Articles | Volume 18, issue 17
Research article 01 Sep 2021
Research article | 01 Sep 2021
Greenhouse gases emissions from riparian wetlands: an example from the Inner Mongolia grassland region in China
Xinyu Liu et al.
No articles found.
Samuel De Xun Chua, Xi Xi Lu, Chantha Oeurng, Ty Sok, and Carl Grundy-Warr
Hydrol. Earth Syst. Sci., 26, 609–625,Short summary
We found that the annual flood at the Cambodian floodplains decreased from 1960 to 2019. Consequently, the Tonle Sap Lake, the largest lake in Southeast Asia, is shrinking. The results are worrying because the local fisheries and planting calendar might be disrupted. This drastic decline of flooding extent is caused mostly by local factors, namely water withdrawal for irrigation and channel incision from sand mining activities.
Lin Lin, Xixi Lu, Shaoda Liu, Shie-Yui Liong, and Kaidao Fu
Biogeosciences, 16, 2205–2219,Short summary
Damming did not significantly increase carbon dioxide emissions from the reservoir surface, as shown in a case study in a reservoir constrained within the narrow upper Mekong River valley. This finding might provide some evidence to the green credits for hydropower in China. One-year monitoring of carbon dioxide emissions from the water surface found that the higher emissions were concentrated at the riverine inlets in winter and more related to the mixing process of inflow and reservoir water.
Mingyang Tian, Xiankun Yang, Lishan Ran, Yuanrong Su, Lingyu Li, Ruihong Yu, Haizhu Hu, and Xi Xi Lu
Preprint withdrawnShort summary
We investigated the spatial and temporal variability of riverine CO2 outgassing characteristics of the Yellow River source region. Riverine CO2 emission were in situ monitored under different land cover types (i.e., glacier, permafrost, wetland, and grassland) in the research area.This study will lead to a better understanding of riverine carbon export, especially for alpine rivers, which will help refine the global estimation of global GHG gas emission.
Thi Phuong Quynh Le, Cyril Marchand, Cuong Tu Ho, Nhu Da Le, Thi Thuy Duong, XiXi Lu, Phuong Kieu Doan, Trung Kien Nguyen, Thi Mai Huong Nguyen, and Duy An Vu
Biogeosciences, 15, 4799–4814,Short summary
The Red River is a typical south-east Asian river, strongly affected by climate and human activity. This study showed the spatial and seasonal variability of CO2 emissions at the water–air interface of the lower part of this river due to natural conditions (meteo-hydrological-geomorphological characteristics) and human activities (dam impoundment, population, land use). The Red River water was supersaturated with CO2, providing a mean water–air CO2 ﬂux of 530 ± 17 mmol m−2 d−1.
Lishan Ran, Mingyang Tian, Nufang Fang, Suiji Wang, Xixi Lu, Xiankun Yang, and Frankie Cho
Biogeosciences, 15, 3857–3871,Short summary
We systematically assessed the transport and fate of riverine carbon in the moderate-sized Wuding catchment on the Chinese Loess Plateau by constructing a riverine carbon budget and further relating it to terrestrial ecosystem productivity. The riverine carbon export accounted for 16 % of the catchment's net ecosystem production (NEP). It seems that a significant fraction of terrestrial NEP in this catchment is laterally transported from the terrestrial biosphere to the drainage network.
Ji-Hyung Park, Omme K. Nayna, Most S. Begum, Eliyan Chea, Jens Hartmann, Richard G. Keil, Sanjeev Kumar, Xixi Lu, Lishan Ran, Jeffrey E. Richey, Vedula V. S. S. Sarma, Shafi M. Tareq, Do Thi Xuan, and Ruihong Yu
Biogeosciences, 15, 3049–3069,Short summary
Human activities are drastically altering water and material flows in river systems across Asia. This review provides a conceptual framework for assessing the human impacts on Asian river C fluxes and an update on anthropogenic alterations of riverine C fluxes, focusing on the impacts of water pollution and river impoundments on CO2 outgassing from the rivers draining South, Southeast, and East Asian regions that account for the largest fraction of river discharge and C exports from Asia.
Hewen Niu, Shichang Kang, Hailong Wang, Rudong Zhang, Xixi Lu, Yun Qian, Rukumesh Paudyal, Shijin Wang, Xiaofei Shi, and Xingguo Yan
Atmos. Chem. Phys., 18, 6441–6460,Short summary
Deposition of light-absorbing carbonaceous aerosol on the surface of glaciers can greatly alter the energy fluxes of glaciers. Two years of continuous observations of carbonaceous aerosols in a glacierized region are analyzed. We mainly studied the light absorption properties of carbonaceous aerosol and have employed a global aerosol–climate model to estimate source attributions of atmospheric black carbon.
Lishan Ran, Xi Xi Lu, and Shaoda Liu
Biogeosciences, 14, 2183–2198,Short summary
Understanding riverine carbon dynamics is critical for not only better estimates of various carbon fluxes but also evaluating their significance in the global carbon budget. In this study, we examined the dynamics of riverine CO2 partial pressure (pCO2) in the Yangtze River basin. Its pCO2 was characterized by strong spatial and temporal variations. With a basin-wide mean pCO2 of 2662(±1240) μatm, substantial CO2 evasion is expected. Future efforts are needed to evaluate its significance.
L. Ran, X. X. Lu, J. E. Richey, H. Sun, J. Han, R. Yu, S. Liao, and Q. Yi
Biogeosciences, 12, 921–932,Short summary
This paper investigated the spatial and temporal variations of pCO2 in the Yellow River watershed. While the pCO2 responded exponentially to total suspended solids (TSS) export when the TSS concentration was less than 100 kg m-3, it decreased and remained stable thereafter if the TSS concentration was greater than 100 kg m-3. The average pCO2 for the watershed was estimated at 2810±1985 μatm, indicating a large potential for CO2 evasion.
X. Ma, X. X. Lu, M. van Noordwijk, J. T. Li, and J. C. Xu
Hydrol. Earth Syst. Sci., 18, 1979–1994,
L. Ran, X. X. Lu, and Z. Xin
Biogeosciences, 11, 945–959,
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Yanan Zhao, Dennis Booge, Christa A. Marandino, Cathleen Schlundt, Astrid Bracher, Elliot L. Atlas, Jonathan Williams, and Hermann W. Bange
Biogeosciences, 19, 701–714,Short summary
We present here, for the first time, simultaneously measured dimethylsulfide (DMS) seawater concentrations and DMS atmospheric mole fractions from the Peruvian upwelling region during two cruises in December 2012 and October 2015. Our results indicate low oceanic DMS concentrations and atmospheric DMS molar fractions in surface waters and the atmosphere, respectively. In addition, the Peruvian upwelling region was identified as an insignificant source of DMS emissions during both periods.
Moussa Moustapha, Loris Deirmendjian, David Sebag, Jean-Jacques Braun, Stéphane Audry, Henriette Ateba Bessa, Thierry Adatte, Carole Causserand, Ibrahima Adamou, Benjamin Ngounou Ngatcha, and Frédéric Guérin
Biogeosciences, 19, 137–163,Short summary
We monitor the spatio-temporal variability of organic and inorganic carbon (C) species in the tropical Nyong River (Cameroon), across groundwater and increasing stream orders. We show the significant contribution of wetland as a C source for tropical rivers. Thus, ignoring the river–wetland connectivity might lead to the misrepresentation of C dynamics in tropical watersheds. Finally, total fluvial carbon losses might offset ~10 % of the net C sink estimated for the whole Nyong watershed.
Alexander J. Turner, Philipp Köhler, Troy S. Magney, Christian Frankenberg, Inez Fung, and Ronald C. Cohen
Biogeosciences, 18, 6579–6588,Short summary
This work builds a high-resolution estimate (500 m) of gross primary productivity (GPP) over the US using satellite measurements of solar-induced chlorophyll fluorescence (SIF) from the TROPOspheric Monitoring Instrument (TROPOMI) between 2018 and 2020. We identify ecosystem-specific scaling factors for estimating gross primary productivity (GPP) from TROPOMI SIF. Extreme precipitation events drive four regional GPP anomalies that account for 28 % of year-to-year GPP differences across the US.
Paul Laris, Moussa Koné, Fadiala Dembélé, Christine M. Rodrigue, Lilian Yang, Rebecca Jacobs, and Quincy Laris
Biogeosciences, 18, 6229–6244,Short summary
Savanna fires play a key role in the global carbon cycle because they release methane. Although it burns the most, there are few studies from West Africa. We conducted 36 experimental fires according to local practice to collect smoke samples. We found that fires set early in the season had higher methane emissions than those set later, and head fires had double the emissions of backfires. We conclude policies to reduce emissions will not have the desired effects if fire type is not considered.
Johan H. Scheller, Mikhail Mastepanov, Hanne H. Christiansen, and Torben R. Christensen
Biogeosciences, 18, 6093–6114,Short summary
Our study presents a time series of methane emissions in a high-Arctic-tundra landscape over 14 summers, which shows large variations between years. The methane emissions from the valley are expected to more than double in the late 21st century. This warming increases permafrost thaw, which could increase surface erosion in the valley. Increased erosion could offset some of the rise in methane fluxes from the valley, but this would require large-scale impacts on vegetated surfaces.
Patryk Łakomiec, Jutta Holst, Thomas Friborg, Patrick Crill, Niklas Rakos, Natascha Kljun, Per-Ola Olsson, Lars Eklundh, Andreas Persson, and Janne Rinne
Biogeosciences, 18, 5811–5830,Short summary
Methane emission from the subarctic mire with heterogeneous permafrost status was measured for the years 2014–2016. Lower methane emission was measured from the palsa mire sector while the thawing wet sector emitted more. Both sectors have a similar annual pattern with a gentle rise during spring and a decrease during autumn. The highest emission was observed in the late summer. Winter emissions were positive during the measurement period and have a significant impact on the annual budgets.
Balázs Grosz, Reinhard Well, Rene Dechow, Jan Reent Köster, Mohammad Ibrahim Khalil, Simone Merl, Andreas Rode, Bianca Ziehmer, Amanda Matson, and Hongxing He
Biogeosciences, 18, 5681–5697,Short summary
To assure quality predictions biogeochemical models must be current. We use data measured using novel incubation methods to test the denitrification sub-modules of three models. We aim to identify limitations in the denitrification modeling to inform next steps for development. Several areas are identified, most urgently improved denitrification control parameters and further testing with high-temporal-resolution datasets. Addressing these would significantly improve denitrification modeling.
Sarah Waldo, Jake J. Beaulieu, William Barnett, D. Adam Balz, Michael J. Vanni, Tanner Williamson, and John T. Walker
Biogeosciences, 18, 5291–5311,Short summary
Human-made reservoirs impact the carbon cycle. In particular, the breakdown of organic matter in reservoir sediments can result in large emissions of greenhouse gases (especially methane) to the atmosphere. This study takes an intensive look at the patterns in greenhouse gas emissions from a single reservoir in Ohio (United States) and the role of water temperature, precipitation, and algal blooms in emissions. We saw a "spring burst" of elevated emissions that challenged our assumptions.
Dong-Gill Kim, Ben Bond-Lamberty, Youngryel Ryu, Bumsuk Seo, and Dario Papale
Revised manuscript accepted for BGShort summary
While carbon (C) and greenhouse gas (GHG) research has adopted appropriate technology and approach (AT&A) such as low-cost instrument, open source software and participatory research and their results were well accepted by scientific communities. In terms of cost, feasibility and performance, integration of low-cost and low-technology, participatory and networking based research approaches can be AT&A for enhancing C and GHG research in developing countries.
Jan Knappe, Celia Somlai, and Laurence Gill
Revised manuscript accepted for BGShort summary
Two domestic on-site wastewater treatment systems have been monitored for greenhouse gas (carbon dioxide, methane and nitrous oxide) emissions coming from the process units, the soil and vent pipes. This has enabled the net greenhouse gas per person to be quantified for the first time, as well as the impact of pre-treatment on the effluent before being discharged to soil. These decentralised wastewater treatment systems serve approx. 20 % of the population in both Europe and the United States.
Lutz Beckebanze, Zoé Rehder, David Holl, Charlotta Mirbach, Christian Wille, and Lars Kutzbach
Revised manuscript accepted for BGShort summary
Arctic permafrost landscapes feature a lot of waterbodies. In contrast to the terrestrial parts of the landscape, the waterbodies release carbon to the atmosphere. We compare carbon dioxide and methane fluxes from small waterbodies to the surrounding tundra and find that the carbon dioxide uptake of the landscape is reduced by 11 % when accounting for waterbodies. Consequently, changes in hydrology and waterbody distribution may substantially impact the overall carbon budget of the Arctic.
Zhaohui Chen, Parvadha Suntharalingam, Andrew J. Watson, Ute Schuster, Jiang Zhu, and Ning Zeng
Biogeosciences, 18, 4549–4570,Short summary
As the global temperature continues to increase, carbon dioxide (CO2) is a major driver of this global warming. The increased CO2 is mainly caused by emissions from fossil fuel use and land use. At the same time, the ocean is a significant sink in the carbon cycle. The North Atlantic is a critical ocean region in reducing CO2 concentration. We estimate the CO2 uptake in this region based on a carbon inverse system and atmospheric CO2 observations.
Brian Scott, Andrew Baldwin, and Stephanie Yarwood
Revised manuscript accepted for BGShort summary
Carbon dioxide and methane contribute to global warming. What can we do? Build wetlands – they store carbon dioxide and should cause global cooling. Except ... when first built they produce excess methane. Eventually built wetlands will cause cooling, but it may take decades or even centuries. How we build wetlands matters. We show that a common practice, using organic matter, such as manure, can make a big difference whether or not the wetlands we build start global cooling within our lifetime.
Sirwan Yamulki, Jack Forster, Georgios Xenakis, Adam Ash, Jacqui Brunt, Mike Perks, and James I. L. Morison
Biogeosciences, 18, 4227–4241,Short summary
The effect of clear-felling on soil greenhouse gas (GHG) fluxes was assessed in a Sitka spruce forest. Measurements over 4 years showed that CO2, CH4, and N2O fluxes responded differently to clear-felling due to significant changes in soil biotic and abiotic factors and showed large variations between years. Over 3 years since felling, the soil GHG flux was reduced by 45% due to a much larger reduction in CO2 efflux than increases in N2O (up to 20%) and CH4 (changed from sink to source) fluxes.
Sarah Shakil, Suzanne Tank, Jorien Vonk, and Scott Zolkos
Revised manuscript accepted for BGShort summary
Permafrost thaw-driven landslides in the western Arctic are increasing organic carbon delivered to headwaters of drainage networks in the western Canadian Arctic by orders of magnitude. Through a series of laboratory experiments, we show that less than 10 % of this organic carbon is likely to be mineralized to greenhouse gases during transport in these networks. Rather most of the organic carbon is likely destined for burial and sequestration for centuries to millennia.
Stefan Theodorus Johannes Weideveld, Weier Liu, Merit van den Berg, Leon Peter Maria Lamers, and Christian Fritz
Biogeosciences, 18, 3881–3902,Short summary
Raising the groundwater table (GWT) trough subsoil irrigation does not lead to a reduction of carbon emissions from drained peat meadows, even though there was a clear increase in the GWT during summer. Most likely, the largest part of the peat oxidation takes place in the top 70 cm of the soil, which stays above the GWT with the use of subsoil irrigation. We conclude that the use of subsoil irrigation is ineffective as a mitigation measure to sufficiently lower peat oxidation rates.
Yanming Gong, Ping Yue, Kaihui Li, Anwar Mohammat, and Yanyan Liu
Biogeosciences, 18, 3529–3537,Short summary
At present, data on the influence of asymmetric warming on the GHG flux on a temporal scale are scarce. GHG fluxes were measured using static chambers and a gas chromatograph. Our study showed that the effect of seasonally asymmetrical warming on CO2 flux was obvious, with the GHG flux being able to adapt to continuous warming. Warming in the non-growing season increased the temperature dependence of GHG flux.
Wolfgang Fischer, Christoph Thomas, Nikita Zimov, and Mathias Göckede
Revised manuscript accepted for BGShort summary
Arctic permafrost ecosystems may release large amounts of carbon under warmer future climates, and may therefore accelerate global climate change. Our study investigated how long-term grazing by large animals influenced ecosystem characteristics and carbon budgets at a Siberian permafrost site. Our results demonstrate that such management can contribute to stabilize ecosystems to keep carbon in the ground, particularly through drying soils and reducing methane emissions.
Hella van Asperen, João Rafael Alves-Oliveira, Thorsten Warneke, Bruce Forsberg, Alessandro Carioca de Araújo, and Justus Notholt
Biogeosciences, 18, 2609–2625,Short summary
Termites are insects that are highly abundant in tropical ecosystems. It is known that termites emit CH4, an important greenhouse gas, but their absolute emission remains uncertain. In the Amazon rainforest, we measured CH4 emissions from termite nests and groups of termites. In addition, we tested a fast and non-destructive field method to estimate termite nest colony size. We found that termites play a significant role in an ecosystem's CH4 budget and probably emit more than currently assumed.
Genevieve L. Noyce and J. Patrick Megonigal
Biogeosciences, 18, 2449–2463,Short summary
Methane (CH4) is a potent greenhouse gas that contributes to global radiative forcing. A mechanistic understanding of how wetland CH4 cycling will respond to global warming is crucial for improving prognostic models. We present results from the first 4 years of a novel whole-ecosystem warming experiment in a coastal wetland, showing that warming increases CH4 emissions and identifying four potential mechanisms that can be added to future modeling efforts.
Yanan Zhao, Cathleen Schlundt, Dennis Booge, and Hermann W. Bange
Biogeosciences, 18, 2161–2179,Short summary
We present a unique and comprehensive time-series study of biogenic sulfur compounds in the southwestern Baltic Sea, from 2009 to 2018. Dimethyl sulfide is one of the key players regulating global climate change, as well as dimethylsulfoniopropionate and dimethyl sulfoxide. Their decadal trends did not follow increasing temperature but followed some algae group abundances at the Boknis Eck Time Series Station.
Ingeborg Bussmann, Irina Fedorova, Bennet Juhls, Pier Paul Overduin, and Matthias Winkel
Biogeosciences, 18, 2047–2061,Short summary
Arctic rivers, lakes, and bays are affected by a warming climate. We measured the amount and consumption of methane in waters from Siberia under ice cover and in open water. In the lake, methane concentrations under ice cover were much higher than in summer, and methane consumption was highest. The ice cover leads to higher methane concentration under ice. In a warmer Arctic, there will be more time with open water when methane is consumed by bacteria, and less methane will escape into the air.
Elisa Vainio, Olli Peltola, Ville Kasurinen, Antti-Jussi Kieloaho, Eeva-Stiina Tuittila, and Mari Pihlatie
Biogeosciences, 18, 2003–2025,Short summary
We studied forest floor methane exchange over an area of 10 ha 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
Biogeosciences, 18, 1619–1627,Short 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
Biogeosciences, 18, 1559–1575,Short 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.
Lutz Merbold, Charlotte Decock, Werner Eugster, Kathrin Fuchs, Benjamin Wolf, Nina Buchmann, and Lukas Hörtnagl
Biogeosciences, 18, 1481–1498,Short summary
Our study investigated the exchange of the three major greenhouse gases (GHGs) over a temperate grassland prior to and after 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 to those observed prior to tillage.
Roland Vernooij, Marcos Giongo, Marco Assis Borges, Máximo Menezes Costa, Ana Carolina Sena Barradas, and Guido R. van der Werf
Biogeosciences, 18, 1375–1393,Short 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 for abating emissions. Although we found some evidence of increased CO and CH4 emission factors, the seasonal effect was smaller than that found in previous studies. For N2O, the third most important greenhouse gas, we found opposite trends in grass- and shrub-dominated areas.
Filippo Vingiani, Nicola Durighetto, Marcus Klaus, Jakob Schelker, Thierry Labasque, and Gianluca Botter
Biogeosciences, 18, 1223–1240,Short summary
Flexible foil chamber design and the anchored deployment might be useful techniques to enhance the robustness and the accuracy of CO2 measurements in low-order streams. Moreover, the study demonstrates the value of analytical and numerical techniques for the estimation of gas exchange velocities. These results may contribute to the development of novel procedures for chamber data analysis which might improve the robustness and reliability of chamber-based CO2 measurements in first-order streams.
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.
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.
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.
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.
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.
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Gradual riparian wetland drying is increasingly sensitive to global warming and contributes to climate change. We analyzed the emissions of CO2, CH4, and N2O from riparian wetlands in the Xilin River basin to understand the role of these ecosystems in greenhouse gas emissions. Our study showed that anthropogenic activities have extensively changed the hydrological characteristics of the riparian wetlands and might accelerate carbon loss, which could further affect greenhouse gas emissions.
Gradual riparian wetland drying is increasingly sensitive to global warming and contributes to...