetation communities require high spectral resolution images, whereas multispectral images may show comparable spectral signatures in different peatland vegetation types. Recently launched hyperspectral sensors offer new possibilities regarding accurate vegetation monitoring in rewetted peatlands. In this study, we investigated multi-date hyperspectral images from DESIS, mounted on the International Space Station (ISS), and satellite-based PRISMA for peatland vegetation mapping. In addition to the increased spectral information, both sensors allow multiple observations per year, which was not the case for airborne hyperspectral data. The 30-m spatial resolution of both sensors, however, brings along multiple peatland vegetation communities within single pixels; hence we used a sub-pixel classification strategy using a Regression-based unmixing approach with synthetic training data. Our analyses focussed on the influence on map accuracy by i) the hyperspectral information and ii) the observation dates. 

We observed that combining April and June PRISMA (MAE = 16.4%) and April and June DESIS (MAE = 17.3%) datasets produced the best results for mapping the peatland vegetation fractions. Analysis of single dates showed that June data leads to slightly better results than April. We found that PRISMA images produced slightly better results than DESIS, which may be caused by the shortwave infrared information missing in the DESIS data. In contrast, DESIS has only visible and near-infrared bands (400-1000 nm) despite having a higher spectral resolution (2.55 nm) than PRISMA (10 nm). 

In conclusion, the hyperspectral information, especially from the short wave infrared > 1 µm, together with the multi-date observation could be shown to contribute to sub-pixel mapping accuracy. In the future, PRISMA and DESIS images can be coupled with EnMAP and the forthcoming SBG and CHIME missions to further improve the space-borne monitoring of rewetted peatlands.

How to cite: Muthusamy, A., Thiel, F., Pham, V. D., Hellmann, C., and van der Linden, S.: Mapping vegetation cover on rewetted fen peatlands using hyperspectral spaceborne images from DESIS and PRISMA, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5352, https://doi.org/10.5194/egusphere-egu23-5352, 2023.

Peatlands are commonly a mosaic of vegetation types, ditches, and open water. Eddy covariance provides a useful way to measure fluxes at the ecosystem scale, however comparing fluxes and annual balances from different source areas in heterogenous field sites can be challenging. Separating fluxes based on wind direction is a commonly used approach to study different source areas, but this method may exclude a substantial amounts of data points that contain some information about flux behaviour, such as when the flux source area covers multiple land cover classes, and as a result the gapfilled timeseries contains greater uncertainty. In this presentation, we present a Bayesian approach that utilises the flux footprint to gapfill CO₂ and CH₄ fluxes. A flux footprint model was used to predict the flux source area and the relative contribution for each land cover class is calculated for each timestep. The net ecosystem exchange (NEE) of a scalar is then assumed to be the linear combination of the different land cover classes weighted by the contribution within the flux footprint. A Bayesian framework was used to estimate model parameters for gapfilling each land cover class for the NEE of CO₂ and CH₄, where the non-linear model approaches were used in both cases. For CO₂, the framework estimated the parameters for the gross primary production (GPP) light response curve and R_eco via the Lloyd-Taylor respiration function, where the NEEof CO₂ was then calculated as the sum of GPP and R_eco. For CH₄, a non-linear temperature dependence model was used.  We show results from multiple eddy covariance towers on peatlands in the Netherlands, including a mixed paludiculture pasture site, natural vegetation sites, and a pasture site with subsurface drainage. We demonstrate that this approach is useful for constraining flux behaviour and obtaining annual balances for each land cover class within the flux footprint.

How to cite: Buzacott, A., van den Berg, M., Kruijt, B., Bataille, L., and van der Velde, Y.: A Bayesian approach to gapfilling fluxes from heterogenous Dutch peatlands measured by eddy covariance, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12916, https://doi.org/10.5194/egusphere-egu23-12916, 2023.

Undisturbed raised bogs are characterised by permanent water saturation which prevents decomposition of peat, limits the spread of vascular plants and makes the ecosystem a peat moss dominated sink of carbon. Lower water levels e.g. due to climate change or drainage endanger ecosystem functions and lead to an altered vegetation composition. In particular, encroaching vascular plant species are a growing thread to natural or restored peatlands in Central Europe. While previous work often focussed on how greenhouse gas emissions or ecosystem functions of raised bogs respond to changing environmental conditions, the impact of encroaching vascular plants is only sparsely covered. As process-based SVAT models are able to simulate different vegetation compositions and their respective water and carbon fluxes, they are an optimal tool to answer this relevant question. However, this requires the relevant processes of a vegetation shift impacting the system’s water and carbon relations to be correctly implemented.

Models capable of simulating bryophyte processes are sparse. We use the process-based SVAT model 'pyAPES' including a bryophyte layer, developed and tested for boreal peatlands, at a bog site in northern Germany. The overall objective of this study is to identify whether pyAPES is able to simulate carbon fluxes of a temperate raised bog under a changing vegetation composition. We addressed four research questions: (i) Does model parametrization need to be changed when using pyAPES for temperate conditions? (ii) How do these changes affect modelled gross primary production (GPP) and ecosystem respiration (R_eco)? (iii) Which photosynthetic and respiratory parameters are most crucial for model performance? (iv) Does the order of crucial parameters depend on vegetation composition and on environmental conditions?

We answer these questions by calibrating pyAPES to measured soil temperature (T_s), water table depth (WTD), seasonal dynamics of vascular plant leaf area index (LAI) and GPP and R_eco fluxes. Morris sensitivity analysis (MSA) is conducted with the calibrated model to investigate parameter impacts on modelled GPP and R_eco.

Preliminary results show that pyAPES performs well for a temperate raised bog after adaptation of the model parameters. Most important parameters for calibrating pyAPES were parameters of the unimodal Van-Genuchten-Mualem water retention model for both moss and peat and Farquhar parameters, which are sparse in literature.

MSA is conducted for GPP and R_eco using annual sums. Boundaries for MSA are set to ± 20% around initial parametrisation in order to derive a standardized rank of parameter importance as well as to observed boundaries from literature to cover the whole range of possible site conditions. Subsequent analysis will give evidence whether meaningful parameter inference with respect to ecosystem carbon fluxes is possible under different site conditions.

Further, we investigate the impact of changing vascular plant LAI and moss biomass due to encroachment on ecosystem carbon fluxes by applying full factorial parameter combinations inferring possible shifts in model sensitivities. In a last step, we investigate intraannual shifts of sensitivities in half-hourly resolution to assess the impact of dynamic environmental conditions like WTD and moss surface temperature.

How to cite: Voigt, C., Piayda, A., Launiainen, S., Dubbert, M., Leppä, K., and Oestmann, J.: Does vascular plant encroachment affect parameter importance for modelling carbon dioxide fluxes in temperate raised bogs?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14384, https://doi.org/10.5194/egusphere-egu23-14384, 2023.

Organic soils are one of the largest natural terrestrial carbon stores, especially in boreal, temperate, and tropical wet climates. In these environments, scarcity of oxygen due to soil wetness has enabled the accumulation of organic carbon deposits over the past millennia. In Europe, organic soils account for only 3% of total agricultural land. Yet, they play a significant role in meeting Europe's 2030 and 2050 climate change mitigation targets. However, drainage of these soils, as a common management practice aiming for higher agricultural productivity, transforms these carbon-rich soils into a significant GHG source.

Water-level management practices are critical in agriculture to minimize soil degradation and nutrient leaching. Fluctuations in water levels may alter soil physical and chemical conditions and potentially cause GHG emissions. Deep draining leads to an increase in carbon dioxide (CO₂) and nitrous oxide (N₂O) emissions due to increased soil mineralization. On the other hand, methane (CH₄) emissions are lower compared to natural wetlands where soil drainage and tillage do not occur. Land use, climate zone, soil nutrient status, fertilization, and drainage status are closely related to estimating GHG budgets from managed sites on organic soils.

Available data on actual GHG emissions from drained and nutrient-rich organic soils under different management practices show considerable variation. Therefore our study's main objectives are: (I) to update GHG emission factors for organic soils in drained croplands and grasslands and (ii) to calculate soil carbon and nitrogen budgets applicable to the Baltic countries. A two-year study was conducted from January 2021 to December 2022 to assess the impact of drainage and land use on GHG fluxes in the Baltic countries.

Fluxes in croplands and perennial grassland on nutrient-rich organic soils with different drainage conditions were determined by groups: (I) excessively drained croplands, (II) excessively drained grasslands, (III) moderately drained grasslands, (IV) rewetted grasslands, and (V) non-managed fens as reference sites. Measurements were done monthly (Latvia and Lithuania) or twice per month (Estonia) using the manual static dark chamber method (N₂O, CH₄), the dynamic transparent chamber method for net ecosystem exchange, and the dynamic dark chamber for soil heterotrophic respiration (CO₂). In addition, we measured associated environmental parameters (water table level, soil moisture and temperature, and solar radiation). For biomass analyses, we took samples once in the measurement period.

Our preliminary results show that all grasslands were annual CH₄ sinks, while fens soils in natural status were a source of CH₄. All studied sites were N₂O sources on an annual basis, and croplands were the strongest emitters, as was expected. Higher N₂O emissions and temporal variability were associated with sites characterized by high groundwater levels with high seasonal fluctuations. Soil heterotrophic respiration fluxes peaked over all the study sites during the summer. As the last field campaign shortly ended, more detailed data analyses will be presented at the conference.

This research was supported by the LIFE programme project "Demonstration of climate change mitigation potential of nutrients rich organic soils in Baltic States and Finland", (2019-2023, LIFE OrgBalt, LIFE18 274CCM/LV/001158).

How to cite: Vahter, H., Sardar Ali, M. K., Schindler, T., Lazdiņš, A., Kull, A., Līcīte, I., Mander, Ü., Butlers, A., Jauhiainen, J., Ciuldiene, D., and Soosaar, K.: Drainage Impact on Greenhouse Gas Emissions from Grasslands and Croplands on Nutrient-rich Organic Soils in Baltic Countries, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16021, https://doi.org/10.5194/egusphere-egu23-16021, 2023.

Drainage for agriculture induces peatland decomposition, subsidence, and nitrogen (N) losess, thereby contributing to climate change. In order to maintain the productivity of agricultural managed peatland, and to counteract soil subsidence, mineral soil coverage is becoming an increasingly used practice in Switzerland and other European countries. Mineral soil coverage may change the N balance from the corronsponding organic soil. To explore the effect of this practice on the N flow within the plant – soil system and the N loss, we carried out a field experiment on a peatland in the Swiss Rhine Valley that was managed as an intensive meadow. The peatland was divided into two parts, either without (Ref) or with mineral soil coverage, thickness ~ 40 cm (Cov). In this experiment, ¹⁵NH₄¹⁵NO₃ were applied on field plots to follow the recovery of ¹⁵N in grass, root, and soil over 11 months. The ¹⁵N that was not recovered was designated as lost via leaching or gaseous emissions. Soil N mineralization was measured in a laboratory incubation. And the gaseous N loss as N₂O was determined by automatic time integrating chamber systems (ATIC) over two years. The experimental results showed that the total ¹⁵N loss from Cov was lower (p < 0.05) than from Ref, even though plant ¹⁵N uptake did not vary between the two sites. The lower net N loss from the Cov site was accompanied by higher soil ¹⁵N retention in the soil. The laboratory incubation revealed a ~2 times higher specific N release per unit soil N at Cov than at Ref, suggesting a faster SOM turnover rate at Cov. Regarding the N loss as N₂O, emissions from Ref were at the upper end of previously measured fluxes in drained peatland. In contrast, N₂O emissions from Cov were reduced by a factor of nine over two years. Overall, the mineral soil cover increased the retention of fertilizer-N in the soil, thus reducing the system N losses, especially N loss as N₂O emissions. Our results indicate agricultural production on drained peatland is less harmful to the environment with mineral soil coverage than using drained peatland directly. 

How to cite: Wang, Y., Paul, S., Alewell, C., and Leifeld, J.: Nitrogen losses from drained temperate agricultural peatland after mineral soil coverage, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13830, https://doi.org/10.5194/egusphere-egu23-13830, 2023.

Although peatlands are a great store of terrestrial carbon they are only a small sink compared to other nature-based or technological approaches to carbon sequestration. So as to exploit the considerable carbon storage potential of peatlands is it possible to enhance the magnitude of the peatland carbon sink with additional inputs of carbon? Biochar is refractory form of carbon that can be sourced from natural woody materials including biomass that may grow on peatlands. Biochar’s refractory nature means that it has commonly been proposed for nature-based carbon storage. The advantage of using biochar on peatlands is that natural accumulation of peat means that the growth of peat may absorb the added biochar where on mineral soils biochar may come to dominate with repeated additions of char. However, the fate and impact of biochar on the natural function of peat soils is not known – this study has aimed to fill this knowledge gap and assess whether biochar could be applied to peatlands?

This study has conducted a random-block design based upon two different application rates of biochar to a former lowland raised bog in Yorkshire. The trial consisted of triplicated plots considered within the water table frame of the peatland and plots visited at least monthly for more than a year. The plots were monitored for: gross primary productivity; net CO2 exchange; ecosystem respiration; soil water quality; albedo; and vegetation coverage alongside measurement of water table depth and weather parameters.

The study shows:

• that although biochar is alkali, and that there was an initial difference in pH due to biochar treatment, this difference did not last;
• the soil water conductivity was dominated by changes in depth to water table and not biochar treatment;
• after 10 months the DOC in soil water on treated plots was significantly higher on biochar treated plots;
• vegetation had recovered from biochar treatment within 6 months; and
• there was no significant difference in NER between treatments showing no ready decomposition of the biochar.

The limitations of biochar to enhance carbon storage in peatlands are more likely to be economic than biogeochemical.

How to cite: Fearns-Nicol, E., Worrall, F., and Knapp, J.: Use of biochar to enhance carbon sequestration in peatlands, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13555, https://doi.org/10.5194/egusphere-egu23-13555, 2023.