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BG3.15

Peatlands under pressure

From pole to pole, peatlands contain up to 30% of the world’s soil carbon pool, illustrating their role in the global carbon cycle. Currently peatlands are under various pressures such as changing climate, land-use or nutrient loading with unknown consequences for their functioning as carbon sinks and stores and the uptake or release of the greenhouse gasses carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O). Simultaneously, increasing amount of restoration activities, aiming to return peatlands back to their original state are ongoing. It is, however, not clear how the carbon reservoir will react to these pressures and how resilient these ecosystems are. This session will focus on the observed or predicted changes on the biogeochemistry at peatlands, caused by climate change, nutrient loading or land-use. We invite studies concentrating, for example, on the effects of climate change on GHG flux or nutrient dynamics on pristine and managed peatlands, impact of drainage or restoration and subsequent vegetation succession on biogeochemistry, atmosphere-biosphere interaction, or studies on carbon stock changes demonstrating the impact of land-use or climate change. Experimental and modelling studies of both high- and low latitude peatlands are welcomed.

Convener: Annalea Lohila | Co-conveners: Jorge Hoyos-Santillan, Claudio Zaccone, Angela Gallego-Sala, Julien Arsenault, Gareth Clay, Maxim Dorodnikov, Frans-Jan W. Parmentier
Presentations
| Thu, 26 May, 08:30–11:40 (CEST)
 
Room 3.16/17

Thu, 26 May, 08:30–10:00

Chairpersons: Annalea Lohila, Claudio Zaccone

08:30–08:40
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EGU22-86
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ECS
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solicited
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On-site presentation
Richard Fewster et al.

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

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

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

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

08:40–08:47
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EGU22-4644
Sofie Sjogersten et al.

Permafrost thaw resulting from climate warming is threatening to release carbon from high latitude peatlands. The aim of this research was to determine subsidence rates linked to permafrost thaw in sub-Arctic peatlands in Sweden using historical orthophotographic (orthophotos), Unoccupied Aerial Vehicle (UAV) and Interferometric Synthetic Aperture Radar (InSAR) data. The orthophotos showed that the permafrost palsa on the study sites have been contracting in their areal extent, with the greatest rates of loss between 2002-2008. The surface motion estimated from differential digital elevation models from the UAV data showed high levels of subsidence (maximum of -25 cm between 2017-2020) around the edges of the raised palsa plateaus. The InSAR data analysis showed that raised palsa areas had the greatest subsidence rates with maximum subsidence rates of 1.5 cm between 2017-2020, however, all wetland vegetation types showed subsidence. We suggest that the difference in spatial units associated with each sensor explains parts of the variation in subsidence levels recorded. We conclude that InSAR was able to identify areas most at risk of subsidence and that it can be used to investigate subsidence over large spatial extents, whereas UAV data can be used to better understand dynamics of permafrost degradation at a local-level. These findings underpin a monitoring approach for these peatlands.

How to cite: Sjogersten, S., de la Barreda Bautista, B., Boyd, D., Ledger, M., Siewert, M., Chandler, C., Bradley, A., Gee, D., Large, D., Olofsson, J., and Sowter, A.: Towards a monitoring approach for understanding permafrost degradation and linked subsidence in Arctic peatlands, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4644, https://doi.org/10.5194/egusphere-egu22-4644, 2022.

08:47–08:54
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EGU22-10353
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ECS
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On-site presentation
Laura Panitz et al.

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

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

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

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

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

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

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

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

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

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

08:54–09:01
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EGU22-11926
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ECS
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On-site presentation
Muhammad Kamil Sardar Ali et al.

Nutrient-rich organic soils are one of the largest key sources of greenhouse gas (GHG) emissions in cool moist climate regions in Europe, and around 15 Mha of wetlands are drained for forestry across the world's temperate and boreal areas. Drainage promotes the decomposition of the organic material stored in these naturally water-saturated organic soils, turning the wetland from a carbon sink into an emitter of CO2. Lower soil water content in drained histosols leads to reduced CH4 emission, while N2O emission can increase due to increased mineralization and more favorable conditions for nitrification. However, detailed information of GHG emissions from drained organic soils under different land use and management in the hemiboreal zone is still scarce.  

We conducted a full-year study at drained peatland sites with different land uses to assess the impact of drainage and land-use on GHG fluxes in Estonia. We investigated ten sites: (I) five forests with different tree species, (II) three grasslands with different water regimes, (III) cropland and (IV) natural wetland (fen). The GHG fluxes were measured twice per month using the manual static (CH4 and N2O) and dynamic (heterotrophic respiration (CO2)) closed chamber method from Jan 2020 to Dec 2021. Additionally, groundwater level, soil temperature and moisture were measured hourly with automatic loggers to determine soil conditions.   

Our preliminary results show that all drained forest soils were annual CH4 sinks (−59.4 ± 2.5 µg m-2 h-1, mean ± SE). However, CH4 uptake from the studied fen, crop and grasslands were lower, –13.2 ± 4.4, -12.2 ± 2.0 and -8.2 ± 3.3 µg m-2 h-1, respectively, while grassland with poor drainage soil was a less source of CH4 emission. Most of the sites were annual emitters of N2O; forest sites were higher emitters (15.9 ± 2.3 µg m-2 h-1) than cropland (12.7 ± 4.1 µg m-2 h-1) and fen soils (6.3 ± 1.1 µg m-2 h-1). N2O fluxes from grasslands depend on drainage intensity and the site with poor drainage emitted less. Higher N2O emissions and temporal variability were associated with sites where the water level had high seasonal fluctuations. Soil CO2 fluxes (heterotrophic respiration) were highest from grasslands and peaked over all the study sites during the summer. Methane flux had a statistically significant correlation with water level and soil moisture, while N2O flux was controlled by soil temperature, having higher emissions in a warmer season. The results provide insights into GHG fluxes over temporal and spatial scales and indicate the need for mitigation measures and further enhancement of modeling tools for climate-friendly land management practices in nutrient-rich organic soils.   

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

How to cite: Sardar Ali, M. K., Schindler, T., Kull, A., Vahter, H., Mander, Ü., and Soosaar, K.: Greenhouse gas fluxes from nutrient-rich organic soils in Estonia, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11926, https://doi.org/10.5194/egusphere-egu22-11926, 2022.

09:01–09:08
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EGU22-2574
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ECS
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Virtual presentation
Mengyu Ge et al.

Recent studies have identified the significant role of plants in controlling methane (CH4) emission from peatlands by acting as conduits and further demonstrated that such conduit effect is species-specific. In most studies, species-specific plant-mediated CH4 transport has been estimated indirectly by comparing CH4 flux from surfaces with different plant communities to that from surfaces where plants responsible for CH4 transport are cut, known as the clipping technique. However, the estimation based on the clipping technique has shown large uncertainty due to the plant residual effect. Thus, directly investigating the variation in CH4 transport between different plant species and the factors affecting it is necessary to more precisely assess changes in the CH4 fluxes of peatland ecosystems in a changing environment.

We measured CH4 emission directly from shoots of Carex rostrata, Menyanthes trifoliata, Betula nana, and Salix lapponum from the early growing season until the beginning of senescence (June-September 2020 and 2021, three campaigns both years), with three specimens per species and campaign. We also measured CH4 emission from Equisetum fluviatile and Comarum palustre during high summer in 2021 to further shed light on species-specific characteristics of plant-mediated CH4 flux. We monitored abiotic factors such as belowground CH4 concentration, potential CH4 production and oxidation rate, water table level, and peat temperature.

During high summer in 2021, C. rostrata had the highest CH4 transport rate per leaf area (6.86 mg m-2 h-1). This value was significantly higher than that from M. trifoliata which was the secondarily important CH4 emitter with the rate of 4.07 mg m-2 h-1. E. fluviatile, C. palustre, B. nana, and S. lapponum had limited CH4 transport rate per leaf area (0.66, 0.02, 0.14, and 0.15 mg m-2 h-1, respectively) and thus were negligible CH4 emitters. CH4 emission from C. rostrata demonstrated the most pronounced seasonal variation (ranging from 0.02 to 24.78 mg m-2 h-1), driven primarily by seasonal vegetation development (phenology) and only secondarily by rhizospheric peat temperature. In contrast, CH4 emission from M. trifoliata, B. nana, and S. lapponum showed little seasonal variation, and no factors that significantly affected the flux from these species were found. Lastly, the sharp decrease in rhizospheric peat CH4 concentration during high summer and the simultaneous increase in emission from C. rostrata, the most dominant species in our site, indicated the conduit effect predominated over the CH4 production and oxidation. The findings highlight the importance of C. rostrata in mediating CH4, which could exacerbate the climatic impact of the thawing permafrost region where C. rostrata can thrive in wet microsites.

How to cite: Ge, M., Koskinen, M., Korrensalo, A., Mäkiranta, P., Lohila, A., and Pihlatie, M.: Species-specific effects of vascular plants on methane transport in northern peatlands, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2574, https://doi.org/10.5194/egusphere-egu22-2574, 2022.

09:08–09:15
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EGU22-7554
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On-site presentation
Klaus Steenberg Larsen et al.

Peatlands store large amounts of organic carbon, which become subject to increased microbial decomposition and mineralization to primarily CO2 upon drainage.  Drained peatlands are often characterized by horizontal variability in soil water content and saturation, with drier parts closer to drainage ditches. CH4 production should take place in the wetter parts, while respiratory CO2 production should dominate in drier parts.

We investigate two neighboring, drained ombrotrophic bogs in Norway close to Trysil, Innlandet, 61.1”N 12.25”E, 640 m a. s. l. One site (South) on an upper slope is about 45 m higher than the other site (North) in a saddle-like flattening.  We use an automated, ecosystem-level, light-dark chamber method to examine the seasonality of CO2, CH4 and N2O fluxes at different microsites along the water table gradient from center of drained patches to the drainage ditches in order to relate GHG fluxes to small scale spatial heterogeneity. With eddy covariance CO2 and CH4 flux measurements, we integrate GHG fluxes of CO2 and CH4 over a larger spatial scale.

We here present a comparative analysis of the first two years of measurements, where we examine shifting spatial patterns of GHG production at different scales and relate them to soil conditions. The automated chambers (five chambers within each footprint of each eddy flux tower) showed higher spatial variability for CH4 fluxes than for CO2 with higher CH4 emissions in the wetter plots furthest away from ditches, i.e. CH4 fluxes correlate well to water table depth at both sites. N2O emissions were observed only in very short events during the early summer of year 1.

While the CO2 fluxes compared very well between the two investigated sites during the first two years of investigation, the CH4 fluxes were higher in the lower and wetter of the two sites (North).  Only in the South site, the CH4 fluxes correlated well with the spatial coverage of well-drained versus less well-drained patches. We will present results on how the spatial variability changed with the seasonality of soil temperatures and the water table. Overall, there was a good alignment of fluxes measured with eddy flux and chamber technologies.

During fall 2021, the drainage ditches were filled and natural hydrology restored at the South site. In following years, GHG fluxes will be monitored continuously at both sites to determine the effect of the restoration on the GHG budget of the ecosystem.

How to cite: Larsen, K. S., Ibrom, A., Pirk, N., and Larsen, P.: Greenhouse gas fluxes in two drained Northern peatlands inferred from eddy covariance and automatic light-dark chambers, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7554, https://doi.org/10.5194/egusphere-egu22-7554, 2022.

09:15–09:22
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EGU22-8978
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ECS
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On-site presentation
Christopher Schulze et al.

The Taiga Plains ecozone in northwestern Canada is characterized by vast peat landscapes consisting of both mostly tree-less, permafrost-free and forested, permafrost-affected peat landscapes. In response to warming due to ongoing climate change, more frequent and severe wildfires and rapid permafrost thaw affect landscape composition, structure and functioning, whereas more and more ice-rich permafrost peat plateaus transform into water-saturated thermokarst wetlands or lakes. Collectively, these three agents of change, namely warming, wildfire, and thermokarst, could turn these boreal peat landscape from atmospheric carbon and nitrogen sinks into sources with potentially positive climate system feedbacks. We studied net ecosystem exchange (NEE) and its two component fluxes, i.e., gross primary productivity (GPP) and ecosystem respiration (ER), from three sites with five eddy covariance towers near the southern limit of permafrost in western Canada. Around the southernmost site Lutose, both footprint areas around the two towers have completely burned in wildfires in 2007 and 2019, respectively. We hypothesized that these two subsites would act as net CO2 sources, because of the recent disturbance history. This has been confirmed by preliminary results. The two other sites mainly differed in permafrost extent, ranging from sporadic (Scotty Creek) to discontinuous (Smith Creek), and in peat plateau-to-wetland ratio and corresponding forest cover (Scotty Creek < Smith Creek). Between the two sites Scotty Creek and Smith Creek, we hypothesized that the overall landscape GPP and ER will be higher at Scotty Creek compared to the northernmost site Smith Creek, due to both more abundant thermokarst wetlands and higher GPP and ER of the peat plateau areas at this more southern site. We further hypothesized that the effects of warming on GPP are greater than on ER and thus that the warmer Scotty Creek site is a greater net CO2 sink. Contrary to expectations, preliminary results have shown that there is no difference in NEE between Scotty Creek and Smith Creek, whereas both, the overall landscape GPP and ER, are actually higher at Smith Creek. To identify differences in the NEE, GPP, and ER between their peat plateaus and thermokarst wetlands, respectively, we move forward by applying footprint analyses for Smith Creek and Scotty Creek. Through these analyses we will be able to shed light on how each of the drivers, i.e., warming, wildfire, and thermokarst, alters magnitude and direction in greenhouse gas fluxes from rapidly thawing boreal peat landscapes.

How to cite: Schulze, C., Olefeldt, D., Emmerton, C., Harris, L., Kljun, N., Chasmer, L., Hopkinson, C., Detto, M., Helbig, M., Gosselin, G. H., and Sonnentag, O.: Effects of Warming, Wildfire, and Permafrost Thaw on Carbon Dioxide Fluxes from Boreal Peat Landscapes in northwestern Canada, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8978, https://doi.org/10.5194/egusphere-egu22-8978, 2022.

09:22–09:29
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EGU22-9625
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ECS
Joel White et al.

The effect of anthropogenic climate change on peatland ecosystems is of major concern since they act as a significant global carbon sinks. One of the largest climatic threats to peatlands are droughts. Combined warming and reduced precipitation result in lower water table depths, which alters methane production, increases soil respiration, and consequently shifts peatlands to carbon sources. Droughts in peatlands facilitate aeration of previously anoxic layers allowing aerobic microbes to populate and consume previously unavailable carbon substrates. Despite clear environmental pressures, the responses from functional groups, such as methanogenic archaea, to short term droughts on community abundance, diversity and composition of functional genes is still poorly understood. To investigate this, we applied the molecular technique “captured metagenomics”, to identify the variability in functional diversity of microorganisms involved in the metabolism of methane during the 2018 summer drought. In addition, we measured methane fluxes, water table depths, and soil and air temperatures. We observed that the drought significantly reduced methane fluxes in plots dominated by R. alba and C. vulgaris, but the same was not observed in sites dominated by E. vaginatum. The proportion of methanogens to methanotrophs reduced by 12% in favour of methanotrophs during the drought. Interestingly, both methanogens and methanotrophs declined in relative abundance during the drought – expect for one genera, the type II methanotroph Methylocellawhich increased in relative abundance. During the non-drought year, the highest β-diversity was observed in E. vaginatum plots, but during the drought the highest β-diversity changed to R. alba plots. Significant differences were observed between the abundance of captured genes when tested via PERMANOVA between the drought and non-drought year (p ≥ 0.01). However, the PERMANOVA revealed that only 15% of the variance in abundances can be explained by year. Interestingly, genes including cutLhdrcoxS, mvhAmetFfdhAfrmB, cutM and cooS were significantly more abundant during the drought when compared to the non-drought year.  We conclude that only small shifts occurred in the structure and function of the microbial community, indicating that methanogens and methanotrophs hold a strong resilience to relatively short-term drought events.

How to cite: White, J., Ahrén, D., Ström, L., Klemedtsson, L., and Parmentier, F.-J.: Methane producing and reducing microorganisms display a high resilience to the effects of short term drought in a Swedish hemi boreal fen. , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9625, https://doi.org/10.5194/egusphere-egu22-9625, 2022.

09:29–09:36
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EGU22-9887
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ECS
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Virtual presentation
Ruchita Ingle and Matthew Saunders

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

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

 

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

09:36–09:43
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EGU22-11470
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ECS
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On-site presentation
Mikk Espenberg et al.

Due to the complexity and diversity of nitrogen cycle processes, different methods, e.g., microbiological and isotope analysis, are used to study them. Their combined application helps make the most accurate estimates of the processes occurring, which is essential for the future management of drained peatlands to mitigate soil degradation and negative atmospheric impact. Nitrification and denitrification processes in soil are the main processes behind the harmful greenhouse gas nitrous oxide (N2O) emission.

This study aimed to investigate the effect of drainage and rewetting on nitrification and denitrification processes and N2O emissions using real-time PCR and isotope methods. In the summer of 2020, the 1 m2 triangle-shaped mesocosms were established to achieve varying oxygen conditions for flooding and drainage experiment in Estonia's Oxalis site-type drained peatland forest. In the experiments, heavy nitrogen tracers of potassium nitrate 15N 98% atom (Sigma Aldrich) and ammonium chloride 15N 98% atom (Sigma Aldrich) were applied to soil to amplify and get an insight into N2O production mechanisms and on its soil moisture dependence. N2O concentration was measured, and soil samples were collected six times from the study sites between October 2020 and January 2021. Besides different physical and chemical parameters measured of soil samples, quantitative real-time PCR was used to measure the abundance of bacterial and archaeal specific 16S rRNA, nitrification (bacterial and archaeal amoA genes) and denitrification (nirK, nirS, nosZI and nosZII genes) marker genes from the samples. Isotope composition of soil and gas samples were also measured.

This study indicates that different hydrological regimes influence nitrification and denitrification processes. Regarding control of N2O fluxes, nitrification played a major role on drained sites, and denitrification was the main process in rewetted sites, which is easily related to the oxygen content in the soils. This is supported by a higher proportion of 15N-N2O in 15N-NO3 treatment in rewetted mesocosms. In the case of 15N-NH4 treatment, the highest proportion of heavy N was found in the drained mesocosms. Overall, heavy nitrogen proportion in both alpha and beta positions was higher in the N2O produced by denitrification, whereas N2O contained only one 15N atom per N2O molecule. Abundances of nosZI and nosZII genes behaved differently in drained and rewetted mesocosms. Both microbiological and isotope methods showed similar results and backed each other very well, which makes either of them a perfect tool for predicting N2O emissions.

How to cite: Espenberg, M., Masta, M., Kuusemets, L., Pärn, J., Sepp, H., and Mander, Ü.: Integrating microbiological and isotope methods for studying nitrification and denitrification processes in soils of drained and rewetted peatland forest, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11470, https://doi.org/10.5194/egusphere-egu22-11470, 2022.

09:43–09:50
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EGU22-13469
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On-site presentation
Juanita Mora-Gomez et al.

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

 

References

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

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

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

09:50–09:57
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EGU22-2844
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ECS
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On-site presentation
Liam Heffernan et al.

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

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

Thu, 26 May, 10:20–11:50

Chairpersons: Frans-Jan W. Parmentier, Gareth Clay

10:20–10:30
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EGU22-8829
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solicited
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On-site presentation
Charlotte Wheeler and Kristell Hergoualc’h

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

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

10:30–10:37
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EGU22-1384
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ECS
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Virtual presentation
Peatland Formation and Carbon Accumulation : A Pantropical Synthesis
(withdrawn)
Alexandra Hedgpeth et al.
10:37–10:44
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EGU22-3524
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Virtual presentation
Tuula Larmola et al.

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

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

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

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

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

10:44–10:51
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EGU22-8859
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ECS
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Virtual presentation
 Interaction between graminoids and shrubs modify responses of these plants to warming and nitrogen addition in a boreal bog
(withdrawn)
Ba Thuong Le and Jianghua Wu
10:51–10:58
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EGU22-9792
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ECS
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On-site presentation
Elisabeth Ramm et al.

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

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

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

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

10:58–11:05
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EGU22-12925
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ECS
Bidhya Sharma et al.

Peat is used as the chief ingredient of growing media in horticulture. The high cation exchange capacity, water retention capacity, low bulk density, and appropriate physical properties make peat-based growing media desirable for horticulture. Peat in its natural form is acidic and low in nutrient composition. Therefore, for suitability as a growing media, peat is mixed with liming agents, nutrients, surfactants, perlite among several other possible additives.

Using lab incubations, we assessed the change in soil biogeochemistry and CO2 fluxes because of horticultural additives. We obtained samples of raw peat and additive mixed growing media (n=52) from four different peat extraction companies in Canada. Our analysis shows that the key soil biogeochemical parameters C: N ratio, pH, dissolved organic carbon, bulk density, C content differs significantly (p<0.01) between raw peat and growing media. There is a more than a two-fold increase in CO2 from growing media as compared to raw peat. Further experiment showed the longer-term contribution of carbonates borne CO2 to the total flux. 

IPCC (2007) calculates that all C from harvested peat is lost in the atmosphere in the first year. However, our initial results estimate less than 10% of peat C loss in the first year from growing media. Although the influence of horticultural additives in C loss from peat is significant, the current accounting from IPCC is an overestimation.

How to cite: Sharma, B., Roulet, N., Moore, T., Knorr, K.-H., Teickner, H., Strachan, I., and Douglas, P.: Horticultural Additives influence soil biogeochemistry and increase CO2 emissions from peat, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12925, https://doi.org/10.5194/egusphere-egu22-12925, 2022.

11:05–11:12
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EGU22-1658
Fred Worrall et al.

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

  • DOC in first-order streams is significantly more oxidised than that in peat pore water but that there is no significant difference in organic carbon oxidation state down the peat profile.
  • The approach predicts the occurrence and speciation of N uptake and release in the peatland with N used and recycled.
  • The relatively high oxidation state of DOC in stream water means that acts as an end point for reaction.
  • Methanogenesis does not develop in deep peat as it requires too much energy to form.
  • Sulphate reduction did result in the formation of deep peat but in this catchment this was inadequate to account for the rate of peat formation.

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

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

11:12–11:19
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EGU22-7334
Ype van der Velde et al.

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

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

11:19–11:26
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EGU22-837
Markku Koskinen et al.

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

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

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

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

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

11:26–11:33
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EGU22-1537
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ECS
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On-site presentation
Marco Assiri et al.

Alpine peatlands occur in alpine, sub-alpine and mountain regions of the world and can be frequently found on the Alps as well as on the Andes, on the Tibetan Plateau, on the Australian Alps and in other regions of the world. Italian Alps host a large number of relatively small bogs and fens that can be found on gently sloping surfaces or in small valleys created by past glaciers. The high precipitation-low temperature climatic regime ensures large water availability to these ecosystems. The uniqueness and importance of peatlands in the Alpine territory is strongly linked to the countless ecosystem services that they provide, including their ability of sequestering and stocking carbon, providing habitat for flora and fauna including endangered species, supporting important biological diversity, being reservoir of high-quality freshwater during warm and dry seasons, and having the role of paleo-climate archives.

Despite their importance, the peatlands of the Alps are still poorly studied and incompletely mapped, probably because they are relatively small and difficult to access. The use of remote sensing techniques provides a possible solution, allowing extending local measurements to wider areas in a fast and cost-effective way. Our hypothesis is that the spatial distribution of different plant associations as well as the spatial variability of vegetation biomass may provide important information for mapping the spatial distribution of peat properties, thus making remote sensing an effective method for peatland studies.

In this work, we present the results obtained by using data collected by Unmanned Aerial Vehicles (UAVs) on the Val di Ciampo alpine peatland (Province of Belluno, northeast Italy) in July 2021. LiDAR data, hyperspectral data and aerial digital photos were simultaneously collected on an area of 88.000 m2. Field observations and measurements were performed in the same period, providing georeferenced ground information on vegetation and peat characteristics. Peat and vegetation samples were collected and analyzed in the lab. For each vegetation association we measured the height of plants and determined their above- and below-ground biomass based on 20 above-ground and 15 below-ground samples. As for the peat, we measured the peat thickness and determined the bulk density and the organic carbon content of 46 samples.

Our results show that some of the correlations found between the parameters that characterize different vegetation associations can be used to calibrate the data collected by UAVs and extend the results from point locations to the entire peatland. For example, we found that the aboveground biomass is significantly correlated (r = 0.81, p < 0.001) to the local average vegetation height, therefore both LiDAR data and the Digital Surface Model (DSM) extracted from the photos can be used to estimate and map the vegetation aboveground biomass. The correlation between the surface microtopography and the aboveground biomass will also be presented, as well as other correlations between vegetation patterns and peat depth and properties. The significance of combining UAVs multi-sensor data with field observations for the characterization of Alpine peatlands will be discussed.

How to cite: Assiri, M., Sartori, A., Vignoli, G., Massironi, M., and Silvestri, S.: Characterizing Alpine peatlands from drones: a case study , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1537, https://doi.org/10.5194/egusphere-egu22-1537, 2022.

11:33–11:40
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EGU22-3490
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Virtual presentation
Kunshan Bao

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

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