Project

WETSCAPES

Goal: WETSCAPES aims to provide a scientific basis for sustainable utilization of rewetted, formerly degrading peatlands and coastal areas. WETSCAPES supports research and development in an internationally competitive structure focusing on primary production, matter dynamics and transport, gas fluxes and peat formation.
The project is funded by the European Union Social Fund through the Excellence Initiative of Mecklenburg Western Pomerania.

Date: 1 January 2017 - 31 December 2020

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Project log

Wakene Negassa
added a research item
Restoring drained peatlands has been practiced to mitigate climate change, regulate water quality, and restore biodiversity. However, no information is available on the long-term impact of drainage and restoration of peatlands on total sulfur (S t), fractions, and S species. We investigated the long-term drained and restored forested and coastal peatlands and percolation mires using the sequential S fractionation and S K-edge X-ray near-edge absorption structure (XANES) spectroscopy analysis to address this knowledge gap. The S t concentrations in the drained forested peatland and percolation mire were low by 4 and 1.5 folds compared to their respective restored peatlands at the topsoil horizons. Similarly, the H 2 O-S and NaH 2 PO 4-S fractions in the drained forested peatland (28 and 18 mg kg − 1) were lower than in the restored forested peatland (165 and 166 mg kg − 1). However, the S fractions were higher in the drained percolation mire (449 and 247 mg kg − 1) than in the restored percolation mire (150 and 41 mg kg − 1). The relative proportion of the residual-S fraction (70-97% of S t) was equivalent to the relative proportion of organic S species (76-97% of S t) derived from the XANES analysis. The XANES analysis revealed the reduced organic S (44-62%), organic S with intermediate oxidation states (16-47%), strongly reduced (0-21%) and oxidized inorganic S species (4-12%) of the S t. The results indicate that long-term restoration conserved S t , decreased labile S fractions and enriched the strongly reduced inorganic and organic S species.
Wakene Negassa
added a research item
Understanding soil organic matter concentration (SOM) and chemistry in different peatlands can help design appropriate management practices for the sustainable use of peatland agroecosystems. However, detailed information on characteristics of SOM concentration and chemistry is not available for most peatland agroecosystems in general and in northern Germany in particular. In this study, we investigated the SOM concentration and chemistry of drained and rewetted percolation mires, forest and coastal peatlands. We used simple chemical analysis, pyrolysis field ionization mass spectroscopy (Py-FIMS), and carbon and nitrogen X-ray absorption near-edge structure (XANES) spectroscopy. The total organic carbon (C org), total nitrogen (N), and total sulfur (S) contents were significantly (P < 0.05) different among the peatlands. The C org at the surface horizons ranged from 164 to 373 g kg −1 , and these values were lower than that of the subsurface horizons of the studied peat-lands except for the drained alder carr forest and coastal peatlands. The Py-FIMS indicated that the labile SOM compound classes (carbohydrates, phenols, and lignin monomers, and amino acids, peptides, and amino-sugars) and stable SOM compounds classes (lignin dimers, heterocyclic nitrogen compounds, and nitriles) were abundant at the surface horizons. However, the stable compound classes such as lipids, alkanes, alkenes, fatty acids, n-alkyl esters, and suberin were more abundant at the subsurface horizons than the surface horizons. The carbon K-edge spectra revealed that aromatic C, carboxylic C, O-alkyl, and aliphatic C were the predominant C functional groups, whereas N K edge spectra indicated that the amide group was the predominated N functional group. The SOM concentrations and some compound classes were higher in the rewetted sites of alder carr forest peatland (more carbohydrates, suberin and fatty acids) and of percolation mires (more lignin dimers, lipids and alkylaromatics). The results indicate that the effects of rewetting peatlands on SOM concentration and chemistry depend on peatland type.
Wakene Negassa
added a research item
Drained peatlands have been rewetted for restoration in Europe and North America for about 25 years. However, information on spatial variability of soil chemical and biochemical properties in long-term drained and restored peatlands is insufficient to design appropriate research methods and soil sampling protocols for monitoring biogeochemical processes. The study aimed to examine the influence of long-term drainage and rewetting of peatlands on smallscale spatial variability of the soil chemical properties and enzyme activities. We collected 400 soil samples from the 0-15 cm and 15-30 cm soil depths of a drained and a corresponding rewetted peatland. The number of grid cells was 100 for each of the drained and the rewetted peatland, and the size of each grid cell was 3 m × 3 m. We analyzed 17 soil parameters from the surfaces and 14 from the subsurface of both sites. The variability (range, SD, and CV) of all the soil properties was higher in the drained peatland than in the restored peatlands except for the soil pH. The geostatistical analysis revealed only the soil pH, acid phosphatase, β-glucosidase, and arylsulfatase activities disclosed the strong spatial dependency at the ≤5 m semivariance range in the drained peatland. However, more than 80% of the soil properties showed a strong spatial dependence within the 4-20 m semivariance ranges in the restored peatland. The strong spatial dependencies of all the soil properties in the long-term restored peatland conclusively call for the spatial soil sampling and geostatistical data analysis methods to capture substantial spatial variability that has important implications in degraded peatland restoration.
Alba Anadon-Rosell
added a research item
Human-driven peatland drainage has occurred in Europe for centuries, causing habitat degradation and leading to the emission of greenhouse gases. As such, in the last decades, there has been an increase in policies aiming at restoring these habitats through rewetting. Alder ( Alnus glutinosa L.) is a widespread species in temperate forest peatlands with a seemingly high waterlogging tolerance. Yet, little is known about its specific response in growth and wood traits relevant for tree functioning when dealing with changing water table levels. In this study, we investigated the effects of rewetting and extreme flooding on alder growth and wood traits in a peatland forest in northern Germany. We took increment cores from several trees at a drained and a rewetted stand and analyzed changes in ring width, wood density, and xylem anatomical traits related to the hydraulic functioning, growth, and mechanical support for the period 1994–2018. This period included both the rewetting action and an extreme flooding event. We additionally used climate-growth and climate-density correlations to identify the stand-specific responses to climatic conditions. Our results showed that alder growth declined after an extreme flooding in the rewetted stand, whereas the opposite occurred in the drained stand. These changes were accompanied by changes in wood traits related to growth (i.e., number of vessels), but not in wood density and hydraulic-related traits. We found poor climate-growth and climate-density correlations, indicating that water table fluctuations have a stronger effect than climate on alder growth. Our results show detrimental effects on the growth of sudden water table changes leading to permanent waterlogging, but little implications for its wood density and hydraulic architecture. Rewetting actions should thus account for the loss of carbon allocation into wood and ensure suitable conditions for alder growth in temperate peatland forests.
Haitao Wang
added a research item
A highly resolved taxonomy for ammonia-oxidizing archaea (AOA) based on the alpha subunit of ammonia monooxygenase (amoA) was recently established, which uncovered novel environmental patterns of AOA, challenging previous generalizations. However, many microbiome studies target the 16S rRNA gene as a marker; thus, the usage of this novel taxonomy is currently limited. Here, we exploited the phylogenetic congruence of archaeal amoA and 16S rRNA genes to link 16S rRNA gene classification to the novel amoA taxonomy. We screened publicly available archaeal genomes and contigs for the co-occurring amoA and 16S rRNA genes and constructed a 16S rRNA gene database with the corresponding amoA clade taxonomy. Phylogenetic trees of both marker genes confirmed congruence, enabling the identification of clades. We validated this approach with 16S rRNA gene amplicon data from peatland soils. We succeeded in linking 16S rRNA gene amplicon sequence variants belonging to the class Nitrososphaeria to seven different AOA (amoA) clades, including two of the most frequently detected clades (Nitrososphaerales g and d clades) for which no pure culture is currently available. Water status significantly impacted the distribution of the AOA clades as well as the whole AOA community structure, which was correlated with pH, nitrate, and ammonium, consistent with previous clade predictions. Our study emphasizes the need to distinguish among AOA clades with distinct ecophysiologies and environmental preferences, for a better understanding of the ecology of the globally abundant AOA.
Haitao Wang
added a research item
In the last decades, rewetting of drained peatlands is on the rise worldwide, to restore their significant carbon sink function. Despite the increasing understanding of peat microbiomes, little is known about the seasonal dynamics and network interactions of the microbial communities in these ecosystems, especially in rewetted fens (groundwater-fed peatlands). Here, we investigated the seasonal dynamics in both prokaryotic and eukaryotic microbiomes in three common fen types in Northern Germany. The eukaryotic microbiomes, including fungi, protists and microbial metazoa, showed significant changes of their community structures across the seasons in contrast to largely unaffected prokaryotic microbiomes. Furthermore, our results proved that the dynamics in eukaryotic microbiomes in the rewetted sites differed between fen types, specifically in terms of saprotrophs, arbuscular mycorrhiza and grazers of bacteria. The co-occurrence networks also exhibited strong seasonal dynamics which differed between rewetted and drained sites, and the correlations involving protists and prokaryotes were the major contributors to these dynamics. Our study provides the insight that microbial eukaryotes mainly define the seasonal dynamics of microbiomes in rewetted fen peatlands. Accordingly, future research should unravel the importance of eukaryotes for biogeochemical processes, especially the under-characterized protists and metazoa, in these poorly understood ecosystems.
Anke Günther
added a research item
Many raised bogs in Central Europe are in an unfavorable state: drainage causes high emissions of carbon dioxide (CO2) and nitrous oxide (N2O), while rewetting may result in high methane (CH4) emissions. Also, the establishment of typical bog species is often hampered during restoration. Measures like topsoil removal (TSR) or introduction of target vegetation are known to improve restoration success in other systems, but experiences on bogs after long-term agricultural use are scarce and their climate effects including carbon losses from TSR are unknown. In a field trial in north-western Germany, consisting of seven plots (intensive grassland, IG, and six restoration approaches), we explored the effects of rewetting, TSR and Sphagnum introduction on greenhouse gas (GHG) emissions. We measured GHG fluxes to obtain two-year GHG budgets and applied a radiative forcing model to assess the time-dependent climate effects. Existing uncertainty of decomposition processes in the translocated topsoil has been incorporated by different topsoil accounting scenarios. According to our data, rewetting alone reduced CO2 emissions by approximately 75% compared to IG, but substantially increased CH4 emissions. After TSR and rewetting, on-site CO2 emissions were close to zero or, with Sphagnum introduction, net negative while CH4 emissions remained very low. The climatic warming effect of TSR including C export becomes less climate warming than rewetting nutrient-rich peatlands after a few decades. For raised bog restoration, we therefore recommend a TSR sufficient to achieve nutrient-poor and acidic conditions needed for rapid Sphagnum establishment.
Anke Günther
added a research item
Small water bodies including drainage ditches can be hotspots for methane (CH4) emissions from peatlands. We assessed the CH4 emissions of a drained and a rewetted temperate fen including emissions of managed and unmanaged drainage ditches over the course of 2.5 years, covering three vegetation periods. Ditch CH4 emissions in the rewetted fen were significantly higher than in the drained fen. In the rewetted fen ditches contributed up to 91% of the annual CH4 budget, despite covering only 1.5% of the area. In the drained fen CH4 emissions were solely made up of ditch emissions. When including CH4 uptake by the peat soil, the CH4 balance of the drained fen was neutral. Dissolved organic carbon concentrations likely had an enhancing effect on CH4 emissions while nitrate and sulfate in the ditch water seem to have had an inhibitory effect. Air and water temperature controlled seasonal variability of ebullitive as well as diffusive CH4 emissions. Ebullition contributed less than 10% to the overall CH4 budget in the ditches. Drainage ditches represent a hotspot of CH4 emissions and need therefore be taken into account when assessing the success of rewetting projects of peatlands.
Sate Ahmad
added a research item
Fens belong to the most threatened ecosystems in Europe. Maintaining a high water table through rewetting is an effective measure to rehabilitate many of their ecosystem functions. However, the impact of meteorological conditions such as vapor pressure deficit (VPD) and precipitation on water tables is still unclear for rewetted fens. Here, we compare the impact of meteorological factors on water table dynamics in a drained and a rewetted fen, using multiple regression with data from continuous high-resolution (temporal) water level monitoring and weather stations. We find that an increase in the daily mean VPD causes a higher drop in the water table at the drained and degraded fen compared to the rewetted fen. Precipitation contributes to recharge, causing the water table to rise higher at the drained site than at the rewetted site. We attribute the differential influence of meteorological conditions on water table dynamics to different soil specific yield values (i.e., water storage capacity) largely driven by lower water table position at the drained site. Our study underlines the importance of understanding how and why water tables in peatlands vary in response to meteorological factors for management decisions (e.g., rewetting). Continuous monitoring of water table and vegetation development in rewetted fen peatlands is advisable to ensure long-term success especially under climate change conditions and associated drought events.
Florian Beyer
added a research item
The rewetting of peatlands is regarded as an important nature-based climate solution and intended to reconcile climate protection with the restoration of self-regulating ecosystems that are resistant to climate impacts. Although the severity and frequency of droughts are predicted to increase as a consequence of climate change, it is not well understood whether such extreme events can jeopardize rewet-ting measures. The goal of this study was to better understand drought effects on vegetation development and the exchange of the two important greenhouse gases CO 2 and CH 4 , especially in rewetted fens. Based on long-term reference records, we investigated anomalies in vegetation dynamics, CH 4 emissions, and net CO 2 exchange, including the component fluxes of ecosystem respiration (R eco) and gross ecosystem productivity (GEP), in a rewetted fen during the extreme European summer drought in 2018. Drought-induced vegetation dynamics were derived from remotely sensed data. Since flooding in 2010, the fen was characterized by a patchy mosaic of open-water surfaces and vegetated areas. After years of stagnant vegetation development, drought acted as a trigger event for pioneer species such as Tephroseris palustris and Ranunculus sceleratus to rapidly close persistent vegetation gaps. The massive spread of vegetation assimilated substantial amounts of CO 2. In 2018, the annual GEP budget increased by 20 % in comparison to average years (2010-2017). R eco increased even by 40 %, but enhanced photosynthetic CO 2 sequestration could compensate for half of the drought-induced increase in respiratory CO 2 release. Altogether, the restored fen remained a net CO 2 sink in the year of drought, though net CO 2 sequestration was lower than in other years. CH 4 emissions were 20 % below average on an annual basis, though stronger reduction effects occurred from August onwards, when daily fluxes were 60 % lower than in reference years. Our study reveals an important regulatory mechanism of restored fens to maintain their net CO 2 sink function even in extremely dry years. It appears that, in times of more frequent climate extremes, fen restoration can create ecosystems resilient to drought. However, in order to comprehensively assess the mitigation prospects of peatland rewetting as a nature-based climate solution, further research needs to focus on the long-term effects of such extreme events beyond the actual drought period.
Anke Günther
added a research item
The Paris Agreement reflects the global endeavour to limit the increase of global average temperature to 2 °C, better 1.5 °C above pre-industrial levels to prevent dangerous climate change. This requires that global anthropogenic net carbon dioxide (CO2) emissions are reduced to zero around 2050. The German Climate Protection Plan substantiates this goal and explicitly mentions peatlands, which make up 5 % of the total area under land use and emit 5.7 % of total annual greenhouse gas emissions in Germany. Based on inventory reporting and assumptions of land use change probability, we have developed emission reduction pathways for organic soils in Germany that on a national level comply with the IPCC 1.5 °C pathways. The more gradual pathway 1 requires the following interim (2030, 2040) and ultimate (2050) milestones: Cropland use stopped and all Cropland converted to Grassland by 2030; Water tables raised to the soil surface on 15 % / 60 % / 100 % of all Grassland, on 50 % / 75 % / 100 % of all Forest land, and ultimately on 2/3 of all Settlements and on 100 % of all Wetlands. Also a more direct pathway 2 without interim 'moist' water tables and the climate effect (radiative forcing) of different scenarios is presented.
Haojie Liu
added a research item
Sulphate (SO42-) concentrations in freshwaters have increased globally over the last decades even though a strong reduction in atmospheric sulphur (S) deposition has occurred across large parts of North America and Europe. However, the extent and effects of increased SO42- concentrations in freshwater and terrestrial ecosystems remain poorly understood regarding many aspects of ecosystem structure and functioning. Here, we review the sources of SO42- pollution, environmental impacts on freshwater ecosystems and bioremediation opportunites and we identify key knowledge gaps and future research needs. Natural sources of dissolved SO42- in freshwater ecosystems include mineral weathering, volcanic activity, decomposition and combustion of organic matter, oxidation of sulphides, and sea spray aerosols. Acid mine drainage, fertiliser leaching from agricultural soils, wetland drainage, agricultural and industrial wastewater runoff as well as sea level changes are the main direct and indirect sources of the anthropogenic SO42- input to waterbodies. Increasing SO42- concentrations in freshwater systems influence the biogeochemical processes of carbon, nitrogen and phosphorus. Similarly, iron availability can be critical in determining the adverse effects of SO42- on environmental receptors. The literature reviewed clearly demonstrates that SO42- pollution may have toxic effects on aquatic plants and animal organisms, including, among others, fishes, invertebrates and amphibians, and it may also have negative implications for human health. Bioremediation systems provide opportunities to mitigate the impacts of SO42-, but removal efficiencies range widely from 0% to 70% across treatment systems such as constructed wetlands, permeable reactive barriers and bioreactors. We conclude that examination of increased SO42- concentrations and fluxes at different spatial scales is urgently needed as the ongoing global perturbation of the S cycle is likely to be accelerated by climate change and human development activities. The adverse effects of this on freshwater organisms worldwide may prove detrimental to the future well-being of humans and ecosystems. Field-scale research to estimate the ecotoxicological effects of elevated SO42- concentrations is recommended as is widespread implementation of large-scale wetland restoration and bioremediation systems to reduce SO42- loads on freshwater ecosystems.
Sarah Schwieger
added a research item
Forest peatlands represent 25% of global peatlands and store large amounts of carbon (C) as peat. Traditionally they have been drained in order to increase forestry yield, which may cause large losses of C from the peat. Rewetting aims to stop these losses and to restore the initial storage function of the peatlands. As roots represent major peat forming elements in these systems, we sampled roots <5 mm in a drained and a rewetted forest peatland in NE Germany to evaluate differences in tree biomass investments belowground, root functional characteristics and root age. We cored soil next to Alnus glutinosa stems and sorted root biomass into <1 mm, 1–2 mm, and 2–5 mm diameter classes. We measured biomass distribution and specific root area (SRA) in 10 cm-depth increments down to 50 cm, and estimated root age from annual growth rings. Root biomass in the rewetted site was more than double that of the drained site. This difference was mostly driven by very fine roots <1 mm, which accounted for 51% of the total root biomass and were mostly (75%) located in the upper 20 cm. For roots <1 mm, SRA did not differ between the sites. However, SRA of the 1-2 mm and 2-5 mm diameter roots was higher in the drained than in the rewetted site. Root age did not differ between sites. The size-dependent opposite patterns between root biomass and their functional characteristics under contrasting water regimes indicate differences between fine and coarse roots in their response to environmental changes. Root age distribution points to similar root turnover rates between the sites, while higher root biomass in the rewetted site clearly indicates larger tree C stocks belowground under rewetting, supporting the C sink function of the ecosystem.
Sarah Schwieger
added a research item
Peatlands are effective carbon sinks as more bio-mass is produced than decomposed under the prevalent anoxic conditions. Draining peatlands coupled with warming releases stored carbon, and subsequent rewetting may or may not restore the original carbon sink. Yet, patterns of plant production and decomposition in rewetted peatlands and how they compare to drained conditions remain largely unexplored. Here, we measured annual above-and belowground biomass production and decomposition in three different drained and rewetted peatland types: alder forest, percolation fen and coastal fen during an exceptionally dry year. We also used standard plant material to compare decomposition between the sites, regardless of the decomposability of the local plant material. Rewetted sites showed higher root and shoot production in the percolation fen and higher root production in the coastal fen, but similar root and leaf production in the alder forest. Decomposition rates were generally similar in drained and rewetted sites, only in the percolation fen and alder forest did aboveground litter decompose faster in the drained sites. The rewetted percolation fen and the two coastal sites had the highest projected potential for organic matter accumulation. Roots accounted for 23-66% of total biomass production, and belowground biomass, rather than above-ground biomass, was particularly important for organic matter accumulation in the coastal fens. This highlights the significance of roots as main peat-forming element in these graminoid-dominated fen peatlands and their crucial role in carbon cycling, and shows that high biomass production supported the peatlands' function as carbon sink even during a dry year.
Jacqueline Berendt
added a research item
Source determination of N2O has often been performed using stable isotope incubation experiments. In situ experiments with isotopic tracers are an important next step. However, the challenge is to distribute the tracers in the field as homogeneously as possible. To examine this, a bromide solution was applied as a stand‐in tracer using either a watering can, a sprayer, or syringes to a relatively dry (25% gravimetric moisture content) or wet (30%) silt loam. After 1 h, samples were taken from three soil depths (0‐10 cm), and analyzed for their water content and bromide concentration. The application with syringes was unsuccessful due to blocked cannulas. Therefore, further laboratory experiments were conducted with side‐port cannulas. Despite a larger calculated gravimetric soil moisture difference with watering can application, more Br‐ tracer was recovered in the sprayer treatment, probably due to faster transport of Br‐ through macropore flow in the wetter conditions caused by the watering can treatment. The losses of Br‐ (33% for the watering can, 28% for the sprayer treatment) are equivalent to potential losses of isotopic tracer solutions. For application of 60 at% 15NH4+, this resulted in theoretical enrichments of 44‐53 at% in the upper 2.5 cm and 7‐48 at% in 5‐10 cm. As there was hardly any NO3‐ in the soil, extrapolations for 15NO3‐ calculated enrichments were 57‐59 at% in the upper 2.5 cm and 26‐57 at% in 5‐10 cm. Overall, no method, including the side‐port cannulas, was able to achieve a homogeneous distribution of the tracer. Future search for optimal tracer application should therefore investigate methods that utilize capillary forces and avoid overhead pressure. We recommend working on rather dry soil when applying tracers, as tracer recovery was larger here. Furthermore, larger amounts of tracer lead to more uniform distributions. Further studies should also investigate the importance of plant surfaces.
Haojie Liu
added a research item
Hydro-physical properties of peat influence the partitioning of rainfall into infiltration versus runoff, determine water flow and solute transport patterns, and regulate the carbon and nitrogen cycles in peatlands. Compared with mineral soils, our understanding of hydraulic properties of peat soils is limited, especially of the temporal dynamics of peat properties. A dataset of peat subsidence as well as the bulk density (BD) change rate following artificial drainage was assembled from the literature. The collected data cover a time period of up to 272 years of land drainage for forestry and agriculture in boreal and temperate climate zones. The results show that the subsidence rate and BD change rate, and hydro-physical properties of peat can be estimated based on land drainage duration and land use. The most severe shift in pore structure of peat occurs within the first 20 years of land drainage. Peatland drainage reduces macroporosity with pore diameter greater than 50 μm, but increases the volume of pores < 5 μm. In the long term, peat thickness loss is responsible for more than 80% of water storage loss. In conclusion, the derived functions between subsidence rate, BD change rate, and drainage duration provide a new approach to estimate the hydro-physical properties of peat (pore structure, saturated hydraulic conductivity, specific yield, and soil water storage) on a centennial-scale. The derived hydro-physical parameter values can be used for long-term hydrological modelling, especially if measured hydraulic parameters of peat are not available.
Haojie Liu
added a research item
Nitrous oxide (N2O) is approximately 265 times more potent than carbon dioxide (CO2) in atmospheric warming. Degraded peatlands are important sources of N2O. The more a peat soil is degraded, the higher the N2O-N emissions from peat. In this study, soil bulk density was used as a proxy for peat degradation to predict N2O-N emissions. Here we report that the annual N2O-N emissions from European managed peatlands (EU-28) sum up to approximately 145 Gg N year−1. From the viewpoint of greenhouse gas emissions, highly degraded agriculturally used peatlands should be rewetted first to optimally reduce cumulative N2O-N emissions. Compared to a business-as-usual scenario (no peatland resetting), rewetting of all drained European peatlands until 2050 using the suggested strategy reduces the cumulative N2O-N emissions by 70%. In conclusion, the status of peat degradation should be made a pivotal criterion in prioritising peatlands for restoration.
Daniel Koehn
added a research item
Tree stems can be a source of the greenhouse gas methane (CH 4 ). However, assessments of the global importance are complicated by a lack of research and a high variability between ecosystems. Here, we determined the contribution of emissions from tree stems of mature black alder ( Alnus glutinosa (L.) Gaertn.) to overall CH 4 exchange in two temperate peatlands. We measured emissions from stems and soils using closed chambers in a drained and a wet alder forest over two years. Further, we studied the importance of alder leaves as substrate for methanogenesis in an incubation experiment. Stem CH 4 emissions were shortlived and occurred only during times of inundation at the wet site. The drained site did not show stem emissions and the soil acted as a small CH 4 sink. The contribution of stem emissions to the overall CH 4 budget was below 0.3% in both sites. Our results show that also mature black alders intermittently can be a source of CH 4 . However, the low share of stem-mediated CH 4 emissions in both forests may indicate that this pathway is only of minor relative importance in temperate peatlands.
Haojie Liu
added a research item
(download final version at https://authors.elsevier.com/a/1bjcsB8ccoKaV) Precipitation is a key factor affecting shallow water table fluctuations. Although the literature on shallow aquifers is vast, groundwater response to precipitation in peatlands has received little attention so far. Characterizing groundwater response to precipitation events in differently managed peatlands can give insight into ecohydrological processes. In this study we determined the groundwater level response rate following precipitation events at a drained and a rewetted fen to characterize the effect of rewetting on hydrological buffer capacity. Multiple regression analysis revealed that groundwater table in the rewetted fen has a two times lower rate of response to precipitation events of a given intensity, compared to that of the drained fen, even after adjusting for antecedent groundwater levels. Thus, the rewetted fen delivers a better hydrological buffer function against heavy precipitation events than the drained fen. We found that for the depths at which the groundwater interacts with incoming precipitation, the peat of the rewetted fen has a higher specific yield causing groundwater to rise slower compared to the response at the drained fen. A period of 20 years of rewetting was sufficient to form a new layer of organic material with a significant fraction of macropores providing storage capacity. Long-term rewetting has the potential to create favorable conditions for new peat accumulation, thereby altering water table response. Our study has implications for evaluating the success of restoration measures with respect to physical functions of percolation fens.
Florian Beyer
added a research item
Rewetting is a necessary measure to stop CO2 emissions of degraded peatlands and to restore their natural habitat and C accumulation function. Although the severity and frequency of droughts is predicted to increase as a consequence of climate change, it is not well understood whether such extreme events can jeopardize rewetting measures. The goal of this study was to better understand drought effects on peatland restoration measures. Based on long-term reference records, we investigated anomalies in vegetation dynamics and CO2 exchange, including ecosystem respiration (Reco) and gross ecosystem productivity (GEP), in a rewetted fen during the extreme European summer drought 2018. Drought-induced vegetation dynamics were derived from remotely sensed data. Since flooding in 2010, the fen was characterized by a patchy mosaic of open water surfaces and vegetated areas. After years of stagnant vegetation development, drought acted as a trigger event for pioneer species such as Tephroseris palustris and Ranunculus sceleratus to rapidly close persistent vegetation gaps. The massive spread of vegetation assimilated substantial amounts of CO2. In 2018, the annual GEP budget increased by 20 % in comparison to average years (2010–2017). Reco increased even by 40 %, but enhanced photosynthetic CO2 sequestration could compensate for half of the drought-induced increase in respiratory CO2 release. Altogether, the restored fen remained a net CO2 sink in the year of drought, though net CO2 sequestration was lower than in other years. Our study reveals an important regulatory mechanism of restored fens to maintain their net CO2 sink function even in extremely dry years. Even in times of more frequent climate extremes, fen restoration can create ecosystems resilient to drought. However, further research needs to focus on the long-term effects of such extreme events beyond the actual drought period.
Tim Urich
added a research item
Drained peatlands are significant sources of the greenhouse gas (GHG) carbon dioxide. Rewetting is a proven strategy used to protect carbon stocks; however, it can lead to increased emissions of the potent GHG methane. The response to rewetting of soil microbiomes as drivers of these processes is poorly understood, as are the biotic and abiotic factors that control community composition. We analyzed the pro- and eukaryotic microbiomes of three contrasting pairs of minerotrophic fens subject to decade-long drainage and subsequent long-term rewetting. Abiotic soil properties including moisture, dissolved organic matter, methane fluxes, and ecosystem respiration rates were also determined. The composition of the microbiomes was fen-type-specific, but all rewetted sites showed higher abundances of anaerobic taxa compared to drained sites. Based on multi-variate statistics and network analyses, we identified soil moisture as a major driver of community composition. Furthermore, salinity drove the separation between coastal and freshwater fen communities. Methanogens were more than 10-fold more abundant in rewetted than in drained sites, while their abundance was lowest in the coastal fen, likely due to competition with sulfate reducers. The microbiome compositions were reflected in methane fluxes from the sites. Our results shed light on the factors that structure fen microbiomes via environmental filtering.
Anke Günther
added a research item
Peatlands are strategic areas for climate change mitigation because of their matchless carbon stocks. Drained peatlands release this carbon to the atmosphere as carbon dioxide (CO2). Peatland rewetting effectively stops these CO2 emissions, but also re-establishes the emission of methane (CH4). Essentially, management must choose between CO2 emissions from drained or CH4 emissions from rewetted peatland. This choice must consider radiative effects and atmospheric lifetimes of both gases, with CO2 being a weak but persistent and CH4 a strong but short-lived greenhouse gas. The resulting climatic effects are, thus, strongly time-dependent. We used a radiative forcing model to compare forcing dynamics of global scenarios for future peatland management using areal data from the Global Peatland Database. Our results show that CH4 radiative forcing does not undermine the climate change mitigation potential of peatland rewetting. Instead, postponing rewetting increases the long-term warming effect through continued CO2 emissions.
Anke Günther
added 2 research items
Peatland restoration is seen as an effective contribution to help achieve the aims of the Paris Agreement because currently huge amounts of peatlands in Northern Central Europe are under unsustainable drainage-based land use. If net zero greenhouse gas emissions from peatlands shall be reached by 2050, restoration measures have to be done as soon as possible. However, rewetting drained peatlands that were under intensive grassland use frequently results in high methane (CH4) emissions, which is often seen as a counter-argument against rewetting. To find the source of high CH4 emissions after rewetting and to explore the best possible way of peatland restoration (i.e., low CH4 emissions after rewetting) under near-natural conditions, we installed a field trial in a drained bog in north-western Germany. The trial consists of seven plots (~8 × 24 m2) representing the status quo—intensive grassland use— and six restoration approaches with combinations of rewetting either on the original surface or after topsoil removal (TSR), biomass harvesting or spreading Sphagnum spp. to initiate vegetation succession. On all seven plots we measured CH4 fluxes using closed chambers. In addition, we investigated CH4 production potential by incubating soil samples and determining methanogen abundance by quantitative PCR. Compared to rewetting on the original surface, CH4 emissions were reduced on TSR plots by factor 30 to 400. Spreading of Sphagnum spp. had only little effect on CH4 emissions during the first year of establishment. TSR also reduced CH4 production potential and methanogen abundance. Further, the response of CH4 fluxes to methanogen abundance was lower after TSR. This suggests that both reduction in labile substrate and in methanogen abundance contribute to near-zero CH4 emissions after TSR. These are the first field-scale results that demonstrate the efficiency of removing degraded topsoil to avoid high CH4 emissions after rewetting.
Drained peatlands are important sources of greenhouse gases and are rewetted to curb these emissions. We study one drained and one rewetted fen in terms of losses-and, after rewetting-gains of organic matter (OM), carbon (C), and peat thickness. We determined bulk density (BD) and ash/OM (and C/OM) ratios for 0.5 cm thick contiguous slices from peat monoliths to calculate losses. Whereas one site has lost 28.5 kg OM m−2 corresponding to annual emissions of~10 t CO2 ha−1 a−1 over 50 years of effective drainage, the other site has lost 102 kg OM m−2 , corresponding to an annual loss of 30 t CO2 ha−1 a−1 for 30 years of intensive drainage and 6 t CO2 ha−1 a−1 during~225 years of weak drainage before that. Height losses ranged from 43 to 162 cm. In the 20 years after rewetting, 2.12 kg C m−2 was accumulated, equaling an average annual uptake of~0.4 kg CO2 m−2 a−1. The results indicate that rewetting can lead to carbon accumulation in fens. This sink function is only small compared with the high emissions that are avoided through rewetting.
Anke Günther
added a research item
Of all terrestrial ecosystems, peatlands store carbon most effectively in long-term scales of millennia. However, many peatlands have been drained for peat extraction or agricultural use. This converts peatlands from sinks to sources of carbon, causing approx. 5% of the anthropogenic Soil Syst. 2020, 4, 14 2 of 27 greenhouse effect and additional negative effects on other ecosystem services. Rewetting peatlands can mitigate climate change and may be combined with management in the form of paludiculture. Rewetted peatlands, however, do not equal their pristine ancestors and their ecological functioning is not understood. This holds true especially for groundwater-fed fens. Their functioning results from manifold interactions and can only be understood following an integrative approach of many relevant fields of science, which we merge in the interdisciplinary project WETSCAPES. Here, we address interactions among water transport and chemistry, primary production, peat formation, matter transformation and transport, microbial community, and greenhouse gas exchange using state of the art methods. We record data on six study sites spread across three common fen types (Alder forest, percolation fen, and coastal fen), each in drained and rewetted states. First results revealed that indicators reflecting more long-term effects like vegetation and soil chemistry showed a stronger differentiation between drained and rewetted states than variables with a more immediate reaction to environmental change, like greenhouse gas (GHG) emissions. Variations in microbial community composition explained differences in soil chemical data as well as vegetation composition and GHG exchange. We show the importance of developing an integrative understanding of managed fen peatlands and their ecosystem functioning.
Haojie Liu
added a research item
Over the past century, mires and peatlands have faced a wide range of degradation by artificial drainage, making them one of the most threatened ecosystems in Europe. However, restoration of drained peatlands has gained much importance over the last three decades, mostly due to the multiple ecosystem services they provide such as carbon storage, habitat provision and water flow regulation. Although there has been an increased focus on such ecosystems, spatial research on hydrophysical soil properties following rewetting in coastal mires is lacking. Therefore, the objectives of the study were to understand the spatial structures of hydrophysical properties of organic soils and spatial patterns of organic matter accumulation in relation to soil surface microtopography. Soil organic matter content (SOM) and hydraulic conductivity (Ks) of topsoils (0-28 cm), along with soil textures of the underlying mineral substrate, were investigated in a rewetted non-tidal coastal flood mire (Baltic Sea). The results indicate that the organic horizon with its relatively low Ks acts as a hydrological barrier to infiltration. Soil organic matter content (SOM), Ks and soil surface microtopography are all spatially auto-correlated within 100, 87 and 53 m, respectively. Bivariate Moran's I revealed a positive but weak spatial correlation between SOM and Ks and a moderately strong negative spatial correlation between SOM and soil surface microtopography. A map of SOM was generated using simple kriging, which predicts higher SOM in the centre of the ecosystem, at lower elevations; and lower SOM at the edges of the study area, at higher elevations. Local depressions in the centre of the ecosystem provide a wetter and therefore more anaerobic environment, thereby decreasing carbon mineralisation rates and enabling peat accumulation. The low hydraulic conductivity of the degraded peat in the presence of lower micro-elevations in the centre of the ecosystem is likely to increase the residence time of floodwater and thus may enhance (new) peat accumulation. Thus, we conclude that, for the restoration of non-tidal coastal mires where flooding events are not as frequent, Ks and soil surface microtopography are even more important factors to consider than for tidal systems.
Wakene Negassa
added 4 research items
Drained peatlands are significant sources of the greenhouse gas (GHG) carbon dioxide. Rewetting is a proven strategy to protect carbon stocks; however, it can lead to increased emissions of the potent GHG methane. The response to rewetting of soil microbiomes as drivers of these processes is poorly understood, as are biotic and abiotic factors that control community composition. We analyzed the pro- and eukaryotic microbiomes of three contrasting pairs of minerotrophic fens subject to decade-long drainage and subsequent rewetting. Also, abiotic soil properties including moisture, dissolved organic matter, methane fluxes and ecosystem respiration rates. The composition of the microbiomes was fen-type-specific, but all rewetted sites showed higher abundance of anaerobic taxa compared to drained sites. Based on multi-variate statistics and network analyses we identified soil moisture as major driver of community composition. Furthermore, salinity drove the separation between coastal and freshwater fen communities. Methanogens were more than tenfold more abundant in rewetted than in drained sites, while their abundance was lowest in the coastal fen, likely due to competition with sulfate reducers. The microbiome compositions were reflected in methane fluxes from the sites. Our results shed light on the factors that structure fen microbiomes via environmental filtering.
There is indication in the literature that degradation of natural peatlands reduced spatial variability of soil chemical and biochemical properties. However, we lack empirical data on the impact of rewetting peatland on the spatial variability of these properties. We investigated the spatial variability of the soil properties of a peatland that has been used for extensive and intensive grazing from 1400 to 1970. The peatland has been rewetted since 1970, and we collected 50 soil samples from 50 grid cells of 0-10, and 10-20 cm soil depths in October 2001. We measured 33 important soil chemical and biochemical properties and evaluated the data with descriptive and geospatial statistical analyses. The concentrations of most plant available nutrients were low with high coefficients of variation (CV) that ranged from 15 to 117%, whereas the CV of most of the total and oxalate extracted elements was ≤15% CV. The degree of phosphorus (P) saturation (DPS) and P saturation ratio (PSR) were 11% and 0.05, which were low as compared to the threshold levels of 25% DPS and 0.11 PSR for mineral and wetland soils. The microbial biomass C and N ranged from 389 to 2,463 mg kg −1 and 32 to 215 mg kg −1 at the depth of 0-10 cm and from 343 to 1570 mg kg −1 and 14 to 160 mg kg −1 at the depth of 10-20 cm, respectively. Similarly, the dehydrogenase and β-glucosidase activities were lower by 76 and 61% at the soil depth of 10-20 cm compared to the upper 10 cm. The geospatial statistical analysis revealed that 87% of the soil chemical properties were spatially correlated and 85% of the spatial correlation was strong with <0.20 nugget to sill ratio at 5 to 12 m ranges. Similarly, 86 and 71% of the biochemical properties were strongly spatially correlated at the depth of 0-10, and 10-20 cm, respectively, with ≤0.16 nugget to sill ratio at the short ranges (4 to 6 m). The strong spatial correlation of most of the soil chemical and biochemical properties at short ranges indicate the high variability of the rewetted peatland.
Drained peatlands are significant sources of the greenhouse gas (GHG) carbon dioxide. Rewetting is a proven strategy to protect carbon stocks; however, it can lead to increased emissions of the potent GHG methane. The response to rewetting of soil microbiomes as drivers of these processes is poorly understood, as are biotic and abiotic factors that control community composition. We analyzed the pro- and eukaryotic microbiomes of three contrasting pairs of minerotrophic fens subject to decade-long drainage and subsequent rewetting. Also, abiotic soil properties including moisture, dissolved organic matter, methane fluxes and ecosystem respiration rates. The composition of the microbiomes was fen-type-specific, but all rewetted sites showed higher abundance of anaerobic taxa compared to drained sites. Based on multi-variate statistics and network analyses we identified soil moisture as major driver of community composition. Furthermore, salinity drove the separation between coastal and freshwater fen communities. Methanogens were more than tenfold more abundant in rewetted than in drained sites, while their abundance was lowest in the coastal fen, likely due to competition with sulfate reducers. The microbiome compositions were reflected in methane fluxes from the sites. Our results shed light on the factors that structure fen microbiomes via environmental filtering.
Wakene Negassa
added a research item
Previous studies, conducted at the inception of rewetting degraded peatlands, reported that rewetting increased phosphorus (P) mobilization but long-term effects of rewetting on the soil P status are unknown. The objectives of this study were to (i) characterize P in the surface and subsurface horizons of long-term drained and rewetted percolation mires, forest, and coastal peatlands and (ii) examine the influence of drainage and rewetting on P speciation and distributions using wet-chemical and advanced spectroscopic analyses. The total P was significantly (p < 0.05) different at the surface horizons. The total concentration of P ranged from 1022 to 2320 mg kg−1 in the surface horizons and decreased by a factor of two to five to the deepest horizons. Results of the chemical, solution 31P nuclear magnetic resonance (NMR), and P K-edge X-ray absorption near-edge structure (XANES) indicated that the major proportions of total P were organic P (Po). In the same peatland types, the relative proportions of Po and stable P fractions were lower in the drained than in the rewetted peatland. The results indicate that long-term rewetting not only locks P in organic matter but also transforms labile P to stable P fractions at the surface horizons of the different peatland types.
Haojie Liu
added a research item
Peat soils are heterogeneous, anisotropic porous media. Compared to mineral soils, there is still limited understanding of physical and solute transport properties of fen peat soils. In this study, we aimed to explore the effect of soil anisotropy on solute transport in degraded fen peat. Undisturbed soil cores, taken in vertical and horizontal direction, were collected from one drained and one restored fen peatland both in a comparable state of soil degradation. Saturated hydraulic conductivity (Ks) and chemical properties of peat were determined for all soil cores. Miscible displacement experiments were conducted under saturated steady state conditions using potassium bromide as a conservative tracer. The results showed that (1) the Ks in vertical direction (Ksv) was significantly higher than that in horizontal direction (Ksh), indicating that Ks of degraded fen peat behaves anisotropically; (2) pronounced preferential flow occurred in vertical direction with a higher immobile water fraction and a higher pore water velocity; (3) the 5% arrival time (a proxy for the strength of preferential flow) was affected by soil anisotropy as well as study site. A strong correlation was found between 5% arrival time and dispersivity, Ks and mobile water fraction; (4) phosphate release was observed from drained peat only. The impact of soil heterogeneity on phosphate leaching was more pronounced than soil anisotropy. The soil core with the strongest preferential flow released the highest amount of phosphate. We conclude that soil anisotropy is crucial This article is protected by copyright. All rights reserved. in peatland hydrology but additional research is required to fully understand anisotropy effects on solute transport.
Anke Günther
added a research item
Of all terrestrial ecosystems, peatlands store carbon most effectively. However, many peatlands have been drained for peat extraction or agricultural use. This converts peatlands from sinks to sources of carbon, causing approx. 5% of the anthropogenic greenhouse effect and additional negative effects on other ecosystem services. Rewetting peatlands can mitigate the climate crisis and may be combined with management in the form of paludiculture. Rewetted peatlands, however, do not equal their pristine ancestors and their ecological functioning is not understood. This holds especially for fens. Their functioning results from complex interactions and can only be understood following an integrative approach of many relevant fields of science, which we develop in the interdisciplinary project WETSCAPES. Here, we introduce our approach in which we are addressing interactions among water transport and chemistry, primary production, peat formation, matter transformation and transport, microorganisms and greenhouse gas exchange using state of the art methods in the relevant research fields. We record data on six study sites spreading across three important fen types (Alder forest, percolation fen, and coastal fen) each in drained and rewetted state. Using exemplary results, we show the importance of developing an integrative understanding of managed fen peatlands and their ecosystem functioning.
Gerald Jurasinski
added a research item
There have been widespread attempts to rewet peatlands in Europe and elsewhere in the world to restore their unique biodiversity as well as their important function as nutrient and carbon sinks. However, changes in hydrological regime and therefore oxygen availability likely alter the abundance of enzyme-inhibiting polyphenolic compounds, which have been suggested as a “latch” preventing large amounts of carbon from being released into the atmosphere by microbial mineralization. In recent years, a variety of factors have been identified that appear to weaken that latch including not only oxygen, but also pH. In minerotrophic fens, it is unknown if long-term peat mineralization during decades of drainage and intense agricultural use causes an enrichment or a decline of enzyme-inhibiting polyphenols. To address this, we collected peat samples and fresh roots of dominating plants (i.e., the peat parent material) from the upper 20 cm peat layer in 5 rewetted and 6 natural fens and quantified total phenolic content as well as hydrolysable and condensed tannins. Polyphenols from less decomposed peat and living roots served partly as an internal standard for polyphenol analysis and to run enzyme inhibition tests. As hypothesized, we found the polyphenol content in highly decomposed peat to be eight times lower than in less decomposed peat, while condensed tannin content was 50 times lower in highly degraded peat. In addition, plant tissue polyphenol contents differed strongly between peat-forming plant species, with the highest amount found in roots of Carex appropinquata at 450 mg g−1 dry mass, and lowest in Sphagnum spp. at 39 mg g−1 dry mass: a 10-fold difference. Despite large and clear differences in peat and porewater chemistry between natural and rewetted sites, enzyme activities determined with Fluorescein diacetate (FDA) hydrolysis and peat degradation were not significantly correlated, indicating no simple linear relationship between polyphenol content and microbial activity. Still, samples with low contents of polyphenols and condensed tannins showed the highest microbial activities as measured with FDA.
Private Profile
added a research item
The global peatland ecosystem has often been overlooked in its importance within the global geochemical cycle. It contains approximately 21% of global carbon, and their maintenance and restoration are vital for lowering atmospheric carbon dioxide, the primary driver of climate change. Dr Bernd Lennartz of the University of Rostock and his team of interdisciplinary scientists are investigating peatlands and how they respond to changing climate conditions.
Micha Weil
added a research item
High-organic drained peatlands are large sources of the greenhouse gas (GHG) carbon dioxide. Rewetting of peatlands is a promising strategy to protect the large C stocks, however, rewetting also causes increased emissions of the potent GHG methane. The net climate effect of rewetting and the role of the microbiome remains uncertain. We aimed at investigating the differences between three pairs of drained and rewetted fen microbiomes across seasons and identify links between methane-cycling functional guilds and magnitudes of methane emissions. DNA was extracted from seasonally sampled profiles at 5 10 cm, 15 20 cm and 25 30 cm below peat surface. Analyses comprised coenzyme:M reductase subunit A gene (mcrA) qPCR, Illumina MiSeq analysis of total prokaryotic 16S rRNA gene amplicons, moisture, redox potential, dissolved organic carbon (DOC), and gas flux measurements. Methanogens were more than tenfold more abundant in rewetted than in drained fens (106-107 vs. 105-106 mcrA copies per gram soil). Abundance was lowest in the brackish coastal mire. Seasonal variations were strong, with highest methanogen abundances in winter. Microbiome composition was fen type-specific, but was similarly impacted by rewetting, with higher prevalence of (facultative) anaerobic taxa. Preliminary data indicate soil moisture, redox potential and salinity as drivers of microbiome composition and methanogen abundance, with the latter being correlated to observed methane fluxes. As hypothesized, higher abundance of methanogens in rewetted fens could be shown. However, coastal fens with their lowest methanogen abundance are suggested as ideal sites for rewetting regarding their potentially lowest methanogen abundance and thus methane emissions.
Haitao Wang
added a research item
A recent study by Alves et al. (2018) established a highly resolved ammonia-oxidizing archaea (AOA) taxonomy based on the marker gene for the alpha subunit of ammonia monooxygenase (amoA) and uncovered novel environmental patterns of AOA that challenged previous generalizations. However, many microbiome studies target the 16S rRNA gene as marker, thus the usage of this taxonomy and the environmental patterns is limited. Here, we exploited the phylogenetic congruence of archaeal amoA and 16S rRNA genes to link AOA 16S rRNA genes to amoA gene clades. We screened publicly available archaeal genomes and metagenome-assembled genomes for the co-occurrence of amoA and 16S rRNA genes and constructed a 16S rRNA gene database with the corresponding amoA clade taxonomy. We validated this approach with 16S rRNA gene amplicon data from peatland soils, for which rich environmental context data are available. For instance, we succeeded to link amplicon sequence variants (ASVs) belonging to class Nitrososphaeria to seven different amoA clades, including two abundant clades for which no pure culture is available. Their distribution in the studied peatlands matched the previous clade predictions in terms of habitat specificity and soil pH. Moreover, the AOA community composition was significantly impacted by the peatland type, hydrology and soil depth. The ASVs belonging to abundant clades Nitrososphaerales-γ and Nitrosopumilales-α were mostly differentially abundant between drained and rewetted sites, which was correlated to pH, nitrate and ammonium. These findings supported physiological preferences of these clades as observed before. This is the first study to exploit the phylogenetic congruence of archaeal 16S rRNA and amoA genes, which paves the way for a better understanding of the ecology of the globally abundant AOA.
Sarah Schwieger
added a research item
Start and end of the growing season determine important ecosystem processes, but their drivers may differ above-and belowground, between autumn and spring, and between ecosystems.Here, we compare above-and belowground spring and autumn phenology, and their abiotic drivers (temperature, water level, and soil moisture) in four temperate ecosystems (beech forest, alder carr, phragmites reed, and sedge reed). Root growth was measured in-situ with minirhizotrons and compared with aboveground phenology assessed with dendrometer data and NDVI. Synchrony of above- and belowground phenology depended on ecosystem. Onset of root growth was later than shoot growth in all three peatlands (12–33 days), but similar in the beech forest. The growing season ended earlier belowground in the two forested ecosystems (beech forest: 27 days, understory of the alder carr: 55 days), but did not differ in the phragmites reed. Generally, root production was correlated with soil temperature (especially in spring) and water level in the peatlands, while abiotic factors were less correlated with leaf activity or root production in either spring or autumn in the beech forest. Root production on organic soils was ten times higher compared to the zonal broadleaf deciduous forest on mineral soils, highlighting the importance of peatlands. Belowground phenology cannot be projected from aboveground phenology and measuring root phenology is crucial to understand temporal dynamics of production and carbon fluxes.
Gerald Jurasinski
added a research item
Peatlands are strategic areas for climate change mitigation because of their matchless carbon stocks. Drained peatlands release this carbon to the atmosphere as carbon dioxide (CO 2 ). Peatland rewetting effectively stops these CO 2 emissions, but also re-establishes the emission of methane (CH 4 ). Essentially, management must choose between CO 2 emissions from drained or CH 4 emissions from rewetted peatland. This choice must consider radiative effects and atmospheric lifetimes of both gases, with CO 2 being a weak but persistent and CH 4 a strong but short-lived greenhouse gas. The resulting climatic effects are, thus, strongly time-dependent. We used a radiative forcing model to compare forcing dynamics of global scenarios for future peatland management using areal data from the Global Peatland Database. Our results show that CH 4 radiative forcing does not undermine the climate change mitigation potential of peatland rewetting. Instead, postponing rewetting increases the long-term warming effect of continued CO 2 emissions. Warnings against CH 4 emissions from rewetted peatlands are therefore unjustified and counterproductive.
Haojie Liu
added a research item
Carbon (C) and nitrogen (N) release from peatlands are closely related to water management and soil degradation. However, peat degradation has not been explicitly accounted for when estimating national greenhouse gas inventories. Here, we assembled a comprehensive dataset covering European, Russian and Canadian peatlands and introduced soil bulk density (BD) as a proxy for peat degradation to estimate nitrous oxide (N2O) and dissolved organic carbon (DOC) release. The results show that physical and biogeochemical properties of peat are sensitive to soil degradation. The BD is superior to other parameters (C/N, pH) to estimate annual N2O emissions and DOC pore water concentrations. The more a peat soil is degraded, the higher the risk of air/water pollution in peaty landscapes. Even after rewetting, highly degraded soils may exhibit high N2O release rates. The estimated annual N2O-N emissions from European, Russian and Canadian degraded peatlands sum up to approximately 81.0 Gg. The derived BD-based functions can assist in computing global matter fluxes from peatlands.
Haojie Liu
added a research item
Over the past two decades, great efforts have been made to restore coastal wetlands through the removal of dikes, but challenges remain because the effects of flooding with saline water on water quality are unknown. We collected soil samples from two adjacent coastal fen peatlands, one drained and diked, the other open to the sea and rewetted, aiming at assessing the mobility and export of various compounds. Microcosm experiments with constant flow-through conditions were conducted to determine the effluent concentrations of dissolved organic carbon (DOC), ammonium (NH 4 +), and phosphate (PO 4 3−) during saline-fresh water cycles. Sodium chloride (NaCl) was used to adjust salinity (saline water, NaCl concentration of 0.12 mol L −1 ; fresh water, NaCl concentration of 0.008 mol L −1) and served as a tracer. A model analysis of the obtained chloride (Cl −) and sodium (Na +) breakthrough curves indicated that peat soils have a dual porosity structure. Sodium was retarded in peat soils with a retardation factor of 1.4 ± 0.2 due to adsorption. The leaching tests revealed that water salinity has a large impact on DOC, NH 4 + , and PO 4 3− release. The concentrations of DOC in the effluent decreased with increasing water salinity because the combination of high ionic strength (NaCl concentration of 0.12 mol L −1) and low pH (3.5 to 4.5) caused a solubility reduction. On the contrary, saline water enhanced NH 4 + release through cation exchange processes. The PO 4 3− concentrations, however, decreased in the effluent with increasing water salinity. Overall, the decommissioning of dikes at coastal wetlands and the flooding of once drained and agriculturally used sites increase the risk that especially nitrogen may be leached at higher rates to the sea.
Gerald Jurasinski
added a research item
As a result of global warming, the frequency of climate extremes is expected to increase, leading to warmer winters and hotter summers in the long-term. Although a change in annual sums of precipitation for northern countries remains uncertain, global warming promotes the occurrence of heavy precipitation events in this region. The summer of 2011 in northern Germany saw exceptionally strong precipitation that lead to prolonged freshwater flooding in many low-lying areas. With access to manual chamber GHG time series for 2011 this gave us the opportunity to measure the effect of heavy precipitation on CH4 effluxes under high summer temperatures. Here, we present CH4 efflux data measured with manual closed chambers during the growing season (April-October) 2011 in eight different study sites on organic soils with 2 to 5 measurement plots. The study sites spread across an area of more than 25,000km2. They stretch over an approximate distance along the climatic gradient from East to West of more than 300km and were affected by different intensities of the monsoon-type precipitation events in June and July 2011. The plots span land-use types from former high-intensity grassland to nature conservation areas and different hydrological regimes from drained over rewetted to inundated. The different site conditions are reflected in the vegetation composition from communities typical for intensive grassland use to emergent macrophytes and open water bodies. We estimated the local severity of the monsoon-type precipitation compared to long-term averages using data of the German Weather Service network. We assessed the response of CH 4 emissions to the local changes in water table following the extreme event by comparing the total fluxes based on all gathered data to the ones that were estimated based on data without the measurements during flooding and to data series were the flood fluxes were substituted by average fluxes during non-flood times. Our results show that the most responsive sites are those with easily decomposable grassland vegetation not adapted to inundation. These sites may reach annual CH4 emissions typical for rewetted or pristine peatlands showing the sensitivity to single measurement years and extreme climatic events. Communities of rewetted sites responded less to the flooding whereas inundated sites did show almost no response of CH4 emissions to the extreme event suggesting that higher overall CH4 emissions following rewetting measures are partly compensated by lower climate vulnerability. Extreme event years, which are predicted to increase under global warming, may, thus, become more important for CH4 estimates from non-flooded sites. Since long-term field trials monitoring CH4 fluxes on organic soils are scarce, meta-analyses usually incorporate data from field trials which rarely exceed two years of duration. In the light of our findings this may become insufficient for deriving reliable emission factors in the future.
Daniel Koehn
added a research item
Rewetting drained peatlands has become a popular measure to prevent high carbon dioxide (CO 2) emissions. Yet, as a consequence of rewetting, anoxic conditions prevail in the water-saturated soils leading to high methane (CH4) emissions. For many years, research has focused on soil to atmosphere fluxes. In recent years, it is becoming apparent, that long-known stem-based emissions of CH4 from trees might be more relevant than previously thought on ecosystem scale CH4 budgets. However, data regarding seasonal and spatial variability are still scarce. Further, it is of great interest to understand the interaction with soil emissions and other environmental variables in order to include stem methane emissions in overall ecosystem GHG-balances. We measured stem emissions regularly for 12 months with 21 chambers on six black alder (Alnus gluti-nosa (L.) J. Gaertn.) trees alongside measurements of soil emissions in a drained and a rewetted alder carr. Due to the variable weather patterns in northern Central Europe in 2017/2018, we collected data under climatically and hydrologically contrary phases. In addition, we ran a sampling campaign to address spatial and diurnal variability. The data reveals that CH4 emissions of tree stems are highly dependent on the hydrologic regime and interact with soil CH4 emissions. Additionally, overall variability is high in time and space, resulting in fluxes being at the upper limit of the range reported for stem methane fluxes for temperate wetland forests. During the study period, the sites showed water table fluctuations of up to 1.4 m. When the water level was above the soil surface soil emissions decreased while stems seem to have acted as shunts for CH4 being produced in the soil. Contrary to this, soil emissions increased strongly when the surface water receded whilst stem emissions came to a quick halt. In conclusion, stem emissions contributed considerably to overall CH4 emissions in the alder carr, however, only under certain conditions and during limited periods of time.
Florian Beyer
added 2 research items
The restoration of drained peatlands to re-establish biodiverse peat-forming plant communities and typical habitats is a long-term process. To document this process, monitoring concepts must be found that are as operational, cost-effective and non-invasive as possible for the new sensitive ecosystems. The monitoring of the developing plant communities using multisensory Unmanned Aerial Vehicle (UAV) data has great potential. We investigated two fen sites in north-eastern Germany that were rewetted in the late 1990s. The areas were flown with a Fixed-Wing UAV and three sensors (RGB, multispectral, thermal). A multisensor dataset consisting of the sensor data, plant height and five spectral indices was classified with a random forest algorithm. The classification accuracies were 87.1 and 89.0% for 10 and 11 classes for the respective sites. Furthermore, the band importance was analyzed using the Gini index. Plant height in combination with the multispectral information were the most important variables. This study underlines the suitability of UAVs for monitoring spectrally similar vegetation because of their capability to generate 3D surface models using structure-from-motion methods and to carry different sensor systems. In addition, they can be used on a regional scale and mostly independent of cloud cover. Secondary results of the study are that the band importance can be determined by Random Forest algorithms even with few trees (e.g. 10 trees), because the order remains very stable independently of the number of trees.
Franziska Schmacka
added an update
Understanding the ecology of restored fen peatlands for protection and sustainable use
Conference topics
  • Greenhouse gas exchange in space and time
  • Element cycling and export
  • Peatland bio-hydrology
  • Plant growth and decomposition
  • Microbial pathways
  • Paleoecological methods in restored peatlands
  • Legacy of degradation in biotic communities
  • Mapping with GIS and remote sensing
Keynote speakers
  • Dr. Rebekka Artz, The James Hutton Institute, Scotland UK
  • Prof. Dr. Philippe van Cappellen, University of Waterloo, Canada
  • Prof. Dr. Chris Evans, Centre for Ecology and Hydrology, Bangor, UK
  • Prof. Dr. Steve Frolking, University of New Hampshire, USA
  • Prof. Dr. Dr. h.c. Reinhard Hüttl, German Research Centre for Geosciences (GFZ), Germany
  • Prof. Dr. Klaus-Holger Knorr, University of Munster, Germany
  • Prof. Dr. Susanne Liebner, German Research Centre for Geosciences (GFZ), Germany
  • Dr. Sunitha Pangala, Lancaster University, UK
  • Dr. Fereidoun Rezanezhad, University of Waterloo, Canada
  • Marcel Silvius, Global Green Growth Institute, Indonesia
  • Dr. Maria Strack, University of Waterloo, Canada
Deadlines
  • Abstract submission until January 31, 2019
  • Early registration until April 30, 2019
  • Late registration until August 10, 2019
MAKE SURE TO BE PART OF IT: www.wetscapes.de/conference
 
Anke Günther
added an update
Happen to be in Iceland and interested in greenhouse gases and peatland restoration? Then come and see the presentations of Wetscapes members at the SER Europe meeting in Reykjavik! These cover the following topics:
 
Daniel Koehn
added a research item
Drained fens frequently show high carbon dioxide emissions. Rewetting is a common measure of restoration, yet it can cause high methane emissions which counteract the initial intention of climate change mitigation. In recent years, high emissions from structural elements like ditches and tree stems also gained attention. While plantations of black alder (Alnus glutinosa (L.) J. Gaertn.) can improve the uptake of carbon dioxide, they can also act as a source of methane. Due to the often anoxic conditions and high availability of substrate, ditches can also be a strong source of methane and carbon dioxide. However, data on the emissions of trees and ditches is still scarce for the temperate region. Here, we present data on the exchange of methane and carbon dioxide from the soil, tree stems and ditches in six temperate fens from the first measurement year of a three-year measuring period. The six study sites comprise three different kinds of fens including percolation fens, coastal fens and forested fens of which there is a drained and rewetted one for each type. In all study sites, we use non-steady-state manual chambers to measure gas exchange at the soil surface. We additionally asses the gas exchange at the stem surface of black alder (stand age: ~40 years) in one drained and one rewetted alder plantation. Additionally, we study the heterogeneity of stem exchange among different trees and different heights in regular campaigns. To quantify gas emissions from ditches we use floating chambers and bubble traps in two non-forested sites (one drained and one rewetted). In this way, we aim to evaluate the relative share of stem and ditch emissions compared to those of soil and herbaceous vegetation. At the same time, we show the wide range of greenhouse gas exchange values that can occur in temperate fens across fen types and hydrologic conditions.
Anke Günther
added a research item
In many European countries, peatland rewetting has become an important measure to restore ecosystem functioning and to mitigate greenhouse gas emissions. However, rewetting degraded peatlands that were under intensive grassland use frequently results in high methane (CH4) emissions. With incubation experiments it has been shown that the removal of the upper degraded peat layer can effectively reduce the potential for high CH4 emissions under inundated conditions. To test this possibility in the field, we installed a field trial in a drained peat bog in north-western Germany. The trial consists of seven blocks (~8 x 24 m) representing the current state (intensive grassland use) as reference and six different restoration approaches. Four of the six restoration approaches represent rewetting after topsoil removal (TSR) down to two depths (~30 cm and ~60 cm). The remaining restoration trials include rewetting on the original surface with and without regular biomass harvesting, and spreading Sphagnum spp. propagules on half of the TSR blocks to initiate vegetation succession. On all seven blocks we measured CH4 fluxes fortnightly using manual closed-chambers. After one year, CH4 emissions of the blocks without TSR were similar to literature values of rewetted sites without TSR. Compared to rewetting on the original surface, TSR showed only very small CH4 emissions that were reduced by several orders of magnitude. Spreading of fresh Sphagnum spp. propagules had only little effect on CH4 emissions during the first year of establishment. In addition, we found that the reference block displayed high CH4 emissions during the non-growing season suggesting that also the current land use can be a significant source of CH4 during wet winters. Overall, these are the first field-scale results demonstrating that TSR likely is the most effective measure to prevent high CH4 emissions after rewetting.
Micha Weil
added a research item
High-organic drained peatlands are large sources of the greenhouse gas (GHG) carbon dioxide. Rewetting of peatlands is a promising strategy to protect the large C stocks, however, rewetting also causes increased emissions of the potent GHG methane. The net climate effect of rewetting and the role of the microbiome remains uncertain. We aimed at investigating the differences between three pairs of drained and rewetted fen microbiomes across seasons and identify links between methane-cycling functional guilds and magnitudes of methane emissions. DNA was extracted from seasonally sampled profiles at 5 10 cm, 15 20 cm and 25 30 cm below peat surface. Analyses comprised coenzyme:M reductase subunit A gene (mcrA) qPCR, Illumina MiSeq analysis of total prokaryotic 16S rRNA gene amplicons, moisture, redox potential, dissolved organic carbon (DOC), and gas flux measurements. Methanogens were more than tenfold more abundant in rewetted than in drained fens (106-107 vs. 105-106 mcrA copies per gram soil). Abundance was lowest in the brackish coastal mire. Seasonal variations were strong, with highest methanogen abundances in winter. Microbiome composition was fen type-specific, but was similarly impacted by rewetting, with higher prevalence of (facultative) anaerobic taxa. Preliminary data indicate soil moisture, redox potential and salinity as drivers of microbiome composition and methanogen abundance, with the latter being correlated to observed methane fluxes. As hypothesized, higher abundance of methanogens in rewetted fens could be shown. However, coastal fens with their lowest methanogen abundance are suggested as ideal sites for rewetting due to their potentially lowest methanogen abundance and thus methane emissions.
Florian Beyer
added a research item
UAS liefern sehr hochaufgelöste multisensorale Daten, mit deren Hilfe und unter Verwendung moderner Klassifikatoren eine präzise Vegetationsklassifikation eines Moores möglich wird. Der im Rahmen einer UAS-Befliegung aufgenommene multisensorale Datensatz (14 Bänder), einer ca. 8 ha großen Moorfläche, besteht aus RGB-Daten, multispektralen Informationen, Thermaldaten, einem digitalen Oberflächenmodell (DOM) und mehreren Vegetationsindizes. Die Klassifikation mit einem Random Forest Ansatz lieferte bei 11 Klassen eine Gesamtgenauigkeit von ca. 89 %. Die vier relevantesten Variablen für die Klassifikation waren das DOM, die Thermaldaten, der normalisierte Vegetationsindex aus Rot und Red-Edge und der NDVI. Somit ermöglichen UAS auf der Skalenebene zwischen Blatt- und Bestandsebene neue erklärende Daten, die herkömmlichen Satelliten- und Flugzeug-basierten Untersuchungen überlegen sind.
Anke Günther
added an update
We performed a basic test for airtightness of our greenhouse gas chambers in the field. Field testing has the advantage that we can assess the tightness of the whole system (chamber, collar, sealing) at once and under realistic conditions. As suggested by Hoffmann et al. 2017, we used smoke from a cartridge as indicator for gas leakage. This worked unexpectedly well and we even found a small leakage around an incorrectly installed plug in the lid of one chamber, visible by a thin whisp of white smoke. Fortunately, this leakage could be fixed very easily. Since the smoke cartridge test is very fast and easy (and fun…), we plan to repeat it each time the chambers or collars are modified to ensure airtightness throughout the study period.
 
Wakene Negassa
added a project reference
Anke Günther
added an update
Our sites are now almost up and running! On June 1, Daniel Koehn, Jacqueline Berendt and I tested some field equipment on the newly-build boardwalks in the alder carr. We found that the chambers and loggers only need some minor adjustments, so we hope to start regular greenhouse gas measurements in the beginning of July.
 
Anke Günther
added an update
On the 5th of April the Wetscapes consortium spent an animated field day visiting the first five of the future study areas (drained and rewetted coastal inundation peatland, drained and rewetted alder carr, rewetted percolation mire) and settling the final location of the sampling sites. A few days later a slightly smaller group also finalized the sampling location for the drained percolation mire site. Since these locations represent the main investigation objects for the next four years, it was important to choose sites that suited the purposes of all Wetscapes groups. We especially checked peat properties by coring the uppermost soil layers, since processes in the peat are the main focus of the Wetscapes project. After this very satisfying field site scouting, we are now looking forward to getting the first installations out in the end of April.
 
Anke Günther
added an update
Project goal
WETSCAPES aims to provide a scientific basis for sustainable utilization of rewetted, formerly degrading peatlands and coastal areas. WETSCAPES supports research and development in an internationally competitive structure focusing on primary production, matter dynamics and transport, gas fluxes and peat formation.
The project is funded by the European Union Social Fund through the Excellence Initiative of Mecklenburg Western Pomerania.
Background and motivation
Covering 13% of the land, peatlands and coastal areas shape the landscape and its use in the federal state of Mecklenburg-Vorpommern (MV). Depending on their management they have a far larger effect on climate and water quality than other ecosystems.
WETSCAPES will provide a scientific basis for sustainable land use of fens and coastal wetlands, with a particular focus on degraded sites that have been rewetted. Considerable deficiencies and gaps in knowledge exist that drive the project to study vegetational, microbial, biogeochemical and hydrological conditions and processes in degraded and rewetted peatlands and coastal wetlands. Individual scientific disciplines will provide details of the specific parts and a multi- and interdisciplinary approach will reach an integrated understanding of the relationships, with the aim to gain a fundamental understanding of the processes involved in these fragile ecosystems.
 
Erik Borg
added a research item
The presentation gives an overview of the aspects: General conditions of remote sensing (Fleet of Earth observation systems for GMES; Analysis of conditions and test sites designed for remote sensing) Observatory characteristic needed for remote sensing (Site characteristic and natural conditions of test site DEMMIN, Heterogenity of test site conditions) Data basis of observatory DEMMIN (Data basis derived from precision farming management, Scientifically campaigns by airborne / spaceborne remote sensing) Further development of the observatory DEMMIN (Implementation of infrastructure, Cooperation aspects)
Anke Günther
added a project goal
WETSCAPES aims to provide a scientific basis for sustainable utilization of rewetted, formerly degrading peatlands and coastal areas. WETSCAPES supports research and development in an internationally competitive structure focusing on primary production, matter dynamics and transport, gas fluxes and peat formation.
The project is funded by the European Union Social Fund through the Excellence Initiative of Mecklenburg Western Pomerania.