In Finland over half of the mire habitat types are endangered mainly due to drainage-induced succession towards more forested type ecosystems. Restoration is thought to be an important tool to improve the status of degraded peatlands. National and European Union level strategies to improve nature conservation have a target of increasing the allocation of restoration actions to peatlands in Finland. Thus, the effects of peatland restoration need to be understood.

Peatland drainage lowers the water table and exposes peat to decomposition. Restoration aims to raise the water table, but it simultaneously causes a new disturbance to surface layers often resulting in elevated nutrient and organic carbon concentrations in pore and runoff waters. Typically, the water quality disturbance starts to dampen out in the subsequent years after restoration. The rate and disturbance level depend on e.g., the actual measures, peatland type, and trophic level. To minimize and avoid impacts as well as to find the best restoration practices, knowledge of the long-term (over 10 years) effects of restoration measures is needed.

The hydrology of drained and restored peatlands and pristine counterpart mires have now been monitored for almost 15 years in the Parks and Wildlife Finland’s (Metsähallitus) peatland monitoring network. The data consists of high-frequency water table data and pore water quality measurements (four times per growing season) from 46 sites all over Finland with varying nutrient levels and openness (as one of the key indicators for peatland type). Additionally, ten sites have been tested for surface peat quality. Runoff water quality and quantity have been monitored in three of the pristine and five drained and restored sites. In this study, we report the long-term effects of peatland restoration on the water table and water quality in different peatland types. We also focus on understanding the connection of water quality variation in pore and runoff waters, intending to simplify the practical evaluation of peatland restoration success.

How to cite: Päkkilä, L., Marttila, H., Korhonen, P., Ikkala, L., Kareksela, S., and Ronkanen, A.-K.: Long-term changes in the pore and runoff water quality in restored boreal peatlands, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5237, https://doi.org/10.5194/egusphere-egu23-5237, 2023.

Peatlands are an important natural terrestrial carbon store. Any impacts on the drivers of hydro-biogeochemical processes in these ecosystems can be particularly severe. Climate change and degradation through drainages and ditches are changing peatlands dramatically. Degraded peats turn from powerful carbon sinks to emitters. They can also threaten drinking water supplies, as (heavy) metals can be leached from degraded peats along with dissolved organic carbon (DOC). However, quantifying DOC discharges from terrestrial to aquatic ecosystems is challenging. The hydro-biogeochemical processes occurring at the soil-aquatic interface are not only complex but also occur at different spatial and temporal scales. These processes depend on a variety of constantly changing external conditions such as temperature, nutrition- as well as oxygen availability. On top, there is no sensor available, which can measure the DOC concentrations of streams in situ and directly.

Here we investigated the DOC concentration in two nested catchments of two adjacent streams in the Ore Mountains of southern Saxony in Germany. One stream is dominated by mineral soils, while the other is dominated by (degraded) peat soils. Each of the four sites is equipped with YSI-EXO fDOM sensors. Further data comprise discharge, water temperature, turbidity and electric conductivity. A machine-learning algorithm (Random Forest) was trained to predict DOC concentration from the available data set (validation r² between 0.85 and 0.98). We investigated the gained 15-minute resolution DOC data on potential driving factors. Interestingly, the area-specific loads of the peat-dominated catchment with 3.5 mg C m^-2 a^-1 did not differ significantly from that of the mineral soil-dominated catchment with 3.1 mg C m^-2 a^-1. However, the loads over the year were almost twice as high as previously detected from data collected on a monthly basis. With the high-resolution DOC data, we can detect the drivers of extreme DOC concentrations (up to 40 mg l^-1) after heavy rainfall events in summer and constant high-level DOC concentrations of 20 mg l^-1 during snowmelt in winter. By applying the algorithm on DOC:DON ratios, we were further able to quantify the different sources of plant-based material from the peat soils and microbial-degraded material from the mineral soil-dominated catchment.

Previous DOC measurements, mostly based on 2-week to monthly measurements, likely greatly underestimate the contribution of DOC to C fluxes in ecosystems. For C-rich ecosystems such as Peatlands, this is particularly significant.

How to cite: Houska, T., Degenkolb, L., Brösing, M., Müller, I., Kaiser, K., Knorr, K.-H., Lau, M., Jackisch, C., and Kalbitz, K.: What causes rising DOC concentrations in streams from peat-affected catchments? Insights with high-resolution water quality analysis, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6146, https://doi.org/10.5194/egusphere-egu23-6146, 2023.

Intact peatlands provide crucial ecosystem services, regulating discharge by retaining water and providing high water quality by retaining solutes. These services can become compromised when peatlands become degraded by natural disturbances such as wildfire and drought. Such disturbances in traditionally non-fire prone regions will likely become more frequent and severe under future climates, potentially impacting downstream water quality. Understanding how fire and drought alter hydrological and biogeochemical processes in these regions is necessary for future risk assessment.

The 2018 Saddleworth moorland wildfire (England) offered a unique opportunity to study the combined impacts of severe wildfire and drought on stream water quality fed from a peatland-dominated catchment in a traditionally non-fire prone region (i.e., northern Europe). Capitalising on this event, our study aimed to (1) quantify stream chemistry changes and (2) understand patterns of element mobilisation and transport within the disturbed catchment. We evaluated concentration-discharge (C-Q) responses for nine variables (dissolved organic carbon, sulphate, Na, Ca, Pb, Zn, Al, Cu and turbidity) in five post-fire storm events over a nine-month period. C-Q responses were considered together with hysteresis and flushing indices (HI and FI, respectively) to further describe solute dynamics within storms.

Highest average concentrations of nutrients and base cations occurred in the storms immediately following the wildfire (~0 – 3 months post-fire) and average concentrations decreased into the autumn and spring (~3 – 9 months post-fire). In contrast, average metal concentrations began increasing in autumn and into the spring storms, coinciding with the timing of catchment re-wetting. Element behaviour patterns inferred from C-Q responses and HI/FI indices suggest rapid mobilisation and flushing of nutrients and base cations following the wildfire, and a shift to dilution behaviours in the spring storms. This shift indicates a change from surface transport and an exhaustion of readily available burnt materials. Metals consistently displayed delayed mobilisation, where concentrations peaked after the discharge peak, indicating a within-peat or distal headwater sources.

Our results suggest that seasonal re-wetting and rejuvenated hydrologic connectivity of the catchment following extreme drought was a dominating factor controlling source zone activation, mobilisation and transport of solutes in our catchment. Additionally, water quality impacts appeared to be limited to the first ~3 months following the wildfire, suggesting certain aspects of wildfire impacts in temperate peatlands may be short-lived. Our results contribute to defining potential water quality risks in drought and wildfire disturbed peat catchments under future climates.

How to cite: Marcotte, A. L., Limpens, J., Nunes, J. P., Khamis, K., Krause, S., Ullah, S., and Kettridge, N.: Impacts of wildfire and drought on hydrological connectivity and solute dynamics in a temperate blanket peat catchment, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2297, https://doi.org/10.5194/egusphere-egu23-2297, 2023.

Extensive erosional gully networks are commonplace in degrading peatlands. Gullying produces local water table drawdown and the increase in drainage density associated with gully networks increases hydrological connectivity between hillslope and channel. Peatland restoration methods commonly involve blocking of gullies with peat or timber dams to limit further erosion and promote higher water tables. Blocking is also demonstrated to attenuate channel flow in peatland catchments, suggesting that gully blocks can provide Natural Flood Management (NFM) benefits. Block design can be further optimised for flood attenuation purposes, such as including an outlet pipe through the block to provide dynamic in-storm storage. 

This paper compares the hydrological functioning of standard peat dams and piped-peat dams optimised for NFM from neighbouring microcatchments (<2.5 ha) in the Peak District National Park, UK. Pre-restoration discharge was monitored for 12 months prior to installation of 6 standard peat dams in one microcatchment and 10 piped-peat dams in the other. Bottom of reach discharge and individual dam pool height was recorded for the following 12 months. The series of piped-peat dams are demonstrated to have a higher impact on catchment discharge than standard peat dams, reducing peak discharges and increasing lag times. Standard peat dams provide little storage volume during storm events compared to the dynamic storage provided by the outlet in piped-peat dams. However, the requirement for maintenance of pipe-peat dams is identified, with pipe blockages compromising dynamic storage. These findings have implications for understanding of NFM benefits from standard and NFM optimised peat dams. 

How to cite: Johnston, A., Shuttleworth, E., Allott, T., Evans, M., Milledge, D., and Brown, D.: Comparing the NFM potential of standard and optimised peat blocks used in peatland gully restoration, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15359, https://doi.org/10.5194/egusphere-egu23-15359, 2023.

Peatlands cover over 20% of Ireland’s landscape, but most have been disturbed by human activities, including land use changes, which alter their natural hydrological functions. As a result, there is a growing need for restoration measures, which require reliable predictive modelling tools for assessing their feasibility and effectiveness. However, choosing a suitable hydrological model, particularly at the catchment scale, can prove challenging. While simplified conceptual rainfall-runoff models remain indispensable water management tools due to their fewer parameters, less input data, and low computational requirements, a critical issue is the limited number of conceptual models that have been successfully applied to peatlands. This is reflected in the lack of intercomparison studies that explore the performance of different model structures for different peatland types. Here, we report on the use of the Modular Assessment of Rainfall-Runoff Models Toolbox (MARRMoT) to analyze the performance of various model structures for three drained, restored, and natural Irish raised bogs. The framework provides a flexible platform for emulating (to a reasonable extent) and comparing different conceptual models within its structure. We emulated the Wageningen Lowland Runoff Simulator (WALRUS) model, which is designed specifically for lowland catchments, and compared it with the other 47 existing models within the framework. The performance of each model was assessed using four goodness-of-fit (GOF) measures. The results revealed a wide range of applicability, which led to several models being excluded from consideration. While the warm-up and calibration periods were limited to less than one year, the reported GOFs provide an invaluable insight into the dynamic performance of the models and the choice of model structure for simulating surface runoff in Irish raised bogs.

How to cite: Mozafari, B., O'Loughlin, F., Bruen, M., Donohue, S., Regan, S., and Renou-Wilson, F.: On the use of MARRMoT for rainfall-runoff modelling in Irish raised bogs, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7981, https://doi.org/10.5194/egusphere-egu23-7981, 2023.

Most northern peatlands are severely degraded by land use and drainage. Peatland restoration is an effective way to return the natural functions of peatlands in the catchment hydrology, discontinue the peat degradation and re-establish the long-term carbon sinks. The main aim of the rewetting is to direct the water flows back to the pristine routes and to increase the water-table levels. Conventional monitoring methods such as stand-pipe wells are typically limited to sparse locations and cannot give a spatially representative overview.

We introduced a novel high-resolution approach to spatially evaluate the surface flow path and wetness changes after restoration. We applied a UAS SfM (Unmanned Aerial System Structure-from-Motion) method supported by ubiquitous LiDAR (Light Detection and Ranging) data to produce digital elevation models, flow accumulation maps and SWI (SAGA Wetness Index) models for two boreal, minerotrophic restoration sites and their pristine control sites. The pristine sites were to represent natural changes and technology-related uncertainty.

According to our results, the hydrological restoration succeeded at the sites showing that the wetness increased by 2.9–6.9% and its deviation decreased by 13–15% 1–10 months after the restoration. Absolute changes derived with data from simultaneous control flights at the pristine sites were 0.4–2.4% for wetness and 3.1–3.6% for the deviation. Also, restoration increased the total length of the main flow routes by 25–37% while the controlling absolute change was 3.1–8.1%.

The validity of the topography-derived wetness was tested with field-gathered soil moisture samples which showed a statistically significant correlation (R² = 0.26–0.42) for the restoration sites but not for the control sites. We conclude the water accumulation modelling based on topographical data potential for assessing the changed surface flows in peatland restoration monitoring. However, the uncertainties related to the heterogenic soil properties and complex groundwater interactions require further method development.

How to cite: Ikkala, L., Ronkanen, A.-K., Ilmonen, J., Similä, M., Rehell, S., Kumpula, T., Päkkilä, L., Kløve, B., and Marttila, H.: UAS-SfM-derived Elevation Models to Evaluate Changes in the Flow Accumulation and Wetness in Minerotrophic Peatland Restoration Monitoring, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11830, https://doi.org/10.5194/egusphere-egu23-11830, 2023.

Montane peatlands are one of the most sensible ecosystems influencing water storage, runoff volume, dynamics of runoff response, and water chemistry. Peat bogs in headwater catchments are also highly vulnerable to climate change's effects, particularly climate warming. 

This study examines the changes in mid-latitude montane peatland in response to the effects of climate warming. We tested a methodological approach for monitoring peatland changes in transient climate using multispectral and thermal Unpiloted Aerial Vehicles (UAV) imaging, enabling the understanding of spatial and temporal dynamics of changes in the peat bog at a high level of spatial detail. Our research aims to test the hypothesis, assuming that the decrease in precipitation and rise in air temperatures translates to drying, degradation, and reduction of the retention potential of montane peatlands. 

The study was conducted on the Rokytka mountain peat bog in Šumava, Czech Republic, which represents the largest complex of mountain peat bogs in Central Europe. The monitoring took place in the 2018-19 growing season, which represented the culmination of a prolonged period of heat and drought in the region, and was compared with 2021-22, representing, on the contrary, a wet season. Images were taken from an altitude of 100 meters using a UAV platform and Micasense RedEdge/Altum and FLIR sensors. The UAV monitoring was combined with continuous hydrological and hydropedological monitoring and in-situ calibration measurements. 

The high-resolution data showed different trajectories of changes in spectral vegetation indices and thermal response in the montane peatland. Multispectral imaging showed a progression of changes in the extent of wetland areas in response to warming and drought. High-resolution thermal mapping using UAVs then showed differential land surface temperatures in different vegetation categories and peatland zones. 

The study showed that the response of montane peatlands to climate change is highly diversified, even at a high level of spatial detail, among different zones of the given peat bog. For montane peatlands in remote areas and with often limited access, UAV monitoring using multispectral and thermal sensors proved to be a reliable tool for determining and modeling changing environmental conditions.

How to cite: Langhammer, J., Lendzioch, T., and Vlček, L.: Multispectral and thermal UAV monitoring of peatland response to climate warming, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15100, https://doi.org/10.5194/egusphere-egu23-15100, 2023.

Drained peatlands have peculiar hydrological properties and cause environmental concerns due to carbon dioxide emissions and nutrient fluxes resulting from decomposition of organic matter in peat. As peat degradation is strongly controlled by soil moisture conditions, it is assumed that flexible water management methods, such as controlled drainage, can be used to reduce the environmental impacts of drained peatlands in agriculture. While peat soils have been extensively researched, there is a need for increased understanding about the hydrological responses of peatlands to various water management schemes. Research is needed to quantify these responses, and a promising approach is to exploit simulation models for describing peatland hydrology at field scale. The goal was to calibrate and validate a hydrological model FLUSH to describe the hydrology of an agricultural field block having a shallow peat cover and managed with controlled drainage. FLUSH is a spatially distributed three-dimensional (3D) process model which simulates the hydrology of agricultural fields managed with controlled subsurface drains and open ditches. The soil description of FLUSH includes both soil matrix and macropores accounting preferential flow. Richards equation and Mualem-van Genuchten water retention model are applied for subsurface flow. The modeled field block is located in Ruukki, northwestern Finland, and the study period was from August 2018 to October 2021. Groundwater table depth and drain discharge observations were used for the calibration and validation. The Kling-Gupta efficiencies for the simulated groundwater table depths in soil matrix and macropore domains were 0.50 and 0.47, respectively, during the calibration period, and 0.23 and 0.33 during the validation period. The efficiency values for the simulated drain discharge during the calibration and validation periods were 0.18 and 0.19, respectively. Limiting the modeled area to the block lead to cumulative drain discharges clearly smaller than the observations. The underprediction was improved by extending the modeled area beyond the block, which suggested a presence of a hydrological connection in terms of groundwater flux originating from outside the block. Thus, the surrounding environment can play a role in the hydrology of peatland fields, and this should be considered in water management design. Despite the large difference between observed and simulated cumulative drain discharges, the main hydrological dynamics were captured, and the model formed a useful tool to simulate drainage scenarios in peatlands and to study the role of the surrounding areas on field hydrology.

How to cite: Salla, A., Koivusalo, H., Salo, H., Tähtikarhu, M., Liimatainen, M., Marttila, H., and Läpikivi, M.: A model-based investigation of hydrological processes in an agricultural peatland field, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15555, https://doi.org/10.5194/egusphere-egu23-15555, 2023.

The presence of water in a peatland determines its proper functioning and is a prerequisite for its provision of ecosystem services other than water retention. Since the majority of degraded peatlands were drained for agriculture through the construction of ditches, the most common first step in the restoration of drained peatlands is rewetting through drain-blocking. The aim of this study was to analyze the hydrological response of three independent drained raised bogs in Norway (Aurstadmåsan, Midtfjellmosen and Kaldvassmyra) to ditch-blocking. The hydrological response to rewetting as well as the drain-blocking efficiency were assessed based on groundwater level monitoring conducted from 2015 to 2021 as a BACI design (Before-After-Control-Impact). The data was retrieved from water level loggers installed in piezometers placed in several locations at each of the sites. Rewetting technique used in the study sites included blocking the ditches draining the mires with peat dams. In each of the sites points with increased mean groundwater levels after rewetting were observed. It was also found, that the differences in precipitation before and after rewetting had no significant effect on groundwater levels. Both in Aurstadmåsan and Midtfjellmosen most of the piezometers reported an increase in average groundwater levels after rewetting. In Kaldvassmyra, 3 out of 8 piezometers reported an increase in mean groundwater levels. Even though in all sites precipitation was very similar before and after performed rewetting actions, comparison in Kaldvassmyra shows that the period after the implementation of restoration measures was noticeably drier. This might have inhibited the rewetting role of the dams in that site, which shows in the results. Considering the data from all impact piezometers, the groundwater levels increased by an average of 0.062 m. The same value for control piezometers was -0.003 m. The influence range of the ditch-blocking was 12.7-24.8 m, with the average of 17.2 m. Obtained results show that ditch-blocking might be an effective tool in restoring the hydrological conditions of peatlands, although it might be limited by meteorological factors, such as low precipitation. Assessment of the success of restoration should be integrated with the analyses of other conditions, including changes in vegetation cover or gas emissions (CO₂, CH₄, N₂O).

How to cite: Stachowicz, M., Osuch, P., Hansen, K. T., and Grygoruk, M.: Hydrological response to rewetting of drained peatlands – case study of three raised bogs in Norway, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9226, https://doi.org/10.5194/egusphere-egu23-9226, 2023.

Geomorphic and vegetation patterns within peatlands are strictly related, and reflect the interactions among topography, hydrogeology, and climate. Vegetation patterns are closely related to soil moisture, drainage patterns, bulk density and carbon content, and the spatial distribution of different plant species as well as the spatial variability of vegetation density may provide important information on key hydrogeological variables at the peatland scale. Therefore, the accurate mapping of vegetation patterns is a fundamental step to study the spatial distribution of peat properties and hydrogeological variables in the near-surface layer, where the roots of living plants develop, and peat accumulation and degradation processes occur. In this study we present the results obtained on two Alpine peatlands located in the Italian Dolomitic area, using field and UAV-based observations. Concurrent acquisitions of LiDAR, VIS/NIR Hyperspectral and VIS/NIR Multispectral sensors onboard of UAV systems were performed in July 2021 and July 2022. Field observations started in spring 2020 and ended in October 2022, including: water table summer monitoring (levels and temperature), soil sampling and analyses (bulk density, carbon content, peat layer thickness), vegetation sampling (plant associations, above- and below-ground biomass), and organic matter degradation assessment (based on the Tea Bag Index – TBI, Keuskamp et al. 2013). The combined analysis of field and UAV data allowed us to explore the correlation between vegetation, microtopography and hydrogeological patterns across the studied peatlands, determining the plant associations that best adapt to specific hydrogeological conditions (a phenomenon called “zonation”). Our results show that plant distribution, leaf area index and biomass are related to microtopography and water table levels and that they can be successfully mapped and monitored using UAV systems. Moreover, applying the TBI we explored the variability of the organic matter decomposition across the different plant associations as well as with depth (from the soil surface to the saturated zone). Our results show that the decomposition rate decreases with depth at all sites, while the stabilization factor increases, showing a significant correlation with the depth of the water table. Since the microtopography spatial variation is strongly linked to different soil moisture conditions, and therefore to different vegetation associations, we show that such associations can be used to map different hydrogeological conditions. The results of this study will be used to calibrate and validate an eco-hydrological model to forecast the future development of Alpine peatlands in different climate-change scenarios.

How to cite: Silvestri, S., Sartori, A., Assiri, M., Faelga, R. A., and Giambastiani, B. M. S.: A multi-sensor approach to the study of geomorphic, vegetation and hydrogeologic patterns of Alpine peatlands, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9984, https://doi.org/10.5194/egusphere-egu23-9984, 2023.

Northern peatlands are experiencing some of the most rapid climate warming on the planet, which is compounded by increases in the extent and severity of climate-related disturbances such as drought, wildfire, and permafrost thaw.  Cumulatively these changes lead to both peatland wetting and drying at various scales. Since 2005, we have maintained large-scale flooding and drought experiments in an Alaskan rich fen. While peatland science is dominated by the paradigm that deep catotelm C is protected from mineralization by lack of O₂ supply, our results show remarkable resilience or lack of sensitivity of ecosystem respiration to fluctuations in water table position. This presentation will outline the rationale and support for three hypotheses we are testing to explain this trend: 1) changes in food web dynamics between detrital and algal channels promotes resilience in peatland autotrophic respiration; 2) changes in plant species composition in response to wetting or drying, such as increases in sedge abundance affects soil redox pool recharge and ultimately controls the ratio of CO₂ to methane production; and 3) humic substances contribute to the regeneration of electron acceptor pools via electron shuttling, leading to more sustained anaerobic respiration rates than previously described.  Support for these hypotheses are not mutually exclusive, and demonstrate that the influence of hydrologic changes on peatland carbon emissions will be mediated by complex vegetation and soil processes.

How to cite: Turetsky, M., Kane, E., Euskirchen, E., Dieleman, C., Rober, A., Wyatt, K., Keller, J., Cox, W., and Webb, H.: The Alaska Peatland Experiment:  two decades of hydrologic experiments show resilience in peatland CO2 respiration, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10683, https://doi.org/10.5194/egusphere-egu23-10683, 2023.

Water table modeling in peatlands is often done on the large scale and, consequently, based on coarsely resolved models. The models commonly used in literature are often either not capable of modelling the full water cycle or they are not purely physically based. In particular in Bavaria there is a high number of small isolated peatlands with a dense drainage network, therefore a coarse model is not feasible. For rewetting success and climate impact analysis the fully integrated and largely physically based Mike She modelling software by DHI was used in the KliMoBay Project.

The main goal was to achieve a temporally and spatially highly resolved model enabling water table investigations for different rewetting stages as well as associated vegetation and soil changes.

For this purpose, the partially rewetted raised bog Königsdorfer Weidfilz in Bavaria was monitored and replicated in Mike She. Active and partially rewetted drainage ditches were implemented in the hydrodynamic model Mike Hydro and coupled with the Mike She model. After calibration and validation on twelve automatic water level gauges, scenario analyses were conducted. Compared with the climatic reference period (1961 – 1990), the dry year 2018 and the average year 2020 were modeled for three different scenarios: 1. current state, 2. drainage ditches deactivated, 3. vegetation and soil property succession after rewetting. The influence on the water table was analyzed based on a reference depth of - 0.15 m which is considered as an average threshold for climate impact. For this purpose, seasonal and annual mean water table maps were created, as well as standard deviation maps to portray high water table dynamics within the respective mean season.   

As the model results show, it is possible to investigate even small peatland areas for their rewetting potential. Furthermore, we could show the positive impact of rewetting measurements on reducing climate active areas with water levels below - 0.15 m in raised bogs. Vegetation and thus soil property changes in the model – which are assumed to occur after sufficient rewetting along with active acrotelm growth – increase the effect even more. Although, the impact of dry seasons is still significant, the resilience of the peatland increases.

Using the example of the partially rewetted raised bog we were able to proof, that areas with different drainage states could be modeled. The areas rewetted in the respective model scenario react similar to the areas already rewetted in nature. Thus, we assume that the method is capable for planning stages. Consequently, it can offer a descriptive decision support tool. However, the process of model setup, calibration and validation is rather time consuming. Regarding fen peatland management, further models can be set up considering the capability of Mike Hydro to model controllable weirs.

How to cite: Friedrich, S., Gerner, A., Gabriele, C., and Disse, M.: Scenario-based groundwater modeling of a raised bog with Mike She, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15608, https://doi.org/10.5194/egusphere-egu23-15608, 2023.

The hydrology of northern peatlands is increasingly recognized to be influenced by groundwater flow between peat and underlying mineral sediments. These hydrologic fluxes have been measured in peatlands of central and northern Maine where peatlands formed in depressions within the complex landscape left after the last glacial ice retreat. Although most of these peatlands formed on top of a low permeability confining glaciomarine clay, surface digital elevation maps and subsurface geophysical datasets (ground penetrating radar, electromagnetic and resistivity imaging) indicate that, in places, they are often in hydrogeological contact with eskers (glacial outwash deposits) and possibly even directly in contact with bedrock. Hydrogeological datasets, including direct hydraulic head observations and indirect observations of seepage fluxes, support the case that these points of hydrogeological contact exert a profound influence on the surface hydrology, including pool formation, and ecology of these peatland systems. The unique properties of peat, including the formation of pipe structures, result in highly focused discharges of mineralized water as evidenced from temperature sensing and aqueous geochemistry data (specific conductance, dissolved iron, dissolved manganese). These pipe networks may exert a control on carbon cycling in peatlands via the delivery of nutrients, or possibly by serving as conduits for the release of free phase gas stored in the deep peat. Preliminary observations using gas traps lend support to this hypothesis.

How to cite: Slater, L., Comas, X., Reeve, A., Moore, H., and Niedzinski, V.: The role of sub-peatland critical zone structure on the hydrology of northern peatlands, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4593, https://doi.org/10.5194/egusphere-egu23-4593, 2023.

Peat soils exist because the rate of accumulation of organic matter is faster than the rate of organic matter decomposition. This balance of rates can be in favour of net organic matter accumulation if: the rate of primary productive is relative high; the decomposition rate is relative slow; or, a combination of both. Slowing the decomposition rate has been ascribed to the presence of plants composed of decay-resistant components and to water-logged conditions. Water-logged conditions limit ingress of oxygen and oxygen is rapidly consumed by the supply of organic matter leaving decomposition dependent on other, less available and less energetically favourable terminal electron acceptors such as nitrate, sulphate and iron. The water-logged conditions can occur due to position in the landscape, high precipitation inputs, and/or restricted drainage within the peatland. Classic texts on peat formation refer to the development of restricted drainage within peat profiles but are vague on how it forms – for example “At first the porous structure survives, just as a wall with a few bricks removed does. But eventually the structure collapses. The dry bulk density increases abruptly” – Clymo and Pearce (1995). However, despite this processing being referred to in most texts the process and role of compaction in the formation of peat is not detailed nor has it been studied. Therefore, in this study we measure the initial development of peat from sphagnum moss and question which is more important in the development of peat soil – is it self-weight compaction or degradation - and are these two processes independent?

Using sphagnum moss mesocosms we compared the change in peat depth with the flux of CO₂ from the peats. Over periods of more than 1 year the surface recession and CO₂ flux were monitored in 12  sphagnum mesocosms relative to water table and climatic conditions.

The results show:

• Dry bulk density did not significantly change over the course of the experiment.
• The initial surface recession was between 1.7 to 35 % of depth with a median = 9.7%
• Young’s modulus had a median = 1.9 MPa ranging between 0.4 and 13.0 MPa.
• Given the values of the Young’s modulus calculated for these mesocosms then the viscosity varied between 2.2 and 20.4 Ns/m² with a median of 6.1 Ns/m². These calculations suggest that the sudden stress is readily adsorbed.
• After 214 days a median of 23.7 % surface recession had occurred or a median of a further 33% surface occurring after the initial surface recession.
• Comparison between the extrapolated CO₂ flux and the measured surface recession across the entire experiment between -2 and 75% with a median of 29% due to self-weight compaction. There is no apparent correlation between length of the experiment and proportion of the effect due to self-weight compaction.

This study has been shown that, although self-weight compaction was a major component of the development of the peat, the initially phases of peat development were dominated by degradation of the peat. Further that degradation was able to equilibrate with initial self-weight compaction.

How to cite: Worrall, F. and Howden, N.: How do peat soils form? Self-weight compaction versus decomposition in the early stages of peat development, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5099, https://doi.org/10.5194/egusphere-egu23-5099, 2023.

Peatlands are important sinks and/or sources of carbon, solutes, and elements of potential concern (e.g., Hg, As, Pb, Cu, Zn) to their surrounding environments. Minerogenic permafrost peatlands that receive input of elements from groundwater and weathering of bedrock and surficial materials accumulate substantial amounts of geogenic-derived elements over millennia, which are then frozen in place. As the Arctic cryosphere thaws due to 21^st. c climate warming, understanding of permafrost contaminant reservoirs and tracking their release is a growing challenge due to a lack of knowledge on the cumulative and interacting influences of bedrock and surficial geology, vegetation, climate, fire, and ecohydrology on contaminant accumulation in permafrost peatlands. We examined the Holocene history of two permafrost peatlands from the Northwest Territories, Canada, that are underlain by mineralized volcanic and metasedimentary (Daigle Lake peatland) and unmineralized granitoid (Handle Lake peatland) bedrock. Laboratory methods included pyrolytic speciation to determine the quality and quantity of solid organic matter; plant macrofossil and macroscopic charcoal analysis to reconstruct vegetation, peatland development, and fire history; testate amoebae to reconstruct paleohydrological conditions; and inorganic geochemical analyses to determine elemental concentration over time. Both sites have undergone several marked and broadly coincident hydrological shifts and phases of ecohydrological development. During the early Holocene (ca. 8000-5000 cal BP) initial shallow lake environments at both sites transitioned to rich fen and were colonized by Picea. Elevated concentrations of Zn (up to 65 mg^.kg^-1), Cu (up to 52 mg^.kg^-1), As (up to 140 mg^.kg-1), and Cr (up to 65 mg^.kg^-1) occur in the basal lacustrine sediments, particularly at the Daigle Lake peatland that is underlain by mineralized bedrock, but become lower in overlying material that accumulated in a fen setting. Depth to water table increased by almost 30 cm in the Handle Lake peatland between ca. 5900 and 4900 cal BP, coincident with the Holocene Thermal Maximum. At this time, local fires were severe and frequent at both sites and associated with elevated Hg (up to 50 µg^.kg^-1) in the peat. After this dry interval, the water table rose at ca. 3000 cal BP at the Handle Lake peatland and by ca. 2200 cal BP at the Daigle Lake peatland. Fire occurrence declined, coincident with the relatively cool and wet conditions of the Neoglacial interval. A bog was established at both sites between ca. 2700 and 2200 cal BP. Fire occurrence and the concentration of Hg (up to 175 µg^.kg^-1), As (up to 300 mg^.kg^-1), and Zn (up to 50 mg^.kg^-1) have increased over the past 1000 cal yrs, likely due to a combination of anthropogenic input of As and Hg associated with gold mining in the region and global industrialization as well as warming climate and permafrost thaw. This study illustrates the influence of ecohydrology and bedrock geology on the chemical stores of permafrost peatlands.

How to cite: Galloway, J. M., Gałka, M., Swindles, G. T., Parsons, M., Taylor, L., Ardakani, O., Wolfe, S. A., Morse, P. D., Amesbury, M., Patterson, R. T., Falck, H., and Palmer, M.: Ecohydrological and geological controls on contaminant reservoirs in degrading permafrost peatlands, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9683, https://doi.org/10.5194/egusphere-egu23-9683, 2023.

Permafrost peatlands are responding to recent high-latitude climate warming in dramatic fashion. These changes in terrain surface characteristics are affecting hydrology in a variety of ways. Increasing summer precipitation is leading to top-down thaw of permafrost across a variety of ecotypes. At smaller scales, studies are reporting the expansion of lateral thaw features and increased rates of thermokarst formation. Surface water plays a critical role in these processes. We have been combining site level field measurements, geophysics, remote sensing, and machine learning geospatial analyses to establish connections between the snowpack, vegetation, and permafrost thaw. The relationships we have identified allow projection of our site scale measurements across broader regions. This presentation summarizes results of recent studies by our research group at a variety of Interior Alaska peatland sites. In the first study, of the seasonal snowpack, we combined airborne hyperspectral and LiDAR measurements with machine learning methods to characterize relationships between ecotype and more than 26,000 snow end of winter snowpack measurements. We focused from 2014-2019 at three field sites representing common boreal ecoregion land cover types. These winters represent anomalously low (2016), typical mean, and high (2018) snowpacks. Hyperspectral measurements account for two thirds or more of the variance in the relationship between ecotype and snow depth. An ensemble analysis of model outputs using hyperspectral and LiDAR measurements yielded the strongest relationships between ecotype and snow depth. Since the seasonal snowpack often provides more than half of the yearly water equivalent these results have ramifications for surface water dynamics. In another study we used Landsat products to estimate fire-induced thaw settlement across the ice-rich Tanana Flats lowland in Interior Alaska that contains fens, bogs, and a variety of other wetland features. After linking fire areal extent, burn severity, land cover changes, and post-fire vegetation recovery we developed an object-based machine learning ensemble approach to estimate fire-induced thaw settlement from comparing repeat LiDAR to Landsat products. Our model delineated thaw settlement patterns across six unique fire scars and explained ~65% of the variance in LiDAR-detected elevation change. Results from a long term study of fen hydrology and climatology across Tanana Flats has tracked changes to hydrologic features and thermokarst development using historical image analysis, site scale measurements, and ground based geophysics. Repeat electrical resistivity tomography and high resolution ground surface elevation measurements identified thaw subsidence at a 10 year fire scar of more than a meter as a result of up to three meters of top-down permafrost thaw. At the same sites we have been able to quantify how lateral thaw of permafrost has led to the expansion of small ponds and bogs. We are now working to combine these geophysical and survey measurements with remote sensing information to project these land cover changes over a larger spatial extent.

How to cite: Douglas, T., Zhang, C., and Jorgenson, T.: Associations between peatland vegetation, the seasonal snowpack, and summer thaw processes in Interior Alaska permafrost with a focus on hydrologic ramifications, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10728, https://doi.org/10.5194/egusphere-egu23-10728, 2023.