Displays

Peatland biological, physical and chemical properties change over time in response to the long-term water table position. Such changes complicate predicting the response of peatland carbon stocks to sustained drying. Here we use Eddy Covariance measurements of CO₂ exchange to study the effect of sustained water table lowering on peatland carbon dynamics. We compare measurements from a near-pristine peatland with those of a drying remnant, both raised bogs dominated by Empodisma robustum (Restionaceae), across two different time periods separated by a 16-year interval. We found that the remnant bog was initially a source of CO₂ following water table lowering. However, the CO₂ sink recovered and strengthened after the 16-year interval between measurements. The increase in CO₂ sink strength in the remnant bog was primarily due to increased photosynthetic uptake of CO₂, which exceeded that of the near-pristine site in both time periods. Additionally we found the loss of CO₂ via ecosystem respiration to have declined with time, however, ecosystem respiration remained elevated compared to the near-pristine site. These trends of increasing photosynthesis and declining ecosystem respiration resulted in the CO₂ sink in the dry bog reaching half the sink strength of the near-pristine bog. We consider two factors to have been key for the recovery of the CO₂ sink in the remnant bog. These were 1) resilience of the peat-forming plant community to water-table change and 2) the expansion of ericoid shrubs. Our results demonstrate that the peatland carbon sink can recover from drying over a multi-decadal timescale, but questions remain as to the long-term trajectory of dry bogs and the stability of carbon fixed after water table lowering.

How to cite: Ratcliffe, J., Campbell, D., Schipper, L., Wall, A., and Clarkson, B.: Long-term feedbacks result in the recovery of the CO2 sink in a remnant peatland following water table lowering, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-773, https://doi.org/10.5194/egusphere-egu2020-773, 2020.

Atmospheric nitrogen (N) deposition is increasing owing to fossil fuel burning and agriculture. In nutrient limited peatland ecosystems, the excess of reactive N has been found to increase vascular plant growth, but decrease Sphagnum growth. Higher vascular plant abundance and higher nutrient content alter decomposability of plant litter. These changes are likely to affect net imbalance of production and decomposition and thus carbon (C) accumulation in peatlands, which store about a third of global soil C. We studied whether the vegetation feedbacks of N deposition lead to stronger or weaker C sink in nutrient-poor peatlands. We investigated vegetation and ecosystem CO₂ exchange at two of the longest-running nutrient addition experiments on peatlands, Mer Bleue Bog, Canada and Degerö Stormyr poor fen, Sweden that have been fertilized with NH₄NO₃ (2-15 times ambient annual wet deposition) for 12-23 years. Gross photosynthesis, ecosystem respiration and net CO₂ exchange were measured weekly during June-August using chambers. To examine vegetation changes with increasing N influx, we determined the peak growing season aboveground biomass and coverage of vascular plants using the point intercept method. After 12-23 years of nutrient addition, the two sites revealed contrasting patterns: At Mer Bleue the highest nutrient additions were associated with up to 3-fold net CO₂ uptake potential than in the control, whereas N addition treatments at Degerö Stormyr showed close to zero net CO₂ uptake potential, only 0.3 fold compared to the control. The stronger C sink potential at Mer Bleue was mainly due to up to 50% increase in the gross photosynthesis and a diminished C sink potential at Degerö Stormyr due to down to 40 % lower gross photosynthesis. Ecosystem respiration showed similar trends at both peatlands: the rates were unaltered or increased to a lesser extent under N load. At both sites, the vegetation structure had changed remarkably. Most of the N addition treatments showed an increase of up to 90% in total vascular aboveground plant abundance and a concomitant loss of Sphagnum. At Mer Bleue along with the decrease in Sphagnum cover, the plots under highest N additions had become wetter, counterbalancing the impact of dry summer conditions in the study year whereas at Degerö Stormyr long term treatments did not alter wetness of the site. Thus, the contrasting C sink responses to long term N load may be explained by the type of vegetation and the water table depth. Shrubs were strong competitors at the dry Mer Bleue Bog while sedges had gained in abundance under N load at the wetter Degerö Stormyr. Our bog-fen comparison emphasizes the value of the long-term experiments in examining the ecosystem response of peatlands to N deposition, possible nonlinear responses and whether the key feedback mechanisms to ecosystem C sink potential differ in two main types of peatlands.

How to cite: Larmola, T., Antila, J., Maanavilja, L., Juutinen, S., Bubier, J. L., Humphreys, E., Kiheri, H., Moore, T. R., Nilsson, M., and Peichl, M.: Does nitrogen deposition lead to a weaker or stronger carbon sink in nutrient-poor peatlands?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2553, https://doi.org/10.5194/egusphere-egu2020-2553, 2020.

Peatlands North of 45˚ represent one of the largest terrestrial carbon (C) stores. They play an important role in the global C-cycle, and their ability to sequester carbon is controlled by multiple, often competing, factors including precipitation, temperature and phenology. Land-atmosphere exchange of carbon dioxide (CO₂) is dynamic, and exhibits marked seasonal and inter-annual variations which can effect the overall carbon sink strength in both the short- and long-term.

Due to increased incidences of climate anomalies in recent years, long-term datasets are essential to disambiguate natural variability in Net Ecosystem Exchange (NEE) from shorter-term fluctuations. This is particularly important at high latitudes (>45˚N) where the majority of global peatlands are found. With increasing pressure from stressors such as climate and land-use change, it has been predicted that with a ca. 3^oC global temperature rise by 2100, UK peatlands could become a net source of C.

NEE of CO₂ has been measured using the eddy-covariance (EC) method at Auchencorth Moss (55°47’32 N, 3°14’35 W, 267 m a.s.l.), a temperate, lowland, ombrotrophic peatland in central Scotland, continuously since 2002. Alongside EC data, we present a range of meteorological parameters measured at site including soil temperature, total solar and photosynthetically active radiation (PAR), rainfall, and, since April 2007, half-hourly water table depth readings. The length of record and range of measurements make this dataset an important resource as one of the longest term records of CO₂ fluxes from a temperate peatland.

Although seasonal cycles of gross primary productivity (GPP) were highly variable between years, the site was a consistent CO₂ sink for the period 2002-2012. However, net annual losses of CO₂ have been recorded on several occasions since 2013. Whilst NEE tends to be positively correlated with the length of growing season, anomalies in winter weather also explain some of the variability in CO₂ sink strength the following summer.

Additionally, water table depth (WTD) plays a crucial role, affecting both GPP and ecosystem respiration (R_eco). Relatively dry summers in recent years have contributed to shifting the balance between R_eco and GPP: prolonged periods of low WTD were typically accompanied by an increase in R_eco, and a decrease in GPP, hence weakening the overall CO₂ sink strength. Extreme events such as drought periods and cold winter temperatures can have significant and complex effects on NEE, particularly when such meteorological anomalies co-occur. For example, a positive annual NEE occurred in 2003 when Europe experienced heatwave and summer drought. More recently, an unusually long spell of snow lasting until the end of March delayed the onset of the 2018 growing season by up to 1.5 months compared to previous years. This was followed by a prolonged dry spell in summer 2018, which weakened GPP, increased R_eco and led to a net annual loss of 47.4 ton CO₂-C km^-2. It is clear that the role of Northern peatlands within the carbon cycle is being modified, driven by changes in climate at both local and global scales.

How to cite: Yeung, K. H.-L., Helfter, C., Mullinger, N., Coyle, M., and Nemitz, E.: From sink to source: long-term (2002-2019) trends and anomalies in net ecosystem exchange of CO2 from a Scottish temperate peatland., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5967, https://doi.org/10.5194/egusphere-egu2020-5967, 2020.

Along the southern limit of permafrost in northwestern Canada rising air temperatures have caused widespread land cover changes at unprecedented rates. A prominent change includes thermokarst wetland expansion at the expense of black spruce-dominated boreal forest stands due to the permafrost thaw-induced collapse of peat plateaus. We present a multi-year (2013 – 2017) net ecosystem carbon (C) balance (NECB, g C m^-2year^-1) at Scotty Creek near Fort Simpson, NT. The highly fragmented study site is dominated by permafrost-free wetlands and forested permafrost peat plateaus. Eddy covariance  measurements of net ecosystem carbon dioxide (CO₂) and methane (CH₄) exchanges (2013 – 2017) are complemented by discharge (2014 – 2016) and water chemistry monitoring (2015 and 2016) at the outlets of three small headwater catchments (<0.5 km²) draining the eddy covariance footprint area. In addition to net ecosystem CO₂and CH₄exchanges, the NECB includes the export of dissolved C (DC) as the sum of inorganic and organic C (DIC and DOC), free CO₂and CH₄through runoff, and the estimated import of DOC through precipitation. We use absorbance spectroscopy for dissolved organic matter (DOM) characterization to distinguish different DOM sources among catchments and characteristic land cover types. Between 2013 and 2017, the NECB varied between a weak net C source (~16 ±5 g C m^-2year^-1) and sink (~-22 ±5 g C m^-2year^-1) in 2015 and 2013, respectively, with a mean value of -1 ±7 g C m^-2year^-1. The net C sink-source strength was largely controlled by variations in net CO₂exchange, ranging between a weak net CO₂ sink (~-29 ±3 g C m^-2year^-1) and source (~8 ±4 g C m^-2year^-1) in 2015 and 2013, respectively. In contrast, our study site was a persistent annual net CH₄source (~8 ±1 g C m^-2year^-1). Compensated by the import of DOC through precipitation, DC exported from the three catchments was a negligible component of the NECB. There were no significant differences in DOC concentrations and absorbance indices among catchments, and thawed and frozen land cover types, overall illustrating high DOM aromaticity (SUVA₂₅₄= 3.3 ± 0.6 L mg^-1m^-1) and high molecular weight (a254:a365 = 4.3 ± 0.3) characteristic for peatlands and peat-dominated landscapes outside the circumpolar permafrost region. We conclude that a rapidly thawing boreal peat landscape along the southern limit of permafrost presently appears to be C neutral.

How to cite: Sonnentag, O., Fouché, J., Helbig, M., Hould Gosselin, G., Detto, M., Connon, R., Quinton, W., and Moore, T.: A thawing boreal peat landscape along the southern limit of permafrost presently is carbon neutral, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6621, https://doi.org/10.5194/egusphere-egu2020-6621, 2020.

Arctic climate is warming twice as much as the global average, due to a number of climate system feedbacks, including albedo change due to retreating snow cover and sea ice, and the forest cover expansion across the open tundra. Northern ecosystems are known to emit trace gases (e.g., methane and volatile organic compounds, VOCs) to the atmosphere, from sources as diverse as soils, vegetation and lakes. These trace gas fluxes are likely to show a trend towards greater emissions with climate warming.

Here we report ecosystem-level VOC fluxes from Stordalen Mire, a subarctic peatland complex with a high fraction of open pond and lake surfaces, underlain by discontinuous permafrost and located in the Subarctic Sweden (68º20' N, 19º03' E).

In 2018, we deployed two online mass spectrometers (PTR-TOF-MS) to measure rapid fluctuations in VOC mixing ratios and to quantify ecosystem-level fluxes with the eddy covariance technique. One of the instruments obtained a growing-season-long dataset of biogenic emissions from palsa mire vegetation dominated by mosses (e.g., Sphagnum spp.), graminoids (such as Eriophorum spp. and Carex spp.), dwarf shrubs (e.g. Empetrum spp. and Betula nana) surrounding the ICOS Sweden Abisko-Stordalen long-term measurement station. The second instrument measured VOC fluxes during two contrasting periods (the peak and the end of the growing season) from a subarctic lake and its adjacent fen, permafrost-free, minerotrophic wetland with vegetation dominated by tall graminoids, mainly Carex rostrata and Eriophorum angustifolium.

At both sites, isoprene was the dominant VOC emitted by vegetation, showing clear diurnal patterns along the season and especially during the peak of the growing season in July. At the ICOS Sweden station, isoprene fluxes exceeded 2 nmol m^-2 s^-1 on several days in July, with a July monthly average midday emission of 1 nmol m^-2 s^-1. The fen site showed average midday emissions of 2 nmol m^-2 s^-1 during the peak growing season. Other VOCs emitted by vegetation at both sites in July were, with decreasing magnitude, methanol, acetone, acetaldehyde and monoterpenes. In contrast, acetaldehyde and acetone were not emitted but mostly deposited to the fen at the end of the season. In contrast to the wetland, the lake was a sink for acetaldehyde and acetone during all measurement periods.

Thermal imaging and spectral analysis of vegetation will be used to assess relationships between VOC fluxes, vegetation surface temperatures and phenology under varying environmental conditions.

How to cite: Seco, R., Holst, T., Westergaard-Nielsen, A., Li, T., Simin, T., Jansen, J., Crill, P., Friborg, T., Holst, J., Rinne, J., and Rinnan, R.: Volatile Organic Compound fluxes in a subarctic peatland and lake, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9007, https://doi.org/10.5194/egusphere-egu2020-9007, 2020.

Although the Arctic tundra is an essential contributor to the global carbon (C) cycle, there is a lack of reference sites from where full C exchange dynamics can be characterized under harsh conditions and remoteness. The Greenland Ecosystem Monitoring (GEM) programme efforts have envisioned integrated and long-term activities to contribute to the basic scientific understanding of the Arctic and their responses to climate changes. Here we present 20+ years across the 2008-2018 period of C flux and ancillary data from two twin ecosystem stations in Greenland: Zackenberg (74°N) and Kobbefjord (64°N). In this project we show that Zackenberg fen has a significant higher C sink strength in a higher latitude during regularly shorter growing seasons compared to Kobbefjord fen. This ecosystem acted as a sink of CO₂ uptaking on average -50 g C m^-2 (range of +21 to -90 g C m^-2), more than twice compared to Kobbefjord (-18 g C m^-2 as average and range of +41 to -41 g C m^-2). We found that Zackenberg is a nutrient richer fen - the increased C uptake strength is associated with 3 times higher levels in soils of dissolved organic carbon and 5 times more plant nutrients, including dissolved organic nitrogen, nitrates. Additional evidences from in-situ sampling point to higher leaf area index (140%), foliar nitrogen (71%), and leaf mass per area (5%) in the northernmost site supporting the nutrient richer hypothesis. To test this overarching hypothesis, we further used the Soil-Plant-Atmosphere (SPA) model. We can explain ~68%, ~80% and ~67% of the variability of daily net ecosystem exchange of CO₂, photosynthesis and respiration respectively applying the model parameterization previously used in Kobbefjord but with increases in initial C stocks, leaf mass per area, N content and Q₁₀ of foliar and root respiration rates. Therefore, we conclude that the limitations of plant phenology timing in Zackenberg regarding net C uptake have not only been counterbalanced but also intensified due to richer compositions of nutrients and minerals. More high-temporal monitoring activities in Arctic ecosystems are needed not only to allow straightforward comparisons of key biogeochemical processes but also to help us understand the underlying differences in sensitive and rapidly changing ecosystems.

How to cite: López-Blanco, E., Jackowicz-Korczynski, M., Mastepanov, M., Skov, K., Westergaard-Nielsen, A., Williams, M., and R. Christensen, T.: Enriched nutrient availability strengthens the net C uptake of the northernmost ecosystem station in Greenland , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11024, https://doi.org/10.5194/egusphere-egu2020-11024, 2020.

Accurate projections of climate change impacts on the vast carbon stores of northern peatlands require detailed knowledge of ecosystem respiration (ER) and its heterotrophic (Rh) and autotrophic (Ra) components. Currently, however, standard measurement techniques (i.e. eddy covariance and manual chambers) generate semi-continuous empirical ER data (i.e. during only night- or daytime, respectively) that are extrapolated to the daily scale based on the paradigm that assumes a uniform diel response to temperature. Here, using continuous autochamber measurements of hourly ER, Rh and Ra in a boreal peatland, we demonstrate a distinct bimodal pattern in diel ER which contrasts the unimodal pattern inherent to the classical assumption. This feature results from divergent temperature dependencies of day- and nighttime ER due to differing contributions from Rh and Ra. We show that the classical approach overestimated daily ER by up to ~2-fold and growing season ER by 16-23%. These findings call for improved process-based understanding of ER to avoid bias in simulations of peatland carbon cycle-climate feedbacks.

How to cite: Peichl, M., Järveoja, J., Crill, P. M., and Nilsson, M. B.: Bimodal diel pattern in peatland ecosystem respiration rebuts uniform temperature response, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20098, https://doi.org/10.5194/egusphere-egu2020-20098, 2020.

Intact accumulating peatlands are a globally important terrestrial carbon sink. Climate change and agricultural drainage are degrading these ecosystems, and through increases in aerobic decomposition, shifting their C balance from sink to source. To argue the effectiveness of restoration activities (such as rewetting), techniques are needed that clearly show differences between drained and natural (or drained and rewetted) peatlands. Because these changes are not always macroscopically visible, molecular analysis methods are especially needed to distinguish between ecosystems experiencing net pet growth (sequestering carbon), and those where aerobic decomposition is still a primary driving mechanism. Molecular biomarkers are a useful way to use chemical composition to distinguish these mechanisms.

This study aimed to compare differences in chemical composition with depth between two peatland sites from a large ombrotrophic mire in Lakkasuo Finland – one natural and one drained. To characterize these chemical shifts, pyrolysis gas chromatography mass spectrometry was used to track changes in relative abundance of various molecular biomarkers and compound classes (ie., aromatics, Sphagnum phenols, lignin, N-containing compounds, n-alkanes, etc.) with depth across both sites. Three replicate cores per site were collected, allowing for statistical evaluation of the relative abundances of these compounds. Using radiocarbon dating at three depths per core, the drained and natural sites were also matched by age for reference purposes. Significant differences were found for the Sphagnum-specific biomarker, p-isopropenylphenol, aromatics, and lignin, to the approximate current depth of the drained peatland water table. Higher phenolic compound class abundance indicated inhibited aerobic decomposition in the natural cores. An increasing trend in lignin biomarker relative abundance with depth was observed in the natural site, despite the identification of comparatively fewer vascular plants during the macroscopic analysis. Rather than a higher abundance of palaeo-ecological vascular plants, this trend is considered to be an indicator of preferential preservation of lignin compounds with anaerobic conditions. Below the depth of the water table, the relative abundances of most biomarkers stabilized, indicating the existance of similar environmental conditions in both sites prior to drainage. These data were compared and are in agreement with findings from elemental analysis (CHNO) and bulk isotopic (¹³C and ¹⁵N) data measured on the same cores. Collectively, these data suggest that observed shifts in chemical composition in the natural and drained cores reflect the effect of different hydrological conditions between the two sites.

How to cite: Klein, K., Groβ-Schmölders, M., Alewell, C., and Leifeld, J.: A tale of two peats: characterizing ecosystem-driven differences in chemical composition with depth in natural and drained Finnish mires using Py-GC/MS analytical techniques, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3477, https://doi.org/10.5194/egusphere-egu2020-3477, 2020.

Worrall et al. (2016, 2017, 2018) have determined the processes of organic matter transfer, transition and peat formation through and into a blanket bog at Moor House, UK (N54:41:18, W2:22:45 – altitude 580 m asl; MAT 5.8 deg C; rainfall 2012 mm/yr). These examinations indicated a transition from plant material to superficial and deeper peat that became thermodynamically limited around 40 cm depth with a continuous increase in the degree of unsaturation of the organic matter. However, it is not clear whether the same processes observed at Moor House are ultimately a universal pattern of peat formation and organic matter transitions or are site–specific. Therefore, to test theories developed at Moor House, peat formation and organic matter transitions were examined at a continental raised bog (Pürgschachen Moor, Austria, N47:34:53, E14:20:48 – altitude 632 m asl; MAT 7.3 deg C; rainfall 1248 mm/yr).

To test our developed theories the following were sampled: vegetation (Sphagnum, cotton grass and pine); dissolved organic carbon (DOC); and peat samples between 0 and 100 cm depth. Samples were dried, ground, and analysed by elemental analysis (for CHN and O), bomb calorimetry, and thermogravimetric analysis.

Results show that the pattern of a continuously rising degree of unsaturation from superficial to deeper peat does not prevail at the raised bog. At Pürgschachen Moor, the degree of unsaturation does not change between vegetation and superficial and deeper peat and there is little difference between the composition of vegetation and peat. At Moor House there appears to be an evolution from a cellulosic/Protein composition towards a lignin/protein composition, while at Pürgschachen, vegetation and peat appears to be composed more strongly of pure cellulose. Furthermore, thermodynamic limitation at the raised bog occurs in the top 10 cm of the peat profile. However, DOC at both sites show signs of strong alteration compared to peat samples. DOC export is an important pathway at Moor House (blanket bog) but not at Pürgschachen Moor (raised bog). Therefore, we deduce that the immobile DOC and the lack of pore water movement lead to a closed system and a rapid preservation of the peat in the raised bog. In contrast, mobile DOC and the fluvial export promotes a relatively open pore water system that drives further chemical reaction in the organic matter.

Our research indicates that, depending on relief and rainfall, there are distinctly different pathways of peat formation in blanket bogs compared to raised bogs. Furthermore, this provides direct chemical evidence of why high and static water tables preserve organic matter in raised bogs leading to higher relative carbon sequestration rates.

References:

Worrall, F., Clay, G.D., Moody, C.S., Burt, T.P., and R.Rose. (2016). The effective oxidation state of a peatland. JGR-Biogeosciences, 121, 145-158.

Worrall, F., Moody, C.S., Clay, G.D., Burt, T.P., and R.Rose. (2017). The flux of organic matter through a peatland ecosystem – the role of cellulose, lignin and their control of the oxidation state. JGR-Biogeosciences 122, 7, 1655-1671.

Worrall, F., Moody, C.S., Clay, G.D., Burt, T.P., and R.Rose. (2018). Thermodynamic control of the carbon budget of a peatland. JGR-Biogeosciences 123, 6, 1863-1878.

How to cite: Glatzel, S., Worrall, F., Boothroyd, I., Drollinger, S., Moody, C., and Clay, G.: Differences in peat formation between an Atlantic blanket bog and a subcontinental raised bog, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7402, https://doi.org/10.5194/egusphere-egu2020-7402, 2020.

Groundwater table depth and peat moisture, exert a first order control on a range of biogeochemical and -physical peatland processes, and the susceptibility to peat fires. Therefore, one of the first critical measures to identify “peatlands under pressure” is the change of hydrological conditions, e.g. due to changing climatic conditions or direct “hydraulic” human influence. In this presentation, we introduce a new opportunity for the global-scale monitoring of moisture conditions in peatlands. We assimilate L-band brightness temperature (Tb) data from the Soil Moisture Ocean Salinity (SMOS) into the Catchment land surface model (CLSM) to improve the simulation of Northern peatland hydrology from 2010 through 2019. We compare four simulation experiments: two open loop and two data assimilation simulations, either using the default CLSM or a recently-developed peatland-specific adaptation of it (PEATCLSM, Bechtold et al. 2019). The assimilation system uses a spatially distributed ensemble Kalman filter to update soil moisture and groundwater table depth. The simulation experiments are evaluated against an in-situ dataset of groundwater table depth in about 20 natural and semi-natural peatlands that are large enough to be dominant in the corresponding 81-km² model grid cells. For PEATCLSM, Tb data assimilation increases the temporal Pearson correlation (R) and anomaly correlation (aR) between simulated and measured groundwater table from 0.53 and 0.38 (open-loop) to 0.58 and 0.45 (analysis), respectively. Time series comparison at monitoring sites demonstrates how the assimilation effectively corrects for remaining deficiencies in model physics and/or errors of the global meteorological data forcing the model. The generally lower coefficients of 0.30 (R) and 0.09 (aR) for the default CLSM also improve after Tb data assimilation to values of 0.39 (R) and 0.28 (aR). However, even with Tb data assimilation, the skill of CLSM remains inferior to that of PEATCLSM. The more realistic model physics of PEATCLSM are also supported by a reduction of the Tb misfits (observed Tb – forecasted Tb) over 94 % of the Northern peatland area. The temporal variance of Tb misfits is reduced by 20 % on average and is largest over the large peatland areas of the Western Siberian (25 %) and Hudson Bay Lowlands (40 %). This study demonstrates, for the first time, an improved estimation of the peatland hydrological dynamics by the assimilation of SMOS L-band brightness data into a global land surface model and suggests a new route of research focusing on the incorporation of additional satellite observations into peatland-specific modeling schemes.

Bechtold, M., De Lannoy, G.J M., Koster, R.D., Reichle, R.H., et al. (2019). PEAT-CLSM: A Specific Treatment of Peatland Hydrology in the NASA Catchment Land Surface Model. JOURNAL OF ADVANCES IN MODELING EARTH SYSTEMS, 11 (7), 2130-2162. doi: 10.1029/2018MS001574.

How to cite: Bechtold, M., De Lannoy, G., Reichle, R. H., Roose, D., Balliston, N., Burdun, I., Devito, K., Kurbatova, J., Strack, M., and Zarov, E. A.: 10 yrs of Improved Groundwater Table Estimates in Northern Peatlands Through Assimilation of Passive Microwave Observations into PEATCLSM, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19972, https://doi.org/10.5194/egusphere-egu2020-19972, 2020.

Ecosystems are increasingly prone to climate extremes, such as drought, with long-lasting effects on both plant and soil communities and, subsequently, on carbon (C) cycling. Unveiling past tipping points is a prerequisite for a better understanding of how individual species and entire ecosystems will respond to future climate changes, especially soil moisture. In the first study we identified the response of peatland vegetation to shifts in hydrological conditions over the past 2000 years using plant macrofossils, testate amoebae-based quantitative hydrological reconstructions from seven Polish peat-records (Lamentowicz et al., 2019). Using threshold indicator taxa analysis (TITAN), we discovered that plant community composition strongly converged at a water level of c. 11.7 cm, indicating a community-level tipping-point. We identified 45 plant taxa that showed either an increase or a decrease in their relative abundance between 8 and 17 cm of water level depth. In other the experimental study (Jassey et al., 2018) we investigated the response of plant and soil fungi to drought of different intensities using a water table gradient in peatlands—a major C sink ecosystem. We show that substantial changes in ecosystem respiration, plant and soil fungal communities occurred when the water level fell below a tipping point of 24 cm. As a corollary, ecosystem respiration was the greatest when graminoids and saprotrophic fungi became prevalent as a response to the extreme drought. Graminoids indirectly influenced fungal functional composition and soil enzyme activities through their direct effect on dissolved organic matter quality, while saprotrophic fungi directly influenced soil enzyme activities. In turn, increasing enzyme activities promoted ecosystem respiration. We show that functional transitions in ecosystem respiration critically depend on the degree of response of graminoids and saprotrophic fungi to drought. Our results represent a major advance in understanding the nonlinear nature of ecosystem properties to drought and pave the way towards a truly mechanistic understanding of tipping points in peatlands with use of experiment and palaeoecology.

References

Jassey, V.E.J., Reczuga, M.K., Zielinska, M., Slowinska, S., Robroek, B.J.M., Mariotte, P., Seppey, C.V.W., Lara, E., Barabach, J., Slowinski, M., Bragazza, L., Chojnicki, B.H., Lamentowicz, M., Mitchell, E.A.D., Buttler, A., 2018. Tipping point in plant-fungal interactions under severe drought causes abrupt rise in peatland ecosystem respiration. Glob Chang Biol. 24, (3) 972–986.

Lamentowicz, M., Gałka, M., Marcisz, K., Słowiński, M., Kajukało-Drygalska, K., Dayras, M.D., Jassey, V.E.J., 2019. Unveiling tipping points in long-term ecological records from Sphagnum -dominated peatlands. Biology Letters. 15, (4) 20190043.

How to cite: Lamentowicz, M., Marcisz, K., Słowiński, M., and Jassey, V. E. J.: Unveiling tipping points in long-term and experimental studies in peatlands, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5072, https://doi.org/10.5194/egusphere-egu2020-5072, 2020.

The Holocene climate shifts had a significant impact on the development of ombrotrophic peatland ecosystems located in various biogeographic zones. Disturbances of the plant communities at peatlands ecosystems took place also due to intensified human activities in the past several centuries, that include peat excavation, fires, as well as deposition of dust and pollutants on peatland surfaces. This merger of natural and human impacts has led to direct hydrological and biochemical disturbances that triggered changes in plant populations, e.g. often leading to the decline of some species, such as Sphagnum austinii in Great Britain.

The knowledge about the development of peatlands across mountain ranges in Europe is still poor. Determining the resilience of peatland vegetation to disturbance is an important and significant task to aid further protection and management of the entire range of ombrotrophic peatlands found in the European mountains, from destroyed or restored to pristine. We carried out high-resolution, multi-proxy studies including plant macrofossils, pollen, testate amoebae, geochemical analyses (XRF and stable carbon isotopes), micro- and macro-charcoal, supported by radiocarbon dating, on replicate peat cores from five well-preserved ombrotrophic peatlands across Europe where peat-forming process is active. The studied peatlands are located along an east west gradient in the Central and Western Europe: Eastern Carpathian Mts. (Calimani-Gurghiu-Harghita, Romania; Bieszczady, Poland), Harz Mts. and Schwarzwald Mts. (Germany), and Vosges Mts (France). In our palaeocological studies we aimed to: i) reconstruct long-term local (mainly Sphagnum populations) and regional (forest communities) vegetation changes at and around selected bogs; ii) reconstruct long-term palaeohydrological shifts; iii) assess mountain peatland ecosystems resilience to Holocene climate shifts and disturbance by fire events and human impact (deforestation, dust and pollution).

Based on our results, we found that: i) despite human activites (pollutants and dust deposition, drainage) some of the mountain peatlands remained in a pristine state, however some plant communities had changed; ii) plant communities composed mainly by Sphagnum species, could repeatedly self-regenerate via autogenic processes following a decline in stressors; iii) recent climate warming has stimulated the spreading of some species indicative of more dry habitats; vi) lack of macrocharcoal in the peat layers indicate that fires did not play a significant role in the development or evolution of local peatland communities. Results from our studies show that palaeoecological records play an important role for the determination of present peatland ecosystem stage and reference conditions for the restoration of damaged ombrotrophic peatlands in European mountains.

The research has received support National Science Centre (Poland) grant No UMO-2016/23/B/ST10/00762 (PI: Mariusz Gałka).

How to cite: Gałka, M., Knorr, K.-H., Diaconu, A.-C., Feurdean, A., Hölzer, A., Loisel, J., Graeme T., S., and Tantau, I.: Can we expect pristine mountain peatland ecosystems in Central Europe? Evidence from multi-proxy palaeoecological studies on the Holocene peatland development, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13830, https://doi.org/10.5194/egusphere-egu2020-13830, 2020.

Hyperspectral imaging (HSI) is a promising precision tool for analysing chronological peat strata from vegetation transitions in peatlands. We explored the potential of HSI in identifying transitions in peat-forming vegetation and degree of peat humification. The changes in aapa mire complexes during recent decades have been assessed by various remote sensing methods (aerial image time series, satellite data and high-resolution UAV multispectral imaging) and HSI methods have been developed to support the data from other sources. Rapid growth of Sphagnum mosses over string-patterned aapa mires in the north-boreal zone has immense significance, since it can alter ecosystem structure and functions such as carbon sequestration. HSI is well suited for analysis of recent ecosystem changes, since it can be applied for large sample sets with extremely fine spatial detail. Additionally, peat layers have complex 3D structures that can be overlooked by other sampling methods.

The HSI data was collected in laboratory conditions with two spectral imaging cameras, covering the visible to near-infrared range (VNIR 400-1000 nm), short-wave infrared range (SWIR, 1000-2500 nm). We used various methods such as PCA, k-means clustering and support vector machines for both quantitative and qualitative analysis of peat.  Our analyses revealed detailed spectral changes that matched with transitions in peat quality and composition. Methodological issues unique to peat samples, such as the effect of oxidation and water content, were assessed for method development. We also used HSI to estimate quality changes that would easily be overlooked or only found by most laborious conventional techniques, like high-frequency microscopic counting of plant remains. Here, the spectral results can be used to guide sampling for microscopic routines, for example.

Results with Carex and Sphagnum peat proved that efficient image-based classification methods for identifying peat transitions can be developed. Our SVM models in the VNIR and SWIR regions were able to distinguish Sphagnum and Carex peat with overall accuracy of validation 80 % and 81 %, respectively. We also developed simple NDI indices for the estimation of von Post humification index that worked with accuracy of 86 % and 59 % for VNIR and SWIR, respectively. In combination with data collected from other sources (remote sensing, ground-truthing, conventional laboratory analysis), peat spectral analyses give strong inference of changes. In our study system, results indicate high sensitivity of northern aapa mires to ecosystem-scale changes.

How to cite: Granlund, L., Tahvanainen, T., and Keinänen, M.: Application of hyperspectral imaging of peat profiles to the case of fen-bog transition in aapa mires, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17715, https://doi.org/10.5194/egusphere-egu2020-17715, 2020.

Recent paleoecological studies have demonstrated an ongoing drying trend in temperate and boreal peatlands in Europe and in Canada. This drying is likely to alter vegetation and carbon gas exchange with atmosphere. However, to revel the expected change in carbon gas dynamics associated with decrease in water level experimental studies and long-term monitoring are needed. In here we present results from long term experiment in Finland where the impact of water level drawdown (WLD) of ~10 cm on three different peatland sites, two fens and a bog, has been studied since year 2000.

Response to WLD differed between the three ecosystem types. In the nutrient rich fen WLD initiated rapid directional succession from sedge dominated system to the dominance of woody species. In the poor fen changes were less drastic: Initially WLD benefitted dwarf scrubs already present at the site, later they were overtaken by pines.  Sedges as a group hold their position but Carex species were replaced by Eriophorum. Similarly to sedges, in the moss layer proportions of different Sphagnum moss species changed. Bog vegetation was more stable than fen vegetation.

In all the ecosystems methane emissions decreased directly after WLD. In contrast, the response of CO2 dynamics was more complex. While long term net ecosystem exchange decreased to lower level than in controls in all studied ecosystems, the response of photosynthesis and respiration differed between the three ecosystems and between short term and long term. Results show how the response of peatlands to climate change is diverse and emphasize the need to understand what factors regulate the stability and resilience of peatland functioning.

How to cite: Tuittila, E.-S., Korrensalo, A., Laine, A., Kokkonen, N., Mehtätalo, L., and Laine, J.: Impact of long-term experimental water level drawdown on vegetation and carbon gas dynamics of boreal mire ecosystems, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18316, https://doi.org/10.5194/egusphere-egu2020-18316, 2020.

The majority of the world’s peatlands are located in northern regions where climate change is occurring most rapidly. Therefore, there is an urgent need to understand whether, and under what conditions, peatlands will remain carbon sinks or become carbon sources. The uncertainties in our predictions stem from a variety of sources, including uncertainty about the competing effects of rising air temperature on ecosystem respiration (R_e) and gross primary production. Furthermore, peatlands contain a mixture of plant communities that respond differently to changes in temperature and precipitation. Such heterogeneity complicates attempts to upscale peatland carbon fluxes and predict the future peatland carbon balance.

We focus on understanding the sensitivity of peatland R_e to temperature and how it relates to vegetation community and the choice of temperature metric. We assess how these relationships changed during and after the severe heatwave and drought (‘hot drought’) in 2018. We conducted manual dark chamber CO₂ efflux measurements in Mycklemossen, an oligotrophic mire in southern Sweden in 2018 and in 2019, when weather conditions were closer to the long-term mean. The measurements covered the two main vegetation communities at the site: hummocks (vascular-plant dominated) and hollows (Sphagnum-dominated). We statistically compared the fluxes for both years and vegetation communities, then modelled them using three temperature metrics (air, surface, soil).

We found that R_e decreased during the hot drought for both vegetation communities, with maximum fluxes of 0.18 and 0.34 mgCO₂ m^-2 s^-1 in 2018 and 2019, respectively. However, the change in R_e during the hot drought was dependent on vegetation community: hummock R_e decreased substantially more than hollow R_e (mean decrease: 48% and 15%, respectively). As a result, hollow R_e was highest during drought whereas hummock R_e was highest during non-drought conditions. Despite significant differences in R_e between the vegetation communities, we found no significant differences in temperature between hummock and hollow vegetation, apart from in July and August 2018, at the peak of the hot drought. Nevertheless, hollow R_e was more temperature-sensitive than hummock R_e both during and after the hot drought. Furthermore, the temperature sensitivity of modelled R_e depended on the choice of driving temperature, such that the surface temperature driven model produced the lowest whilst the soil temperature driven model produced the highest temperature sensitivity. Differences in temperature sensitivity of R_e between the drought and non-drought conditions were similarly dependent on the temperature metric used to drive the R_e model.

We found that peatland R_e almost halved during a hot drought. Our results show that predictions of peatland response to warming must account for the proportion of different vegetation communities present, and how this may change, due to their differing responses to warming. The choice of driving temperature in peatland R_e models does not impact model accuracy but it does influence the temperature-sensitivity, and thus the impact of temperature variations on the modelled flux. Modellers should therefore base parameter choices on vegetation community and driving temperature. Furthermore, comparisons of R_e sensitivity to warming between studies using different driving temperatures may be misleading.  

How to cite: Kelly, J., Kljun, N., Eklundh, L., Klemedtsson, L., Liljebladh, B., Vestin, P., and Weslien, P.: Sensitivity of peatland respiration to vegetation community and temperature metric during a hot drought, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1161, https://doi.org/10.5194/egusphere-egu2020-1161, 2020.

The ecological functions of bog ecosystems and their resistance to external influences are largely determined by the structure and chemical composition of peat.

The structure of thick peat deposits of oligotrophic bogs typical for the west of the Arctic ecoregion of Russia is studied.  The investigated peatlands are affected by the seas of the Arctic Ocean (the White and Barents).  Bog massifs in the continental climate zone without marine influence outside the Arctic territories were studied for comparison purposes. The studied bog natural complexes all belong to the oligotrophic type, are similar in structure to the deposit profile, have a peat layer of the comparable thickness and a similar homogeneous botanical composition. The peat of all studied bogs is characterized by a low degree of decomposition over the entire depth of the profile (not more than 15-20%).

The degree of decomposition, the botanical composition and the structure of the samples was studied by transmitted-light-microscopy. Fractionation was carried out by elutriation on sieves with a mesh size of 100 μm and 250 μm.

The macrostructure of the studied peat bogs is formed by the undecomposed and weakly decomposed residues of peat-forming plants - mainly sphagnum mosses mixed with cotton-grass in certain layers. Analysis of peat samples from the Arctic ecoregion showed a high degree of grinding of sphagnum moss residues without visible signs of biochemical disturbance of cellular structures. This feature is most noticeable when considering the fraction of 100-250 μm, where particles of such plant residues are concentrated. Leaves of sphagnum mosses in peat samples from the Arctic maritime territories are broken, but the cellular structures retain their integrity. In peat samples from bogs of the continental climatic zone, this phenomenon is not observed. Plant residues retain their integrity quite well, both in the upper and lower layers, and the fraction of 100-250 μm is composed of undisturbed leaves of sphagnum mosses.

The revealed specific nature of defragmentation of plant residues in the conditions of oligotrophic bog massifs of the Arctic ecoregion can be explained by the freezing-thawing cycles during the formation of a stable snow cover. In the conditions of a maritime subarctic climate, a stable snow cover is formed for a long period in the multiple transitions of air and soil temperatures through the zero-temperature mark. The thickness of the snow cover under the influence of winds in the open spaces of the bogs can decrease to the minimum values. The noted structural features are traced throughout the depth of the deposit. However, increased content of physically destroyed particles of sphagnum mosses in the upper horizons of the peat deposit in the maritime subarctic climate is observed, which may well be associated with global warming and an increase in freezing-thawing cycles.

The obtained results require confirmation in the framework of model experiments both in the conditions of a mesocosm and laboratory. Besides, the extensive comparative studies on similar peat deposits in a maritime and continental climate must be made.

How to cite: Selyanina, S. and Ponomareva, T.: Specific features of the structure of oligotrophic peatlands in the Arctic ecoregions, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2881, https://doi.org/10.5194/egusphere-egu2020-2881, 2020.

The purpose of this study is to investigate the Tl distribution and accumulation rates in Czech peatbogs with contrasting anthropogenic loads. Nine peat cores were sampled in the mountain areas of the Czech Republic (6 cores in the northern part affected by emissions from coal-burning power plants and 3 in the pristine southern part). In addition, 3 cores were collected close to the Pb mining and smelting area of Pribram. Cores were 210-Pb dated and trace metals/metalloids were measured in the digests by ICP-MS. Maximum Tl concentrations in peat were significantly higher in the polluted northern areas (1.16 mg/kg) and close to the Pb smelter (0.83 mg/kg) than in the pristine area (0.45 mg/kg). Thallium distribution well correlated with other metals (Pb, Hg) and metalloids (As, Sb). Thallium enrichment factors (EFs) calculated against Sc reached the maximum value of 17 indicating significant input of anthropogenic Tl. Thallium accumulation rates in peat varied between 20 and 50 µg/m2/y until 1930s, followed by a significant increase related to industrial activities in the northern part of the Czech Republic (up to 290 µg/m2/y in 1980s). In contrast, maximum Tl accumulation rate at the pristine site was 88 µg/m2/y. Data from the vicinity of Pb mines/smelter indicated higher accumulation rates even in the second half of the 19th century (between 50 and 200 µg/m2/y) followed by a significant decrease in late 1970s as a result of more efficient flue gas cleaning technology installed in the smelter during this period. 

How to cite: Mihaljevic, M., Ettler, V., and Vanek, A.: Historial thallium deposition trends as recorded in peat bogs - examples from Czech sites with contrasting pollution histories, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3376, https://doi.org/10.5194/egusphere-egu2020-3376, 2020.

Emission of greenhouse gases (GHG) from inland waters is recognized as highly important and understudied part of terrestrial carbon (C) biogeochemical cycle. These emissions are still poorly quantified in permafrost regions containing a vast amount of surface C in frozen peatlands. This is especially true for NE European peatlands, located within sporadic to discontinuous permafrost zone which is highly vulnerable to thaw. For a first quantification of the C emission from lentic waters of the Bolshezemelskaya Tundra (BZT, 200,000 km²), we measured CO2 and CH4 concentrations and fluxes to the atmosphere in 98 depressions, thaw ponds and thermokarst lakes ranging from 0.5 to 5x10⁶ m² in size. The CO2 fluxes decreased by an order of magnitude when lake size increased by > 3 orders of magnitude, while CH4 fluxes showed large variability that were not related to lake size By using a combination of Landsat-8 and GeoEye-1 images we found that lakes cover 4% of BZT, and calculated the overall C emission (CO₂+CH₄) from the lakes of the territory to 3.8 Tg C y^-1 (99% C-CO₂, 1% C-CH₄). Large lakes (> 10,000 m²) dominated GHG emissions whereas small thaw ponds (< 1000 m²) had a minor contribution to overall lake surface area (< 2%) and GHG emission (< 5 % of CO₂; < 20% of CH₄). The results suggest that, if permafrost thaw in NE Europe leads to the disappearance of large thermokarst lakes and formation of new small thaw ponds and depressions, this will decrease GHG emission from lentic waters of this region. However, due to temporal and spatial variations of C fluxes, the uncertainties on areal GHG emission are at least one order of magnitude in small thaw ponds and a factor of 3 to 5 in thermokarst lakes.

This work was supported by the State Task AAAA-A18-118012390200-5, RFBR grant No. 18-05-70087 “Arctic Resources”, 19-07-00282, 18-45-860002, 18-45-703001 and 18-47-700001, and the Swedish Research Council (grant no. 2016-05275).

How to cite: Zabelina, S., Shirokova, L., Klimov, S., Chupakov, A., Lim, A., Polishchuk, Y., Polishchuk, V., Bogdanov, A., Muratov, I., Guerin, F., Karlsson, J., and Pokrovsky, O.: Carbon emission related to thermokarst processes in wetlands of NE European Tundra, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3452, https://doi.org/10.5194/egusphere-egu2020-3452, 2020.

Peatlands are important carbon reserves in the terrestrial ecosystem and cover 3% of the terrestrial land surface. Peatlands have stored around 350-500 Petagrams [10¹⁵] of carbon over the last thousands of years, comprising around 30% of the present-day soil organic carbon pool. Peatlands share many characteristics with upland mineral soils and non-peat wetland ecosystems. However, they constitute a unique ecosystem type with many special characteristics, such as a shallow water table depth, carbon-rich soils, a unique vegetation cover, spatial heterogeneity, anaerobic biogeochemistry and permafrost in the high latitude regions (>45°N). The recent changes in climate and land-use patterns have disturbed the Earth’s climate-carbon cycle equilibrium. These changes trigger some potentially important land-surface feedbacks, which will further modify the Earth’s climate. The ongoing changes in peatland carbon balance as a result of climate warming have the potential for strong positive and negative feedbacks to climate, but these impacts are poorly constrained. To assess the importance of these feedbacks, the interactions between the peatland carbon cycle and climate should be taken into account. However, the absence of peatlands in current Earth system models limits our understanding of the peatland-mediated feedbacks at different scales. LPJ-GUESS peatland-vegetation model showed a reasonable demonstration of capturing the right carbon accumulation rates and permafrost dynamics at different spatial and temporal scales and will be further improved and employed to quantify the hypothesized peatland-mediated feedbacks when coupled with regional/global climate models.

How to cite: Chaudhary, N., Zhang, W., Schurgers, G., Page, S., and Westermann, S.: Quantification of peatland-mediated feedbacks to the climate system, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3660, https://doi.org/10.5194/egusphere-egu2020-3660, 2020.

Methane is one of the most important greenhouse gases. The largest natural source of this gas are wetlands. Quantification emission from this source, especially from subarctic regions, which are exposed to fast climate changes, is important for our understanding of biogeochemical climate feedbacks. Abisko Stordalen is one of few mires in this climatic zone in which the methane emission is being measured continuously. Here we analyze eddy covariance data from the ICOS Sweden site with respect to environmental parameters possibly controlling the methane emissions.

Due to the large scale topography at Abisko, wind is channeled along the valley, resulting in to two main wind directions. This divides the measurements into two different surface type groups. On easterly winds, the flux footprint is dominated by permafrost features, while for westerly winds it is dominated by non-permafrost fen. Measured methane fluxes from these to wetland types, exposed for the same environmental conditions, differ considerably being higher from non-permafrost area.  We will further analyze the differences in the annual methane emission from the two systems, and their dependencies from environmental parameters.

How to cite: Łakomiec, P., Holst, J., and Rinne, J.: Methane emissions from a palsa-mire underlayed by sporadic permafrost under rapid degradation, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4748, https://doi.org/10.5194/egusphere-egu2020-4748, 2020.

Boreal and temperate peatlands cover less than 3% of the earth's surface but store nearly 30% of the terrestrial carbon. Natural raised bogs are characterized by a Sphagnum-moss dominated vegetation cover. The majority of bogs has been used for peat extraction or agriculture for centuries, but in the last decades the focus on restoration to protect climate and biodiversity was increasing. This includes the re-establishment of quasi-natural hydrological conditions as well as of ecosystem-typical vegetation.

Recently, a change in species composition of restored bogs from Sphagnum-dominated bryophyte communities to multi-layered tree and graminoid vegetation was observed. Current investigations report contradictory effects for the impact on throughfall, evapotranspiration (ET), gross primary productivity, respiration, net CO₂ balance (NEE) as well as soil carbon sink strength. A final conclusion with respect to altered ecosystem functioning through changing conditions for vegetation development in the light of climate change is missing.

The VESBO project aims at the mechanistic analysis of ET, NEE and soil carbon sink strength of a restored, atlantic-temperate raised bog during vascular plant encroachment. The two study areas are former peat extraction sites, with one being Sphagnum-dominated while the other one has been populated by Betula pubescens during the last years. Focus will be placed on the partitioning of total ecosystem ET and NEE fluxes by Eddy Covariance and chamber measurements in situ into bryophyte, graminoid and tree contributions. Results are used to parameterize a modern soil-vegetation-atmosphere-transport model able to simulate bryophyte and vascular plant layers on peat soil. The model, jointly with the empirical data, is used to quantify seasonal changes in plant functional group flux contributions depending on altered environmental conditions. The holistic process understanding is of high relevance for the NEE estimation of restored bog ecosystems under changing climatic conditions and vegetation compositions. The knowledge about different interactions of plant functional groups with mass and energy fluxes of the bog ecosystem will be valorised by the assessment of restoration and emission mitigation measures throughout Europe.

How to cite: Welpelo, C., Dubbert, M., Tiemeyer, B., Dettmann, U., Beuster, T., Launiainen, S., Kieloaho, A.-J., Haahti, K., and Piayda, A.: Introducing the VESBO Project - Impact assessment of vascular plant encroachment on water and carbon cycling in a Sphagnum dominated bog, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5143, https://doi.org/10.5194/egusphere-egu2020-5143, 2020.

Root exudates are a key driver of carbon cycling in peatlands. They have been found to influence substrate quality in and methane release from peat (Ström et al., 2003), peat decomposition (Crow & Wieder, 2005) and to cause priming effects (Basiliko et al., 2012). However, investigating the fate of added root exudates in peatlands is very challenging, as it requires the consideration of the gaseous, liquid, and soil phase, a traceable substrate, and as little disturbance as possible.

We sampled 6 undisturbed peat cores from Pürgschachen Moor, Austria in September 2019. Following transport of the cores to the laboratory in Vienna, we stored the mesocosms in daylight with intact vegetation at 22°C and created ports for pore water sampling in 5, 15, and 25 cm depth. The water table was set to 3 cm below surface by daily addition of artificial Pürgschachen rainfall (20 kg N ha^-1 yr^-1). After 1 week of incubation for establishment of a baseline, three cores were spiked with 140 mg artificial root exudates consisting of 99% glucose-, acetic acid- and amino acid ¹³C following Basiliko et al. (2012) at 15 cm depth. We monitored carbon dioxide (CO₂), and methane (CH₄) and ¹³CO₂ and ¹³CH₄ efflux from the cores daily and sampled dissolved organic carbon (DOC) weekly from the ports. Three weeks after spiking, all cores were drained, drainage water collected, and peat at 5, 15, and 25 cm depth sampled. Upon drying at 60°C, peat C and ¹³C content was determined and DOC samples were analysed for C and ¹³C content.

Results show that ca. 20% of spiked substrates were incorporated into peat, but this effect was restricted to 15 cm peat depth and ca. 30% were respired as CO₂. No priming effect was detected; the spiked cores did not release more CO₂ and CH₄ than the control cores. ¹³C concentration in peat at 5 and 25 cm depth showed no increased ¹³C concentration.

These results indicate a low mobility of DOC and a limited effect of root exudate derived substrate in peat bogs with a low water table oscillation, explaining remarkably constant CH₄ release rates reported by Drollinger et al. (2019b).

References:

Basiliko, N., Stewart, H., Roulet, N.T., Moore, T.R. (2012): Do Root Exudates Enhance Peat Decomposition? Geomicrobiology Journal 29: 374-378.

Crow SE, Wieder RK. 2005. Sources of CO2 emission from a northern peatland:

root respiration, exudation, and decomposition. Ecology 86:1825–1834.

Drollinger, S., Kuzyakov, Y., Glatzel, S. (2019a): Effects of peat decomposition on d13C and d15N depth profiles of Alpine bogs. Catena 187: 1-10.

Drollinger, S., Maier, A. Glatzel, S. (2019b): Interannual and seasonal variability in carbon dioxide and methane fluxes of a pine peat bog in the Eastern Alps, Austria. Agricultural and Forest Meteorology 275: 69-78.

Ström, L. Ekberg, A., Mastepanov, M., Christensen, T.R. (2003): The effect of vascular plants on carbon turnover and methane emissions from a tundra wetland. Global Change Biology 9: 1185-1192.

How to cite: Müller, R., Clay, G., Blauensteiner, C., Inselsbacher, E., Kalbitz, K., Maier, A., Peticzka, R., Wang, G., and Glatzel, S.: The effect of the addition of 13C labelled artificial root exudates on carbon cycling in intact peat bog mesocosms , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7693, https://doi.org/10.5194/egusphere-egu2020-7693, 2020.

Peatlands are important terrestrial carbon stores and it is important to understand the processes involved in carbon cycling. At Moor House, an upland blanket bog in the United Kingdom (UK), stoichiometric approaches have been adopted to understand carbon cycling through the peatland and this has been used to understand the production, transport and transformation of organic matter from terrestrial to aquatic systems.

Previous results analysing vegetation, peat cores, soil pore water from shallow and deep sample depths, and stream water from Moor House assessed how the composition of organic matter changes through the peatland system, to its export in the stream network. Results showed that there was an increase in the nominal carbon oxidation state (C_ox) of dissolved organic matter (DOM) transferred from soil pore water to stream water. The composition of DOM in soil pore water evolved from near-surface peat layers but stream water DOM was quite distinct in composition. This study assessed the role of DOM in the degradation of peat organic matter by examining the composition of DOM through the peat profile and in separate flow pathways. Sampling was undertaken at Moor House, with sampling from surface, shallow and deep soil water; surface runoff and stream water. Samples were analysed for their elemental content (C, H, N and O), and differential scanning calorimetry and bomb calorimetry.

How to cite: Boothroyd, I., Worrall, F., Abbott, G., Moody, C., Clay, G., and Rose, R.: Transfer of organic matter through a peatland system – from terrestrial to aquatic systems, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8893, https://doi.org/10.5194/egusphere-egu2020-8893, 2020.

While peatlands constitute the largest soil carbon stock in Ireland with 75% of soil carbon stored in an area covering an estimated 20% of the land surface, carbon stocks of peatlands are affected by past and present disturbances related to various land uses. Afforestation, grazing and peat extraction for energy and horticultural use often are major drivers of peatland soil degradation. A comparative assessment of the impact of land disturbance on peatland soil carbon stocks on a national scale has been lacking so far. Current research, funded by the Irish Environmental Protection Agency (EPA), addresses this issue with the goal to fill various gaps related to mapping and modeling changes of soil carbon stock in Irish peatlands. Data from the first nationwide peatland survey forms the basis for this study, in which the influence of different factors and covariates on soil carbon distribution in peatlands is examined. After data exploratory analysis, a mixed linear modeling approach is tested for its suitability to explain peatland soil carbon distribution within the Republic of Ireland. Parameters are identified which are responsible for changes across the country. In addition, model performance to map peat soil carbon stock within a three-dimensional space is evaluated.

How to cite: Walz, K., Byrne, K. A., Wilson, D., and Renou-Wilson, F.: Modeling relevant factors and covariates of carbon stock changes in peatlands using a hierarchical linear mixed modeling approach, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10948, https://doi.org/10.5194/egusphere-egu2020-10948, 2020.

Interest in peatland environments, especially in terms of their carbon storage, has increased markedly in response to the heightened awareness of future, global climatic conditions. However, significant gaps remain in the spatial coverage of our knowledge of mires; including some major wetland systems. This paucity has implications, not only for our understanding of their origins, development and functioning, but also for adequately predicting future changes and providing scientifically based recommendations for mire environmental management. Our INTERACT-supported study provides a radiometrically dated, well-characterised millennial-scale peat record from two contrasting undisturbed and impacted (ditched) sites, respectively in the Great Vasyugan Mire (GVM) near Tomsk, Siberia, which is reputedly the largest peat system in the world. In addition to their palaeoecological characterisation, we identified both natural (lithogenic) and anthropogenic geochemical signals recording human impacts with site-specific variations. Elevated trace element concentrations in both peat profiles align with the time frame of the region’s wider agricultural and economic development with the annexation of Siberia by Russia (from ca. 1600 AD) when pollen assemblage characteristics suggest a decline in forest cover and an increase in herbaceous plants associated with human disturbance. Trace element concentrations peak with the subsequent industrialisation of centres around the Ob river (after ca. 1950 AD). On a global scale, our sites, together with evidence from the few other comparable studies in the region, suggest that the GVM is relatively uncontaminated by human activities with a mean lead (Pb) level of < 4 mg/kg. However, via lithogenic elements including Rb, Ti and Zr we detected both a geochemical signal as a result of historical land cover changes, which enhanced mineral dust deposition following disturbance, as well as fossil fuel derived pollutants, as relatively elevated, subsurface As and Pb concentrations of ca. 10 and 25 mg/kg respectively, with the development of industry in the region. Moreover, we identify the local effects of drainage for afforestation (ca. 1960s) on the peat profile. At the impacted site, which was ditched, but subsequently abandoned, the influence of arrested peat growth on the site’s geochemical depth profile highlights the potential significance of local factors. Although relatively remote and vast, the GVM appears to hold a legacy of human activity that can be detected as a geochemical signal supporting the inferences of other palaeoenvironmental proxies. Such geochemical peat core records, from Eurasia in particular, remain relatively scarce in the international scientific literature. Therefore, our study contributes to an understanding of a less well known and, as yet, inadequately characterised and quantified region. 

How to cite: Hutchinson, S., Diaconu, A., Kirpotin, S., and Feurdean, A.: A geochemical peat record from the Great Vasyugan Mire, Tomsk, Siberia evidencing a regionally coherent pattern of human impact over the last five centuries. , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11170, https://doi.org/10.5194/egusphere-egu2020-11170, 2020.

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

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

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

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

How to cite: Koskinen, M., Finné, H., Virtanen, T., Lohila, A., Laiho, R., Laurila, T., and Aurela, M.: Redox state affects methane flux in a northern boreal flark fen, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12952, https://doi.org/10.5194/egusphere-egu2020-12952, 2020.

Regeneration of natural hydrology in previously drained peatlands is becoming a widespread practice in nature restoration projects around the world. The drained peatlands are well known for their high emissions of CO₂ caused by increased microbial decomposition rates in these very organic soils when suddenly exposed to higher levels of oxygen availability. Restoring natural water levels reduces again the decomposition rates and CO₂ emissions. It remains uncertain, however, how rates of the much stronger greenhouse gases, CH₄ and N₂O, respond to the restored water table and these fluxes can potentially offset the GHG balance of rewetting peatlands.

In a new project in Norway (close to Trysil, Innlandet), we installed five ECO₂flux automated chambers and one eddy flux tower in each of two areas of drained peatlands.  The automatic chambers were placed with different distances to the ditches reflecting variation in water table with greatest water level variability at the edges of the ditches. After two years, the ditches will be filled and the natural water table will be regenerated in one of the areas in order to follow the differences in the fluxes of CO₂, CH₄ and N₂O upon rewetting.

We here present an analysis of the first year’s data from the ECO₂flux chambers including the total greenhouse gas budget for the period measured. The fluxes of CO₂ showed only little spatial heterogeneity whereas we observed a significant spatial pattern of higher fluxes of CH₄ in plots where the water table was closer to the surface. The driest plots, i.e. the edges of the drain ditches, showed also the lowest emissions of CH₄. The trend was similar in the two areas. This is an indicating that planned rewetting after two years of the project may lead to enhanced production and emission of CH₄ in the area. So far, we observed no N₂O emissions above the detection limit of the system indicating that CO₂ and CH₄ are the major components of the GHG budget.

How to cite: Avila, L., Steenberg Larsen, K., Ibrom, A., Pirk, N., and Larsen, P.: High temporal resolution measurements of CO2, CH4 and N2O in a Norwegian mire ecosystem using automated light-dark chambers, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19966, https://doi.org/10.5194/egusphere-egu2020-19966, 2020.

Peatlands are a very important ecosystem which are characterized by distinctive vegetation, hydrology, and local climate. In the last decades, much effort was made a better understanding of microrefugia and their importance. Nevertheless, we still have little knowledge about the histories of the refugia. In the day of rapid climate change and increasing anthropogenic pressure, knowledge about the history of sites that represent a refugium of flora or fauna is a key aspect. The aim of this study is reconstructing the history of the glacial relict Betula nana in northern Poland located far from the southern range of its natural distribution. We suppose that the persistence of Betula nana is driven by a) the morphology and geology of the catchment, b) the maintenance of open vegetation on the peatland surface and c) exceptional microclimatic and hydrological conditions. Here, based on recent eco-hydrological monitoring and long-term palaeoecological proxy we try to be understated postglacial refugia of Betula nana from Central Europe (Linje mire). Detailed research was carried out on the peat profile using pollen analysis, to reconstruct the presence of open habitat on the mire during the Holocene. Pollen and macrofossils analysis revealed a continuous presence of Betula nana in the postglacial history of the peatland. Palaeoecological results show the variable situation of the Betula nana population in the peatland over the past 12 ka, indicating a strong relationship between paleohydrology and changes in the occurrence of this species. Our results of 12 years of local monitoring indicated that the mire is characterized by specific local climate and diverse water table depth. A synergy of local relief, microclimates, hydrology, and geology of the catchment affects the Betula nana population during the post-glacial history.

How to cite: Słowińska, S., Słowiński, M., Noryśkiewicz, A. M., Lamentowicz, M., and Kołaczek, P.: Microrefugia - limiting factors and unique synergy of environment, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20203, https://doi.org/10.5194/egusphere-egu2020-20203, 2020.

Greenhouse gas emissions from damaged peatlands in the UK contribute around 5% to the annual national UK emissions. This has prompted a large national effort to restore these ecosystems as part of the package of action that aims to deliver net zero by 2050 in the UK and 2045 in Scotland. Eroded peatlands cover an estimated 275kha in Scotland, yet continuous monitoring data on the carbon losses from such sites are very sparse, in part due to the challenge in instrumenting such remote and complex terrain with eddy covariance equipment. We present a full, pre-restoration, 18-month data series of carbon dioxide and energy budget from a typical Scottish eroded peatland and show initial data that suggests sensitivity of the sign of the net annual CO2 budget to interannual climate variability.

How to cite: Coyle, M., Morrison, R., Artz, R., Yeluripati, J., and Donaldson-Selby, G.: Pre-restoration carbon dioxide exchange and energy balance dynamics in an eroded upland blanket bog peatland, Scotland, UK, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20705, https://doi.org/10.5194/egusphere-egu2020-20705, 2020.

The effects of 21^st century climate change are projected to be most severe in the northern hemisphere, where the majority of peatlands are located. Peatlands represent important long-term terrestrial stores of carbon (C), containing an estimated c.600-1055GT C, despite covering only 3% of total land area globally. In addition, pristine peatlands act as net sinks of atmospheric CO₂, imparting a negative feedback mechanism cooling global climate, whilst simultaneously acting as sources of CO₂ and CH₄. Peatlands remain net sinks of C as long as the rate of carbon sequestration exceeds that of decomposition. Projected changes in temperature, precipitation and other environmental variables threaten to disrupt this precarious balance, however, and the future direction of carbon feedback mechanisms are poorly understood, due to the complex nature of the peatland carbon cycle.

Two methods are used in order to help understand future the carbon dynamics of peat bogs under climate change. These are experimental studies, which measure greenhouse gas fluxes under manipulated climatic and environmental conditions (warmer, drier), and palaeoecological studies, which examine the effects of past climate change upon carbon sequestration throughout the peat profile. However, both methods fundamentally contradict each other. Palaeoecological studies suggest that carbon accumulation increases during warming periods, whereas warming experiments observe greater carbon loss with increased temperature.

The aim of this project is to link contemporary experimental and palaeoecological approaches to explain this discrepancy. This will be achieved by comparing greenhouse gas fluxes between plots which have been subjected to 10 years of passive warming and drought simulation at an experimental climate manipulation site on Cors Fochno, Ceredigion, Wales. Long term rates of carbon accumulation will be compared with net ecosystem contemporary carbon budgets from each plot. Surface samples from each plot will be analysed by a range of palaeoenvironmental proxies to test how well the climate manipulations are represented by each proxy. Finally, a high-resolution multi-proxy palaeoenvironmental reconstruction spanning the past 1000 years will be compared with reconstructions derived from short-cores from each plot covering the duration of the experiment from each treatment, to see how faithfully climate manipulation mirrors real periods of climate change.

Understanding the future role of peatlands in future carbon sequestration and storage is of vital importance for modelling future climate change, in terms of both quantifying the potential ecosystem services peatlands may offer in mitigating the effects of climate change, as well as enhancing the predictive capabilities of global climate models. Currently, the uncertainty associated with peatland carbon cycling is such that peatlands are rarely included in global climate models.

How to cite: Andrews, L., Rowson, J., Payne, R., Caporn, S., Dise, N., Gehrels, M., and Gehrels, R.: Cores for concern: Peatland carbon dynamics in a changing climate; a multidisciplinary approach., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6222, https://doi.org/10.5194/egusphere-egu2020-6222, 2020.

Peatlands have been traditionally drained to increase productivity. Aeration of the topsoil increases decomposition of peat, which results in increased CO₂ emissions contributing to warming of the global climate. Peatland restauration tries to reestablish the natural state by blocking the drainage and increasing the ground water table. Two questions arise, whether the establishment of anaerobic conditions in the peat will increase methane production and whether the net CO₂ uptake by plants will be reduced, both of which offsetting the anticipated positive climate effect from peatland restauration. In order to claim a positive climate effect from peatland restauration, the effect on the total greenhouse gas (GHG) balance must be demonstrated[VH1]  at different time scales.

In a new project in Norway (close to Trysil, Innlandet), we established a paired plot design in an ombrotrophic bog, where one of the two plots will be restored, while the other will remain drained. The two sites differ slightly in elevation and lie 1.5 km apart from each other. We report results from the first phase of the experiment, i.e. examining the comparability of the two plots. We use eddy covariance and ecosystem chambers to measure CO₂, CH₄ and N₂O fluxes.

While the CO₂ fluxes are remarkably similar between the two plots, the CH₄ fluxes tend to be slightly higher in the lower of the two plots. With flux footprint simulations and spatio-temporal analysis of the chamber flux measurements it is examined, whether these differences are caused by small scale horizontal heterogeneity, i.e. by CH₄ emission hotspots, or whether these are a general feature of the lower experimental site. Options to improve the comparability of the two experimental plots, namely source area filtering versus relational approaches will be discussed.

The methodology that is developed in the project is relevant for monitoring, reporting and verification of climate change mitigation measures within terrestrial ecosystems.

Acknowledgements:

The project is funded by the Norwegian Environment Agency (Miljødirektoratet), Oslo, Norway, (project number 18088061).

How to cite: Ibrom, A., Pirk, N., Steenberg Larsen, K., Kindler, P. A., and Larsen, P.: Experimental approach to study the climate effects from drained peatland restauration, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6602, https://doi.org/10.5194/egusphere-egu2020-6602, 2020.

In 2018, North-Western Europe experienced very dry and warm summer. These conditions can have considerable effects on the functioning and greenhouse gas exchange of terrestrial ecosystems. Peat-forming wetlands, or mires, are a characteristic component of the North-European boreal landscape, and crucial for long-term carbon storage as well as for methane emission. We have analyzed the effect of the drought on greenhouse gas (GHG) exchange of five North European mire ecosystems in Sweden and Finland in 2018. The low precipitation and high summer temperatures in Fennoscandia led to a lowered water table in majority of the mires. This lowered both carbon dioxide (CO₂) uptake and methane (CH₄) emission during 2018, turning many of the mires from CO₂sinks to sources during this year. The changes in methane emission and total GHG exchange, expressed as CO₂equivalent, were significantly correlated with change in water table position. The calculated time-evolving radiative forcing due to the changes in GHG fluxes in 2018 showed that the drought-induced changes in GHG fluxes first resulted in a cooling effect lasting 15-50 years, due to the lowered CH₄emission, which was followed by longer-term warming phase due to the lower CO₂ uptake in 2018.

How to cite: Rinne, J., Tuovinen, J.-P., Klemendtsson, L., Aurela, M., Holst, J., Lohila, A., Weslien, P., Vestin, P., Peichl, M., Tuittila, E.-S., Heiskanen, L., Laurila, T., Li, X., Alekseychik, P., Mammarella, I., Ström, L., Crill, P., and Nilsson, M.: Effect of the 2018 drought on methane and carbon dioxide exchange of northern mire ecosystems, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7329, https://doi.org/10.5194/egusphere-egu2020-7329, 2020.

Peatlands across the globe are experiencing external pressures such as land use change, drainage and climatic changes, but are also directly impacted e.g. through peat harvesting. As a result, the dynamics of these peatlands, and their role in long-term carbon storage, has changed. In contrast to many other regions around the globe, temperate Europe has known a long history of human impact. In the northwest European lowlands, peat growth occurs mostly in floodplains under the form of alluvial peatlands. In central Belgian river valleys, alluvial peatlands developed since the Early Holocene, with a typical peat thickness between 1.5 and 2.5 metres, but reaching values of more than 6 metres at some locations.

Alluvial peatlands therefore are an important store of soil organic carbon reaching values of up to 2754 t ha^-1, thus providing an important ecosystem service. However, the fate of this carbon reservoir is challenged through many different types of human actions since at least the Middle Ages including peat cutting for fuel, drainage for land reclamation and changes in catchment hydrology through land use change. For instance, a comparison of field-based peatland carbon budgets for different river valleys indicates that floodplains where cutting of topsoil peat has been important in the Late Holocene, store significantly less carbon (729 ± 397 t ha^-1) than floodplains where Early to Mid-Holocene peat has been buried by mineral sediments originating from agricultural erosion on hillslopes (1991 ± 877 t ha^-1). Adequate modelling can provide a powerful tool to study peatland dynamics and the interaction between internal and external processes in peatlands, but unfortunately, there are currently no available modelling tools to study the long-term dynamics of alluvial peatlands.

A long-term peatland model (Digibog) was adapted to be applicable to the context of alluvial peatlands. Changes were made to both the hydrological and biological modules to include variations in the river water level, flooding, anthropogenic peat cutting and a wide variety of vegetation types, ranging from open meadows to carr forests. In a first step, the Holocene evolution of an alluvial peatland was simulated under the conditions which were typical for lowland Belgium to provide a Holocene peat sequence with an annual resolution. In a second step, this peatland was subjected to a wide set of alternative management scenarios that have been in place since the Middle Ages. The simulations allow to estimate the effect of these scenarios on the peatland dynamics in terms of peatland hydrology, productivity and carbon storage. Based on this modelling study, the sensitivity of these systems to human activities can be quantified. The resultant magnitudes and rates of change under different scenarios can provide useful information for future management of alluvial peatlands and a better understanding of long-term peatland dynamics in general.

How to cite: Swinnen, W., Broothaerts, N., and Verstraeten, G.: Long-term human impact on alluvial peatland dynamics in temperate climates, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7655, https://doi.org/10.5194/egusphere-egu2020-7655, 2020.

Many peatland areas in Great Britain are managed as grouse moors, with regular burns as part of management practice to encourage heather growth. Remote sensing has the potential to monitor the size, location, and impact of these burns using new fine resolution satellites such as Sentinel-2. Google Earth Engine allows large areas to be analysed at small scale over several years, building up a visual record of fire occurrence. This study uses satellite data to map managed burns on several areas of moorland around Great Britain, and uses remote sensing methods to assess the impact of this management strategy on vegetation cover. The project also considers how areas subject to managed burns react to wildfire occurrence, with the 2018 Saddleworth wildfire as a case study.

How to cite: Lees, K., Buxton, J., Boulton, C., and Lenton, T.: Using remote sensing to monitor peatland fire occurrence and recovery, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8836, https://doi.org/10.5194/egusphere-egu2020-8836, 2020.

We present the Net Ecosystem Carbon Balance (NECB) of a Northern mire ecosystem for the period 2016-2019. The Mycklemossen peatland is located in the hemi-boreal region in the Southwestern part of Sweden and is classified as a fen with bog-like vegetation. The NECB was determined from eddy covariance (EC) measurements of carbon dioxide (CO₂) and methane (CH₄) and continuous water discharge measurements with biweekly measurements of dissolved organic carbon (DOC), dissolved inorganic carbon (DIC) and dissolved CH₄.
We focus on the carbon dynamics of the Mycklemossen ecosystem during summer droughts and on its recovery during normal years. During 2016-2018, the annual precipitation was lower than the 30-year average while 2019 was a normal year in terms of weather conditions. 2018 sticks out as an extreme year with a severe drought and unusually high air temperature at Mycklemossen, as was the case in much of Northern and Central Europe.
The EC results indicate that Mycklemossen lost carbon during 2016-2018. While CH₄ emissions decreased, the mire became a strong source of CO₂ these years, especially 2018. There were also large losses of DOC during this period, which were further enhanced during 2019.

How to cite: Vestin, P., Weslien, P., Wallin, M., Bastviken, D., Kljun, N., Edvardsson, J., Holst, J., Lindroth, A., Crill, P., Rinne, J., and Klemedtsson, L.: Carbon dynamics and full carbon balance of a Northern mire ecosystem, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9842, https://doi.org/10.5194/egusphere-egu2020-9842, 2020.

Peatlands are a globally important store of approximately 500 Gt carbon (C), with northern blanket bogs accumulating ca. 23 g C m^-2 y^-1 from undecomposed organic material due to prevailing cool wet conditions. As a sink of carbon dioxide (CO₂) they act as an important brake on anthropogenic climate change, but in the warming climate the likelihood of drought will increase. However, it is unknown how drought will affect the GHG balance of peatlands: dryer, warmer conditions will likely reduce net ecosystem exchange (NEE) of CO₂ and increase soil respiration, potentially tipping these landscapes from sinks to sources of C. High water tables mean blanket bogs are major source of methane (CH₄), an important greenhouse gas (GHG) with a global warming potential (GWP) 34 times that of CO₂ over 100 years, but this may change in the future climate. It is further expected that the changing climate will alter blanket bog species composition, which may also influence the GHG balance, due to differences in plant traits such as those which form aerenchyma, e.g. Eriophorum vaginatum (eriophorum) and non-aerenchymatous species, e.g. Calluna vulgaris (heather). In order to understand how these important C stores will respond to climate change, it is vital to measure GHG responses to drought at the species level.   

We used an automated chamber system, SkyLine2D, to measure NEE and CH₄ fluxes near-continuously from an ombrotrophic blanket peat bog. Five general ecotypes were identified: sphagnum (Sphagnum spp), eriophorum, heather, water and mixtures of species, with five replicates of each sampled. We followed the fluxes of CO₂ throughout 2017- 2019 and CH₄ throughout 2017- 2018, hypothesising that GHG fluxes would significantly differ between ecotypes. In 2018, the bog experienced drought conditions, allowing the comparison of NEE between drought and non-drought years, and the potential to recover the following year. Contemporaneous measurements of environmental variables were collected to infer details regarding the drivers of GHG fluxes.

We found significant differences in CH₄ emissions between ecotypes, F= 2.71, p< 0.02, ordered high to low: eriophorum > sphagnum > water > heather> mix, ranging from ca. 1.5 mg CH₄-C m^-2 d^-1 to 0.5 mg CH₄-C m^-2 d^-1. There were no significant differences in NEE between ecotypes, F= 0.54, p> 0.7, however, under 2018 drought conditions all ecotypes were net sources of CO₂. We will also present NEE from 2019, when precipitation levels returned to typical conditions. Our results indicate that drought and shifts in vegetation composition under future climate may alter the C balance of hemi-boreal and potentially act as a positive feedback to climate change in a long-term scenario.

How to cite: Keane, J. B., Toet, S., Ineson, P., Weslien, P., and Klemedtsson, L.: Carbon flux response and recovery to drought years in a hemi-boreal peat bog between different vegetation types, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13187, https://doi.org/10.5194/egusphere-egu2020-13187, 2020.

Peatlands play a key role in the global carbon cycle and the greenhouse gas balance of the biosphere, due to the amount of stored organic carbon and rather big methane (CH₄) emissions. Climate change can make these very valuable and vulnerable ecosystems a net emitter of greenhouse gases to the atmosphere. The question is however, how the anticipated climate changes may impact the methane emission. Will it decrease due to expected drier conditions, or other processes and factors may play a role leading to higher emissions? To answer this question we carried out a field climate manipulation experiment at Rzecin peatland in Poland to assess how, increased temperature and reduced precipitation may impact the CH₄ emission. The field site consists of three times replicated treatments [control (CO); simulated warming (W); reduced precipitation (RP), and warming & RP (WRP)]. Temperature (T) was increased year around with infrared heaters (400Wx4 per site), while precipitation was reduced with an automatic curtain working during growth seasons at night. The average yearly peat (at 5 cm depth) and air temperatures (at 30 cm) increased at manipulated plots by ca. 1.0^oC and 0.4^oC, respectively, while the precipitation was reduced from 24% in 2017 to 38% in 2016. Methane and carbon dioxide fluxes were measured with an automated prototyped mobile chamber system equipped with LGR and Picarro gas analyzers.

                Here we present data from three years; very dry and warm 2015 (417 mm, 9.5°C), more wet and colder 2016 (678 mm, 8.9°C) ad very wet and warm 2017 (929 mm, 9.3°C). The net CH₄ emissions at the control site were at the same rate of 25 gC·m^-2yr^-1 for both 2015 and 2016 years, and significantly higher (by 55%) in the very wet 2017 (39 gCH₄-C·m²·yr^-1). This may indicate that 1) temperature and precipitation play a role in driving the methane emissions from peatland, 2) increase of methane emissions due to higher precipitation can be compensated by lower temperature leading to smaller emission, 3) at more wet and warm years methane emissions may be higher than presently. However, our manipulation clearly indicated that at manipulated sites (W, WRP and RP) methane fluxes were significantly higher (by 28%) than on control plots for both 2015 and 2016 years, while no significant differences between sites exposed for manipulation were found for wet and warm 2017 (although peat temperatures at W, WRD and RD were higher than on CO). This can indicate that in conditions of a high level of groundwater in peatland (due to high rainfall) the sensitivity of methane production processes to temperature changes caused by manipulations may be lower. On the other hand, we found that higher methane fluxes at the manipulated plots are significantly correlated to a higher biomass of vascular plants. This may indicate how important might be the plant species composition on peatland in defining the transport pathways of methane to the atmosphere and overall methane emissions with respect to anticipated climate change.

Research was funded within the NCN projects (017/25/N/ST10/02212, 72016/21/B/ST10/02271) and WETMAN project.

How to cite: Strozecki, M., Rastogi, A., Chojnicki, B., Leśny, J., Urbaniak, M., Olejnik, J., Basińska, A., Lamentowicz, M., Łuców, D., Gąbka, M., Józefczyk, D., Samson, M., Hoffmann, M., Silvennoinen, H., and Juszczak, R.: Impact of reduced precipitation and increased temperature on CH4 emission from peatland in Western Poland, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17989, https://doi.org/10.5194/egusphere-egu2020-17989, 2020.