Project leaders: Prof. Dr. Jürgen Kreyling (University of Greifswald), PD Dr. Franziska Tanneberger (University of Greifswald)

The peat of temperate fens is predominantly formed from roots and rhizomes of vascular plants and from brown mosses. These mosses, however, do not reappear well after rewetting. Root production and inhibition of their decomposition is therefore key to the understanding of peat formation and C and nutrient cycling in rewetted fen peatlands. Rewetting alters plant species composition towards wetland specialists with aerenchymatic roots. Through the aeration of the rhizosphere, these plants affect microbial composition and activity as well as key redox-driven peatland processes such as GHG production and nutrient cycling. These processes are essential for the formation of new organic deposits but may also affect the old peat. A1 will determine root production and decomposition at all experimental levels of WETSCAPES2.0, and link them to abiotic and biotic drivers, contributing to the causal understanding of peat formation, GHG and nutrient cycling. If brown mosses occur, their production and decomposition will also be quantified. Besides annual production and decomposition, A1 will reach unprecedented temporal resolution in determining root dynamics by the use of automated minirhizotrones at Core Sites. Continuation of existing long-term data series of root dynamics and dedicated mesocosm experiments will furthermore shed light on the importance of extreme hydrological events for root production. Finally, A1 will quantify the effects of root exudates and of the presence of plant roots on priming and decomposition of old peat.

Project leader: Prof. Dr. Nicole Wrage-Mönnig (University of Rostock)

Decomposing fen peat can be a major source of GHG, including the long-lived and potent GHG nitrous oxide (N2O). However, fens can also act as sinks for N2O, e.g. by reducing it to atmospheric N (N2). So far, systematic research on N2O reduction in fens is lacking. Rewetting affects N2O production and consumption by altering plant diversity, microbial activity and community composition, and thus nutrient cycling. So far, N2O in rewetted fens has mainly been attributed to denitrification. However, other sources of N2O can also play an important role. A2 will systematically investigate N2O production and consumption at all experimental levels of WETSCAPES2.0. State-of-the-art instrumentation (isotope ratio mass spectrometry (IRMS), cavity ring-down spectroscopy (CRDS)) and a combination of natural abundance isotope mapping and dual-isotope tracer methods will allow us to quantify the sources and sinks of N2O and, together with other projects within Wetscapes 2.0, link them to peat and biomass production, microbial community composition and activity, production and consumption of other GHG, nutrient cycling, and water dynamics.

Project leader: Dr. Tjorven Hinzke (University of Greifswald)

Rhizosphere microbiomes (rhizobiomes) are the central interaction interface between plants, soil, and the atmosphere. Interactions between peatland rhizobiomes and plants influence plant performance, plant biomass production and decomposition, plant reactions to changing environmental conditions, and thus, ultimately, GHG production and peat formation potential. In A3, we will analyze how key plant-rhizobiome interactions in fen peatlands change during a long-term chronosequence of rewetting, as well as during short-term extreme events. We will contrast plant–rhizobiome interactions in peatland soil with those in shallow water bodies, and link plant–rhizobiome interactions to plant growth performance, GHG emissions, and environmental conditions including peat quality. For this, we will use meta-omics analyses supplemented by microscopic techniques. On this basis, we will identify potential and realized key interactions, their correlation with environmental conditions, and postulate how these interactions might shape the further development of wetscapes 2.0.

Project leaders: Prof. Dr. Tim Urich (University of Greifswald), Prof. Dr. Andreas Kuss (University of Greifswald)

The below-ground (micro-)biome is central to peat biogeochemistry. Rewetting changes the peat microbiome (bacteria, archaea, fungi, protists; Weil et al. 2020; Wang et al. 2021, 2022) and the composition of the micro- and mesofauna as compared to drained fens (Emsens et al. 2020; Jurasinski et al. 2020; Kreyling et al. 2021). These shifts indicate drastically changed functions in the below-ground biome and consequently in the flow of C and energy to higher trophic levels in the food web. We postulate that the lack of oxygen restricts the activity of most micropredators, due to their obligatory aerobic lifestyle. This lowered predation pressure on bacteria and fungi may result in a reduced C turnover and ultimately in soil organic C storage, i.e., a „trophic latch“ on C mineralisation. Using cutting-edge quantitative meta-omics approaches, we aim to assess the consequences of rewetting and limited oxygen availability on the trophic structure and on interactions among prokaryotes, fungi, and fauna in temperate fens.  In a series of complementary work packages the structure and function of the below-ground (micro-)biome in rewetted fens  will be analysed. (1) Using > 100 rewetted Screening Sites we will create the first broad census of below-ground biota in rewetted fens. (2) Spatially and temporally resolved sampling and analysis of Core Sites will enable an understanding of the spatio-temporal microbiome dynamics. (3) To verify the hypothesis of a trophic latch on C mineralization, we will conduct microcosm and mesocosm experiments with peat microbiota and model plant species under oxic and anoxic conditions. (4) NGS and amplicon profiling services will be provided for other subprojects. Results will be shared and integrated with the outcomes of other subprojects, especially A3, A5, A6, A7, B3 and S1.

Project leader: Prof. Dr. Susanne Liebner (GFZ German Research Centre for Geosciences)

In wetlands, microbial CH4 oxidizers (methanotrophs) determine the emission of CH4 to the atmosphere through soil CH4 uptake (SMU). After rewetting of degraded temperate fens, biotic and abiotic drivers on methanotroph community development appear to differ from those in natural wetlands. In the few rewetted temperate fens studied so far, the SMU remained poorly developed even several years post rewetting (Wen et al. 2018). This likely contributed to an overrepresentation of microbial CH4 production relative to microbial CH4 oxidation, an apparent lack of soil CH4 oxidation in situ (Fig A5.1), and consequently high observed CH4 fluxes. Natural drought events, however, appear to stimulate methanotrophic community development. The severe drought in 2018, for example, triggered sustainably lower in situ CH4 fluxes via profound and positive effects on peat methanotrophic diversity and activity (Unger et al., 2021). Thus, soil methanotrophic activity and comunity composition seem to be directly coupled to changes in peatland biogeochemistry. To date, we know only little about the establishment and vulnerability of soil methanotrophic communities and their activity in rewetted temperate fens despite their importance for the GHG budget. Project A5 tackles to fill this gap with the aim to to achieve a predictive understanding on SMU in the heterogeneous landscape of wetscapes 2.0. Poject A5 takes a holistic approach on soil methanotrophic research taking into account spatiotemporal links with biogeochemistry and ecosystem CH4 fluxes, the role of yet poorly constrained methanotrophic taxa, and the vulnerability of soil methanotroph communities post-rewetting. The project specifically investigates soil methanotrophic communities and SMU of rewetted temperate fens in relation to their biotic and abiotic drivers on diverse spatial and temporal scales. It quantifies the role of methanotrophs, including that of anaerobic methanotrophic taxa, in GHG fluxes which is central to projects B1 and S1. A5 realizes its goals through molecular and bioinformatic techniques like -omics and pangenome analysis, through physiological and process studies, and statistical modeling using all experimental levels of WETSCAPES2.0.

Project leaders: Prof. Dr. Tim Urich (University of Greifswald), Prof. Dr. Dörte Becher (University of Greifswald)

Methanogenic archaea are, together with methanotrophs (see A5) the most important determinants of the potential flux of CH4 from wetlands to the atmosphere. To date, there is no census of methanogen identity, abundance and activity in rewetted fens, and their abiotic and biotic drivers, although the latter are thought to be different from those in natural wetlands. Project A6 aims to provide such a census, by mapping the abundance and identity of methanogenic archaea in the Screening Sites. Furthermore A6 aims to assess their role for the GHG budget in rewetted fens by probing spatio-temporal compositional dynamics and activity relative to measured GHG fluxes, based on microbiomics, and process studies where feasible. We hypothesize that methylotrophic methanogens are more important for the methane balance of rewetted fens than previously assumed. Furthermore, we anticipate that antagonistic interactions with sulfur-cycling bacteria might reduce methanogen abundance and activity. A6 will investigate methanogens at all experimental levels of WETSCAPES2.0. Using cutting-edge proteomics, we will specifically look into the ecophysiology of novel, as yet poorly constrained methanogens, i.e. the methylotrophic Methanomassiliicoccales.

Project leader: Dr. Bernhard Ahrens (Max-Planck-Institute for Biogeochemistry)

Peatlands contain a large share of the total terrestrial soil C reservoir, and the dynamics caused by drainage and rewetting have important implications for GHG emissions. Understanding underlying processes and their representation in soil and ecosystem models is therefore crucial for their climate-smart management and for predicting GHG emissions under changing management and climate. A7 will develop a process-based modeling and data assimilation framework based on the soil profile model COMISSION to identify the relative importance of different mechanisms for peat decomposition and formation. Besides CO2 production, we will also model the production and consumption of the GHG CH4 and N2O, taking into account the availability of oxygen and other terminal electron acceptors at different peat depths. This will be achieved by model-data comparison and integration with data from the mesocosm experiment MCExp rewetted peat, Screening Sites, and Core Sites (A2, A4, A5, A6, B1, S2).

Project leader: Prof. Dr. Gerald Jurasinski (University of Greifswald)

In B1 we investigate the drivers of GHG exchange in rewetted fens and provide data for process-based modeling of C turnover. We combine GHG exchange measurements (CO2 and CH4) at Core Sites (mainly Eddy Covariance (EC) measurements, closed chamber measurements at selected sites), Screening Sites (short term, campaign-based chamber measurements in combination with lab incubations of sampled topsoil peat) and mesocosm experiments (automated chamber measurements of CO2, CH4, N2O) with a wealth of additionally recorded variables provided by the interdisciplinary collaboration. EC based evapotranspiration rates are fed into process-based hydrological models (C1) through analysis by S3. We use low-cost sensors for measuring CH4 and CO2 exchange in screening campaigns on a large number of sites and investigate iron turnover as a proxy for decomposition of organic matter in a subset of Screening Sites with an in-situ incubation approach.

The GHG exchange measurements in B1 are embedded in a growing network of GHG measurement sites on rewetted peatlands. Since rewetted peatlands have to be understood as novel ecosystems (Kreyling et al. 2021), it is important to accompany peatland rewetting and restoration projects with extensive monitoring. The innovation in WETSCAPES2.0 lays in the focus on interdisciplinary analyses of the data, including many variables that are not available in standard monitoring projects where the production of reliable GHG balances is the main focus. Here, in contrast, we focus on fostering our understanding of processes in the biogeochemical cycling of C. This approach, which is only possible in such a broad collaborative project with in-depth expertise in many critical fields of science like microbiology, biogeochemistry, experimental plant ecology, hydrology, and associated modelling, is unique and promises real breakthroughs in our understanding of rewetted peatlands as novel ecosystems.

Project leader: Prof. Dr. Torsten Sachs (GFZ German Research Centre for Geosciences)

Peatlands are highly complex and spatially heterogeneous ecosystems and current in-situ methods to quantify energy and matter fluxes are inherently limited in their spatial coverage: closed chambers typically cover ≤ 1 m² and provide spatially explicit, temporally discrete data, while Eddy Covariance (EC) integrates over few hectares at most, but provides temporally continuous measurements. Neither method is able to cover an entire peatland complex with all its heterogeneity in vegetation types and density, open water areas, and microtopography, nor do they allow for quantifying peatland energy and matter exchange relative to the surrounding landscape mosaic defining a larger region. Aggregation approaches for upscaling require that fluxes are known for all characteristic heterogeneity elements, while upsclaing via process based modeling demands far-reaching assumptions such as the closure of energy and water balances. Instead, here we use airborne EC deployed from an unmanned aircraft system (UAS) to provide spatially extensive in-situ energy and matter flux measurements covering both peatlands and their adjacent areas. In addition, B2 contributes Core Site EC data to RQ1.b, RQ1.c and RQ4.a and makes use of regional data (such as DAMM-GHG output, soil moisture, and vegetation cover fraction) provided by other projects in RQ4.b.

Project leader: Dr. Mia Bengtsson

Peatland microbiomes encompass prokaryotic and eukaryotic microbes that inhabit the peat itself, the water that connects micro- and macro-environments in the landscape, as well as the diverse plant species that make up peatland vegetation. Microbiomes are central in all ecosystem processes leading to or mitigating GHG emissions as they decompose peat, produce N2O, CH4 and CO2, but also consume N2O and CH4 and interact closely with plants that fix C and are responsible for peat formation. Rewetted fens, in contrast to natural fens, feature altered conditions for microbial colonization and activity, such as the formation of shallow water bodies resting on degraded peat. The massive complexity of peatland microbiomes, including the diversity of microbial taxa present, presents a challenge in understanding the underlying processes leading to GHG emissions or accumulation of organic matter. However, the information contained in these diverse communities is an untapped goldmine with power to predict patterns in GHG fluxes if deciphered. As a C store, peat is extremely vulnerable to microbial degradation, therefore it is crucial to understand how microbiomes vary, function, and are transported in the terrestrial-aquatic interfaces of rewetted fens. In subproject B3, we investigate how fen peatland microbiomes vary on regional (WP B3.1) and landscape (WP B3.2) scales and how this variation can be used to predict ecosystem function. On a local scale (WP B3.3), we zoom in on shallow water bodies, a distinct feature of rewetted fens and a hotspot of CH4 emissions, and investigate the role of aquatic macrophytes and their microbiomes for carbon and nutrient cycling during extreme conditions of flooding and drought in the mesocosm experiment MCExp shallow water.

Project leader: Dr. Anke Günther (University of Rostock)

Vegetation is a core layer of the Earth’s Critical Zone, a prerequisite for most of its life, as well as an important part of the nutrient and C cycles. Plants are both the product of and the cause for many of the processes studied in WETCAPES 2.0. Rewetting alters the plant species composition which mediates the water and GHG balance of peatlands by changing water transpiration as well as C sequestration and biomass decomposition rates, housing different soil microbial communities, and in the long-term determines the peat structure. Vegetation is therefore an indicator of site conditions, habitats and GHG fluxes. B4 will study vegetation within the peatlands at all experimental levels of WETSCAPES2.0 and link them to abiotic and biotic drivers in time and space. Vegetation surveys and analyses will reveal the complex spatial and temporal patterning in rewetted peatlands, contributing to the understanding of several processes explored in WETSCAPES 2.0, like C or water cycling.

Project leader: Dr. Manon Janssen (University of Rostock)

Peat soils strongly differ from mineral soils in terms of hydro-physical properties. They are characterized by a low bulk density and a high porosity of up to >90 vol% depending on their origin and degradation state. Peat soils have, thus, an important water storage function substantially facilitating the resilience of landscapes to precipitation and temperature extremes. The total soil water storage capacity refers to the water the peat can store under saturated conditions. The drainage of peatlands reduces their water storage capacity considerably and it is unknown to what extent it can be restored upon rewetting. The accumulation of new peat after rewetting is expected to play a crucial role, and also modifies water fluxes in the peat profile. Increasing frequency and intensity of summer droughts as extreme events are expected even in rewetted peatlands. The associated drying of the peat causes shrinkage and alters its hydro-physical properties, with potentially irreversible changes to the soil structure. Also the release and transport of dissolved substances such as DOC are severely impacted by droughts and subsequent rewetting.

The objectives of B5 are thus (1) to characterize the hydro-physical characteristics of newly accumulated fen peat in rewetted peatlands, and to assess its effect on water storage, water fluxes and resilience against extreme events in peat soil profiles, (2) to evaluate the consequences of alternate drying and wetting on hydro-physical properties of fen peat as a function of peat type and drying intensity, and (3) to understand how droughts effect the release of DOC from rewetted fens. We hypothesize that the regulative functions of peat soils in the water cycle recover upon rewetting by the formation of new peat, and that droughts alter both the soil hydraulic functions and the release of DOC. We will address the objectives using a combination of state-of-the-art techniques including laboratory soil column experiments, X-ray computed tomography, field monitoring, and Richard’s equation based numerical soil hydrological modelling. We will explore the dynamics of hydro-physical peat properties, state variables and DOC export as a function of drought-associated drying and rewetting scenarios at the laboratory and soil profile scale. Peat column experiments and analysis of field water samples will reveal the effect of droughts on the hydro-physical soil properties and on the release of DOC as a function of peat and pore water properties as well on the solute transport properties of peat under rewetting conditions. We will characterize how peat functions that are related to the pore structure recover upon rewetting to relate peat pore structure information to water storage and flux.

Project leader: Prof. Dr. Philip Marzahn (University of Rostock)

The overarching aim of B6 is to deepen the spatio-temporal knowledge of rewetted fen peat and corresponding processes observed by remote sensing techniques. It is hypothesized that peatlands can be monitored by different remote sensing techniques at high precision and consequently show that mire breathing increases and inundated areas decrease over space and  time in rewetting fen peatlands. Furthermore we adress the hypothesis that peat and C sequestration in  rewetted fens is heterogenuous in space and that these spatial patterns can consequently be quantified by remote sensing techniques. We will prove the hypothesis by advancing the spatio-temporal retrieval of mire breathing by innovative techniques such as SBAS interferometry and link it to peat development as well as C sequestration. This will allow to delineate areas where rewetting is successful and those where it failed. The specific objectives are, thus, to (i) quantify the dynamic of peat soil subsidence at field and regional scale, (ii) to map inundated areas in wetscapes, (iii) to determine the soil moisture dynamics at regional scale, and, finally, (iv) to identify areas of rewetting success, which will enable C accumulation calculations.

The use of remote sensing data from the frequency range of microwaves allows to obtain information from the peat body over large areas. Subsidence of the peat in the mm range will be measured by LIDAR and interferometric techniques. This information will be used to directly derive GHG emission estimates by a GHG balance method proposed by Weinzierl and Waldmann (2015) or Minasny et al. (2024) and validated against in-situ data from the project. Furthermore, we will identify areas of success or failure of the rewetting measures by analyzing the spatio-temporal subsidence patterns. Spatio-temporal patterns of inundation will be monitored using Sentinel-1 as well as drone-based data streams. Spatially distributed soil moisture retrievals from Sentinel-1 data over MV will be delivered to the consortium. The applied techniques of observing spatio-temporal patterns of peat surface characteristics enable us to assess the resilience and vulnerability of peatlands to droughts and floods.

Project Leader: Prof. Dr. Doerthe Tetzlaff (IGB Leibniz Institute of Freshwater Ecology and Inland Fisheries)

C1 will use and assess the value of stable water isotope data in conjunction with other environmental variables (e.g. data on C dynamics (from project B1); ecosystem-atmosphere fluxes (from B2); 13C and soil physical characteristics (from B5, S2); root and vegetation dynamics (from A1, B4, C2, C3, S3) obtained spatially distributed at plot – peatland – landscape scales within WETSCAPES2.0. Stable water isotopes can be used as “fingerprints” of water allowing to quantify sources and pathways of water but also estimating the ages of different waters. Water age is an important metric of hydrological functioning in terms of response and recovery times after climatic perturbations. The passage of conservative, environmental tracers (e.g., water isotopes, chloride, tritium) through the landscape allows quantifying the dampening of precipitation input signals by internal mixing processes and connections between different spatial units, including deeper groundwater. This provides estimates of the storage water volumes needed to damp the tracer input signal, and thus, quantifies total storage dynamics in landscapes (which is usually only derived from soil moisture dynamics). When isotopes are integrated into so-called isotope-aided models, new insights into mechanisms of water cycling and total storage dynamics are possible, e.g. on heterogeneous vertical and lateral flows of soil water, fluctuations in groundwater recharge, preferential uptake of soil water held under different tensions and at different (rooting) depths by plants for transpiration, storage connectivity, etc. So far, such integrated investigation and analysis of hydrological dynamics has not been done in rewetted fens. The objectives of C1 are to (i) fundamentally advance and test the capacity of process-based, tracer-aided, ecohydrological modeling frameworks and thus, to (ii) investigate the hydrological functioning of rewetted fens from the plot scale (ca. 10*10m²) up to the landscape scale (ca. 100km2) in terms of spatial patterns and temporal dynamics of water storage, pathways and release. To achieve this, C1 will (1) use water isotope data measured across spatial scales and from different waters from different fen landscape compartments to drive a process-based, tracer-aided ecohydrological model; (2) develop new modules and codes to incorporate fen specific ecohydrological processes and test different data streams in multi-criteria model calibration and uncertainty assessment to improve the quantification of ecohydrological partitioning of rewetted fens (i.e. water storage versus release); and (3) assess how such model improvements aid upscaling of ecohydrological fluxes and storage from the plot to the landscape scale. C1 will further use forcing data (remote sensing data on vegetation dynamics, data on local climate) from C4, C5 and parametrization of GHG fluxes from A7 and CO2  fluxes from C5 to improve model parametrisation in terms of vegetation dynamics. C1 will also feed into and be closely linked with S4 as the tracer-aided model used and enhanced in C1 will be one of the models used in S4. Thus, C1 will play an essential integrating role in WETSCAPES2.0 through data-driven, process-based modeling of water cycling, storage dynamics and pathways in restored fens across different spatial and temporal scales. C1 will contribute quantifications of spatio-temporal dynamics of water storage, sources, pathways and ages (which provide important hydrological indices of the timescales of water cycling and resilience to perturbation) up to the landscape-scale.

Project leader: Prof. Dr. Martin Wilmking (University of Greifswald)

Tree growth, C sequestration and the resilience of forest ecosystems to extreme events are intrinsically linked to water availability, and trees and forests in turn influence the green water cycle at local to regional scales. When rewetting a landscape (wetscape), these naturally linked water and C cycles are clearly affected, which then in turn influences many forest ecosystem services, both on peatlands and in the hydrologically linked surrounding area. But to which extent is an open question. Therefore, C2 will use (1) state-of-the art tree growth monitoring to assess the response of trees and forests to rewetting on peatlands and their surroundings, hydrologically linked mineral soils of the wider wetscapes; and (2) extensive retrospective tree-ring analysis for the temporal and spatial context. Combining temporal analyses of growth at resolutions of decades to hours with spatial and functional information will constrain assessments of the effect of extreme events, such as droughts and flooding, on forest productivity and C dynamics, resilience and local to regional water balance. C2 will make use of the extensive network of Screening and Core Sites for more generalized assessments. C2 will instrument Core sites and the L-LExps to better elucidate the mechanisms driving tree growth under variable water regimes.

Project leader: Prof. Dr. Florian Jansen (University of Rostock)

C3 will investigate the influence of rewetted peatlands on non-forest vegetation in their surroundings. This influence is much debated, both as a possible antidote to the drying of the whole landscape due to climate change, and at the same time as a possible hydrological threat to arable land and human settlements.

For this investigation C3 will use high precision DEM's, vegetation maps from C4, soil maps, a detailed analysis of transects at the Core/L-LExp sites, and data from several of the other WETSCPAES2.0 projects. While C1 will focus on the landscape scale water dynamics in wetscapes, C3 will focus on direct and indirect influences of the rewetting on vegetation dynamics. It will make use of Screening Sites and aims at a quantitative instead of functional estimation of impact. C3 will furthermore use the large amount of available vegetation data from the region to make predictions about biodiversity effects but also to improve vegetation typifications in a way that the influence of rewetting on surrounding non-peatland areas can be estimated.

Bioindicative analyses of the vegetation around the Screening Sites of WETSCAPES 2.0 as well as direct measurements of evapotranspiration will provide insight into the influence of rewetted peatlands on evapotranspiration, groundwater dynamic, mesoclimate, and species distribution.

The objectives of C3 are  (i) to estimate the spatial extent and strength of the influence of rewetted peatlands on their surroundings and thus (ii) to investigate how rewetting and associated vegetation changes affect landscape stability (through hydrological buffering), biodiversity, and the contribution of wetscapes to mitigating climate warming at local and regional scales, and (iii) in which cases rewetting might lead to unwanted collateral damage on agricultural land and in residential areas in the screening sites investigated.

To accomplish this, C3 will (1) use vegetation data across spatial scales obtained from vegetation surveys and transects as well as the spatio-temporal vegetation monitoring of C4 to derive detailed maps of plant available water within and beyond rewetted Screening and Core Sites; will (2) model the local groundwater dynamic across boundaries of monitoring sites based on measured water tables, and (3) measure evapotranspiration along transects across wetscapes to quantify energy fluxes and test the contribution of rewetted fens to mesoclimate.

C3 will use vegetation data from B4 (surveys) and C4 (remote sensing data and dynamics) to make bioindicative maps of water availability in and around rewetted peatlands. This will improve the predictions of landscape dynamics during the prospective rewetting by estimating the extent of influences for different mire types and spatial relationships . C3 will use the water table measurements of Z2 in combination with indicative vegetation mapping to model the hydrology at the borders of peatlands. C3 will feed into and be closely linked with S3 as the vegetation data and maps of plant available groundwater from C3 will be used in S3. Thus, C3 will provide essential outcomes for WETSCAPES2.0 and will contribute mapping of groundwater, changes in evapotranspiration and heat flux as well as biodiversity in restored wetscapes.

Project leader: Prof. Dr. Sebastian van der Linden (University of Greifswald)

A better understanding of functional processes in and around rewetted fens requires information on vegetation cover and its dynamics at high spatial and temporal resolution and at a very high level of thematic detail, including, e.g., cover fractions of (peatland) vegetation types or species, vitality or biomass. Data from current and imminent Earth observation (EO) satellites provide this information on vegetation cover with the required level of detail, accuracy and spatial resolution, and with an areal/temporal coverage that cannot be achieved with drone-based or airborne imagery. C4 aims to produce spatially continuous maps that (i) achieve a higher level of thematic detail than regularly available maps (e.g. by introducing additional peatland vegetation classes), (ii) quantify vegetation cover annually (species coverage) and intra-annually (fractions of green and non-photosynthetic vegetation throughout time), and (iii) help to extrapolate biomass estimates. This will be used to analyse the effects of rewetting on vegetation cover and to discribe or disaggregate identified processes throughout space and/or time. Furthermore, the input for process-based modelling shall be refined. We will use a Sentinel-1/Sentinel-2 (Sen1/Sen2) and Landsat 8/9 (L8/L9) data cube (2017 onwards, for all sites) to (i) derive time series and spectral-temporal metrics, (ii) create machine learning-based maps of annual (peat-)land cover classes and percent cover fractions and (iii) quantify the intra-annual dynamics of green and dead vegetation components (e.g. for reed). This will allow to describe abundance and vitality of vegetation on the WETSCAPES2.0 research sites and beyond at high spatial and temporal resolution, to be used in B1-6, C1-3, C5, S1-4. By integrating hyperspectral spaceborne data from EnMAP and PRISMA for the Core Sites and the L-LExps, we will achieve an even higher level of thematic detail and accuracy, and derive spatially and temporally resolved biomass estimates that will provide new opportunities for several other projects of the CRC, e.g. A1, B1, B3, B4, B6, C5, S3-4. Results from C4 will function as baseline products for the historical analyses in S3. Our work is based on reference data from very high-resolution satellite images, airborne and drone campaigns and high-frequency field spectroscopy as well as field data especially from A1, B1, B2, B4, B6, C2, C3.

Project leaders: Prof. Dr. Julia Pongratz (Ludgwigs Maximilians University München), Dr. Wolfgang Obermeier (Ludwig Maximilians University München)

Related to their very high C densities, emissions from global peatland drainage may cumulate to around 80 Pg C, if no further areas are exploited (Leifeld and Menichetti 2018). This corresponds to annual GHG emissions of 1.91 (0.31-3.38) GtCO2-eq, mostly emitted as CO2, that could be reduced or even averted by peatland restoration via rewetting - making it a key yet often underappreciated climate change mitigation option (Leifeld and Menichetti 2018). Despite the clearly beneficial effects of stopping (long-lasting) CO2 emissions from drained peatlands, effects of rewetting drained peatlands on climate are complex and go beyond the often-discussed CO2 fluxes. Biogeophysical effects need to be considered in parallel to changes in GHG fluxes. Land cover conversions and modifications such as those imposed by peatland rewetting alter vegetation and surface properties (albedo, roughness, evaporative efficiency), affecting the exchange of momentum, energy and water and thus local, regional and global climate (Pongratz et al. 2021). Vice versa, climatic changes (particularly, rising air temperatures and an increased frequency and intensity of individual and compound extreme weather events) and local hydrological conditions (particularly, water table height) strongly impact ecosystem functioning and thus, resilience in peatlands as well as the net C balance (e.g. Antala et al. 2022). Further, biodiversity and the provisioning of ecosystem services such as food, fiber and bioenergy production should not be compromised, requiring adapted and multifunctional land use practices (e.g., paludiculture; Wichtmann et al. 2016). C5 will incorporate peatland specific vegetation, hydrological and soil properties via in-situ-based parametrization and a cross-scale hybrid modelling framework into a Dynamic Global Vegetation Model (DGVM, namely JSBACH4). By linking biogeochemical as well as local and nonlocal biogeophysical effects, we will be able to develop a tool for a comprehensive assessment of the contribution of temperate fen rewetting to mitigation of and adaptation to climate change. By conducting simulations using different global climate scenarios, we further address the uncertainties associated with the climate change mitigation potential of peatland rewetting, with a particular focus on the impacts of individual and compound extreme events and legacy effects, as well as adaptation options.

Project leaders: Prof. Dr. Nicole Wrage-Mönnig (University of Rostock), Prof Dr. Tim Uirch (University of Greifswald)

In this synthesis project, we tackle the complex relationships between autotrophic and heterotrophic macro- and micro-organisms that determine whether rewetted peatlands are sources or sinks of the GHG CO2, CH4, and N2O. Generally, C is fixed by plants and autotrophic microbes, while heterotrophic microorganisms are the main decomposers, ultimately controlling the C and N emissions. All microbial processes are governed by (1) physico-chemical properties and (2) biotic interactions. Thus, the quality and quantity of plant biomass are important determinants of the substrate for the below-ground (micro-)biota, which in turn control biomass decomposition (Zak et al. 2019; Hinzke et al. 2021) and mineralization, supplying nutrients to the plants and producing/consuming the GHG CO2, CH4 and N2O.

We aim to understand the complex interactions between physico-chemical properties, plants and below-ground (micro-)biota composition/activity, and the production and consumption of organic matter and GHG. We hypothesize that a) plant growth dynamics as well as trophic interactions drive GHG production, and b) that a microbiome-based proxy for the methane sink or source status of wetscapes can be developed. For this purpose, S1 aims to integrate information from subprojects spanning all project areas to obtain a comprehensive picture of the various players and their interactions. (1) We will assess the effect of plant exudates and root aeration on microbial composition/activities and GHG production. (2) We will carry out an integrated multidimensional analysis of available data on factors controlling mineralization and GHG production. (3) We will develop a simple microbiome-based proxy for the methane sink or source status of rewetted fens using eDNA and/or eRNA approaches.

Project leaders: Dr. John Couwenberg (University of Greifswald), Prof. Dr. Gerald Jurasinski (University of Greifswald), Prof. Dr. Bernd Lennartz (University of Rostock)

Contributing to the Overarching Research Question 2, S2 will quantify four key ecosystem functions of peatlands, i.e. the storage of C, nutrients, water and information, all of which are related to services to humans. In S2 we develop a conceptual model of fen peat formation (KAARLO), describing peat growth after rewetting, explicitly considering that rewetted peatlands are novel ecosystems (Kreyling et al. 2021). In contrast to pristine peat, rewetted, formerly drained fen peat is characterized by degraded peat horizons, which are modified upon rewetting by hydraulic/mechanical forces and biological processes such as root growth and microbiological activity. The accumulation of plant litter or organic mud and eventually fresh peat on top of the degraded peat horizon is the second central process resulting from rewetting. Both the degraded and the newly developed peat horizons together form a novel type of peat. In S2 we characterize and quantify multiple processes that control the storage functions of this peat. The conceptual model describes peat formation at the pedon-scale including hydro-physical and geochemical properties with depth and time after rewetting as a function of state variables, such as water table, concentrations of relevant elements (C, N, sulur, phosphorus) and plant community composition. Resulting transport, exchange, and biogeochemical processes as well as feedback-loops impacting the development of displacement peat will be characterized.

Project leaders: Prof. Dr. Florian Jansen (University of Rostock), Dr. Mia Bengtsson (University of Greifswald), Prof. Dr. Philip Marzahn (University of Rostock), Prof. Dr. Sebastian van der Linden (University of Greifswald)

Natural peatlands are characterized by strong self-regulating mechanisms, which have been well studied in bogs but less so in fens. These mechanisms are lost when peatlands are drained and rewetting does not lead to rapid regeneration. Rewetted fens typically exhibit a high degree of spatio-temporal heterogeneity in soil properties, micro-relief, vegetation patterns, and microbial communities. The spatial decoupling of processes during drainage leads to idiosyncratic patterns in rewetted fens of, inter alia, microrelief, conductivity, and most obviously vegetation, which hinder the predictability of the processes responsible for the biodiversity, GHG balance and paludiculture potential of these novel ecosystems. The rewetting process in general and the spatial patterns mentioned in particular, are related to the land use and land cover during drainage and the degree of peat degradation, e.g. by peat extraction, drainage, and differences in shrinkage. At the same time, these spatial patterns and the resulting differences in processes and distribution of information (e.g. eDNA and microbiota) are expected to determine the development pathways of rewetted fens, in particular the desirable return to near-natural conditions, including reduction of GHG emissions, new peat accumulation and the regeneration of natural habitats or a sustainable paludiculture. A deeper understanding of the spatial dependencies, intra- and inter-annual variability, and the future trajectories of restored wetscapes is urgently needed. Particular attention will be paid to the distribution of microbial communities and their relationship with other elements such as vegetation, biomass, hydrology and GHG emissions. The hydrological connectivity between patches, the ability to intercept residual runoff with suitable vegetation and the development of a porous topsoil are considered prerequisites for renewed self-regulation.

Project leaders: Prof. Dr. Doerthe Tetzlaff (IGB Leibniz Institute of Freshwater Ecology and Inland Fisheries), Prof. Dr. Gerald Jurasinski (University of Greifswald), Prof. Dr. Julia Pongratz (Ludwig Maximilians University München)

Although the concept that peatlands are closely linked to and embedded in their landscapes is old, the quantification of energy, material, and information flows, based on a thorough understanding of the associated processes involved is relatively new. For example, there is still limited understanding of how physical and biogeochemical processes and the microclimate in fens influence important ecosystem functioning of entire peatland landscapes. It is also fairly unclear how global change will affect the peatland capacities in terms of adaptation and mitigation. While projects C1, C5 and A7 focus on specific scales and on the processes the models used in these projects were specifically developed for, synthesis project S4 will integrate these processes and feedbacks across and beyond individual models’ answering ORQ4: How do rewetted peatlands interact with and feed back to the landscape and beyond? In S4, we will integrate novel data obtained from the monitoring in WETSCAPES2.0 into process-based modeling approaches, with improved model parametrisation via data assimilation products and machine learning approaches to quantify physical and biogeochemical process interactions and feedbacks between rewetted peatlands and the landscapes they are imbedded in. These feedback mechanisms include ecohydrological fluxes (such as transpiration, evaporation, lateral subsurface and surface fluxes), surface energy fluxes (such as from altered roughness length and bowen ratio), and GHG fluxes with the novel, improved, integrated modeling of S4 allowing us to quantify these feedbacks across spatial scales. Thus, S4 aims to quantify the heterogeneous spatio-temporal process patterns and dynamics in restored wetscapes as well as their potentials of climate change mitigation and adaptation at various scales. The specific objectives are: (1) to quantify physical and biogeochemical process-interactions and feedbacks between peatlands, their landscapes and beyond, (2) to identify the challenges and uncertainties in quantifying these feedbacks at larger areas and across scales via multiple, integrated approaches; (3) to use process-based models as learning frameworks by informing and enhancing data collection and experimental setup schemes as well as model structures to reduce uncertainties in the future. Different process-based modeling frameworks (details in C1, C5 and A7) will be integrated to assess the consequences of peatland rewetting from local to regional scale. We are neither proposing interactive model coupling nor ensemble modeling, but rather take advantage of the individual modeling strengths and foci, while improving model parametrization through collaboration and exchange both with the different projects actually measuring on the sites as well as the modeling projects, and making use of the experimental WETSCAPES2.0 sites. The site-level simulations of peat formation and decomposition (A7, S2) will complement the assessment of GHG fluxes and climate impacts providing process insights to improve the landscape-scale ecohydrological model (C1) and the regional-scale dynamic vegetation model (C5). The tracer-based landscape-scale model (C1) provides simulated quantification of water fluxes (E, T, Q, GW recharge) and stores (interception, storages). C5 provides (simulated results on) biomass productivity, vegetation CO2 fluxes, albedo, roughness length, heat and land surface energy fluxes. Linked to the landscape-scale ecohydrological model (C1), the calibrated DAMM-GHG model from A7 will be forced by landscape-scale differences in soil moisture to compare GHG emissions from rewetted peatlands and the surrounding landscapes. C1 will further use the local climate data from C5. It is important to note and to distinguish between the projects A7, C1 and C5: the actual processes will be quantified in these respective projects, but to be able to quantify the feedbacks across scales and between fens and landscapes, an integrated approach like the one proposed in S4 is crucial. Close collaboration during parametrization will ensure maximum consistency between the models. To improve model parametrization, S4 will further incorporate spatially and temporally highly resolved information on biophysical conditions from Earth Observation (B6, C4, S3: e.g. soil moisture, vegetation type/fractions, biomass, state variables). Through these inter-linked modeling experiments, we can improve model parametrization moving beyond the use of literature values (which is the common approach) and holistically assess GHG as well as water and energy fluxes. Parametrization will further be improved by Machine Learning Models, used to extrapolate sparse parameter sets in time and/or space (closely collaborating with S3). These modelling experiments will provide the basis for a later assessment of the importance of temperate fen rewetting for the global climate system and sets up the process-based modeling framework for the explicit consideration of different land use management scenarios in phase 2 of WETSCAPES2.0. Further, S4 has a strong focus on upscaling and testing which parametrization is required at coarser grid scales of the regional climate modeling systems. Therefore, a major added value from S4 derives from linking peatland landscape scales with regional scales as well as linking water and energy fluxes and water storage with vegetation and peat dynamics. S4 will fuse process-based modelling and machine learning models with findings from field and remote sensing data (from the relevant projects), and thus, provide an integrated peatland-landscape perspective on ecosystem functioning and feedbacks to local and regional climates when temperate fens are rewetted or land use is altered to investigate the potential (extreme) impacts of land use decision making. The resulting novel understanding gained by S4 will be cross-fertilized with insights from synthesis projects S1-S3 to reconcile our process understanding of peatland rewetting, from the micro to the macro scale.

Project leaders: Prof. Dr. Jürgen Kreyling (University of Greifswald), Prof. Dr. Nicole Wrage-Mönnig (University of Rostock)

Z1 coordinates the interdisciplinary research and supports the whole consortium administratively. The internal communication and integration are fostered by project meetings in various compositions and formats. Our five Mercator Fellows, an annual lecture series and an international symposium to be held in year four of the first phase will support networking and mutual exchange of ideas and developments. All these activities are coordinated in Z1, where a central Scientific Coordinator will support the spokespersons in the operative management of WETSCAPES2.0. In this regard, the central Scientific Coordinator will liaise closely with the technical staff (Z2), the Integrator-Postdocs (S1-S4) and the central Data Steward (postdoc Z3) to ensure that experiments and sampling campaigns are synchronized and can be used for joint analyses beyond the single projects. The Coordinator will furthermore manage the communication with the DFG.

Administratively, Z1 provides the central management of WETSCAPES2.0, including the organization of internal meetings, caring for guests (e.g. the Mercator Fellows described below or speakers in the WETSCAPES2.0 colloquium), interacting with the land owners and relevant administrative authorities concerning the study sites, and establishing gender equality and family support measures. The Scientific Coordinator is based at UG. For these foreseeable and any unexpected tasks that come up in particular with the coordination of all field sites and the WETSCAPES2.0 administration at UR, the Scientific Coordinator will be supported by an administrative manager (100% administrative position) at UR, who is funded by UR.

Z1 provides the project-related travel such as frequent field trips with university-owned cars and conferences for the staff of the central projects, i.e. the Scientific Coordinator (Z1), the technical staff (Z2), the Data Steward (postdoc Z3), the Coordinator of the IRTG (Z4), PR Manager (Z5) and the spokespersons. Z1 furthermore manages all general travel expenses of all WETSCAPES2.0 members (project meetings, workshops, participation at conferences, lab exchanges). Project-specific travel to field sites, though, is organized by each project to its own needs (see each single project‘s funding plans). We furthermore request funds to invite guests such as the speakers in the annual WETSCAPES2.0 colloquium organized together with the Alfried Krupp Wissenschaftskolleg Greifswald, cooperation partners and members of the advisory board to Greifswald or Rostock.

We will integrate renowned, internationally-based researchers into WETSCAPES2.0 via five Mercator Fellowships. The Mercator Fellows will contribute additional disciplinary expertise and international background (see 1.2.2.7 ‘Cooperation concept’ and the single project descriptions for details). They will visit WETSCAPES2.0 for field work and joint analyses, will provide additional input to annual meetings and workshops, will be available for lab exchanges of our doctoral and postdoctoral researchers, and will generally be linked to WETSCAPES2.0 for the full first phase. This will lead to intensive and sustainable exchange with researchers from abroad and add additional value to the consortium. We request lump sums to remunerate their expenses during stays in Rostock or Greifswald as well as to enable additional experiments and analyses. The Coordinating Board will decide upon the use of the lump sums upon request.

We ask for the full standard allowance for gender equality measures in order to increase the number of female researchers’ project leadership level in the future, increase the career qualifications in addition to the academic qualifications of early-career female researchers working in WETSCAPES2.0, and to make jobs in science and academia more family-friendly. See 1.4.2 for details on gender equality measures.

We request funding for an international conference ‘Wetscapes 2.0 - local to global consequences of peatland rewetting’ in order to discuss our results of the first phase with international colleagues and practitioners and get their input on recent insights into the topic. We draw on the very positive experience of our international ‘WETSCAPES Conference - Understanding the ecology of restored fen peatlands for protection and sustainable use’ with 157 participants from 21 countries in 2019. Introductory and further specific workshops fostering international communication are covered in the IRTG (Z4).

We apply for lump-sum funds covering open-access publication costs, postdoc start-up grants, and an innovation fund. We strongly believe in the benefits of open science and open publication and will invest parts of the lump sums into gold open-access publications. Excellent early-career researchers who have recently completed their doctoral degree will be offered start-up grants to prepare them for a role as PI in the upcoming phases of WETSCAPES2.0. They will be able to use the funds as needed, e.g. to finance student research assistants, lab exchanges and/or provide them with short-term contracts. Any early-career researcher from within WETSCAPES2.0 or outside can apply for postdoc start-up funding at any time. This will be prominently announced and transparently managed on the project’s website. Finally, we will create an innovation fund to facilitate rapid investment into novel equipment or project ideas. Any member of WETSCAPES2.0 can apply for innovation funds at any time. The Coordinating Board decides upon all applications for start-up funding and to the innovation fund.

Project leaders: Dr. Anke Günther (University of Rostock), Prof. Dr. Jürgen Kreyling (University of Greifswald)

WETSCAPES2.0 hinges on joint field sites and experiments that require central coordination and maintenance in order to fully exploit their value for interdisciplinary research and to maintain them in a state undisturbed by the expected scientific traffic. In project Z2, we set up the basic infrastructure for all field sites, assemble the (land use) history of the sites and support the sampling campaigns of all Research Projects. This includes for instance the installation of boardwalks to reduce disturbance at sensitive sites. Z2 conducts monitoring of all field sites with respect to basic environmental state variables such as groundwater table, soil moisture, or temperature. These data will be monitored live and continuously. Z2 also provides a basic characterization of all sites concerning their peat and stores frozen samples for long-term scientific use. In the L-LExps sites, the basic instrumentation for monitoring environmental conditions described above will be set up in higher spatial resolution and will be augmented by more sophisticated infrastructure such as additional EC towers. Taken together, Z2 provides the infrastructure and the basic environmental data for the sophisticated research of all research projects in WETSCAPES2.0 and will thus provide the data backbone of WETSCAPES2.0.

Project leaders: Prof. Dr. Florian Jansen (University of Rostock), Prof. Dr.-Ing. Kristina Yordanova (University of Greifswald)

In Z3 we will professionally manage the research data along the entire research data life cycle, i.e. from planning and data collection through analysis, visualization and sharing to archiving, publication and re-use. Our goal is to ensure the quality and productivity of WETSCAPES2.0 in terms of data management, but also to promote FAIR data and open, reproducible science. To achieve this, we will survey existing practices and conceptualize seamless workflows for WETSCAPES2.0 in a set of hierarchical data management plans. A comprehensive virtual research environment will be created to promote data acquisition, harmonisation and collaboration among partners. We will develop and implement automated methods to ensure the quality and reproducibility of the collected data following the FAIR principles (Findability, Accessibility, Interoperability, and Reuse). We will provide a training and qualification program for reproducible research, open science and data management in collaboration with Z4 (WETSKILLS). All of these provisions will be implemented in collaboration with the local, joint research data management (RDM) teams including the IT centers and libraries, to ensure transfer and seamless integration into the existing infrastructure. In order to ensure the application of RDM best practices, domain-specific and RDM initiatives such as NFDI4BioDiv, NFDI4Earth, FAIRagro as well as the RDM state initiatives, the Research Data Alliance (RDA), and the Deutsche Initiative für Netzwerkinformation e.V. (DINI/nestor) will be taken into account in the conceptual design and implementation of the RDM solutions. Figure Z3.1 illustrates the framework in which Z3 is embedded for the collaborative design, adaptation and implementation of RDM best practices within WETSCAPES2.0.

Project leaders: PD Dr. Franziska Tanneberger (University of Greifswald), Prof. Dr. Gerald Jurasinski (University of Greifswald)

Our main research topic - rewetted fen peatlands in their landscape setting - is not only of scientific interest, but also of high societal and political relevance. In an interdisciplinary and large project like WETSCAPES2.0 effective Public Relations (PR) is vital to ensure that the newest results are presented appropriately and immediately to a variety of audiences at the local, regional, national, and international level. The objectives of the project PR are

• to translate a broad range of different research activities and results into clear messages and knowledge for stakeholders and the general public;

• to transfer the outcome of the project to the target audiences at the local, regional, national, and international level using both ‚classic‘ science-PR measures and a bi-directional, dialogue-oriented approach;

• to employ innovative, collaborative measures on (1) past, current and future perceptions of peatlands in landscapes (wetscapes) and (2) on land use and livelihoods in/with wet peatlands (in collaboration with the DFG excellence cluster Matters of Activitiy).

Together with all consortium partners and the PR units of the applicant universities, we are developing our communication strategy, building on the experience from previous projects and identification of key target groups and objectives. This communication strategy will be a dynamic document and take up outcomes and feedback gathered from dialogue with stakeholders. Main target groups are 1) the general public, 2) the scientific community, and 3) key peatland-related stakeholders at the regional MV, national, EU, and global level.

An exemplary list of selected topics, working methods, results or findings from WETSCAPES2.0 we deem suitable to be put into the centre of communication includes,

• Plant-microbe interactions in the rhizosphere using meta-omics and CARD-FISH ( A3) —> Visualizes how plants and microbes interact in the hidden world of peat, showcases the interdependencies between these partners;

• UAS based Eddy Covariance measurements to explore the spatial aspect of heat and carbon fluxes (B2) —> Visualize „hotspots of success“ (e.g. particularly strong CO2 uptake), pin-points spots with room for improvement, shows effects of rewetting in the larger landscape context;

• Process-based model simulations to visualize dynamics of water stores and fluxes at different spatial and temporal scales (C1) —> Visualizes and animates water dynamics for stakeholder communication and engagement.

The ‚classic‘ PR measures will be implemented in coordination with the PR units of the two applicant universities UG and UR (through quaterly strategic meetings and rapid exchange in everyday work). The measures will be outlined in the communication strategy and include, e.g., supporting the set-up of a dedicated WETSCAPES2.0 website; creating a corporate design, templates and an editorial plan for social media channels; creating printed products such as flyers; sending out media information (frequency depends on project outcomes, minimum one per year) and integrating the new results on the knowledge platform www.moorWissen.de; supporting WETSCAPES2.0 researchers in presenting their results to the media, e.g. through media training as part of WETSKILLS; developing three short video courses (one each for project area A, B and C) in year 2; supporting researchers in the preparation of policy briefs (one per year); organising a journalist in residence grant (one for a German language media outlet in year 3 and one for an international media outlet in year 4) of 2 months length; contributing to the regular ‚peatland jour fixe‘ of GMC and the Ministry of Agriculture and Environment MV; and organising a Parliamentary Evening at the federal level in the representation of the state of MV in Berlin in year 3.

The transformative collaborative activity 1) looks at past, current, and future appearances of peatlands in landscapes, i.e. wetscapes. It revolves around the question „What do we see and how do we feel in wetscapes?“ and uses artistic interpretation to stimulate and capture emotions and to raise awareness. In 2026-2027, we will run a twinning programme of artists and scientists, bringing together 10 WETSCAPES2.0-scientists with 10 artists interested in peatlands. The results will feed into an art competition „Wetscapes 2.0“. The transformative collaborative activity 2) will address land use in wet peatlands and, thus, builds a bridge towards further works of the WETSCAPES2.0 consortium towards various aspects of paludiculture. It will revolve around the question „How can we live well in wetscapes?“ and is planned in collaboration with Prof. Dr. Lucy Norris and colleagues of the DFG excellence cluster Matters of Activitiy (HU Berlin).