Articles | Volume 15, issue 12
Research article 20 Jun 2018
Research article | 20 Jun 2018
The devil's in the disequilibrium: multi-component analysis of dissolved carbon and oxygen changes under a broad range of forcings in a general circulation model
Sarah Eggleston and Eric D. Galbraith
Related subject area
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Sedimentary fluxes rather than pelagic production in oxic conditions sustain methanotrophy and emissions to the atmosphereOrganic matter and sediment properties determine in-lake variability of sediment CO2 and CH4 production and emissions of a small and shallow lakeEvaluating stream CO2 outgassing via Drifting and Anchored flux chambers in a controlled flume experimentMineralization of organic matter in boreal lake sediments: rates, pathways, and nature of the fermenting substratesTopography-based modelling reveals high spatial variability and seasonal emission patches in forest floor methane fluxTechnical note: CO2 is not like CH4 – limits of and corrections to the headspace method to analyse pCO2 in waterComparison of greenhouse gas fluxes and microbial communities from tropical forest and adjacent oil palm plantations on mineral soilTechnical note: Facilitating the use of low-cost methane (CH4) sensors in flux chambers – calibration, data processing, and an open-source make-it-yourself loggerN2O changes from the Last Glacial Maximum to the preindustrial – Part 2: terrestrial N2O emissions and carbon–nitrogen cycle interactionsCarbon dioxide and methane fluxes from different surface types in a created urban wetlandA decade of methane measurements at the Boknis Eck Time Series Station in Eckernförde Bay (southwestern Baltic Sea)Dissolved CH4 coupled to photosynthetic picoeukaryotes in oxic waters and to cumulative chlorophyll a in anoxic waters of reservoirsMemory effects on greenhouse gas emissions (CO2, N2O and CH4) following grassland restoration?Carbon dioxide dynamics in an agricultural headwater stream driven by hydrology and primary productionDecadal variation in CO2 fluxes and its budget in a wheat and maize rotation cropland over the North China PlainSoil greenhouse gas emissions under different land-use types in savanna ecosystems of KenyaSeasonality of greenhouse gas emission factors from biomass burning in the Brazilian CerradoWarming enhances carbon dioxide and methane fluxes from Red Sea seagrass (Halophila stipulacea) sedimentsCarbon–nitrogen interactions in European forests and semi-natural vegetation – Part 1: Fluxes and budgets of carbon, nitrogen and greenhouse gases from ecosystem monitoring and modellingCarbon–nitrogen interactions in European forests and semi-natural vegetation – Part 2: Untangling climatic, edaphic, management and nitrogen deposition effects on carbon sequestration potentialsMaize root and shoot litter quality controls short-term CO2 and N2O emissions and bacterial community structure of arable soilThe carbon footprint of a Malaysian tropical reservoir: measured versus modelled estimates highlight the underestimated key role of downstream processesEffect of legume intercropping on N2O emissions and CH4 uptake during maize production in the Great Rift Valley, EthiopiaRegulation of N2O emissions from acid organic soil drained for agricultureNitrous oxide (N2O) and methane (CH4) in rivers and estuaries of northwestern BorneoRegulation of carbon dioxide and methane in small agricultural reservoirs: optimizing potential for greenhouse gas uptakeMethane production by three widespread marine phytoplankton species: release rates, precursor compounds, and potential relevance for the environmentCO2 and CH4 budgets and global warming potential modifications in Sphagnum-dominated peat mesocosms invaded by Molinia caeruleaA multi-year observation of nitrous oxide at the Boknis Eck Time Series Station in the Eckernförde Bay (southwestern Baltic Sea)Air–sea fluxes of greenhouse gases and oxygen in the northern Benguela Current region during upwelling eventsN2O changes from the Last Glacial Maximum to the preindustrial – Part 1: Quantitative reconstruction of terrestrial and marine emissions using N2O stable isotopes in ice coresVariations in dissolved greenhouse gases (CO2, CH4, N2O) in the Congo River network overwhelmingly driven by fluvial-wetland connectivityGreenhouse gas and energy fluxes in a boreal peatland forest after clear-cuttingCarbon dioxide (CO2) concentrations and emission in the newly constructed Belo Monte hydropower complex in the Xingu River, AmazoniaTechnical note: Interferences of volatile organic compounds (VOCs) on methane concentration measurementsApplicability and consequences of the integration of alternative models for CO2 transfer velocity into a process-based lake modelAttribution of N2O sources in a grassland soil with laser spectroscopy based isotopocule analysisThe ratio of methanogens to methanotrophs and water-level dynamics drive methane transfer velocity in a temperate kettle-hole peat bogTechnical Note: Isotopic corrections for the radiocarbon composition of CO2 in the soil gas environment must account for diffusion and diffusive mixingQuantifying the impact of emission outbursts and non-stationary flow on eddy-covariance CH4 flux measurements using wavelet techniquesIdeas and perspectives: is shale gas a major driver of recent increase in global atmospheric methane?
Lauri Heiskanen, Juha-Pekka Tuovinen, Aleksi Räsänen, Tarmo Virtanen, Sari Juutinen, Annalea Lohila, Timo Penttilä, Maiju Linkosalmi, Juha Mikola, Tuomas Laurila, and Mika Aurela
Biogeosciences, 18, 873–896,Short summary
We studied ecosystem- and plant-community-level carbon (C) exchange between subarctic mire and the atmosphere during 2017–2018. We found strong spatial variation in CO2 and CH4 dynamics between the main plant communities. The earlier onset of growing season in 2018 strengthened the CO2 sink of the ecosystem, but this gain was counterbalanced by a later drought period. Variation in water table level, soil temperature and vegetation explained most of the variation in ecosystem-level C exchange.
Sudhanshu Pandey, Sander Houweling, Alba Lorente, Tobias Borsdorff, Maria Tsivlidou, A. Anthony Bloom, Benjamin Poulter, Zhen Zhang, and Ilse Aben
Biogeosciences, 18, 557–572,Short summary
We use atmospheric methane observations from the novel TROPOspheric Monitoring Instrument (TROPOMI; Sentinel-5p) to estimate methane emissions from South Sudan's wetlands. Our emission estimates are an order of magnitude larger than the estimate of process-based wetland models. We find that this underestimation by the models is likely due to their misrepresentation of the wetlands' inundation extent and temperature dependences.
Paula Alejandra Lamprea Pineda, Marijn Bauters, Hans Verbeeck, Selene Baez, Matti Barthel, Samuel Bodé, and Pascal Boeckx
Biogeosciences, 18, 413–421,Short summary
Tropical forest soils are an important source and sink of greenhouse gases (GHGs) with tropical montane forests having been poorly studied. In this pilot study, we explored soil fluxes of CO2, CH4, and N2O in an Ecuadorian neotropical montane forest, where a net consumption of N2O at higher altitudes was observed. Our results highlight the importance of short-term variations in N2O and provide arguments and insights for future, more detailed studies on GHG fluxes from montane forest soils.
Bruna R. F. Oliveira, Carsten Schaller, J. Jacob Keizer, and Thomas Foken
Biogeosciences, 18, 285–302,Short summary
Forest fires have a significant impact on carbon dioxide emissions. The present study from a pine forest in Portugal is one of the few where measurements of CO2 fluxes were started immediately (1.5 months) after the forest fire. Carbon dioxide emissions were linked to soil humidity. Therefore, they started after the beginning of the rainfall in autumn. Due to the beginning of vegetation, the site was already a carbon dioxide sink the following year.
Hui Zhang, Eeva-Stiina Tuittila, Aino Korrensalo, Aleksi Räsänen, Tarmo Virtanen, Mika Aurela, Timo Penttilä, Tuomas Laurila, Stephanie Gerin, Viivi Lindholm, and Annalea Lohila
Biogeosciences, 17, 6247–6270,Short summary
We studied the impact of a stream on peatland microhabitats and CH4 emissions in a northern boreal fen. We found that there were higher water levels, lower peat temperatures, and greater oxygen concentrations close to the stream; these supported the highest biomass production but resulted in the lowest CH4 emissions. Further from the stream, the conditions were drier and CH4 emissions were also low. CH4 emissions were highest at an intermediate distance from the stream.
Simon Baumgartner, Matti Barthel, Travis William Drake, Marijn Bauters, Isaac Ahanamungu Makelele, John Kalume Mugula, Laura Summerauer, Nora Gallarotti, Landry Cizungu Ntaboba, Kristof Van Oost, Pascal Boeckx, Sebastian Doetterl, Roland Anton Werner, and Johan Six
Biogeosciences, 17, 6207–6218,Short summary
Soil respiration is an important carbon flux and key process determining the net ecosystem production of terrestrial ecosystems. The Congo Basin lacks studies quantifying carbon fluxes. We measured soil CO2 fluxes from different forest types in the Congo Basin and were able to show that, even though soil CO2 fluxes are similarly high in lowland and montane forests, the drivers were different: soil moisture in montane forests and C availability in the lowland forests.
Bettina K. Gier, Michael Buchwitz, Maximilian Reuter, Peter M. Cox, Pierre Friedlingstein, and Veronika Eyring
Biogeosciences, 17, 6115–6144,Short summary
Models from Coupled Model Intercomparison Project (CMIP) phases 5 and 6 are compared to a satellite data product of column-averaged CO2 mole fractions (XCO2). The previously believed discrepancy of the negative trend in seasonal cycle amplitude in the satellite product, which is not seen in in situ data nor in the models, is attributed to a sampling characteristic. Furthermore, CMIP6 models are shown to have made progress in reproducing the observed XCO2 time series compared to CMIP5.
Samuel T. Wilson, Alia N. Al-Haj, Annie Bourbonnais, Claudia Frey, Robinson W. Fulweiler, John D. Kessler, Hannah K. Marchant, Jana Milucka, Nicholas E. Ray, Parvadha Suntharalingam, Brett F. Thornton, Robert C. Upstill-Goddard, Thomas S. Weber, Damian L. Arévalo-Martínez, Hermann W. Bange, Heather M. Benway, Daniele Bianchi, Alberto V. Borges, Bonnie X. Chang, Patrick M. Crill, Daniela A. del Valle, Laura Farías, Samantha B. Joye, Annette Kock, Jabrane Labidi, Cara C. Manning, John W. Pohlman, Gregor Rehder, Katy J. Sparrow, Philippe D. Tortell, Tina Treude, David L. Valentine, Bess B. Ward, Simon Yang, and Leonid N. Yurganov
Biogeosciences, 17, 5809–5828,Short summary
The oceans are a net source of the major greenhouse gases; however there has been little coordination of oceanic methane and nitrous oxide measurements. The scientific community has recently embarked on a series of capacity-building exercises to improve the interoperability of dissolved methane and nitrous oxide measurements. This paper derives from a workshop which discussed the challenges and opportunities for oceanic methane and nitrous oxide research in the near future.
Najeeb Al-Amin Iddris, Marife D. Corre, Martin Yemefack, Oliver van Straaten, and Edzo Veldkamp
Biogeosciences, 17, 5377–5397,Short summary
We quantified the changes in stem and soil nitrous oxide (N2O) fluxes with forest conversion to cacao agroforestry in the Congo Basin, Cameroon. All forest and cacao trees consistently emitted N2O, contributing 8–38 % of the total (soil and stem) emissions. Forest conversion to extensively managed (>–20 years old) cacao agroforestry had no effect on stem and soil N2O fluxes. Our results highlight the importance of including tree-mediated fluxes in the ecosystem-level N2O budget.
Cédric Morana, Steven Bouillon, Vimac Nolla-Ardèvol, Fleur A. E. Roland, William Okello, Jean-Pierre Descy, Angela Nankabirwa, Erina Nabafu, Dirk Springael, and Alberto V. Borges
Biogeosciences, 17, 5209–5221,Short summary
A growing body of studies challenges the paradigm that methane (CH4) production occurs only under anaerobic conditions. Our field experiments revealed that oxic CH4 production is closely related to phytoplankton metabolism and is indeed a common feature in five contrasting African lakes. Nevertheless, we found that methanotrophic activity in surface waters and CH4 emissions to the atmosphere were predominantly fuelled by CH4 generated in sediments and physically transported to the surface.
Leandra Stephanie Emilia Praetzel, Nora Plenter, Sabrina Schilling, Marcel Schmiedeskamp, Gabriele Broll, and Klaus-Holger Knorr
Biogeosciences, 17, 5057–5078,Short summary
Small lakes are important but variable sources of greenhouse gas emissions. We performed lab experiments to determine spatial patterns and drivers of CO2 and CH4 emission and sediment gas production within a lake. The observed high spatial variability of emissions and production could be explained by the degradability of the sediment organic matter. We did not see correlations between production and emissions and suggest on-site flux measurements as the most accurate way for determing emissions.
Filippo Vingiani, Nicola Durighetto, Marcus Klaus, Jakob Schelker, Thierry Labasque, and Gianluca Botter
Revised manuscript accepted for BG
François Clayer, Yves Gélinas, André Tessier, and Charles Gobeil
Biogeosciences, 17, 4571–4589,Short summary
Here, we quantified the sediment production of methane and carbon dioxide in lake sediments to better characterize the nature of the organic matter at the origin of these two greenhouse gases. We demonstrate that the production of these gases is not adequately represented in models for deep lake sediments. We thus propose to improve the representation of organic matter degradation reactions in current models for improving predictions of greenhouse gas cycling in aquatic sediments.
Elisa Vainio, Olli Peltola, Ville Kasurinen, Antti-Jussi Kieloaho, Eeva-Stiina Tuittila, and Mari Pihlatie
Revised manuscript accepted for BGShort summary
We studied forest floor methane exchange over an area of ten hectares in a boreal pine forest. The results demonstrate high spatial variability in soil moisture and consequently in the methane flux. We detected wet patches emitting high amounts of methane in the early summer, however, these patches turned to methane uptake in the autumn. We concluded that the small-scale spatial variability of the boreal forest methane flux highlights the importance of soil chamber placement in similar studies.
Matthias Koschorreck, Yves T. Prairie, Jihyeon Kim, and Rafael Marcé
Revised manuscript accepted for BGShort summary
The concentration of carbon dioxide (CO2) in water samples is often measured using a gas chromatograph. Depending on the chemical composition of the water this method can produce wrong results. We quantified the possible error and how it depends on water composition and the analytical procedure. We propose a method to correct wrong results by additionally analysing alkalinity in the samples. We provide an easily usable computer code to perform the correction calculations.
Julia Drewer, Melissa M. Leduning, Robert I. Griffiths, Tim Goodall, Peter E. Levy, Nicholas Cowan, Edward Comynn-Platt, Garry Hayman, Justin Sentian, Noreen Majalap, and Ute M. Skiba
Revised manuscript accepted for BGShort summary
In Southeast Asia, oil palm plantations have largely replaced tropical forests. The impact of this shift in land-use on greenhouse gas fluxes and soil microbial communities remains uncertain. We have found emission rates of the potent greenhouse gas nitrous oxide on mineral soil to be higher from oil palm plantations than logged forest over a 2-year study and concluded that emissions have increased over the last 42 years in Sabah, with the proportion of emissions from plantations increasing.
David Bastviken, Jonatan Nygren, Jonathan Schenk, Roser Parellada Massana, and Nguyen Thanh Duc
Biogeosciences, 17, 3659–3667,Short summary
This study presents a low-cost way to measure methane emissions applicable in nature and society. This facilitates widespread and affordable methane measurements, which are greatly needed for verifying that greenhouse gas mitigation is effective and for improved quantification of fluxes and how they are regulated. The paper also describes an open-source do-it-yourself methane–carbon dioxide–humidity–temperature logger, to increase the distributed capacity to measure greenhouse gases.
Fortunat Joos, Renato Spahni, Benjamin D. Stocker, Sebastian Lienert, Jurek Müller, Hubertus Fischer, Jochen Schmitt, I. Colin Prentice, Bette Otto-Bliesner, and Zhengyu Liu
Biogeosciences, 17, 3511–3543,Short summary
Results of the first globally resolved simulations of terrestrial carbon and nitrogen (N) cycling and N2O emissions over the past 21 000 years are compared with reconstructed N2O emissions. Modelled and reconstructed emissions increased strongly during past abrupt warming events. This evidence appears consistent with a dynamic response of biological N fixation to increasing N demand by ecosystems, thereby reducing N limitation of plant productivity and supporting a land sink for atmospheric CO2.
Xuefei Li, Outi Wahlroos, Sami Haapanala, Jukka Pumpanen, Harri Vasander, Anne Ojala, Timo Vesala, and Ivan Mammarella
Biogeosciences, 17, 3409–3425,Short summary
We measured CO2 and CH4 fluxes and quantified the global warming potential of different surface areas in a recently created urban wetland in Southern Finland. The ecosystem has a small net climate warming effect which was mainly contributed by the open-water areas. Our results suggest that limiting open-water areas and setting a design preference for areas of emergent vegetation in the establishment of urban wetlands can be a beneficial practice when considering solely the climate impact.
Xiao Ma, Mingshuang Sun, Sinikka T. Lennartz, and Hermann W. Bange
Biogeosciences, 17, 3427–3438,Short summary
Monthly measurements of dissolved methane (CH4), a potent greenhouse gas, were conducted at Boknis Eck (BE), a time-series station in the southwestern Baltic Sea, from June 2006. In general CH4 concentrations increased with depth. High concentrations in the upper layer were linked to saline water inflow. Eckernförde Bay emitted CH4 to the atmosphere throughout the monitoring period. No significant trend was detected in CH4 concentrations or emissions during 2006–2017.
Elizabeth León-Palmero, Alba Contreras-Ruiz, Ana Sierra, Rafael Morales-Baquero, and Isabel Reche
Biogeosciences, 17, 3223–3245,Short summary
CH4 emissions from reservoirs are responsible for the majority of the climatic forcing of these ecosystems. The origin of the recurrent CH4 supersaturation in oxic waters is still controversial. We found that the dissolved CH4 concentration varied by up to 4 orders of magnitude in the water column of 12 reservoirs and was consistently supersaturated. Our findings suggest that photosynthetic picoeukaryotes can play a significant role in determining CH4 concentration in oxic waters.
Lutz Merbold, Charlotte Decock, Werner Eugster, Kathrin Fuchs, Benjamin Wolf, Nina Buchmann, and Lukas Hörtnagl
Revised manuscript accepted for BGShort summary
Our study investigated the exchange of the three major greenhouse gases (GHG) over a temperate grassland prior and post restoration through tillage in Central Switzerland. Our results show that irregular management events, such as tillage, have considerable effects on GHG emissions in the year of tillage, while leading to enhanced carbon uptake and similar nitrogen losses via nitrous oxide in the years following tillage as observed prior to tillage.
Marcus B. Wallin, Joachim Audet, Mike Peacock, Erik Sahlée, and Mattias Winterdahl
Biogeosciences, 17, 2487–2498,Short summary
Here we show that small streams draining agricultural areas are potential hotspots for emissions of CO2 to the atmosphere. We further conclude that the variability in stream CO2 concentration over time is very high, caused by variations in both water discharge and primary production. Given the observed high levels of CO2 and its temporally variable nature, agricultural streams clearly need more attention in order to understand and incorporate these dynamics in large-scale extrapolations.
Quan Zhang, Huimin Lei, Dawen Yang, Lihua Xiong, Pan Liu, and Beijing Fang
Biogeosciences, 17, 2245–2262,Short summary
Research into climate change has been popular over the past few decades. Greenhouse gas emissions are found to be responsible for climate change. Among all the ecosystems, cropland is the main food source for mankind, therefore its carbon cycle and contribution to the global carbon balance interest us. Our evaluation of the typical wheat–maize rotation cropland over the North China Plain shows it is a net CO2 emission to the atmosphere and that emissions will continue to rise in the future.
Sheila Wachiye, Lutz Merbold, Timo Vesala, Janne Rinne, Matti Räsänen, Sonja Leitner, and Petri Pellikka
Biogeosciences, 17, 2149–2167,Short summary
Limited data on emissions in Africa translate into uncertainty during GHG budgeting. We studied annual CO2, N2O, and CH4 emissions in four land-use types in Kenyan savanna using static chambers and gas chromatography. CO2 emissions varied between seasons and land-use types. Soil moisture and vegetation explained the seasonal variation, while soil temperature was insignificant. N2O and CH4 emissions did not vary at all sites. Our results are useful in climate change mitigation interventions.
Roland Vernooij, Marcos Vinicius Giongo Alves, Marco Assis Borges, Máximo Menezes Costa, Ana Carolina Sena Barradas, and Guido R. van der Werf
Revised manuscript accepted for BGShort summary
We used drones to measure greenhouse gas emission factors from fires in the Brazilian Cerrado. We compared early dry season management fires and late dry season fires to determine if fire management can be a tool in abating emissions. Although we found some evidence of increased CO and CH4 emission factors, the seasonal effect was smaller than in previous studies. For N2O, the third most important greenhouse gas, we found opposite trends in grasses and shrub dominated areas.
Celina Burkholz, Neus Garcias-Bonet, and Carlos M. Duarte
Biogeosciences, 17, 1717–1730,Short summary
Seagrass meadows store carbon in their biomass and sediments, but they have also been shown to be sources of carbon dioxide (CO2) and methane (CH4). We experimentally investigated the effect of warming and prolonged darkness on CO2 and CH4 fluxes in Red Sea seagrass (Halophila stipulacea) communities. Our results indicated that sublethal warming may lead to increased emissions of greenhouse gases from seagrass meadows which may contribute to further enhance global warming.
Chris R. Flechard, Andreas Ibrom, Ute M. Skiba, Wim de Vries, Marcel van Oijen, David R. Cameron, Nancy B. Dise, Janne F. J. Korhonen, Nina Buchmann, Arnaud Legout, David Simpson, Maria J. Sanz, Marc Aubinet, Denis Loustau, Leonardo Montagnani, Johan Neirynck, Ivan A. Janssens, Mari Pihlatie, Ralf Kiese, Jan Siemens, André-Jean Francez, Jürgen Augustin, Andrej Varlagin, Janusz Olejnik, Radosław Juszczak, Mika Aurela, Daniel Berveiller, Bogdan H. Chojnicki, Ulrich Dämmgen, Nicolas Delpierre, Vesna Djuricic, Julia Drewer, Eric Dufrêne, Werner Eugster, Yannick Fauvel, David Fowler, Arnoud Frumau, André Granier, Patrick Gross, Yannick Hamon, Carole Helfter, Arjan Hensen, László Horváth, Barbara Kitzler, Bart Kruijt, Werner L. Kutsch, Raquel Lobo-do-Vale, Annalea Lohila, Bernard Longdoz, Michal V. Marek, Giorgio Matteucci, Marta Mitosinkova, Virginie Moreaux, Albrecht Neftel, Jean-Marc Ourcival, Kim Pilegaard, Gabriel Pita, Francisco Sanz, Jan K. Schjoerring, Maria-Teresa Sebastià, Y. Sim Tang, Hilde Uggerud, Marek Urbaniak, Netty van Dijk, Timo Vesala, Sonja Vidic, Caroline Vincke, Tamás Weidinger, Sophie Zechmeister-Boltenstern, Klaus Butterbach-Bahl, Eiko Nemitz, and Mark A. Sutton
Biogeosciences, 17, 1583–1620,Short summary
Experimental evidence from a network of 40 monitoring sites in Europe suggests that atmospheric nitrogen deposition to forests and other semi-natural vegetation impacts the carbon sequestration rates in ecosystems, as well as the net greenhouse gas balance including other greenhouse gases such as nitrous oxide and methane. Excess nitrogen deposition in polluted areas also leads to other environmental impacts such as nitrogen leaching to groundwater and other pollutant gaseous emissions.
Chris R. Flechard, Marcel van Oijen, David R. Cameron, Wim de Vries, Andreas Ibrom, Nina Buchmann, Nancy B. Dise, Ivan A. Janssens, Johan Neirynck, Leonardo Montagnani, Andrej Varlagin, Denis Loustau, Arnaud Legout, Klaudia Ziemblińska, Marc Aubinet, Mika Aurela, Bogdan H. Chojnicki, Julia Drewer, Werner Eugster, André-Jean Francez, Radosław Juszczak, Barbara Kitzler, Werner L. Kutsch, Annalea Lohila, Bernard Longdoz, Giorgio Matteucci, Virginie Moreaux, Albrecht Neftel, Janusz Olejnik, Maria J. Sanz, Jan Siemens, Timo Vesala, Caroline Vincke, Eiko Nemitz, Sophie Zechmeister-Boltenstern, Klaus Butterbach-Bahl, Ute M. Skiba, and Mark A. Sutton
Biogeosciences, 17, 1621–1654,Short summary
Nitrogen deposition from the atmosphere to unfertilized terrestrial vegetation such as forests can increase carbon dioxide uptake and favour carbon sequestration by ecosystems. However the data from observational networks are difficult to interpret in terms of a carbon-to-nitrogen response, because there are a number of other confounding factors, such as climate, soil physical properties and fertility, and forest age. We propose a model-based method to untangle the different influences.
Pauline Sophie Rummel, Birgit Pfeiffer, Johanna Pausch, Reinhard Well, Dominik Schneider, and Klaus Dittert
Biogeosciences, 17, 1181–1198,Short summary
Chemical composition of plant litter controls C availability for biological N transformation processes in soil. In this study, we showed that easily degradable maize shoots stimulated microbial respiration and mineralization leading to high N2O formation in litter-associated hot spots. A higher share of slowly degradable C compounds and lower concentrations of water-soluble N restricted N2O emissions from maize roots. Bacterial community structure reflected degradability of maize litter.
Cynthia Soued and Yves T. Prairie
Biogeosciences, 17, 515–527,Short summary
Freshwater reservoirs emit greenhouse gases (GHGs) due to organic matter decay after landscape flooding. In order to better understand this phenomenon, we performed a comprehensive carbon footprint assessment of a tropical reservoir. Contrary to predictions, 89 % of measured emissions occurred downstream of the dam. Comparing predicted vs. measured emissions revealed weaknesses in our current modeling framework and insights to improve our ability to quantify and reduce reservoir GHG emissions.
Shimelis Gizachew Raji and Peter Dörsch
Biogeosciences, 17, 345–359,Short summary
Intercropping maize with forage legumes can benefit Ethiopian smallholder farmers by providing cheap nitrogen and valuable livestock feed. We measured N2O emissions and maize yields and found that high legume biomasses may enhance N2O emissions per unit of harvested maize but that, after mulching, legume N can partly replace expensive mineral N. Thus, legume intercropping can be a valid strategy in the framework of climate-smart agriculture in sub-Saharan Africa.
Arezoo Taghizadeh-Toosi, Lars Elsgaard, Tim J. Clough, Rodrigo Labouriau, Vibeke Ernstsen, and Søren O. Petersen
Biogeosciences, 16, 4555–4575,Short summary
Organic soils drained for crop production or grazing land have high potential for nitrous oxide emissions. The present study investigated the regulation of N2O emissions in a raised bog area drained for agriculture. It seems that archaeal ammonia oxidation and either chemodenitrification or nitrifier denitrification were considered to be plausible pathways of N2O production in spring, whereas in the autumn heterotrophic denitrification may have been more important at arable sites.
Hermann W. Bange, Chun Hock Sim, Daniel Bastian, Jennifer Kallert, Annette Kock, Aazani Mujahid, and Moritz Müller
Biogeosciences, 16, 4321–4335,Short summary
Nitrous oxide (N2O) and methane (CH4) are atmospheric trace gases which play important roles in the climate and atmospheric chemistry of the Earth. However, little is known about their emissions from rivers and estuaries. To this end, concentrations of N2O and CH4 were measured during a seasonal study in six rivers and estuaries in northwestern Borneo. The concentrations of both gases were mainly driven by rainfall. The rivers and estuaries were an overall net source of atmospheric N2O and CH4.
Jackie R. Webb, Peter R. Leavitt, Gavin L. Simpson, Helen M. Baulch, Heather A. Haig, Kyle R. Hodder, and Kerri Finlay
Biogeosciences, 16, 4211–4227,Short summary
Small farm reservoirs are key features within agricultural landscapes, yet these waterbodies can contribute substantial greenhouse gas (GHG) emissions to the atmosphere. This study assessed some of the environmental factors that may impact the production of these GHGs. We found promise that farm reservoirs can act as net greenhouse gas sinks and identified some of the key water quality, landscape, and design features that may support GHG mitigation.
Thomas Klintzsch, Gerald Langer, Gernot Nehrke, Anna Wieland, Katharina Lenhart, and Frank Keppler
Biogeosciences, 16, 4129–4144,Short summary
Marine algae might contribute to the observed methane oversaturation in oxic waters, but so far direct evidence for methane production by marine algae is limited. We investigated three widespread haptophytes for methane formation. Our results provide unambiguous evidence that all investigated marine algae produce methane per se and at substantial rates. We conclude that each of the three algae studied here could substantially account for the methane production observed in field studies.
Fabien Leroy, Sébastien Gogo, Christophe Guimbaud, Léonard Bernard-Jannin, Xiaole Yin, Guillaume Belot, Wang Shuguang, and Fatima Laggoun-Défarge
Biogeosciences, 16, 4085–4095,Short summary
This study demonstrates the implications of Molinia caerulea colonization in Sphagnum peatland on the C fluxes by enhancing the CO2 uptake by photosynthesis (but which led to higher CO2 and CH4 emissions) and also on the parameters controlling it (by increasing the temperature sensitivity of the CH4 emissions). Furthermore, roots and litter of Molinia caerulea could provide additional substrates for C emissions and should be taken into account in further works.
Xiao Ma, Sinikka T. Lennartz, and Hermann W. Bange
Biogeosciences, 16, 4097–4111,Short summary
Monthly measurements of nitrous oxide (N2O), a potent greenhouse gas and ozone depletion agent, were conducted at Boknis Eck (BE), a time series station in the southwestern Baltic Sea, since July 2005. Low N2O concentrations were observed in autumn and high in winter and early spring. Dissolved nutrients and oxygen played important roles in N2O distribution. Although we did not observe a significant N2O trend during 2005–2017, a decrease in N2O concentration and emission seems likely in future.
Eric J. Morgan, Jost V. Lavric, Damian L. Arévalo-Martínez, Hermann W. Bange, Tobias Steinhoff, Thomas Seifert, and Martin Heimann
Biogeosciences, 16, 4065–4084,Short summary
Taking a 2-year atmospheric record of atmospheric oxygen and the greenhouse gases N2O, CO2, and CH4, made at a coastal site in the Namib Desert, we estimated the fluxes of these gases from upwelling events in the northern Benguela Current region. We compared these results with flux measurements made on a research vessel in the study area at the same time and found that the two approaches agreed well. The study region was a source of N2O, CO2, and CH4 to the atmosphere during upwelling events.
Hubertus Fischer, Jochen Schmitt, Michael Bock, Barbara Seth, Fortunat Joos, Renato Spahni, Sebastian Lienert, Gianna Battaglia, Benjamin D. Stocker, Adrian Schilt, and Edward J. Brook
Biogeosciences, 16, 3997–4021,Short summary
N2O concentrations were subject to strong variations accompanying glacial–interglacial but also rapid climate changes over the last 21 kyr. The sources of these N2O changes can be identified by measuring the isotopic composition of N2O in ice cores and using the distinct isotopic composition of terrestrial and marine N2O. We show that both marine and terrestrial sources increased from the last glacial to the Holocene but that only terrestrial emissions responded quickly to rapid climate changes.
Alberto V. Borges, François Darchambeau, Thibault Lambert, Cédric Morana, George H. Allen, Ernest Tambwe, Alfred Toengaho Sembaito, Taylor Mambo, José Nlandu Wabakhangazi, Jean-Pierre Descy, Cristian R. Teodoru, and Steven Bouillon
Biogeosciences, 16, 3801–3834,Short summary
Tropical rivers might be strong sources of CO2 and CH4 to the atmosphere, although there is an enormous data gap. The origin of CO2 in lowland tropical rivers is not well characterized and can be from terra firme or from wetlands (flooded forests and aquatic macrophytes). We obtained a large field dataset of CO2, CH4 and N2O in the Congo, the second-largest river in the world, which allows us to quantity the emission of these greenhouse gases to the atmosphere and investigate their origin.
Mika Korkiakoski, Juha-Pekka Tuovinen, Timo Penttilä, Sakari Sarkkola, Paavo Ojanen, Kari Minkkinen, Juuso Rainne, Tuomas Laurila, and Annalea Lohila
Biogeosciences, 16, 3703–3723,Short summary
We measured greenhouse gas and energy fluxes for 2 years after clear-cutting in a peatland forest. We found high carbon dioxide and nitrous oxide emissions. However, in the second year after clear-cutting, the carbon dioxide emissions had already decreased by 33 % from the first year. Also, clear-cutting turned the site from a methane sink into a methane source. We conclude that clear-cutting peatland forests exerts a strong climatic warming effect through accelerated emission of greenhouse gas.
Kleiton R. de Araújo, Henrique O. Sawakuchi, Dailson J. Bertassoli Jr., André O. Sawakuchi, Karina D. da Silva, Thiago B. Vieira, Nicholas D. Ward, and Tatiana S. Pereira
Biogeosciences, 16, 3527–3542,Short summary
Run-of-the-river (ROR) reservoirs have reduced flooded areas that maintain natural river characteristics; however, little is known about their influence on carbon dioxide (CO2) emission. In this regard, we evaluated the spatiotemporal CO2 fluxes (FCO2) and partial CO2 pressure (pCO2) of the Belo Monte hydropower complex. Our results emphasize that ROR dams contribute to CO2) emissions. Only FCO2 varies through reservoirs; in addition, both FCO2 and pCO2 are spatially heterogeneous.
Lukas Kohl, Markku Koskinen, Kaisa Rissanen, Iikka Haikarainen, Tatu Polvinen, Heidi Hellén, and Mari Pihlatie
Biogeosciences, 16, 3319–3332,Short summary
Plants emit small amounts of methane and large amounts of volatile organic compounds (VOCs). Measurements of plant methane emissions therefore require analysers that can provide accurate measurements of CH4 concentrations in the presence of changing amounts of VOCs. We therefore quantified to which degree various VOCs bias methane concentration measurements on different analysers. Our results show that some analysers are more sensitive to the presence of VOCs than others.
Petri Kiuru, Anne Ojala, Ivan Mammarella, Jouni Heiskanen, Kukka-Maaria Erkkilä, Heli Miettinen, Timo Vesala, and Timo Huttula
Biogeosciences, 16, 3297–3317,Short summary
Many boreal lakes emit the greenhouse gas carbon dioxide (CO2) to the atmosphere. We incorporated four different gas exchange models into a physico-biochemical lake model and studied their ability to simulate lake air–water CO2 fluxes. The inclusion of refined gas exchange models in lake models that simulate carbon cycling is important to assess lake carbon budgets. However, higher estimates for inorganic carbon sources in boreal lakes are needed to balance the CO2 losses to the atmosphere.
Erkan Ibraim, Benjamin Wolf, Eliza Harris, Rainer Gasche, Jing Wei, Longfei Yu, Ralf Kiese, Sarah Eggleston, Klaus Butterbach-Bahl, Matthias Zeeman, Béla Tuzson, Lukas Emmenegger, Johan Six, Stephan Henne, and Joachim Mohn
Biogeosciences, 16, 3247–3266,Short summary
Nitrous oxide (N2O) is an important greenhouse gas and the major stratospheric ozone-depleting substance; therefore, mitigation of anthropogenic N2O emissions is needed. To trace N2O-emitting source processes, in this study, we observed N2O isotopocules above an intensively managed grassland research site with a recently developed laser spectroscopy method. Our results indicate that the domain of denitrification or nitrifier denitrification was the major N2O source.
Camilo Rey-Sanchez, Gil Bohrer, Julie Slater, Yueh-Fen Li, Roger Grau-Andrés, Yushan Hao, Virginia I. Rich, and G. Matt Davies
Biogeosciences, 16, 3207–3231,Short summary
It is estimated that natural wetlands emit approximately 30 % of all the methane released to the atmosphere; yet these estimates are highly uncertain due to the complexity of biological, chemical, and physical processes controlling methane emissions. In this study, we explore how some of these key processes drive methane emissions in a temperate peat bog. We show that the composition of microbial methane cyclers in the upper portion of the peat drives the velocity of methane release to the air.
Jocelyn E. Egan, David R. Bowling, and David A. Risk
Biogeosciences, 16, 3197–3205,Short summary
Traditionally a mass-dependent correction is made when measuring the radiocarbon composition in organic samples. This correction has not been evaluated for the soil gas environment where gas transport processes are important. Here, we show using theory that this traditional correction is not appropriate for estimating the radiocarbon composition of soil biological production. We also propose a new solution that accounts for soil gas transport processes.
Mathias Göckede, Fanny Kittler, and Carsten Schaller
Biogeosciences, 16, 3113–3131,Short summary
Methane is one of the most important greenhouse gases. Methane emissions from land sources to the atmosphere often occur in the form of short but intense outbursts, which are difficult to measure. We developed a new software tool based on wavelets which reliably quantifies such methane outbursts. Using these results as a reference, our study shows that regular data processing using the eddy-covariance technique provides solid long-term methane budgets, but short-term uncertainties can be high.
Robert W. Howarth
Biogeosciences, 16, 3033–3046,Short summary
Atmospheric methane has risen rapidly since 2008 and has become more depleted in 13C, in contrast to the trend towards more 13C enrichment in the late 20th century. Many have used this isotopic evidence to infer an increased biogenic source. Here I analyze the 13C trend with the consideration that methane from shale gas is somewhat depleted in 13C compared to other fossil fuels. I conclude that shale gas may be responsible for a third of the global increase from all sources.
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To better understand why atmospheric carbon dioxide has changed over the course of Earth's history, we analyze carbon dissolved in the ocean in a state-of-the-art model. While primary producers in the surface ocean are important to the global carbon cycle, the carbon in the ocean and atmosphere are not in equilibrium in most places, and our results indicate that the degree of this disequilibrium, which has previously been largely ignored in similar studies, could be just as significant.
To better understand why atmospheric carbon dioxide has changed over the course of Earth's...