BG3.8

Many peatlands in Central Europe are under unsustainable drainage-based land use with high greenhouse gas emissions counteracting the aims of the Paris Agreement. After decades of drained and intensive land use many peat bogs are in pitiful state. Rewetting can stop the carbon dioxide (CO₂) source function but may result in high methane (CH₄) emissions and eutrophication. Further, lack of diaspores my hamper the establishment of typical bog species. Restoration measures like topsoil removal (TSR) or spreading target vegetation propagules are known to improve restoration success in fen peatlands or after peat extraction. However, experience on restoration of bogs after previous agricultural use is scarce and the climate effects of these restoration measures including carbon losses from TSR are unknown.

We installed a field trial in a drained bog in North-West Germany to explore the effect of TSR and Sphagnum spreading on greenhouse (GHG) emissions. The trial consists of seven plots (~8 x 24 m each) representing the status quo—intensive grassland use—and six different restoration approaches. Two approaches are rewetting on the original surface with or without regular biomass harvesting. The remaining four represent TSR prior rewetting where two of the four were inoculated with Sphagnum spp. On all plots we measured GHG fluxes fortnightly using closed chambers to obtain two-year GHG budgets. We assessed the climate effects of the status quo and the six restoration approaches by applying a radiative forcing model to the GHG budgets and to published emission factors while incorporating the effect of TSR through different depletion scenarios of the exported topsoil carbon.

Compared to the status quo, rewetting alone reduced CO₂ emissions by ~75% but substantially increased CH₄ emissions, which were much higher than published emission factors for a similar peatland category. After TSR, on-site CO₂ emissions were close to 0 or—with Sphagnum spreading—net negative while CH₄ emissions remained very low. Based on our GHG budgets, TSR quickly becomes less climate warming than keeping the status quo and rewetting at the original surface. In contrast, based on emission factors, rewetting at the original surface is initially the least climate warming option. 

In general, the climatic effect of TSR is likely lowest when removing only as much topsoil as necessary to implement nutrient-poor and acidic conditions thereby ensuring rapid establishment of a Sphagnum carpet and by conserving the removed topsoil as long as possible. Here, the climate warming effect of TSR of ~30 cm in combination with rewetting roughly corresponds to the climate warming of rewetted nutrient-rich temperate peatlands without TSR. Therefore, from a climate perspective, we can recommend a shallow TSR of up to 30 cm for peat bog restoration given that the goal is to re-establish typical bog habitats.

How to cite: Jurasinski, G., Huth, V., Rosinski, E., Gutekunst, C., Koebsch, F., Hofer, B., Heinze, S., Ullrich, K., and Günther, A.: Topsoil removal and Sphagnum spreading improve the climate balance of peat bog restoration, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3357, https://doi.org/10.5194/egusphere-egu21-3357, 2021.

Restoring wetlands for climate mitigation purposes could provide an effective method to protect existing soil carbon stocks, as well as act as a negative emission technology by sequestering atmospheric carbon for 100-1000s of years. However, many peatlands have low productivity limiting carbon sequestration, while high productivity marshes often emit large amounts of methane. Studies on water level management to control methane emissions have shown differing results depending on wetland type, climate, as well as measurement method and duration. Here we show with multi-year flux measurements that water level changes were likely responsible for significantly reducing annual methane emissions. To assess management impacts on annual greenhouse gas budgets, continuous high frequency measurements of fluxes are needed, such as by eddy covariance. However, this method is less suited to monitor concurrent manipulation experiments to compare treatments.  We compared the impact of water level fluctuations by creating a second timeseries where water drawdown events were removed, which was then gap-filled by a random forest model trained only on measurements from periods when the water table was above the surface. These estimates were used to compare the annual budgets with the complete data and showed that annual methane emissions were up to 50% lower in years where water levels went sufficiently below the peat surface. This threshold was key, as only reductions in water depth above the surface were related to temporary increases in emissions. We further show that in some cases the drawdowns tipped the greenhouse gas budgets so that marshes were net greenhouse gas sinks, as long as the drawdown did not also reduce plant productivity through drought stress. In comparison, wetlands with average annual fluxes would require between approx. 50 and 200 years given current levels of net carbon uptake to offset high methane emissions and become cumulative greenhouse gas sinks. 

How to cite: Valach, A., Eichelmann, E., Hemes, K., Kasak, K., Knox, S., Oikawa, P., Szutu, D., Verfaillie, J., and Baldocchi, D.: Managing hydrology can reduce methane emissions of high-emitting freshwater marshes by half making them present-day net greenhouse gas sinks, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4393, https://doi.org/10.5194/egusphere-egu21-4393, 2021.

Most of the organic soils in Denmark are drained and used for agriculture. Greenhouse gas (GHG) emissions from these soils alone account for approximately 6-7 % of the total Danish emission. Rewetting, a relatively new climate change mitigation practice, of organic soils and peatland (i.e. lowland) ecosystems has the potential to reduce the net ecosystem GHG emission and over time turn the ecosystem to a net GHG sink. However, our knowledge of the ecosystem’s mitigation potential 50- or 100 years after abandonment is very limited and related to unknown interactions between soil biogeochemistry, vegetation type and growth and hydrology. Few studies have reported the GHG budgets of CO₂ and CH₄ for rewetted European peatland, and none includes the long-term response of these fluxes to rewetting. Continuous in-situ measurements of GHG emissions are complicated, time consuming and expensive which explains the data- and knowledge gap on long-term climate effects to some degree.  

Within the Danish research project RePeat, one of our main study-aims is to investigate how the long-term (0 – 71 years) ecosystem development (from grassland to secondary succession of woody vegetation) after rewetting impact the soil CO₂ and CH₄ fluxes in relation to changes in soil and biomass carbon stocks and biogeochemistry. We hypothesize that ‘rewetting and secondary succession of forest of farmed peatland will turn the ecosystem into a net carbon sink faster than if the ecosystem is maintained as extensively managed grasslands’. We expect that our research activities in 2021 and 2022 will allow us to test this hypothesis.

For this study, we have selected four abandoned/rewetted agricultural sites on organic drained soils that represent a chronosequence spanning 7 decades. Two of the sites have recently been rewetted or will be (site A in 2020 and B in 2021) and the other two sites (C, D) have been abandoned and left for secondary succession since 1994 and 1950, respectively. At each site, two subplots with 5 replicate collars serve to measure the net CO₂/CH₄ exchange by the static chamber approach and use of the Ultra-Portable Greenhouse Gas Analyzer model 915-0011 (© Los Gatos Research). Soil moisture- and temperature and groundwater depth are measured for each collar. Basic meteorological parameters (precipitation, barometric pressure, photosynthetically active radiation (PAR) and wind- speed and direction) are measured at- or nearby each site. In addition to the GHG, soil physical- and meteorological measurements, we will estimate above- and belowground biomass and collect soil- and groundwater samples for a biogeochemical characterization.

Our presentation will show the experimental setup and preliminary findings on CO₂/CH₄ fluxes and ecosystem hydrology for the four sites.

How to cite: Nielsen, A. S., Larsen, K. S., Vesterdal, L., Gundersen, P., and Christiansen, J. R.: Abandoned Peatland Ecosystem Response to Secondary Succession, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11064, https://doi.org/10.5194/egusphere-egu21-11064, 2021.

It was established recently that gravity drainage is inefficient on Kolkheti Lowland along the Black Sea coast of Georgia and that novel approaches are urgently recommend, such as implementing rewetting schemes to restore ecosystem services and enhance economic values of these areas through wet agriculture, biofuel production with native wetland species, and/or afforestation, to achieve sustainable outcomes in both ecologic and economic terms. Water Detection, Fractional Cover and Urbanization remote sensing tools, provided by Georgian Data Cube (comprising Landsat sensor Analysis Ready Data), developed recently with UNEP/GRID support, were applied on multi-year timescale basis for Kolkheti lowland to identify priority areas with high potential for rewetting. Water Detection tool allowed establishment of low effectiveness drainage areas, as demonstrated by high cumulative values for the presence of water, indicating water-logged areas as potential intervention sites for wet agroforestry. Water Detection combined with Fractional Cover tool allowed comparative analysis of non-photosynthetic vegetation and bare soil areas versus high water detection areas to single out those lands on the Kolkheti lowland, where drainage seems effective and dry agriculture is pursued versus those lands where drainage is not effective and dry agriculture is not actually happening. Urbanization tool can also be applied to detect human activities, such as agricultural activities, visualising those areas, which are subjected to active vegetation removal on an annual basis due to crop harvesting and those areas, where vegetation was not removed, staying vegetated most of the time, interpreted as abandoned agricultural lands. Regular patters combining non-use agricultural with cumulative water covered areas could thus help locate candidate sites for piloting wet agriculture on Kolkheti Lowland in Georgia. In addition to sustainable economic practices, rewetting could certainly benefit core ecological areas of Kolkheti Lowland, protected by both national designation as Kolkheti National Park and international designation as Central Kolkheti Ramsar Site.

How to cite: Matchutadze, I., Bakuridze, A., Abuladze, I., Shakarishvili, N., and Gvilava, M.: Time to "Rewet the Swamp" – Application of Georgian Data Cube to Elucidate Drainage Patterns and Potential for Wet Agriculture and Forestry on Kolkheti Lowland, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16511, https://doi.org/10.5194/egusphere-egu21-16511, 2021.

Almost all peatlands in the Netherlands are drained for agricultural purposes or in the past for peat extraction. What remains is a peatland area of about 300.000 ha of which 85 % is used for agriculture. As a result of peat oxidation, these areas are still subsiding by about 1 cm per year. Another effect is the enormous emission of CO₂, which contributes to about 4% of total Dutch greenhouse gas emissions. With the awareness of a changing climate and the need for protection against flooding of coastal areas, solutions are being searched to reduce or stop peat oxidation and coinciding land subsidence and CO₂ emission.

In this presentation we will show different management options (subsoil irrigation, pressurized subsoil irrigation, paludiculture) which are currently being tested in the Netherlands. They will be put into perspective of data from other European studies. These options all focus on increasing the groundwater table to lower oxygen intrusion and consequently lower aerobic decomposition. Depending on crop choices, water levels may need to stay 40 cm below the surface to maximize fodder plant yields, or go to surface level to increase peat ecosystem functions like C-sequestration. The management options range from maintaining the current land-use by elevating summer water levels, with submerged drainage, to the development of peat-forming plant species by complete rewetting. Data of the effects of these management options on CO₂ emission show that Sphagnum farming is the most promising mitigation option to reduce greenhouse gas emission from drained peatlands. It turned the land from a carbon and greenhouse gas source into a sink.

How to cite: van den Berg, M., Fritz, C., van de Riet, B., Weideveld, S., Gremmen, T., van den Elzen, E., Vroom, R., Geurts, J., and Lamers, L.: Which management option has the highest greenhouse gas reduction potential for drained peatlands?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8175, https://doi.org/10.5194/egusphere-egu21-8175, 2021.

In Germany, 90% of peatlands are drained and mostly used for agriculture. As a result, carbon storage and water retention capabilities are mostly lost. Instead, drained peatlands are significant sources of greenhouse gases. The comprehensive gain of near-natural peatlands and thus their restoration has increasingly come into focus in recent years. Until now, it has very rarely been possible to directly measure and investigate the changes in greenhouse gas emissions during rewetting. We have the unique opportunity to investigate the rewetting of two drained pre-alpine fens used as grassland in southern Bavaria with chamber measurements of CO₂, CH₄ and N₂O.

The first one in Karolinenfeld (60 km south-east from Munich) has an intensive management (with three cuts per year, application of manure/fertilizer and a really low water-table: mean value around 90cm). The other one in Benediktbeuern (60 km south-west from Munich) has an extensive management (with two cuts per year, no use of manure/fertilizer since 1990, and mean water-table around 30cm). For each study sites, we have several plots, which have significant different water-table depths. Since December 2019, CO₂, CH₄ and N₂O emissions are measured with closed chambers method. Climate data are monitored and recorded every half hour (as ground temperatures, air temperature, photosynthetic photon flux density, water-table depth, air pressure …). We also collected data of environmental parameters with biomass analyses, vegetation description, soil analyses, and we measure regularly vegetation indexes (NDVI and LAI).

During the first year of measurement, we already noticed a significant difference between the two study sites. The depth of the water table seems to be the major explanatory parameter for the different emissions. Moreover, the impact of the cuts on CO₂ emissions is notable, whereas we did not measure any difference after the application of fertilizer.

At the end of 2020 the Karolinenfeld has been rewetted while keeping the management types unchanged. Benediktbeuern will be rewetted during the year 2021. In order to achieve this goal, water management practices have been introduced using the existing drainage pipes in combination with a pumping system for subsurface irrigation. We expect to gain insight into the greenhouse gas exchange of peatlands according to water management and agricultural activities and to highlight the short-term effects of the transitional stage during and after rewetting. We also would like to determinate the key factors who drive the greenhouse gases emissions on grasslands according to different water management and land-use.

The work is part of the KliMoBay project, funded by the Bavarian State Ministry for the Environment and Consumer Protection through the European Regional Development Fund (ERDF).

How to cite: Brehier, C., Klatt, J., Schlaipfer, M., Meyer, H., and Drösler, M.: Effects of different land management strategies on greenhouse gas emissions from pre-alpine fens under grassland use., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10162, https://doi.org/10.5194/egusphere-egu21-10162, 2021.

Peat soils are an important carbon stock in the global carbon cycle containing more than two third of the atmospheric carbon amount (600 GtC of 760 GtC) despite their relatively small landmass of 3% worldwide. Drainage of peatlands contributes significantly to the enhanced global warming, as it allows oxygen to intrude the soil, intensifying aerobic microbial decomposition associated with carbon dioxide emission. Water management strategies that result in a raise in (summer) groundwater tables can have the opposite effect. These measures, such as raising the surface water level and/or the application of submerged drain subsurface irrigation systems, are already being applied. However, the outcome of these strategies remains debated and is still largely to be tested. We aim to explore the potential effects of these water management strategies on reducing GHG emission in peatlands.

We simulated the effects of several water management strategies on potential aerobic peat decomposition in a managed Dutch grassland on sedge peat under various hydrological and climatological conditions. To estimate potential microbial activity in the unsaturated zone two main drivers, temperature and water filled pore space (WFPS) were used. We found that increasing ditch water levels yields a decrease in potential aerobic peat decomposition independent of summer drought, hydrological regime and peat hydrological conductivity. Furthermore, we found that submerged drainage-irrigation systems tend to establish a stable moist zone relatively close to the warm soil surface in which potential microbial activity can remain high over the complete summer period. Due to these stable conditions, we expect peat decomposition in this layer to be high, possibly counteracting the effects of decreased aeration depth due to higher water tables. Submerged drainage-irrigation systems generally decrease potential microbial activity in environments with downward flow, but increase the activity in environments with upward flow. Increased benefits of the submerged systems are found for dry years, with high surface water levels and/or decreasing hydrological conductivity of the intact peat.

How to cite: Boonman, J., Hefting, M., van Huissteden, K., Dolman, H., and van der Velde, Y.: Reducing agricultural peatland CO2 emissions with hydrological conservation measures, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2640, https://doi.org/10.5194/egusphere-egu21-2640, 2021.

Peatlands store large amounts of organic carbon, which is subject to microbial decomposition and mineralization to either CO₂ or CH₄.  Drained peatlands are characterized by large horizontal variability in soil water contents and saturation, with dryer parts closer to the drainage ditches. The greenhouse gas (GHG) production in these systems is expected to be sensitive to temperature, substrate chemistry, oxygen concentration thus on soil water contents. Methane production should take place in the wetter parts, while respiration should dominate in drier parts. The seasonality of weather conditions modulates the spatial variability. In this complex situation, we are interested in how the seasonal weather variability triggers the microbial processes in the different micro-topographical situations and how this affects the overall GHG budgets of such sites.

We investigate two neighboring, drained ombrotrophic bogs in Norway close to Trysil, Innlandet, 61.1N- 12.25E, 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 chamber method to examine the seasonality of GHG production at microsites that cover some contrasting local situations with in the large range of small scale spatial heterogeneity. With eddy covariance CO₂ and CH₄ flux measurements, we integrate over a larger spatial scale, with, however, shifting footprints depending on weather conditions and wind direction. We present a comparative  analysis of 1.5 years continuous measurements, where we examine shifting spatial patterns of GHG production at different scales and relate them to soil conditions.

While the CO₂ fluxes compared very well between the two investigated sites, the CH₄ fluxes in the lower and wetter of the two sites (North) was higher and their spatial variability was lower than in the South site. Only in the South site, the CH₄ fluxes correlated with the coverage of well drained versus less well drained areas. We will present results on how the spatial variability changed with the seasonality of soil temperatures and the water table.

The automated chambers (five chambers within each footprint of the eddy flux towers) 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 ground water depth at both sites. N₂O emissions were observed in short events during the early summer season. Overall, there was a good alignment of fluxes measured with eddy flux and chamber technologies.

Information on factors that constrain the spatio-temporal variability are important for estimating areal GHG budgets and for predicting possible effects of peatland management, such as draining or re-wetting on the climate effects from these ecosystems.  From the results, we expect higher effects of peatland restoration on GHG budgets in the South site.

How to cite: Ibrom, A., Pirk, N., Steenberg Larsen, K., Avila, L. M., Kissas, K., and Larsen, P.: Spatial variability of greenhouse gas fluxes in two drained Northern peatlands, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8829, https://doi.org/10.5194/egusphere-egu21-8829, 2021.

Land-use change in tropical peatlands substantially impacts emissions of methane (CH₄) and nitrous oxide (N₂O) in addition to emissions of carbon dioxide (CO₂). However, assessments of peat GHG budgets are scarce and the contributions of CH₄ and N₂O remain highly uncertain. The objective of our research was to assess changes in peat GHG flux and budget associated with peat swamp forest disturbance and conversion to oil palm plantation and to evaluate drivers of variation in trace gas fluxes. Over a period of one and a half year, we monitored monthly CH₄ and N₂O fluxes together with environmental variables in three undrained peat swamp forests and three oil palm plantations on peat in Central Kalimantan. The forests included two primary forests and one 30-year-old secondary forest. We calculated the peat GHG budget in both ecosystems using soil respiration and litterfall rates measured concurrently with CH₄ and N₂O fluxes, site-specific soil respiration partitioning ratios, and literature-based values of root inputs and dissolved organic carbon export. Peat CH₄ fluxes (kg CH₄ ha^-1 yr^-1) were insignificant in oil palm (0.3 ± 0.4) while emissions in forest were high (14.0 ± 2.8), and larger in wet than in dry months. N₂O emissions (kg N₂O ha^-1 yr^-1) were highly variable spatially and temporally and similar across land-uses (5.0 ± 3.9 and 5.2 ± 3.7 in oil palm and forest). Temporal variation of CH₄ was controlled by water table level and soil water-filled pore space in forest and oil palm, respectively. Monthly fluctuations of N₂O were linked to water table level in forest. The peat GHG budget (Mg CO₂ equivalent ha^-1 yr^-1) in oil palm (31.7 ± 8.6) was nearly eight times the budget in forest (4.0 ± 4.8) owing mainly to decreased peat C inputs and increased peat C outputs. The GHG budget was also ten times higher in the secondary forest (10.2 ± 4.5) than in the primary forests (0.9 ± 3.9) on the account of a larger peat C budget and N₂O emission rate. In oil palm 96% of emissions were released as CO₂ whereas in forest CH₄ and N₂O together contributed 65% to the budget. Our study highlights the disastrous atmospheric impact associated with forest degradation and conversion to oil palm in tropical peatlands and stresses the need to investigate GHG fluxes in disturbed undrained lands.

How to cite: Swails, E., Hergoualc'h, K., Verchot, L., and Lawrence, D.: Contributions of methane and nitrous oxide to peat greenhouse gas emissions from forests and oil palm plantations in an Indonesian peatland, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10119, https://doi.org/10.5194/egusphere-egu21-10119, 2021.

ABSTRACT

Drained peatlands often act as carbon source and their drainage characteristics can be challenging to accommodate in biogeochemical models. This study uses the ECOSSE process-based  biogeochemical model [to simulate water-table level and CO₂ fluxes (heterotrophic respiration) _[1]], and empirical data from two Irish drained peatlands: Blackwater and Moyarwood, which were partly rewetted (both sites are extensively described in earlier studies _[2]). Here we explain details on the development of a new drainage factor with seasonal variability Dfa(i) for drained peatlands, based on our recently published work _[3]  that we hope can contribute towards the potential future development of IPCC Tier 3 emissions reporting. The Dfa(i) was developed using empirical data from Blackwater drained bare-peat site (BWdr) and its application was further tested at the Moyarwood site under drained (MOdr) and rewetted conditions (MOrw) _[3]. The development of the Dfa(i) was carried out in three main steps _[3]: 1 - identification of the ‘wt-discrepancy event’; 2 - development of Dfa without seasonal variability, and 3 - accounting for seasonal variability and development of Dfa(i). Dfa(i) was then applied to the rainfall inputs for the periods of active drainage in conjunction with the measured water-table inputs _[3]. As explained in our published work _[3], the results indicate that the application of Dfa(i) could improve the model performance to predict water-table level (BWdr: r² = 0.89 MOdr: r² =  0.94); and CO₂ fluxes [BWdr: r² = 0.66 and MOdr: r² = 0.78) under drained conditions, along with ability of the model to capture seasonal trends _[2]. The model simulation of CO₂ fluxes at MOrw site was also satisfactory (r²=0.75); however, the MOrw water-table simulation results suggest that additional work on the water model component under rewetted conditions is still needed _[3]. We further discuss our insights into potential opportunities for future additional improvements and upgrading of the ECOSSE model water module.

Acknowledgements

The authors are grateful to the Irish Environmental Protection Agency (EPA) for funding the AUGER: Project (2015-CCRP-MS.30) under EPA Research Programme 2014–2020. Full acknowledgements are provided in Premrov et. al (2020) _[3].

Literature

[1] Smith, J., et al. 2010. ECOSSE. User Manual.

[2] Renou-Wilson, F., et. al. 2019. Rewetting degraded peatlands for climate and biodiversity benefits: Results from two raised bogs. Ecol. Eng. 127:547-560.

[3] Premrov, A., D. Wilson, M. Saunders, J. Yeluripati and F. Renou-Wilson (2020). CO₂ fluxes from drained and rewetted peatlands using a new ECOSSE model water table simulation approach. Sci. Total Environ. (https://doi.org/10.1016/j.scitotenv.2020.142433; on-line 2020; in print Vol. 754, 2021; under CC BY 4.0).

How to cite: Premrov, A., Wilson, D., Saunders, M., Yeluripati, J., and Renou-Wilson, F.: Development of new drainage factor in ECOSSE model to improve water dynamics and prediction of CO2 fluxes from drained peatlands, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1871, https://doi.org/10.5194/egusphere-egu21-1871, 2021.

Nutrient rich peat soils have earlier been shown to loose carbon despite higher photosynthesis and litter production compared to nutrient poor soils, where instead carbon accumulated. To understand this phenomena data from two drained Finnish sites, nutrient poor Kalevansuo and nutrient rich Lettosuo, was combined with a process-oriented model (CoupModel). Uncertainty based calibrations were made using eddy-covariance data (hourly values of net ecosystem exchange) and tree growth data. The model design was three vegetation layers: trees, smaller vascular plants and a bottom layer with mosses, all with different LAI and degree of coverage. Adding a moss layer was a new approach, having a modified physiology compared to vascular plants. Soil organic carbon was described by two separate litter pools for vascular plants and mosses together with a common inert pool of decomposed organic matter. Over a period of 10 years the model showed similar photosynthesis rate for the two sites but higher biomass accumulation for the fertile stand. Moss biomass did not increase, instead mosses delivered high litter inputs with low turnover rates compared with litter from vascular plants. Both the soil organic carbon received from vascular plant litter and the old decomposed matter declined by time, while litter originating from mosses was accumulating by time. Large differences between the sites were obtained during dry spells where soil heterotrophic decomposition was enhanced in the vascular plants dominated site, due to a larger water depletion by roots. Important for carbon accumulation in the poor soil was the mosses, adding larger litter quantities with a resistant quality together with less water depletion in dry spells.

This project was funded by the Swedish Research Council FORMAS, the Research Council of Norway (MYR-project), and the Swedish strategic research area BECC.

How to cite: Kasimir, Å. and Jansson, P.-E.: Importance of mosses and vascular plants in peat soil carbon sequestration, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9170, https://doi.org/10.5194/egusphere-egu21-9170, 2021.

Mathematical models of peatland growth have been developed for many purposes, including understanding the effect of past or future climate change on peatland carbon accumulation. This is important because peatland contains a vast amount of carbon and has a significant role in the global carbon cycle through carbon dioxide and methane exchange with the atmosphere. In general, the models produced so far suffer from the fact that the mechanical process has an essential role in the peatland carbon stock resilience because they only focus on ecohydrological feedback. We propose a one-dimensional mathematical model that includes ecological, hydrological, and mechanical feedback on the peatland through the poroelasticity concept, which coupling between fluid flow and solid deformation. The formulation is divided into two categories, fully saturated and unsaturated, to accommodate peatland characteristics. We compare the numerical solution of the fully saturated case with analytical solutions of Terzaghi’s problem for validation. We assume that peat is an elastic material with flat, impermeable, and stiff substrate properties.  Based on the initial simulation results,  we find that compression reduces the thickness of acrotelm, leading to the shorter residence time of plant litter, and consequently, higher cumulative carbon is obtained. Furthermore, mechanical deformation of the pore structure effectively maintains carbon stock in the peatland against climate change because it reduces water table depth fluctuations.

How to cite: Mahdiyasa, A., Large, D., Muljadi, B., and Icardi, M.: Modelling the effect of mechanical deformation on the peatland carbon stock resilience, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4530, https://doi.org/10.5194/egusphere-egu21-4530, 2021.

It is well known that C accumulation rates are much higher when focusing on short-term measurement periods in areas with active peat growth when compared to the net C storage at longer timescales as obtained from palaeo-studies. When selecting effective management options that aim to sustain or increase rates of peat development and, hence, C sequestration, a detailed insight into the factors controlling C storage in peatlands at longer timescales is therefore required. Several peatland models have been developed to simulate long-term peatland development and such models thus can be a useful tool to evaluate the effect of environmental changes and management on peatland dynamics at centennial to millennial scales. Many of these models assume the peat to form in a geomorphically stable environment. However, for river floodplains these assumptions cannot always be made. In temperate Europe for example, many river floodplains have known phases of active peat growth throughout the Holocene, influenced by the local geomorphic dynamics of the river channel(s) and associated sediment dynamics. In addition, many restoration efforts in floodplain environments are accompanied by allowing the river channel(s) to behave more freely, with increased meandering and more natural channel dynamics. As these dynamics are currently lacking in peatland models, a detailed assessment of the interactions between river channel(s) and the adjacent peatland in terms of long-term peat growth and carbon accumulation remains difficult.

Here, we developed a new peatland model, specifically designed for alluvial environments, by modifying an existing local peat growth model (1D version of Digibog), coupled with a raster-based river basin hydrology model (STREAM). This model allows to assess the effect of changes in both the river hydrology and local river channel properties on alluvial peatland development and the associated carbon dynamics. The model was applied at two contrasting lowland river basins in northern Belgium, located in the European loess (Dijle river) and sand (Grote Nete river) belts. Local peat growth was simulated at an annual resolution over a period of 10,000 years under a range of climate and land cover scenarios, as well as varying river channel characteristics (number of channels, channel dimensions, channel roughness and channel slope).

The results demonstrate that changes in river discharge through regional climate or land cover changes have a negligible effect on the floodplain peat growth as these changes mostly affect the magnitude of peak discharges. In contrast, the configuration of the local river network such as the number of river channels and their position relative to the peatland surface show to have a strong effect on the equilibrium peat thickness. Especially the number of drainage channels strongly affects the peat thickness with a fourfold reduction in number of channels leading to a threefold increase in simulated peat thickness. This demonstrates that limiting the number of drainage channels in a floodplain and raising the elevation of the channel bed can be effective strategies in stimulating floodplain peat formation and allow to quantify the long-term carbon sequestration potential of these different management practices.

How to cite: Swinnen, W., Broothaerts, N., and Verstraeten, G.: Modelling peatland development in temperate alluvial environments, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7136, https://doi.org/10.5194/egusphere-egu21-7136, 2021.