TY  - JOUR
A1  - Hoffmann, Mathias
A1  - Schulz-Hanke, Maximilian
A1  - Alba, Juana Garcia
A1  - Jurisch, Nicole
A1  - Hagemann, Ulrike
A1  - Sachs, Torsten
A1  - Sommer, Michael
A1  - Augustin, Jürgen
T1  - A simple calculation algorithm to separate high-resolution CH4 flux measurements into ebullition- and diffusion-derived components
JF  - Atmospheric measurement techniques : an interactive open access journal of the European Geosciences Union
N2  - Processes driving the production, transformation and transport of methane (CH4 / in wetland ecosystems are highly complex. We present a simple calculation algorithm to separate open-water CH4 fluxes measured with automatic chambers into diffusion-and ebullition-derived components. This helps to reveal underlying dynamics, to identify potential environmental drivers and, thus, to calculate reliable CH4 emission estimates. The flux separation is based on identification of ebullition-related sudden concentration changes during single measurements. Therefore, a variable ebullition filter is applied, using the lower and upper quartile and the interquartile range (IQR). Automation of data processing is achieved by using an established R script, adjusted for the purpose of CH4 flux calculation. The algorithm was validated by performing a laboratory experiment and tested using flux measurement data (July to September 2013) from a former fen grassland site, which converted into a shallow lake as a result of rewetting. Ebullition and diffusion contributed equally (46 and 55 %) to total CH4 emissions, which is comparable to ratios given in the literature. Moreover, the separation algorithm revealed a concealed shift in the diurnal trend of diffusive fluxes throughout the measurement period. The water temperature gradient was identified as one of the major drivers of diffusive CH4 emissions, whereas no significant driver was found in the case of erratic CH4 ebullition events.
Y1  - 2017
U6  - https://doi.org/10.5194/amt-10-109-2017
SN  - 1867-1381
SN  - 1867-8548
VL  - 10
IS  - 1
SP  - 109
EP  - 118
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - GEN
A1  - Hoffmann, Mathias
A1  - Schulz-Hanke, Maximilian
A1  - Alba, Juana Garcia
A1  - Jurisch, Nicole
A1  - Hagemann, Ulrike
A1  - Sachs, Torsten
A1  - Sommer, Michael
A1  - Augustin, Jürgen
T1  - A simple calculation algorithm to separate high-resolution CH4 flux measurements into ebullition- and diffusion-derived components
T2  - Postprints der Universität Potsdam : Mathematisch Naturwissenschaftliche Reihe
N2  - Processes driving the production, transformation and transport of methane (CH4) in wetland ecosystems are highly complex. We present a simple calculation algorithm to separate open-water CH4 fluxes measured with automatic chambers into diffusion- and ebullition-derived components. This helps to reveal underlying dynamics, to identify potential environmental drivers and, thus, to calculate reliable CH4 emission estimates. The flux separation is based on identification of ebullition-related sudden concentration changes during single measurements. Therefore, a variable ebullition filter is applied, using the lower and upper quartile and the interquartile range (IQR). Automation of data processing is achieved by using an established R script, adjusted for the purpose of CH4 flux calculation. The algorithm was validated by performing a laboratory experiment and tested using flux measurement data (July to September 2013) from a former fen grassland site, which converted into a shallow lake as a result of rewetting. Ebullition and diffusion contributed equally (46 and 55 %) to total CH4 emissions, which is comparable to ratios given in the literature. Moreover, the separation algorithm revealed a concealed shift in the diurnal trend of diffusive fluxes throughout the measurement period. The water temperature gradient was identified as one of the major drivers of diffusive CH4 emissions, whereas no significant driver was found in the case of erratic CH4 ebullition events.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 604 
KW  - water methane emissions
KW  - chamber system
KW  - CO2
KW  - lake
KW  - fen
KW  - exchange
KW  - mechanism
KW  - turbulence
KW  - transport
KW  - reservior
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-416659
SN  - 1866-8372
IS  - 604
SP  - 109
EP  - 118
ER  - 
TY  - JOUR
A1  - Walther, Sophia
A1  - Guanter, Luis
A1  - Heim, Birgit
A1  - Jung, Martin
A1  - Duveiller, Gregory
A1  - Wolanin, Aleksandra
A1  - Sachs, Torsten
T1  - Assessing the dynamics of vegetation productivity in circumpolar regions with different satellite indicators of greenness and photosynthesis
JF  - Biogeosciences
N2  - High-latitude treeless ecosystems represent spatially highly heterogeneous landscapes with small net carbon fluxes and a short growing season. Reliable observations and process understanding are critical for projections of the carbon balance of the climate-sensitive tundra. Space-borne remote sensing is the only tool to obtain spatially continuous and temporally resolved information on vegetation greenness and activity in remote circumpolar areas. However, confounding effects from persistent clouds, low sun elevation angles, numerous lakes, widespread surface inundation, and the sparseness of the vegetation render it highly challenging. Here, we conduct an extensive analysis of the timing of peak vegetation productivity as shown by satellite observations of complementary indicators of plant greenness and photosynthesis. We choose to focus on productivity during the peak of the growing season, as it importantly affects the total annual carbon uptake. The suite of indicators are as follows: (1) MODIS-based vegetation indices (VIs) as proxies for the fraction of incident photosynthetically active radiation (PAR) that is absorbed (fPAR), (2) VIs combined with estimates of PAR as a proxy of the total absorbed radiation (APAR), (3) sun-induced chlorophyll fluorescence (SIF) serving as a proxy for photosynthesis, (4) vegetation optical depth (VOD), indicative of total water content and (5) empirically upscaled modelled gross primary productivity (GPP). Averaged over the pan-Arctic we find a clear order of the annual peak as APAR <= GPP < SIF < VIs/VOD. SIF as an indicator of photosynthesis is maximised around the time of highest annual temperatures. The modelled GPP peaks at a similar time to APAR. The time lag of the annual peak between APAR and instantaneous SIF fluxes indicates that the SIF data do contain information on light-use efficiency of tundra vegetation, but further detailed studies are necessary to verify this. Delayed peak greenness compared to peak photosynthesis is consistently found across years and land-cover classes. A particularly late peak of the normalised difference vegetation index (NDVI) in regions with very small seasonality in greenness and a high amount of lakes probably originates from artefacts. Given the very short growing season in circumpolar areas, the average time difference in maximum annual photosynthetic activity and greenness or growth of 3 to 25 days (depending on the data sets chosen) is important and needs to be considered when using satellite observations as drivers in vegetation models.
Y1  - 2018
U6  - https://doi.org/10.5194/bg-15-6221-2018
SN  - 1726-4170
SN  - 1726-4189
VL  - 15
IS  - 20
SP  - 6221
EP  - 6256
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - GEN
A1  - Walther, Sophia
A1  - Guanter, Luis
A1  - Heim, Birgit
A1  - Jung, Martin
A1  - Duveiller, Gregory
A1  - Wolanin, Aleksandra
A1  - Sachs, Torsten
T1  - Assessing the dynamics of vegetation productivity in circumpolar regions with different satellite indicators of greenness and photosynthesis
T2  - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - High-latitude treeless ecosystems represent spatially highly heterogeneous landscapes with small net carbon fluxes and a short growing season. Reliable observations and process understanding are critical for projections of the carbon balance of the climate-sensitive tundra. Space-borne remote sensing is the only tool to obtain spatially continuous and temporally resolved information on vegetation greenness and activity in remote circumpolar areas. However, confounding effects from persistent clouds, low sun elevation angles, numerous lakes, widespread surface inundation, and the sparseness of the vegetation render it highly challenging. Here, we conduct an extensive analysis of the timing of peak vegetation productivity as shown by satellite observations of complementary indicators of plant greenness and photosynthesis. We choose to focus on productivity during the peak of the growing season, as it importantly affects the total annual carbon uptake. The suite of indicators are as follows: (1) MODIS-based vegetation indices (VIs) as proxies for the fraction of incident photosynthetically active radiation (PAR) that is absorbed (fPAR), (2) VIs combined with estimates of PAR as a proxy of the total absorbed radiation (APAR), (3) sun-induced chlorophyll fluorescence (SIF) serving as a proxy for photosynthesis, (4) vegetation optical depth (VOD), indicative of total water content and (5) empirically upscaled modelled gross primary productivity (GPP). Averaged over the pan-Arctic we find a clear order of the annual peak as APAR ≦ GPP<SIF<VIs/VOD. SIF as an indicator of photosynthesis is maximised around the time of highest annual temperatures. The modelled GPP peaks at a similar time to APAR. The time lag of the annual peak between APAR and instantaneous SIF fluxes indicates that the SIF data do contain information on light-use efficiency of tundra vegetation, but further detailed studies are necessary to verify this. Delayed peak greenness compared to peak photosynthesis is consistently found across years and land-cover classes. A particularly late peak of the normalised difference vegetation index (NDVI) in regions with very small seasonality in greenness and a high amount of lakes probably originates from artefacts. Given the very short growing season in circumpolar areas, the average time difference in maximum annual photosynthetic activity and greenness or growth of 3 to 25 days (depending on the data sets chosen) is important and needs to be considered when using satellite observations as drivers in vegetation models.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1025 
KW  - induced chlorophyll Fluorescence
KW  - net ecosystem exchange
KW  - Arctic tundra ecosystems
KW  - gross primary production
KW  - carbon dioxide exchange
KW  - earth system models
KW  - growing season
KW  - climate-change
KW  - alaskan tundra
KW  - high latitudes
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-446205
SN  - 1866-8372
IS  - 1025
SP  - 6221
EP  - 6256
ER  - 
TY  - GEN
A1  - Radosavljevic, Boris
A1  - Lantuit, Hugues
A1  - Pollard, Wayne
A1  - Overduin, Pier Paul
A1  - Couture, Nicole
A1  - Sachs, Torsten
A1  - Helm, Veit
A1  - Fritz, Michael
T1  - Erosion and Flooding - Threats to Coastal Infrastructure in the Arctic: A Case Study from Herschel Island, Yukon Territory, Canada (vol 39, pg 900, 2016)
T2  - Estuaries and coasts : journal of the Estuarine Research Federation
Y1  - 2016
U6  - https://doi.org/10.1007/s12237-016-0115-z
SN  - 1559-2723
SN  - 1559-2731
VL  - 39
SP  - 1294
EP  - 1295
PB  - Springer
CY  - New York
ER  - 
TY  - GEN
A1  - Radosavljevic, Boris
A1  - Lantuit, Hugues
A1  - Pollard, Wayne
A1  - Overduin, Pier Paul
A1  - Couture, Nicole
A1  - Sachs, Torsten
A1  - Helm, Veit
A1  - Fritz, Michael
T1  - Erosion and flooding-threats to coastal Infrastructure in the Arctic
BT  - a case study from Herschel Island, Yukon Territory, Canada
T2  - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - Arctic coastal infrastructure and cultural and archeological sites are increasingly vulnerable to erosion and flooding due to amplified warming of the Arctic, sea level rise, lengthening of open water periods, and a predicted increase in frequency of major storms. Mitigating these hazards necessitates decision-making tools at an appropriate scale. The objectives of this paper are to provide such a tool by assessing potential erosion and flood hazards at Herschel Island, a UNESCO World Heritage candidate site. This study focused on Simpson Point and the adjacent coastal sections because of their archeological, historical, and cultural significance. Shoreline movement was analyzed using the Digital Shoreline Analysis System (DSAS) after digitizing shorelines from 1952, 1970, 2000, and 2011. For purposes of this analysis, the coast was divided in seven coastal reaches (CRs) reflecting different morphologies and/or exposures. Using linear regression rates obtained from these data, projections of shoreline position were made for 20 and 50 years into the future. Flood hazard was assessed using a least cost path analysis based on a high-resolution light detection and ranging (LiDAR) dataset and current Intergovernmental Panel on Climate Change sea level estimates. Widespread erosion characterizes the study area. The rate of shoreline movement in different periods of the study ranges from −5.5 to 2.7 m·a⁻¹ (mean −0.6 m·a⁻¹). Mean coastal retreat decreased from −0.6 m·a⁻¹ to −0.5 m·a⁻¹, for 1952–1970 and 1970–2000, respectively, and increased to −1.3 m·a⁻¹ in the period 2000–2011. Ice-rich coastal sections most exposed to wave attack exhibited the highest rates of coastal retreat. The geohazard map combines shoreline projections and flood hazard analyses to show that most of the spit area has extreme or very high flood hazard potential, and some buildings are vulnerable to coastal erosion. This study demonstrates that transgressive forcing may provide ample sediment for the expansion of depositional landforms, while growing more susceptible to overwash and flooding.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 996 
KW  - Arctic
KW  - coastal erosion
KW  - UNESCO
KW  - vulnerability mapping;
KW  - permafrost coasts
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-432279
SN  - 1866-8372
IS  - 996
ER  - 
TY  - JOUR
A1  - Radosavljevic, Boris
A1  - Lantuit, Hugues
A1  - Pollard, Wayne
A1  - Overduin, Pier Paul
A1  - Couture, Nicole
A1  - Sachs, Torsten
A1  - Helm, Veit
A1  - Fritz, Michael
T1  - Erosion and Flooding-Threats to Coastal Infrastructure in the Arctic: A Case Study from Herschel Island, Yukon Territory, Canada
JF  - Estuaries and coasts : journal of the Estuarine Research Federation
N2  - Arctic coastal infrastructure and cultural and archeological sites are increasingly vulnerable to erosion and flooding due to amplified warming of the Arctic, sea level rise, lengthening of open water periods, and a predicted increase in frequency of major storms. Mitigating these hazards necessitates decision-making tools at an appropriate scale. The objectives of this paper are to provide such a tool by assessing potential erosion and flood hazards at Herschel Island, a UNESCO World Heritage candidate site. This study focused on Simpson Point and the adjacent coastal sections because of their archeological, historical, and cultural significance. Shoreline movement was analyzed using the Digital Shoreline Analysis System (DSAS) after digitizing shorelines from 1952, 1970, 2000, and 2011. For purposes of this analysis, the coast was divided in seven coastal reaches (CRs) reflecting different morphologies and/or exposures. Using linear regression rates obtained from these data, projections of shoreline position were made for 20 and 50 years into the future. Flood hazard was assessed using a least cost path analysis based on a high-resolution light detection and ranging (LiDAR) dataset and current Intergovernmental Panel on Climate Change sea level estimates. Widespread erosion characterizes the study area. The rate of shoreline movement in different periods of the study ranges from -5.5 to 2.7 mI double dagger a(-1) (mean -0.6 mI double dagger a(-1)). Mean coastal retreat decreased from -0.6 mI double dagger a(-1) to -0.5 mI double dagger a(-1), for 1952-1970 and 1970-2000, respectively, and increased to -1.3 mI double dagger a(-1) in the period 2000-2011. Ice-rich coastal sections most exposed to wave attack exhibited the highest rates of coastal retreat. The geohazard map combines shoreline projections and flood hazard analyses to show that most of the spit area has extreme or very high flood hazard potential, and some buildings are vulnerable to coastal erosion. This study demonstrates that transgressive forcing may provide ample sediment for the expansion of depositional landforms, while growing more susceptible to overwash and flooding.
KW  - Arctic
KW  - Coastal erosion
KW  - UNESCO
KW  - Vulnerability mapping
KW  - Permafrost coasts
Y1  - 2016
U6  - https://doi.org/10.1007/s12237-015-0046-0
SN  - 1559-2723
SN  - 1559-2731
VL  - 39
SP  - 900
EP  - 915
PB  - Springer
CY  - New York
ER  - 
TY  - JOUR
A1  - Heinrich, Ingo
A1  - Balanzategui, Daniel
A1  - Bens, Oliver
A1  - Blasch, Gerald
A1  - Blume, Theresa
A1  - Boettcher, Falk
A1  - Borg, Erik
A1  - Brademann, Brian
A1  - Brauer, Achim
A1  - Conrad, Christopher
A1  - Dietze, Elisabeth
A1  - Dräger, Nadine
A1  - Fiener, Peter
A1  - Gerke, Horst H.
A1  - Güntner, Andreas
A1  - Heine, Iris
A1  - Helle, Gerhard
A1  - Herbrich, Marcus
A1  - Harfenmeister, Katharina
A1  - Heussner, Karl-Uwe
A1  - Hohmann, Christian
A1  - Itzerott, Sibylle
A1  - Jurasinski, Gerald
A1  - Kaiser, Knut
A1  - Kappler, Christoph
A1  - Koebsch, Franziska
A1  - Liebner, Susanne
A1  - Lischeid, Gunnar
A1  - Merz, Bruno
A1  - Missling, Klaus Dieter
A1  - Morgner, Markus
A1  - Pinkerneil, Sylvia
A1  - Plessen, Birgit
A1  - Raab, Thomas
A1  - Ruhtz, Thomas
A1  - Sachs, Torsten
A1  - Sommer, Michael
A1  - Spengler, Daniel
A1  - Stender, Vivien
A1  - Stüve, Peter
A1  - Wilken, Florian
T1  - Interdisciplinary Geo-ecological Research across Time Scales in the Northeast German Lowland Observatory (TERENO-NE)
JF  - Vadose zone journal
N2  - The Northeast German Lowland Observatory (TERENO-NE) was established to investigate the regional impact of climate and land use change. TERENO-NE focuses on the Northeast German lowlands, for which a high vulnerability has been determined due to increasing temperatures and decreasing amounts of precipitation projected for the coming decades. To facilitate in-depth evaluations of the effects of climate and land use changes and to separate the effects of natural and anthropogenic drivers in the region, six sites were chosen for comprehensive monitoring. In addition, at selected sites, geoarchives were used to substantially extend the instrumental records back in time. It is this combination of diverse disciplines working across different time scales that makes the observatory TERENO-NE a unique observation platform. We provide information about the general characteristics of the observatory and its six monitoring sites and present examples of interdisciplinary research activities at some of these sites. We also illustrate how monitoring improves process understanding, how remote sensing techniques are fine-tuned by the most comprehensive ground-truthing site DEMMIN, how soil erosion dynamics have evolved, how greenhouse gas monitoring of rewetted peatlands can reveal unexpected mechanisms, and how proxy data provides a long-term perspective of current ongoing changes.
Y1  - 2018
U6  - https://doi.org/10.2136/vzj2018.06.0116
SN  - 1539-1663
VL  - 17
IS  - 1
PB  - Soil Science Society of America
CY  - Madison
ER  - 
TY  - THES
A1  - Sachs, Torsten
T1  - Land-atmosphere interactions on different scales
Y1  - 2009
CY  - Potsdam
ER  - 
TY  - JOUR
A1  - Wen, Xi
A1  - Unger, Viktoria
A1  - Jurasinski, Gerald
A1  - Koebsch, Franziska
A1  - Horn, Fabian
A1  - Rehder, Gregor
A1  - Sachs, Torsten
A1  - Zak, Dominik
A1  - Lischeid, Gunnar
A1  - Knorr, Klaus-Holger
A1  - Boettcher, Michael E.
A1  - Winkel, Matthias
A1  - Bodelier, Paul L. E.
A1  - Liebner, Susanne
T1  - Predominance of methanogens over methanotrophs in rewetted fens characterized by high methane emissions
JF  - Biogeosciences
N2  - The rewetting of drained peatlands alters peat geochemistry and often leads to sustained elevated methane emission. Although this methane is produced entirely by microbial activity, the distribution and abundance of methane-cycling microbes in rewetted peatlands, especially in fens, is rarely described. In this study, we compare the community composition and abundance of methane-cycling microbes in relation to peat porewater geochemistry in two rewetted fens in northeastern Germany, a coastal brackish fen and a freshwater riparian fen, with known high methane fluxes. We utilized 16S rRNA high-throughput sequencing and quantitative polymerase chain reaction (qPCR) on 16S rRNA, mcrA, and pmoA genes to determine microbial community composition and the abundance of total bacteria, methanogens, and methanotrophs. Electrical conductivity (EC) was more than 3 times higher in the coastal fen than in the riparian fen, averaging 5.3 and 1.5 mS cm(-1), respectively. Porewater concentrations of terminal electron acceptors (TEAs) varied within and among the fens. This was also reflected in similarly high intra- and inter-site variations of microbial community composition. Despite these differences in environmental conditions and electron acceptor availability, we found a low abundance of methanotrophs and a high abundance of methanogens, represented in particular by Methanosaetaceae, in both fens. This suggests that rapid (re) establishment of methanogens and slow (re) establishment of methanotrophs contributes to prolonged increased methane emissions following rewetting.
Y1  - 2018
U6  - https://doi.org/10.5194/bg-15-6519-2018
SN  - 1726-4170
SN  - 1726-4189
VL  - 15
IS  - 21
SP  - 6519
EP  - 6536
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Tanski, Georg
A1  - Wagner, Dirk
A1  - Knoblauch, Christian
A1  - Fritz, Michael
A1  - Sachs, Torsten
A1  - Lantuit, Hugues
T1  - Rapid CO2 Release From Eroding Permafrost in Seawater
JF  - Geophysical research letters
Y1  - 2019
U6  - https://doi.org/10.1029/2019GL084303
SN  - 0094-8276
SN  - 1944-8007
VL  - 46
IS  - 20
SP  - 11244
EP  - 11252
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Obu, Jaroslav
A1  - Lantuit, Hugues
A1  - Fritz, Michael
A1  - Pollard, Wayne H.
A1  - Sachs, Torsten
A1  - Guenther, Frank
T1  - Relation between planimetric and volumetric measurements of permafrost coast erosion: a case study from Herschel Island, western Canadian Arctic
JF  - Polar research : a Norwegian journal of Polar research
N2  - Ice-rich permafrost coasts often undergo rapid erosion, which results in land loss and release of considerable amounts of sediment, organic carbon and nutrients, impacting the near-shore ecosystems. Because of the lack of volumetric erosion data, Arctic coastal erosion studies typically report on planimetric erosion. Our aim is to explore the relationship between planimetric and volumetric coastal erosion measurements and to update the coastal erosion rates on Herschel Island in the Canadian Arctic. We used high-resolution digital elevation models to compute sediment release and compare volumetric data to planimetric estimations of coastline movements digitized from satellite imagery. Our results show that volumetric erosion is locally less variable and likely corresponds better with environmental forcing than planimetric erosion. Average sediment release volumes are in the same range as sediment release volumes calculated from coastline movements combined with cliff height. However, the differences between these estimates are significant for small coastal sections. We attribute the differences between planimetric and volumetric coastal erosion measurements to mass wasting, which is abundant along the coasts of Herschel Island. The average recorded coastline retreat on Herschel Island was 0.68m a(-1) for the period 2000-2011. Erosion rates increased by more than 50% in comparison with the period 1970-2000, which is in accordance with a recently observed increase along the Alaskan Beaufort Sea. The estimated annual sediment release was 28.2 m(3) m(-1) with resulting fluxes of 590 kg C m(-1) and 104 kg N m(-1).
KW  - Coastal erosion
KW  - LiDAR
KW  - carbon fluxes
KW  - mass wasting
KW  - landslides
KW  - digital elevation model
Y1  - 2016
U6  - https://doi.org/10.3402/polar.v35.30313
SN  - 0800-0395
SN  - 1751-8369
VL  - 35
SP  - 57
EP  - 99
PB  - Co-Action Publ.
CY  - Jarfalla
ER  - 
TY  - JOUR
A1  - Koebsch, Franziska
A1  - Winkel, Matthias
A1  - Liebner, Susanne
A1  - Liu, Bo
A1  - Westphal, Julia
A1  - Schmiedinger, Iris
A1  - Spitzy, Alejandro
A1  - Gehre, Matthias
A1  - Jurasinski, Gerald
A1  - Köhler, Stefan
A1  - Unger, Viktoria
A1  - Koch, Marian
A1  - Sachs, Torsten
A1  - Böttcher, Michael E.
T1  - Sulfate deprivation triggers high methane production in a disturbed and rewetted coastal peatland
JF  - Biogeosciences
N2  - In natural coastal wetlands, high supplies of marine sulfate suppress methanogenesis. Coastal wetlands are, however, often subject to disturbance by diking and drainage for agricultural use and can turn to potent methane sources when rewetted for remediation. This suggests that preceding land use measures can suspend the sulfate-related methane suppressing mechanisms. Here, we unravel the hydrological relocation and biogeochemical S and C transformation processes that induced high methane emissions in a disturbed and rewetted peatland despite former brackish impact. The underlying processes were investigated along a transect of increasing distance to the coastline using a combination of concentration patterns, stable isotope partitioning, and analysis of the microbial community structure. We found that diking and freshwater rewetting caused a distinct freshening and an efficient depletion of the brackish sulfate reservoir by dissimilatory sulfate reduction (DSR). Despite some legacy effects of brackish impact expressed as high amounts of sedimentary S and elevated electrical conductivities, contemporary metabolic processes operated mainly under sulfate-limited conditions. This opened up favorable conditions for the establishment of a prospering methanogenic community in the top 30-40 cm of peat, the structure and physiology of which resemble those of terrestrial organic-rich environments. Locally, high amounts of sulfate persisted in deeper peat layers through the inhibition of DSR, probably by competitive electron acceptors of terrestrial origin, for example Fe(III). However, as sulfate occurred only in peat layers below 30-40 cm, it did not interfere with high methane emissions on an ecosystem scale. Our results indicate that the climate effect of disturbed and remediated coastal wetlands cannot simply be derived by analogy with their natural counterparts. From a greenhouse gas perspective, the re-exposure of diked wetlands to natural coastal dynamics would literally open up the floodgates for a replenishment of the marine sulfate pool and therefore constitute an efficient measure to reduce methane emissions.
Y1  - 2019
U6  - https://doi.org/10.5194/bg-16-1937-2019
SN  - 1726-4170
SN  - 1726-4189
VL  - 16
IS  - 9
SP  - 1937
EP  - 1953
PB  - Copernicus
CY  - Göttingen
ER  -